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Many challenges persist with traditional self-sensing cementitious composites, such as selecting conductive fillers, determining optimal aspect ratios, controlling dosage, achieving filler dispersion, designing practical electrodes, and overcoming fabrication difficulties. Therefore, this paper proposes a novel self-sensing technique for cementitious composites by incorporating a 2-dimensional (2-D) carbon-fibre textile network to address these challenges. Additionally, instead of using the entire composite volume as the sensor, an alternative approach is explored, which involves utilising the interlaminar interface by incorporating the 2-D carbon-fibre textile network. This approach provides an integrated self-sensing system, including electrical leads and conductive pathways, which can be tailored based on the design requirements. The paper introduces fundamental concepts and measurement circuit design, followed by a comprehensive study covering measurement techniques, electromechanical properties, and microstructural analysis. Furthermore, it discusses the impact of ambient conditions, such as temperature and relative humidity, on the measurements. Experimental results demonstrate a remarkable maximum fractional change in contact resistivity, reaching up to 70%. The reversibility during cyclic compression is excellent, with a maximum negative gauge factor of − 2500. These findings represent a significant step toward achieving a practical and simplified method for manufacturing self-sensing cementitious composites and open avenues for self-sensing, sustainable textile-reinforced concrete structures (TRC). [Display omitted] • A novel self-sensing system for cementitious composites has been introduced. • The system can be considered as an integrated solution, encompassing the essential components required for self-sensing. • A simplified equivalent circuit model and an equation to calculate the overall contact resistivity have been proposed. • A remarkable maximum fractional change in the overall contact resistivity, reaching up to 70%, has been achieved. • The reversibility during cyclic compression has been excellent, with a maximum negative gauge factor of − 2500. [ABSTRACT FROM AUTHOR]

This paper performed the research on the autogenous shrinkage mitigation mechanism and mechanical properties of alkali-activated high strength mortar (AAHSM) incorporating hydroxypropyl methylcellulose (HPMC). The increase in HPMC content causes the lower slump flow and the longer setting time of AAHSM due to the flocculation effect of HPMC. Because of strong interaction between the hydroxyls of HPMC and water, the higher internal relative humidity is achieved, leading to the much lower capillary pressure. The unreacted precursors and reaction products are wrapped by the HPMC molecular network, causing that the depolymerization-polymerization reaction is prevented, which leads to the lower reaction degree. The increase in HPMC content promotes less generation of C(N)-A-S-H gels and more generation of hydrotalcite. The adhesion forces between reaction products particles are enhanced by the flocculation effect caused by the HPMC molecular network, indicating that the AAHSM containing HPMC has larger resistance to the deformation. Adding HPMC has a slight effect on the element compositions of reaction products and the pore types and a slight adverse effect on the Yang's modulus of reaction products micro region. Thus, the 56 days autogenous shrinkage of AAHSM is reduced by 22.2 % when the HPMC content is 2.0 wt%. Although the proportion of meso pore is increased by adding HPMC, the higher porosity and coarser pore structure are achieved, thus the autogenous shrinkage is still reduced. The lower reaction degree and generation of C(N)-A-S-H gels caused by adding HPMC lead to the higher porosity, which is related to the lower compressive and flexural strength. When the HPMC content is 2.0 wt%, the 28 days compressive and flexural strength of AAHSM are 89.2 MPa and 8.2 MPa, which are decreased by 17.3 % and 16.3 % compared to that of AAHSM without HPMC. At longer curing age, the reaction degree is improved and more Ca-rich C(N)-A-S-H gels are generated regardless of with or without HPMC, causing the lower porosity and higher Yang's modulus of reaction products micro region, which leads to the improvement of mechanical properties. ● Alkali-activated high-strength mortar (AAHSM) with strength of over 90 MPa was prepared. ● Autogenous shrinkage mitigation mechanism of HPMC for AAHSM was revealed. ● Mechanical properties effects of HPMC for AAHSM was studied. ● Compressive strength of AAHSM was slight reduced and the flexural strength and toughness were improved by HPMC. ● Autogenous shrinkage of AAHSM was reduced due to the lower capillary pressure and stronger adhesive force between gel particles caused by HPMC. [ABSTRACT FROM AUTHOR]

This paper investigates the synergic effect of both hydrated lime and guar gum stabilisation on the mechanical, thermal and hygroscopic properties of a compressed earth material for building applications. The stiffness, strength and compression energy at failure of both unstabilised and stabilised earth samples were measured at different curing times by means of compression tests. The moisture-dependent thermal conductivity was instead determined via the hot disk technique at a constant temperature of 25 °C and at the three different relative humidity levels of 0 %, 50 % and 95 %. The specific heat capacity was measured by means of calorimetry tests at the three temperature levels of 32–34 °C, 34–36 °C and 36–38 °C. The moisture adsorption-desorption curves were measured by performing a cyclic variation of relative humidity between 0 % and 95 % at a constant temperature of 25 °C via the dynamic vapour sorption (DVS) technique. Results from the experimental campaign show that the proposed stabilisation methods increase both the peak compressive strength and compression energy at failure while the addition of the biopolymer guar gum induces a progressive reduction of stiffness. The thermal properties of the earth are only marginally affected by the addition of hydrated lime and guar gum, with stabilised samples exhibiting similar levels of thermal conductivity and specific heat capacity to those of the unstabilised ones. Finally, the biopolymer stabilised samples exhibited a similar hygroscopic behaviour to that of unstabilised ones, whereas the addition of hydrated lime deteriorates the moisture adsorption capacity of the material. • Earth samples are stabilised with hydrated lime and the biopolymer guar gam. • Biopolymer stabilisation increases strength and compression energy while reducing stiffness. • Lime stabilisation increases stiffness and strength but reduces ductility. • Lime and guar gum stabilisations marginally affect the thermal properties of the earth. • Moisture adsorption is preserved by guar gum stabilisation and reduced by lime stabilisation. [ABSTRACT FROM AUTHOR]

This study focuses on the heat and moisture transfer behaviours in the Phyllostachys edulis (Moso bamboo) panels at various temperature and relative humidity (RH) conditions. Moso bamboo panels with different lamination methods were prepared by assembling bamboo strips from different layers of the bamboo culm wall. Dynamic coupled heat and moisture transfer experiments were conducted. Unsteady state numerical modelling was conducted by COMSOL Multiphysics™. A rigorous approach was adopted in this paper. A series of parametric studies of numerical simulation are firstly presented in this paper and then validated by the experiments. Both experimental and simulation results appear to be consistent with the results of measurements of the basic hygrothermal parameters, which demonstrates the robustness of the results. The temperature and RH results indicated that although the panel made from layers of the internal part of bamboo culm wall can provide good insulation performance, its ability to resist high RH variation is inferior to the layer from the external part of bamboo culm wall. The parametric study found that density is the most critical parameters to influence the temperature distributions in the transient state. The thermal conductivity dominates the temperature variation in the steady state. The water vapour diffusion resistance factor is the key parameter which influences the RH simulation results. Numerical simulation with moisture transfer shows better consistency than the simulation without moisture in both equilibrium and transient states. The results of this study demonstrated that the external part of the bamboo culm wall can be utilised to minimise the RH variation of the panel while the internal part is suitable for increasing the thermal insulation performance of the panel. [ABSTRACT FROM AUTHOR]

This paper presents a systematic literature review about the development of criteria and models representing mould growth in wood-based materials. First, results from experimental research regarding factors governing mould growth are discussed; afterwards, they are used to analyse the comprehensiveness of current mould models. The review shows substantial discrepancies between criteria reported for mould growth. Moreover, mould models differ with respect to governing factors and their interrelations, applied methodology, experimental set-ups and nutrients, and how they express mould. Lastly, this paper proposes solutions that account for or reduce uncertainties related to the representation and design against mould occurrence. [ABSTRACT FROM AUTHOR]

Cement-based materials with addition of superabsorbent polymer have attracted widespread attention due to their excellent shrinkage resistance and durability. This paper investigated the effects of three internal curing materials with different swelling behavior on mortar related shrinkage, corresponding durability at 50% humidity. The composite microgel with high water retention and controllable water release kept the relative humidity inside the mortar at a high level, and the total shrinkage in the low humidity condition decreased by 126.22 µm/m compared with the reference sample. The correlation analysis showed that the composite microgel reduced the autogenous shrinkage of mortar at the early hydration stage, and significantly alleviated the drying shrinkage with the reduction of internal relative humidity. Composite microgel compacted the microstructure of mortar, and compressive strength is higher than that of microgel modified mortar. At the same time, the role of composite microgel in refining microstructure prevented the water penetration of mortar, and the freeze-thaw resistance of mortar can be better improved by entrained air void of composite microgels. • The influence of SAP with different water absorption behaviors and chemical structures on the shrinkage of mortar has been studied. • The correlation between IRH and shrinkage of mortar was analyzed. • The freeze-thaw resistance, impermeability property of cement mortar at 50% RH can be promoted by composite microgel. [ABSTRACT FROM AUTHOR]

This manuscript focuses on the use of foam glass aggregates (FGAs) as insulator to protect pavements against frost action. The ultimate objective of the paper was to develop design tools for the thermal design of pavements insulated with FGAs. A mathematical model was outlined to describe the complex thermal behavior of FGAs and calculate temperature levels within a domain representing a pavement insulated with FGAs. The formulation is based on the one-dimensional heat equation which was discretized with a forward finite-difference technique and subsequently coded in Fortran90. This code was executed to successfully replicate temperature measurements collected within an experimental pavement insulated with FGAs, enabling the validation of the model. The model was then re-executed to perform three different sensitivity analyses and investigate the effects of the pavement geometry, layers humidity, and FGAs' effective particle size on the maximal frost front penetration. Compared to a pavement without insulation, utilizing FGAs reduced the maximal frost front depth. The sensitivity analyses were summarized in design charts to guide the utilization of FGAs for the thermal design of pavements. The code utilized to generate these charts is freely available on GitHub. • Foam glass aggregates (FGAs) layers can mitigate frost action in flexible pavements. • A thermal model is outlined to obtain temperature levels in FGAs-insulated pavements. • Conduction, radiation, and convection are considered within the model. • The model is successfully validated against a full-scale FGAs-insulated pavement. • The model is made freely accessible and design guides are provided. [ABSTRACT FROM AUTHOR]

This paper presents results of an experimental investigation on the effect of moisture transport on chloride penetration in partially saturated concrete. The paper includes the development of an experimental setup, analysis of experimental data, and formulation of the governing equations to characterize the moisture-chloride interaction in non-saturated concrete. The experimental setup consisted of two sets of fully and partially saturated concrete specimens that were exposed to chloride solutions. Humidity sensors were embedded in the concrete specimens to measure the internal relative humidity and the variation of humidity profiles over time. The governing equation that describes the chloride transport in saturated concrete was modified to account for the chloride movement induced by the moisture transport. The comparison of the chloride profiles obtained from the partially and fully saturated concrete specimens confirmed the coupling effect between the moisture transport and chloride penetration in concrete. The measured chloride and humidity profiles were analyzed to determine the coupling parameter in the governing equation. The analysis of the experimental data indicated that the coupling term in the governing equation is concentration dependent which means that the governing equation is nonlinear. [ABSTRACT FROM AUTHOR]

The water status within concrete under low air pressure (AP) condition has been reported to affect the long-term properties of concrete in plateau regions, however, the underlying mechanism for the microstructural changes is not fully understood yet. In this paper, the confined water statuses within cement pastes curing at 98% RH and different APs (i.e. 101 kPa, 60 kPa, and 20 kPa) were first demonstrated and then correlated to the nanomechanical property changes of calcium-silicate-hydrates (C-S-H) phase by means of the 1H NMR relaxometry and nanoindentation techniques. The results show that low AP conditions increase the evaporable water content and drive the water movement from interlayer spaces to gel pores during wetting at 98% RH. According to the nanoindentation investigations, low AP conditions increase the volume fraction of high-density (HD) C-S-H and improve the nanomechanical and creep characteristics and bending strength of hardened cement pastes, which is attributed to the water redistribution within C-S-H phase. • Water statuses within cement pastes were identified by 1H NMR relaxometry. • Low air pressures drove water redistribution from interlayer space to gel pores. • Low air pressures changed nanomechanical characteristics of cement pastes. • Nanomechanical characteristics changed with water statuses of cement pastes. [ABSTRACT FROM AUTHOR]

• Rh6G fluorescent molecules can visualize the humidity evolution of mud-based materials. • As humidity evolves, the polymeric state transition of fluorescent molecules leads to changes in fluorescence intensity, which peaks at 65 %RH under the ACQ effect. • The temperature sensitivity is weakened by the methyl action of the molecules and the thermostatic properties of the insulation board. • The fluorescent molecules maintained good fluorescence intensity stability under multiple temperature and humidity cycles. In situ detection technology for cement-based materials typically produces unclear physical meanings, which limits research on durability issues such as heat-moisture transfer, dry-wet cycles and microcrack propagation. Taking the external thermal insulation system of building exterior walls as an example, this paper explores in-situ fluorescence sensing techniques for moisture evolution of cementitious materials using the quenching effect caused by the aggregation of fluorescent molecules. This study includes the monitoring of fluorescence intensity under humidity evolution and a stability study of fluorescence intensity under different temperatures and humidity cycles. Results showed that the gradual transition of the polymeric state of fluorescent molecules led to the first increase and then decrease of fluorescence intensity with increasing humidity (0 % RH-95 % RH). The fluorescence intensity peaked at 65 % RH, decreases at high humidity due to aggregated caused quenching effects, and maintained good stability after 8 humidity cycles. With regard to ambient temperature, the fluorescence intensity decreased with increasing temperature (5 °C – 40 °C), and the fluorescence intensity peaked at 5 °C. The temperature sensitivity of the fluorescence is weakened by the methyl effect of the rhodamine 6G fluorescent molecules and the thermostatic properties of the insulation boards. Fluorescence sensing technology for humidity evolution of cement-based materials has moisture sensitivity and fluorescence stability, and thus has a wide range of applications in the sensing of humidity evolution of civil engineering materials. [ABSTRACT FROM AUTHOR]

• Including SF into the AAFA mixture decreased workability, whilst STPP increased it. • Including 5–15% SF or/and 4% STPP in AAFA increased compressive strength. • Exposing specimens to outdoor natural weathering showed an adverse effect on their strength. • The adverse effect of weathering could be decreased with including up to 15% SF and 4% STPP. As known, exposure of any material to outdoor natural weathering, which has varied changes in temperature, relative humidity, percentage of sunny/cloudy, precipitation, CO 2 and polluted air may adversely affect its properties compared to its unexposed counterpart cured at the lab. This paper aims to evaluate the effect of one year of outdoor natural weathering exposure on the properties of neat alkali-activated fly ash (AAFA) mortars and those modified with silica fume (SF) and sodium tripolyphosphate (STPP). To increase the resistivity of AAFA mortars to weathering exposure, the FA was partially substituted with 5–20 wt% SF. To further improvement, a fixed ratio of 4% STPP was added to the neat FA mortar specimens and those containing SF. After initial curing, half of the specimens were cured inside the lab for one year (unexposed specimens), whilst the other half were exposed to outdoor natural weathering conditions for the same period. The variations in the compressive strength, mineral composition, hydration products and microstructure were compared. The results showed that exposing specimens to natural weathering has a negative effect on their compressive strength. This negative effect can be mitigated by introducing SF up to 15%. To further reduce this negative effect, 4% STPP can be added. [ABSTRACT FROM AUTHOR]

• The hygrometric properties of homogeneous and dual composite bio-sourced materials were investigated. • The moisture content, moisture transfer resistance, moisture flux and the adsorption, diffusivity decreases. • Water content, sorption capacity and volumetric water content were correlated using the Freundlich model. • The bio-sourced material moisture diffusivity distribution is investigated versus relative humidity. With the world's population increasing and energy demand on the rise, innovative materials are becoming one of the most important solutions for building designers. This paper focuses on the hygrometric properties of bio-sourced materials, specifically new cob mixes used for insulation and load-bearing wall elements, those materials consist of various mixes of French soils and fibers with different water contents. Experiments are conducted using the isothermal sorption and the one-sided moisture transmission tests in transient and steady states. The hygrometric properties of the homogeneous bio-sourced samples (a thermally insulating material, and a structurally mechanical material), and composite bio-sourced materials (both structural and insulating materials) were investigated. Five salt solutions were used to measure distribution of the relative humidity in each material. The moisture content and moisture transfer resistance of the insulating material is more important than the structural material. The composite material has the lowest moisture flux and the adsorption is influenced by the multilayers. Results show that as much as the material contains fibers, as much as its impermeability increases and its diffusivity decreases. Diminution of the bio-sourced material density increases its resistance to the moisture transfer. Using the Freundlich isotherm model, the volumetric water content, sorption capacity and water content were correlated for all the tested samples. The Moisture diffusivity for the studied bio-sourced materials drops strongly in the dry region where the relative humidity is lower than 30%. In the wet state, the moisture diffusivity decreases slightly. [ABSTRACT FROM AUTHOR]

Abstract: Natural weather changes due to diurnal and seasonal temperature and relative humidity cycles affect micro-environment of concrete; temperature and moisture content in the concrete fluctuate correspondingly with variations in the weather. At the same time, for concrete structures, the temperature and relative humidity in both the atmosphere and the concrete show obvious differences due to thermal conduction and pore structure densification of the concrete. Therefore, the temperature and moisture content in the concrete, which are defined as the micro-environmental indexes in the concrete in this paper, are main factors directly influencing concrete carbonation, chloride diffusion and the corrosion rate of steel bars. This paper mainly discusses the climate load based on natural weather and the effects of the climate load. The climate load includes the temperature, relative humidity, wind speed, sun shine and rain in a natural climate environment. The effects of the climate load are the responses of the micro-environment in the concrete under action of the climate load. Firstly, the experiments on responses of temperature and relative humidity in concrete were carried out in an artificial constant climate environment; at the same time, the behaviors about thermal conduction and moisture diffusion of the concrete were measured and modeled. Thereafter, a method for predicting the responses in concrete under a natural climate environment condition was built. In present studies, the temperature and the relative humidity responses in concrete under a natural climate environment condition show obvious hysteresis characteristics. The research findings illustrate that the predictions of the rate of the concrete carbonation, the chloride diffusion and the corrosion of bar in concrete should be depended on the micro-environment and the predictions based on the natural climate environment are not appropriate. [Copyright &y& Elsevier]

• BC shows varying influence on flowability, strength and drying shrinkage. • BC increases the humidity adsorption capacity of cement paste. • Humidity adsorption is attributed to the combined effects on pore volume and area. This paper investigates the incorporation of bamboo charcoal (BC) in cement to prepare cement-based humidity adsorption material. Cement pastes with BC were prepared and their flowability, compressive strength, drying shrinkage and humidity adsorption were measured. Pore information of hardened paste was determined by both N 2 adsorption (NAD) and mercury intrusion porosimetry (MIP) analyses. Results indicate that BC decreases flowability of cement paste but favorable flowability of blended paste with BC can be provided by adjusting superplasticizer dosage. BC decreases compressive strength of hardened cement paste before 7 d while its influence on later strength depends on its particle size and replacement ratio. Specifically, BC with average size of 8 μm increases compressive strength at later ages at 10% replacement ratio. But this improvement is diminishing with the increase of either BC size or replacement ratio and adverse effects on compressive strength are found for mixtures with BC of larger size, especially at higher replacement ratios. BC of 23 μm shows little influence on drying shrinkage of mixtures while that of 8 μm significantly increases this value as replacement ratio rises. The humidity adsorption results demonstrate that BC increases the humidity adsorption capacity of cement paste and this improvement is more prominent when BC ratio is higher or BC is finer. The calculated humidity adsorption results show a favorable agreement with experimental ones with the deviation probably attributed to experiment technique limits. It is inferred that humidity adsorption promotion is mainly due to the combined effects of BC on pore volume and specific surface area of hardened paste. [ABSTRACT FROM AUTHOR]

Highlights • Coupled heat and moisture process was simulated for bamboo exterior walls in Hot-Humid climate region. • Indicators involved annual dynamic exterior walls performance, indoor environment and HVAC demand. • Factor impact analysis was carried out to investigate the effect of material and construction parameters. • Climate responsive design in terms of partition boards, thermal insulation infill and air layer arrangement were generated. Abstract Bamboo forest distributes largely in Hot-Humid climate regions, where the local application of bamboo in building industry possesses multiple potentials such as high-value utilization of bamboo resources and improvement of building sustainability. To support the application of bamboo in building envelope, the paper carried out study on the bamboo construction design optimization in Hot-Humid climate region. For bamboo as a hygroscopic material, the coupled heat and moisture process model was adopted for the hygrothermal performance study of bamboo construction. With 4 groups of meteorological data from 2 representative cities in the Hot-Humid climate region of North America as external conditions, exterior walls were constructed in WUFI Plus and the coupled heat and moisture process simulation was performed. Based on the statistical analyses of a large sample of simulation results, scientific laws for promoting the parameter optimization were generated, for which the simulation results were grouped to the indicators on three level, including annual exterior walls hygrothermal performance, indoor hygrothermal environment and HVAC demand. Factor impact analyses were carried out to investigate the effect of the partition boards, thermal insulation infill and air layer arrangement. Hygrothermal performance design optimization suggestions were generated, in terms of material and construction parameters optimization, which would support the climate adaptive design of bamboo building envelope in Hot-Humid climate region. [ABSTRACT FROM AUTHOR]

Highlights • Moisture buffering improves indoor air quality and hygrothermal comfort. • The lack of a globally agreed method makes comparisons difficult. • Dynamic sorption properties should be quantified by in situ testing. • Modelled moisture buffering does not fully represent the performance. • A novel method of full scale moisture buffering is required. Abstract It is important to control indoor humidity level in buildings as it influences occupant's health and comfort. Hygroscopic building materials present great potential to passively regulate air humidity due to their ability to adsorb and desorb moisture. In recent years researchers have focused on this capacity, referred to as Moisture Buffering, as it has the potential to improve indoor thermal comfort and reduce HVAC usage and their consequent energy consumption. However, building designers generally do not consider this property an important factor, due to its unclear influence and difficulty in the quantification of its effects in real buildings. Therefore, it is complicated to develop an appropriate laboratory scale testing. The aim of this paper is to investigate the challenges related to moisture buffering measurement and to examine the approaches adopted by researchers. The significance of this study is to identify discrepancies between existing methods in the evaluation of the dynamic adsorption properties and presents areas for further development in testing. [ABSTRACT FROM AUTHOR]

Highlights • Mechanical properties of bamboos in aggressive wet condition. • Statistical analysis of measures of central tendency. • Models for predicting mechanical properties in dependence on the number of days of exposure to wet conditions. Abstract This paper presents an investigation into the influence of humidity on the mass changes and the mechanical (buckling, toughness) properties of Pseudosasa amabilis bamboo. The tests were carried out in different conditions, the dry laboratory conditions and the wet chamber conditions. A detailed statistical analysis of measures of central tendency was carried out and models for predicting the behaviour of properties in dependence on the number of days spent in wet conditions were obtained. The COV results for mass and mechanical properties are below 30%. The values of R2 obtained from the model are: mass = 0.9652, buckling = 0.1630, and toughness = 0.0000. [ABSTRACT FROM AUTHOR]

Highlights • A new method that performed for the materials with diverse hygroscopic behaviors. • A comprehensive dataset of material properties for five building materials. • Determination of the mass diffusion coefficient is possible at short times. • Consistency with geometric parameters obtained via 3D analysis is studied. Abstract In this study, we use a novel method to determine the mass diffusion coefficients of hygroscopic materials. The experiment involves subjecting one face of the sample to relative humidity (RH) variations over time and measuring the RH at the back face. The imposed RH and temperature are measured during the experiment, and they are used as boundary conditions in a comprehensive computational code to address heat and mass transfer in porous media. This new method is utilized to characterize the following building materials: autoclave aerated concrete, plaster, poplar wood, pine wood, medium-density fiberboard and low-density fiberboard. This paper provides the details regarding the determination of the sorption isotherms of the selected materials that are required for the determination of mass diffusivity. The obtained electrical tortuosity values are compared with geometrical tortuosity values determined via microtomography and three-dimensional image processing. The agreement between the two tortuosity values is applicable only for porous media with narrow pore size distribution. [ABSTRACT FROM AUTHOR]

Highlights • Hydration of OPC pastes blended with recycled OPC paste was studied. • Whatever T°, decreasing RH accelerates drying and decreases hydration level. • Whatever RH, decreasing T° decreases the hydration level. • The lower the clinker content, the higher the critical RH hampering hydration. • The critical curing RH depends on properties intrinsic to the material. Abstract The paper presents an experimental study performed on OPC pastes blended with recycled OPC paste fine powder. Pastes with different OPC contents: 25, 50, 70 and 100% were dried, immediately after demolding at one day, in controlled environmental conditions with different relative humidities: 57, 76, 82, 88, 95 and 98% and temperatures: 5, 10, 20 and 30 °C. During the drying of the pastes, their hydration was monitored for 90 days by thermogravimetric analysis (TGA). The results showed that the critical curing relative humidity hampering hydration depends on properties intrinsic to the material, as hydration level, total porosity and microstructure fineness. [ABSTRACT FROM AUTHOR]

Abstract: El Prado Museum in Madrid has been recently submitted to a refurbishment of its roof which from been made with the traditional tiles has been changed to the use of modern waterproofing layers covered with a metallic lead finishing. Due to an unexpected damp patch that produced leaking in the hall in which Las Meninas by Velázquez was exhibited, the authors were commissioned by the Ministry of Education and Culture to study the suitability of the roof and its waterproofing properties. The study led to suggestions of modifications in the design of the roof layers, which are out of the scope of present paper. In present paper are given the behaviour of the sensors embedded in two specific areas of the roof. The sensors installed were of: temperature, relative humidity, measurement of local strain and detection of liquid water. The liquid water sensors reveal that some water is withheld in the layer just below the thermal insulation material, although it is standing. The results of over four years of readings show that the temperature attenuates over distance away from the outermost layer, where the readings are very high in summer, due to it consists of lead. During the colder seasons, in turn, the temperature in the inner layers of the roof is higher than in the outer layers. The strain recorded follows the logical evolution of temperature with no abnormal behaviour being detected. Some of relative humidity sensors had measuring problems due to water condensing on them. In summary however, if the behaviour in this area is extrapolated to the rest of the roof, it can be considered to perform correctly as intended. No more leaking events have been detected from the design modifications were incorporated to the existing roof. [ABSTRACT FROM AUTHOR]

The paper characterizes concurrent effects of gamma-irradiation and presence of water in Portland cement pastes. An extensive nanomechanical quantification (Young's modulus, hardness, and creep compliance) at two scales is performed after exposure to two gamma-ray doses and a wide range of relative humidities (RH 0%–100%). Competing microstructural mechanisms such as water radiolysis, hydration, carbonation and drying were identified and their effects de-coupled with the aid of nanoindentation and other supporting techniques. Maximum radiation resistance was found for samples in medium humidities (33%–57%). Samples irradiated below 11% RH exhibited compaction of C-S-H phases at the level of 100 nm, ∼ 25% increase of Young's modulus and decrease of creep compliance due to water radiolysis and drying. The compaction resulted in microcracking at higher paste scale and caused ∼ 17% decrease of elastic modulus. Samples irradiated in water showed large (∼ 26%) decrease of Young's modulus and increased creep compliance accompanied by 9%–10% Portlandite loss. • Nanomechanical properties of irradiated cement pastes studied at various humidities. • Medium humidity helps cement pastes best withstand gamma radiation. • Radiolysis and drying leads to cement paste microcracking but also C-S-H compaction. • Gamma-irradiation counteracts with the hydration process of cement paste. • Decreased paste stiffness but increased creep is caused by radiation in the water. [ABSTRACT FROM AUTHOR]

• A multi-field model of early-age cement-based materials was optimized. • The development of various deformations in early-age cement-based materials were discussed. • The development of CTE and CSI and their effects on deformation were discussed. Early-age cement-based materials undergo significant physical and chemical changes and have a complex mutual relationship among their temperature, humidity and mechanical behavior. As the second part of this study, this paper builds a multi-field coupling equation model taking into account the staged characteristics of the deformation for early-age cement-based materials based on the Hybrid Mixture Theory, and the accuracy of calculation results are verified with the test results obtained in the first part of this study. Moreover, the multi-field coupling model has been adopted to simulate the evolution of the different types of deformation for early-age cement-based materials. The results show that the multi-field coupling model established in this paper and the staged deformation calculation model established for early-age cement-based materials in the first part of this study can be used to better describe the development of their early-age temperature, humidity and deformation. Moreover, thermal strain is the earliest deformation that may cause cracking of cement-based materials, and chemical shrinkage has a certain compensation effect on thermal strain. In addition, the coefficient of thermal expansion (CTE) and the coefficient of stiffness influence (CSI) as well as their effects on thermal and chemical deformations have been analyzed. The results of this study can provide an important reference for analyzing the performance evolution of early-age cement-based materials. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of permeability and its influence on the durability of recycled concrete exposed to an aggressive environment. Recycled concretes with 20%, 50% and 100% in weight of recycled aggregate and 24 effective w/c ratios have been exposed directly to a marine environment. Control specimens cured in a humidity chamber have been also tested in order to compare the influence of the curing environment. The durability of recycled aggregate concretes exposed to aggressive conditions decreases in terms of permeability, as the results show. However, the influence of the environment on the recycled concrete also depends on the quality of the cement paste. The differences between the control and the exposed concrete are lower for low water/cement (w/c) ratios. The lower capillarity obtained in the new cement paste of the recycled concretes with low w/c ratios isolates the porosity of the recycled aggregate, increasing the durability but with a rise in the cement content. [ABSTRACT FROM AUTHOR]

The properties of cement asphalt emulsion mixture (CAEM) are influenced by curing conditions. In this paper, the strength properties of CAEM are investigated at different curing humidities and periods. Then, the moisture susceptibility test and rutting resistance test are performed to evaluate the effect of typical curing procedures on the emulsion-based mixtures. In order to understand the diversity of different curing procedures, the chemical composition and microstructure of cement asphalt mastic (CAM) are analyzed by Fourier transform infrared (FTIR) spectrometer, X-ray diffraction (XRD) analyzer, and environmental scanning electron microscope (ESEM). The results indicate that the effect of curing humidity on strength development depends on the cement content and curing period. It is recommended to cure all mixtures with lower humidity. The higher temperature accelerated curing for several days can stimulate a normal temperature curing for several months. The equivalent relationships between accelerated curing and normal temperature curing are developed based on the strength and performance analysis. By comparing FTIR results at different curing regimes, it can be found that no obvious asphalt binder aging appears in CAM with the typical accelerated curing procedure. XRD analysis founds that the accelerated curing improves the content of some hydration products content, while leads to the more cement particles encapsulated by asphalt film. Considering results of FTIR and XRD, it is testified that the microstructure characteristics of hydration products in CAM with two curing regimes are obviously different, which can explain the performance variations of CAEM with these curing procedures. [ABSTRACT FROM AUTHOR]

This paper reports a study done on the impact of a shrinkage-reducing agent (SRA) and polypropylene fiber (PPF), individually and jointly, on ceramsite concrete (CC). The results indicate the following: (1) CC mixed with SRA alone, results in early micro-expansion increases as SRA content increases while self-shrinkage and drying shrinkage decreases. (2) CC mixed only PPF, results in early micro-expansion, self-shrinkage and drying shrinkage decreases as PPF content increases; amplitude decrease is large for early micro-expansion, but insignificant for self-shrinkage and drying-shrinkage, and shrinkage reduction is smaller compared to SRA. (3) If an SRA-PPF mix is added to CC, both contributed significantly to self-shrinkage, drying shrinkage, and reduction. [ABSTRACT FROM AUTHOR]

Hemp concrete is a sustainable material with low embodied energy. However, its development as a building material requires a better evaluation of its moisture-thermal buffering abilities behavior, which are known to strongly depend on the amount of water contained in wall pores and its evolution. In this context, the aim of this paper is to study the experimental determination of sorption-desorption curves of hemp concretes following two methods and at two temperatures (23 °C and 40 °C). The former considers the total sorption-desorption loop, from the dried state to a relative humidity of 85%, while the second one is based on partial relative humidity cycles between 23% and 85%. At first, the difference between the curves obtained through these two methods were analysed. They were then implemented in a simple hygrothermal model to simulate dynamic hygroscopic and hygrothermal loadings. The comparison between the theoretical calculations and the experimental results eventually allows to scan which of these relations is more representative of the real dynamic behaviour of the tested hemp concretes. [ABSTRACT FROM AUTHOR]

A new kind of advanced composite reinforcement, basalt fiber reinforced polymer (BFRP) bars, has not yet been widely adopted by design codes/guidelines worldwide, likely due to the lack of reliable long-term performance data. This paper proposed a refined prediction method for the long-term performance of BFRP bars that considers the effects of service year, concrete-wrap, environmental humidity and seasonal temperature fluctuations. According to the available accelerated aging tests data in the literature, the environmental reduction factors (ERFs) for a BFRP bar used as a concrete internal reinforcement in a field environment are predicted. The results showed that the ERF for BFRP bars can be recommended to be 0.84 or 0.72 for an RH < 90% and a moisture saturated environment (RH = 100%), respectively. [ABSTRACT FROM AUTHOR]

A new kind of advanced composite reinforcement, basalt fiber reinforced polymer (BFRP) bars, has not yet been widely adopted by design codes/guidelines worldwide, likely due to the lack of reliable long-term performance data. This paper proposed a refined prediction method for the long-term performance of BFRP bars that considers the effects of service year, concrete-wrap, environmental humidity and seasonal temperature fluctuations. According to the available accelerated aging tests data in the literature, the environmental reduction factors (ERFs) for a BFRP bar used as a concrete internal reinforcement in a field environment are predicted. The results showed that the ERF for BFRP bars can be recommended to be 0.84 or 0.72 for an RH < 90% and a moisture saturated environment (RH = 100%), respectively. [ABSTRACT FROM AUTHOR]

This paper presents thermogradient and hygrogradient coefficients as indicators for evaluation of coupled effects of heat and moisture transport in concrete. A numerical model for coupled heat and moisture transport was established and solved as well as a method to determine thermogradient and hygrogradient coefficients. Effects of temperature and humidity gradients were investigated through experiments, which covered also the effects of damage on moisture transport, temperature and humidity distributions along with coupled transport. The experimental results showed that temperature and humidity gradients accelerated moisture transport along with increased damage. In addition, the effect of temperature gradient on temperature distributions was significant, while the effect of humidity gradient was small. However, both temperature and humidity gradients had significant effects on relative humidity distributions. Hence, coupled heat and moisture transport in concrete had a significant effect on moisture transport, and the effect of damage on moisture transport must be considered when determining humidity field in damaged concrete. [ABSTRACT FROM AUTHOR]

This paper proposes a V-shaped cone model to modify the Kelvin equation and thus obtaining an accurate connection between the effective aperture of hygroscopic material and its governing factors. A dimensional equation of equilibrium moisture content is presented based on the modified Kelvin equation. A series of experiments assessing the pore feature, mechanical property, performance of adsorption/desorption and MBV (moisture buffering value) of homemade hygroscopic material are conducted. The effective aperture of hygroscopic material is accurately modified by the angle θ of the V-shaped cone model. A dimensional equation of equilibrium moisture is established by the specific surface area, temperature and humidity, and an effective coefficient of equilibrium moisture is put forward. Deviation between the calculated results of dimensional equation and the tested results of MBV practical are modified by compressive strength. This research mainly contributes to establishing a significant basis for selection and application of hygroscopic material and providing boundary conditions for further Computational Fluid Dynamics (CFD) study. [ABSTRACT FROM AUTHOR]

This paper characterizes the oxygen permeability of structural lightweight aggregate concrete (SLWAC). The influence of different parameters is analysed, namely water/binder (w/b) ratio, type of binder and aggregate, relative humidity, water content and concrete age. The correlation between this and other properties is investigated. The oxygen permeability varied over a broad range. Nevertheless, the oxygen permeability of SLWAC with denser aggregates could be as low as that of normal weight concrete. The influence of the type of aggregate tended to increase with w/b ratio, aggregate porosity and percentage of additions. Small differences between mixtures were masked by the high variability of the test. [ABSTRACT FROM AUTHOR]

It has been demonstrated that water vapor consistently transports in asphalt pavements. The relative humidity differential, which exists between the subgrade below and the atmosphere above the pavement, is a major contributor to the water vapor diffusion. However, the effect of the relative humidity differential has not been quantified on the water vapor diffusion in asphalt mixtures. This paper designed a laboratory experiment to investigate the water vapor diffusion in asphalt mixtures under a number of relative humidity differentials. The designed experiment consisted of five individual water vapor diffusion tests, each of which was performed at a specific relative humidity differential in the pre-vacuumed measuring cell of the test equipment. Two diffusion models were developed based on the Fick’s second law of diffusion. It was found that the two-dimensional model provided an accurate characterization of the water vapor diffusion in both radial and axial directions of the cylindrical test specimens. A linear model was established between the relative humidity differential and the total diffused mass based on the real gas law. An inverse proportionality was identified between the relative humidity differential and the diffusivity in both radial and axial directions. The determined diffusivity values were further converted to the corresponding diffusivity values under 1 atmosphere, which were in agreement with the diffusivity data reported in the literature. A linear model was derived for the relationship between the relative humidity differential and the diffusivity under 1 atmosphere, which indicated faster water vapor diffusion in asphalt pavements when subjected to a larger relative humidity differential between the subgrade and the atmosphere. The diffusivity in the radial direction was always larger than that in the axial direction despite the variation of the relative humidity differential. This fact implied the anisotropic distributions of air voids and aggregates in the asphalt mixture specimens, which assisted water vapor in diffusing more easily in the radial direction than in the axial direction. [ABSTRACT FROM AUTHOR]

In this paper, shrinkage and internal relative humidity of internal cured with calcinated zeolite particles of high strength engineerined cementitious composite (HSECC) are experimentally investigated, in which the natural sand-like zeolite particles with average particle size of 0.18 mm were used as internal curing agent. Impacting factors, such as calcination, pre-wetting process and amount of internal curing agent, on shrinkage of HSECC were considered in the test program; meanwhile their effects on compressive strength of the composites were included as well. The test results show: 1) Two-stage progressing mode of shrinkage and internal relative humidity of HSECC are observed; 2) Applying the pre-wetted calcined zeolite particles in HSECC, more than 60% of autogenous and/or drying shrinkage at 28 days is reduced while the strength of the composite remains as higher as the reference; 3) Calcination on zeolite particles is necessary for internal curing of high strength cementitious composites. [ABSTRACT FROM AUTHOR]

Numerical research discovers a phenomenon that chloride content first climbs to the maximum then descends with depth increasing in surface layer of concrete under cyclic drying-wetting environments, which is temporally called “maximum phenomenon” in this paper for convenience. This phenomenon consists of two characteristic parameters: the maximum chloride content C max and the depth Δx at which C max appears. This research mainly focuses on the impact of pore structure and moisture distribution on maximum phenomenon, specifically the two parameters of it. The influence of pore structure on maximum phenomenon is illustrated from three aspects: total porosity, the critical pore size and water absorption porosity ( P c ). The increase of total porosity leads to increase of C max . And larger critical pore size renders C max occur at a deeper position. Moreover, C max and Δx both increase with water absorption porosity ( P c ). The impact of moisture distribution on maximum phenomenon is investigated from non-saturation degree ( S non ) and relative humidity ( RH ). The higher the S non is, the greater the C max and Δx are. However, both C max and Δx decline with RH rising up, and the influence of RH on them is more significant approximating the exposed surface. [ABSTRACT FROM AUTHOR]

Water-to-binder ratio (w/b) directly affects the pore structure and performance of concrete, and drying conditions enhance the influence of water-to-binder ratio. Superabsorbent polymer (SAP) is effective to adjust the water in the concrete. In this paper, the effect of SAP and extra water on drying shrinkage, pore structure and the permeability of high performance cement-based material with w/b from 0.18 to 0.24 were studied to reveal the adjusting role of SAP for the influence of water-binder ratio at a 60% of relative humidity (RH). The permeability was determined through the vacuum saturation method, the diffusion of steady-state Cl − ion and carbonation testing. The structure of harden mortar and SAP voids were evaluated by mercury intrusion porosimetry (MIP) and backscatter electronic microscopy (BSEM). At the same effective w/b, SAP reduces the strength, and raises the drying shrinkage and permeability. However, the effect of SAP on the above properties is exactly opposite when the same total w/b is used. The greater the SAP particle size is, the more obvious those favorable effects are. SAP can weaken the effect of total w/b. The addition of SAP also results in the formation of the hydration diffusion layer in SAP void and the refinement of pore structures. [ABSTRACT FROM AUTHOR]

• The multiphysics model is proposed for non-shrinkage concrete early age behavior. • The coupling simulation is built with chemical, humidity and mechanical process. • The differences between material behavior and structural performance are tested. • The mulitphysics behaviors of clustered shearing connector pocket is simulated. • Numerical optimizations are conducted about material, curing and structural design. Early age behavior of shearing connectors is of great significance for the performance of composite structures. To improve the structural mechanical state and reduce the risk of shrinkage cracks, the non-shrinkage concrete and the clustered shearing connector pocket are used in engineering applications, but the existing empirical model can hardly describe the physicochemical process in the actual structure. Focusing onresponsestiphysics mechanism of concrete shrinkage and the contribution of expansion additive, a comprehensive model is proposed for non-shrinkage concrete in this paper, and the processes of the hydration reaction, the humidity transport, and the mechanical response are included. The free shrinkage test regresses the parameter of material shrinkage, and the corresponding structural test verifies the multiphysics model of the clustered shearing connector pocket. With the volume increasing along the hydration reaction of expansion additives, the −120 με shrinkage of normal concrete is compensated to the 160 με expansion. In the clustered shearing connector pocket, the slight expansion of non-shrinkage concrete can keep the structural compression state and eliminate the risk of local cracks. According to structural test, the early age behavior is constrained by the prefabricated deck, reinforcement and clustered studs greatly, and the expansion strains at the pocket upper and bottom are reduced by about 16% and 72%, respectively. In the multiphysics simulation, not only the time-dependent shrinkage strains at different positions are predicted accurately, but also the detailed distributions of hydration ratio, relative humidity and mechanical stress are also presented. Eventually, the numerical comparison discusses the improvement of non-shrinkage concrete, the influence of relative humidity in the curing environment and the design modification of stud layout, and the peak stress in stud bodies can be reduced by about 18.42%, which is significant and practical for improving related construction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Compressive strength and modulus of elasticity of earthen materials are linearly correlated with the relative humidity. • Strength and deformation characteristics of earth masonry do not depend on the temperature at constant relative humidity. • Influence of relative humidity on the strength and deformation characteristics can be approximated by a suggested equation. • The correlation is generally applicable to unstabilised earth masonry without high contents of organic aggregates. • Influence of the material moisture content can be considered in structural design without extensive testing. The mechanical properties of unstabilised earthen building materials are distinctively influenced by changes in material moisture content. However, this moisture-dependency often remains unconsidered in the calculation of the load-bearing capacity of earth constructions. This paper aims to derive a convenient way to sufficiently consider the impact of different material moisture contents on the mechanical properties of unstabilised earth masonry. Therefore, the influence of relative humidity and temperature on the strength and deformation characteristics of unstabilised earth blocks, earth mortar and earth masonry is evaluated by conducting compression tests under various climate conditions. The results show that the compressive strength and the modulus of elasticity are linearly correlated with the relative humidity, whereas changes in temperature at constant relative humidity have no significant influence. To account the distinct moisture-dependency, a general applicable modification factor for unstabilised earthen materials is provided, which enables the adjustment of the compressive strength and the modulus of elasticity in dependency of arbitrary hygroscopic material moisture contents. [ABSTRACT FROM AUTHOR]

• Thermal and hygric characteristics of novel insulation prototypes. • Development and characterisation of prototype insulation using maize pith, recycled bedding, and wheat straw insulating. • Large-scale thermal conductivity and hygric investigations were conducted on bio- and waste-based insulating materials. • Insulation protypes with a timber framed wall was studied under steady state and variable environmental conditions. A growing awareness of the environmental impact of construction materials is leading to development of more sustainable building products, with particular attention focussed on bio-based resources and circularity. In recent years the market share of bio-based building products has grown significantly, supported by research on materials such as wood fibre, hemp, and straw bale. At the same time there has been growing awareness of the potential for greater circularity in construction, prolonging the life of existing products and materials, thus minimising embodied carbon emissions of future projects, as well as reducing reliance on primary resources and impact on landfill. This paper presents results of an investigation into the thermal and hygric characteristics of three novel insulation prototypes developed from bio-based or waste-stream materials. The experimental development and characterisation of insulation using maize pith, recycled bedding (polyester duvet) materials, and wheat straw insulating prototypes are presented. Hygric and thermal performance are compared to a mineral wool insulation product. As part of this work a series of large-scale thermal conductivity and hygric investigations were also conducted in which the performance of each insulation product with a timber framed wall was studied under steady state and variable environmental conditions. This work was part of a larger international research project aimed at developing insulating materials from bio-based and waste streams and will support market development of novel materials and products into mainstream construction. [ABSTRACT FROM AUTHOR]

In order to comprehensively understand the drying behavior of cementitious materials, this paper presents a microstructure-based model to simulate the water evaporation process in capillary pores, the drying-induced deformation of cement paste with free boundary condition and the microcracking of cement paste under constraint. This model is applicable to high relative humidity ranges where the capillary pressure effect quantified by the Kelvin equation is the primary loading stimulus. Mainly two parts of modeling work are carried out. (1) From a microstructure model of cement paste HYMOSTRUC3D, the water evaporation in capillary pores is captured by a multi-step digitalization algorithm. (2) The drying-induced shrinkage deformation and internal microcracking of hardened cement paste with different boundary constraints are simulated by a 3D lattice fracture model. In order to reduce the computational cost, a two-scale modeling regime is employed where the microstructure of cement paste and the nanostructure of C-S-H are incorporated. Experimental test about free shrinkage of cement paste is utilized to validate the model. At last, the model is compared with poro-elastic-mechanical models, and is applied to study the influences of water-to-cement ratio and hydration time on the free shrinkage as well as the influence of constraints on the internal microcracking. [ABSTRACT FROM AUTHOR]

• MB tests do not give quantitative information on materials' behaviour in buildings. • Simulations help understanding moisture buffering impact of materials in buildings. • Plasters reduce humidity peaks due to sorption capacity and vapour permeability. • Plasters' moisture buffeting capacity is smaller in simulations than in laboratory testing. • Ventilation and moisture transport through the enclosure influence materials' MBV. The regulation of indoor relative humidity is a key factor for the provision of occupant health and comfort. Passive humidity regulation is possible if porous materials, for example clay and gypsum plasters, are exposed to the indoor environment. Materials that are highly hygroscopic can help regulate relative humidity levels through their capacity to adsorb and release water vapour from and to the indoor air via a dynamic process referred to as moisture buffering. Laboratory test methods have been developed to measure this moisture buffering capacity, which are well-suited for comparative testing of relatively small material samples under controlled conditions. However, quantification of the impact of hygroscopic materials in real buildings requires additional evaluation, like field testing and the support of simulation models, which can successively be used for the development of new protocols capable of giving information about materials' moisture buffering performances indoors. This paper investigates moisture buffering capacity of three hygroscopic plasters (clay, gypsum and lime), and compares measurements obtained in the laboratory to those from numerical simulations of a single-zone room space. The dynamic sorption capacity of the plasters was investigated using the NORDTEST protocol and results compared to those from hygrothermal simulation. Differences are identified between the two methods in the quantification of the moisture buffering potential, which lead to further investigation on the effect of ventilation and moisture transport through the entire wall assembly. The significance of this paper is to show building moisture regulation involves also different factors, such as ventilation and walls moisture transport, which will impact the moisture buffering potentials indoors. Consequently, it is necessary to better understand moisture buffering in real buildings, to quantify the influence of hygroscopic materials indoors, and introduce alternative laboratory testing, to give quantitative information about their impact in buildings. [ABSTRACT FROM AUTHOR]

• Effect of SAP and NS on the mass loss history of hardened cement pastes. • Low-cost apparatus to measure mass loss history of thin specimens of cement pastes. • Evolution of the diffusion coefficient of hardened cement pastes with SAP and NS. • Relation of diffusion coefficients of pastes and concrete content SAP and NS. • Drying depth from the humidity profile modeling in paste specimens with SAP and NS. This paper aims to characterize and model the internal relative humidity profiles and drying depth in hardened cement pastes containing superabsorbent polymers (SAP) and nano-silica (NS) particles. Five different cement pastes were considered with the incorporation of SAP, NS, and simultaneous SAP and NS to reference mixtures with different water/cement ratios. Characterization of mass loss history, the evolution of the diffusion coefficient, and modeling of relative humidity profiles were performed for the five cement pastes in three different ages and three drying times. This paper also proposes a low-cost apparatus to monitor the mass loss history of thin specimens of cement pastes. The characterization was determined by the drying process with a gradual variation of the RH environment from 100% to 43%. The diffusion coefficient and the profile of the internal relative humidity through the drying depth in specimens of different ages and drying periods were estimated by the mass loss evolution. The results show that the pastes containing SAP presents a higher mass loss, higher diffusivity and deeper drying depths for all ages and drying periods investigated. Although the incorporation of NS to the reference paste improved their performance, this improvement is observed only in 28-day old pastes with SAP. [ABSTRACT FROM AUTHOR]

• CatBoost regression model for prediction of surface chloride level. • The regression model has MAE and RMSE scores of 0.11 and 0.16 respectively. • Increase in chloride ingress with the increase in temperature and humidity. • Exposure zone has a significant effect on chloride ingress. • Temperature and humidity of RCP 2.6 and RCP 8.5 considered for analysis. This paper presents the effect of climate change on the long-term reliability of concrete structures due to chloride ingress. The impact has been demonstrated for three regions across the globe for the best and worst-case climate change scenarios. The methodology adopted here can be divided into three main steps. The first one is the development of a machine learning regression model using CatBoost for estimation of surface chloride levels, which is a function of temperature, concrete material properties, exposure conditions, and chloride levels in the seawater. The CatBoost model fitted over the experimental data has a mean absolute error (MAE) and root mean square error (RMSE) value of 0.11 and 0.16, respectively, and a high R2 value of 0.82. The second step is solving the coupled non-linear partial differential equation for temperature, humidity, and chloride ingress in concrete with time. A parametric study considering the effect of external parameters (temperature, humidity, exposure condition, and chloride levels in water) reveals the complexity and the dependencies of the chloride ingress process on external parameters. The final step involves the reliability analysis to estimate the time for chlorides to reach threshold levels at the rebar level using the numerical model. The input for the numerical model is temperature and humidity condition for different representative concentration pathways (RCP) scenarios, the material properties of concrete, and the exposure conditions. The reliability analysis shows that, for the concrete structure located in Dubai, UAE, and Cascais, Portugal, the mean time to corrosion initiation decreases due to climate change and it increases for the structure located in Tasmania, Australia. Further, the structures that are built in the future may have lower service life compared to the structures that were built in the past. Based on the study it concluded that it is necessary to consider the impact of climate change on service life to design resilient structures. [ABSTRACT FROM AUTHOR]

The development and application of bio-based insulation materials can contribute to the minimization of the environmental impacts of buildings through reduction of embodied and in-use energy demand, in addition to many other major impacts such as resource depletion and waste generation. The hygrothermal performance of natural building materials has direct and indirect impacts on moderating indoor environmental conditions and can contribute to energy savings provided that such aspects are taken into account during the design and construction phases. This requires in-depth knowledge of the thermal and hygroscopic properties of the materials and their dependence on the moisture content. In this paper, the hygrothermal properties of six insulation materials is determined; four are commercially available materials while the other two are experimental materials based on crop by-products and natural binders. The influence of relative humidity on such properties is analysed. Moreover, the experimental Moisture Buffer Values are obtained for the six insulations, according to the protocol of the standard ISO 24353. Finally, a mass and heat coupled model is numerically solved to simulate this protocol for two of the materials, obtaining a good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Earthen buildings can provide an answer to face difficulties in modern constructions in both terms of sociology, economics as well as ecology. However, the difficulty to understand and to predict their long term behavior represents an obstacle to their spreading. In some cases for example, unsuitable repairs on old constructions can lead to catastrophic situations. More specifically, during their lifetime, earthen walls have to face important variations of indoor and outdoor relative humidity, which induces variations and gradients in their water content. In this context, this paper aims at addressing an important aspect, not yet fully understood: the impact of these variations on the deformability and the strength of unstabilized earth. To that purpose, unconfined compression tests, with and without unload–reload cycles, were performed on different compacted earth samples conditioned at different relative humidities. Tested samples were prepared from materials coming from different existing constructions and sieved at 10 mm. During the tests, the axial and radial strains were measured using non-contact sensors and an image correlation system. This study shows that earthen materials have a complex mechanical behavior, involving the phenomena of plastic straining and mechanical damage. Moreover, both of these phenomena show a strong dependence on the relative humidity at which the samples were stored, as well as on the activity of the clayey portion of the earth. [ABSTRACT FROM AUTHOR]

High-performance concrete is used extensively in practice. However, the water-to-cement ratio of this concrete is low and causes self-desiccation. Due to moisture diffusion and this self-desiccation, internal relative humidity (IRH) decreases in concrete structures that are exposed to ambient air and induces autogenous shrinkage. Internal curing with super absorbent polymer (SAP) is used to mitigate this shrinkage in high-performance concrete; nonetheless, IRH variation influences changes in the autogenous shrinkage of concrete with SAPs. Although tests have been performed to mitigate the autogenous shrinkage of concrete that was internally cured through SAPs, experimental study on IRH variation in such concrete remains lacking. Thus, such a study was conducted to determine the effect of internal curing with SAPs on the IRH of early-age concrete under sealed and unsealed conditions, as detailed in this paper. Test results showed that: (1) the IRH of concrete that was internally cured with SAPs increased with an increase in the content of internal curing water 28 days after casting under sealed and unsealed conditions. (2) The degree of decrease in the IRH of internally cured concrete was lower under sealed conditions than under unsealed conditions 28 days after casting. (3) The critical time of the IRH of internally cured concrete increased with increases in the content of internal curing water under both sealed and unsealed conditions. (4) The decrease rate of the IRH in early-age concrete that was internally cured with SAPs dropped with an increase in the content of internal curing water under sealed and unsealed conditions. (5) A formula was proposed to calculate the IRH of early-age concrete that was internally cured with SAPs in consideration of the content of internal curing water under unsealed conditions. This formula indicates the good accuracy of the experimental results. [ABSTRACT FROM AUTHOR]

• A novel environmental effects in terms of heating, freezing, and humidity. • The bond behaviors under temperature elevation and repeated environmental effects. • Analysis and determination of interfacial shear traction stress and separation. • Numerical simulation under temperature elevation and repeated environmental effects. This paper investigated the influences of the temperature elevation and the repeated environmental effects on the bond behavior of the notched concrete beams with CFRP externally bonded through four-point bending tests. The corresponding numerical model was established and the FE results were compared with the test results. Two failure modes were observed in the test, both of which occurred to be sudden and brittle. The failure mode of the specimens changed from concrete failure to CFRP debonding after the temperature exceeded 150 °C or the cycle number reached 50 times. The ultimate loads of the specimens decreased linearly with the increase of both the temperature and the cyclic number, and the slopes of load-displacement curves in the first phase of the specimens were also reduced by both heating and cycling. Before CFRP debonding, the average maximum interfacial shear stresses at 0–30 mm from the mid-span decreased linearly with the increase of both the temperature and the cyclic number. The average shear traction stresses and the average interface stiffnesses were decreased with the increase of both the temperature and the cyclic number. The results obtained from the FE were similar to that from the test, which confirms the suitability of the FE model in the test conditions. [ABSTRACT FROM AUTHOR]

Use of pre-soaked lightweight aggregate (PSLWA) as an internal reservoir to provide water as the concrete dries is an effective method to reduce shrinkage of concrete. In this paper, a moisture distribution model of concrete internal cured with PSLWA is developed based on the experimental measurement on internal relative humidity of concrete with and without internal curing under sealing status. The function of internal curing with PSLWA is considered in the model through a parameter called critically released water, W c , that was experimentally determined from experiments. Meanwhile, self-desiccation and moisture capacity are taken into account in development of the diffusion equation. To verify the model, a series tests to measure the internal relative humidity of three kinds of internal cured concrete under drying and sealing conditions were conducted. Through comparing the model and test results of humidity profiles, the moisture dependent diffusivity of the three internal cured concretes is obtained. The developed moisture movement model and finite differential method can well predict the moisture distribution as well as its variations with time of concrete internal cured with PSLWA. [ABSTRACT FROM AUTHOR]

The transport of chloride into concrete is affected by many factors, including temperature, relative humidity, load cracks, and material properties. The purpose of this paper is to analyze the influence of various factors on the chloride ingression process through a case study for Hangzhou Bay Bridge located in marine environment. Firstly, based on the concentration of free chloride in pore solution, a porous media diffusion model is derived, considering the chloride adsorption term. Then, chloride adsorption isotherm, time-varying diffusion coefficient, temperature, relative humidity, and macroscopic cracks are simulated respectively by the porous media diffusion model. The main conclusions are as follows: (1) The chloride adsorption effect and time-varying diffusion coefficient have a great influence on the numerical results, which cannot be ignored in any case. (2) The natural temperature and relative humidity conditions of the case have a small effect on the simulation results. (3) Under the marine atmospheric environment, the macroscopic load cracks have a small influence on chloride ingression in the long term. • A transport model based on free chloride in concrete pore solution is established. • Chloride adsorption isotherm of concrete is assumed to be a transient process. • Effect of air relative humidity on concrete saturation is analyzed and simplified. • A none flux boundary condition is applied to the opening of macro load crack. • Five years of natural air temperature and relative humidity data were employed. [ABSTRACT FROM AUTHOR]

Cereal straw, including wheat, barley and rice, offers a renewable and sustainable resource stream for a variety of construction products, including compressed board panels, thatched roofing and bales. The successful use of straw bales as thermal insulation within the external envelope of buildings has been demonstrated by the increasing number of successful contemporary projects around the world. However, the warranty, insurance and financing of such projects is often still not as straightforward as competing solutions, which can be attributed to concerns relating to the long-term durability of the straw. This paper presents findings from an on-going experimental study into the condition monitoring of modern straw bale construction, and also reports on a study investigating the degradation behaviour of wheat straw cyclically exposed to elevated humidity levels. The findings of the study provide encouraging insight into the robustness of straw bale construction. [ABSTRACT FROM AUTHOR]

In Japan, demolished concrete is often recycled as crusher-run material that captures CO2 because new surface is exposed to the air. This uptake is enabled by carbonations of hydration products in hardened cement paste. The amount of extra CO2 captured during storage varies with the particle size and exposed storage humidity conditions. This paper presents the results of an investigation by the working group of the JSCE subcommittee 219. The group evaluated various methods for visualizing rapid CO2 uptake by demolished concrete. An intuitive and educational method using a gas sampling bag was selected for experimentation. [ABSTRACT FROM AUTHOR]