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Some errors exist in the above paper. [ABSTRACT FROM AUTHOR]

Highlights • The cracking behavior of cementitious materials can be monitored by EIS. • The semi-circle in Nyquist plot is present in the cracked mortar at high frequency, • R ct in Nyquist plots, Z and θ° in Bode plots sensitively reflect the cracking behavior. • The stability and smoothness (fluctuation) of Bode plot can response the cracking degree. Abstract In this paper, electrochemical impedance spectroscopy (EIS) is used as a non-destructive testing method for investigating the cracking behavior of two kinds of cement-based materials with/without fiber, which are engineered cementitious composites (ECC) and plain mortar. The experimental results show that the cracking patterns and deflection-load curves of plain mortar and ECC are different when the external load reaches to the first-cracking load and ultimate load. The EIS results show that the parameter value of R ct and plural modulus value Z in fractured mortar increase several hundred times compared with correspondingly origin plain mortar. Moreover, the semi-circle presents in the fractured mortar at high frequency and the diagonal lines are deviated from less than 45 deg at low frequency, and the phase angle (θ°) in cracked mortar decreases as the frequency decreases in Bode plots. However, the values of R ct and Z in cracked ECC increase dozens of times compared to origin ECC, and the phase angle decreases as the frequency decreases. The variation of R ct in Nyquist plots, and the stability and smoothness of Bode plot sensitively reflect the cracking degree of cementitious system. In this paper, it is proposed that as a non-destructive method, electrochemical impedance measurement can be used to evaluate the cracking behavior of cement-based materials. [ABSTRACT FROM AUTHOR]

• Low temperatures improve ultimate compressive behaviours of SCS sandwich wall (SCSSW) • Thickness of steel faceplate and strength of concrete increases compressive resistance of SCSSW. • Increasing spacing of connectors weakens compressive behaviours of SCSSW. • Proposed models predict well compressive resistances of SCSSW at low temperatures. • Step-by-step prediction procedures were proposed for ultimate compressive resistance of SCSSW. Recently, gravity base offshore platforms consisting of novel steel-concrete-steel (SCS) sandwich ice-resistant walls with J-hook connectors have been developed for the Arctic oil & gas production. This paper made pioneer studies on compressive behaviours of SCS sandwich composite walls with J-hook connectors (SCSSWJ) at the Arctic low temperatures through a nine-specimen testing program. The low temperatures ranging from 20 to −80 °C, thickness of steel faceplate, spacing of connectors, and concrete strength were selected as key parameters in this experimental study. The test results revealed the failure modes and load versus shortening/strain behaviours of the SCSSWJ at low temperatures. These studied parameters were found to have significant influences on the compressive behaviours of this novel SCSSWJ. Including experimental studies, this paper also developed theoretical models to predict the ultimate compressive resistance of SCSSWJ at the low temperature environment. The validations of predictions against results of nine reported tests confirmed that the theoretical models were capable of provide reasonable but conservative estimations on the compressive resistance of such novel SCSSWJ. [ABSTRACT FROM AUTHOR]

• Study of the influence of superplasticizers on the fresh and hardened state characteristics of lime mortars. • Superplasticizers based on polycarboxylate ether (PCE) and on polynaphthalene sulfonate (PNS) were used. • PCE was found to be more effective (higher dispersing ability) and efficient (less quantity needed) than PNS. • Both superplasticizers led to a vast strength increase and only small changes in the porous structure. • Resulting lime mortars with superplasticizer have potential to be used in restoration. Water-reducing admixtures have the potential to minimize the disadvantages that typically discourage the use of lime in restoration works. However, the knowledge on the effect of these admixtures on the properties of lime mortars is not as consolidated as it is for cement-based materials. Therefore, this paper aims at studying the influence of two types of superplasticizer, one based on polycarboxylate ether (PCE) and the other on polynaphthalene sulfonate (PNS), on the fresh and hardened state properties of lime mortars. PCE was found to be more effective (higher dispersing ability) and efficient (less quantity needed) than PNS, leading to a lower fluidity loss over time, but to a higher tendency towards bleeding. Both admixtures led to a substantial mechanical strength increase, even at early ages, and just to small changes in the porous structure of the mortars, which suggests that lime mortars with superplasticizer have potential to be used in restoration. [ABSTRACT FROM AUTHOR]

• Investigated conditions of sustained loading, pre-existing damage and reinforcement coating. • Presents the mechanical behavior of tunnel lining with cracks under accelerated corrosion. • Reveals the resistance of polypyrrole-coated rebar against chloride-induced corrosion of linings. This paper presents an experimental study on the mechanical behavior of a tunnel lining with pre-existing cracks that is subjected to accelerated corrosion. The surface strain, deflection, and load capacity of the concrete liner material were recorded, as well as the degree of rebar corrosion and the crack patterns that developed. The efficacy of the polypyrrole reinforcement coating in minimizing the effects of corrosion and the reinforcement effect on the physical properties of the concrete specimens were examined. The results show that both the pre-existing cracks and sustained loading have noticeable influence on the corrosion behavior of tunnel lining. The specimens with polypyrrole coating exhibited a delayed onset of reinforcement corrosion, less steel mass loss, smaller specimen surface strains and smaller transverse and longitudinal crack width. [ABSTRACT FROM AUTHOR]

• Load sharing mechanism between the outer frame and infill midply subsystems. • Hold-down connectors are unnecessary for the infill midply shear walls. • The post-peak lateral resistance is no less than 70% of load-carrying capacity. • Midply shear wall is more efficient as an infill than standard wood shear wall. This paper presents the results of an experimental study on the lateral loading behavior of glulam frame-midply hybrid lateral systems. Such systems are composed of glulam post-and-beam frames and infill midply shear walls. Reversed cyclic tests of six full-scale glulam frame-midply hybrid systems and two bare post-and-beam frames were conducted. The initial lateral stiffness, lateral load-carrying capacity, ductility and hysteresis characteristics of the hybrid systems were investigated. The load sharing mechanism between the outer frame and the infill midply subsystems was evaluated. Test results show that the installation of the infill midply shear walls can bring great improvements in the lateral resistance and the energy dissipation to the bare post-and-beam frames. The outer post-and-beam frames are basically in elastic range and can effectively restrain the infill midply shear walls from suffering further severe damages. For this reason, the post-peak lateral resistances of the hybrid systems can keep no less than 70% of their own load-carrying capacities within 4.41% drift ratio, and there is no need to install hold-down connectors in the infill midply shear walls. The load-carrying capacity of frame-midply hybrid lateral system is at least 1.5 times that of comparable frame infilled with standard wood-frame shear wall. [ABSTRACT FROM AUTHOR]

Highlights • An experimental study on FRP-confined rubber concrete with a large range of replacement ratio was conducted. • The effects of replacement ratio and FRP thickness were clarified. • An existing model was modified for predicting the behaviour of FRP-confined rubber concrete. Abstract Extensive research has been conducted on the use of tyre-derived products (e.g. rubber crumb and granule) to replace aggregates in producing concrete (i.e. rubber concrete). However, rubber concrete has so far been mainly limited to non-structural applications due to its well-known disadvantages including the relatively low stiffness and strength as well as early cracking as a result of lack of proper bonding between rubber and the paste matrix. The weaknesses of rubber concrete may be minimised in a hybrid column through lateral confinement by a fibre-reinforced polymer (FRP) tube and longitudinal reinforcement by steel or FRP. This paper presents an experimental study on FRP-confined rubber concrete (FCRC), which covers a large range of replacement ratio (0–75% by volume) of fine aggregates and three thicknesses of FRP. The test results confirmed the effectiveness of FRP confinement in improving the axial behaviour of rubber concrete, and clarified the effects of the two important parameters (i.e. replacement ratio of fine aggregates and FRP thickness). The test results also show that the behaviour of FCRC can be significantly different from that of FRP-confined natural aggregate concrete (NAC) with the same unconfined strength and confinement stiffness. By the inclusion of a simple coefficient to consider the effects of rubber aggregates, the existing models for FRP-confined NAC can be modified to provide reasonable prediction of the test results of FCRC. [ABSTRACT FROM AUTHOR]

Highlights • UHPC jacket significantly improves compressive behaviors of stub concrete column. • UHPC jacket offers better confinements on circular concrete columns than square ones. • Analytical models predict well compressive behaviours of columns with UHPC jacket. • Developed FEM predicts well compressive behaviours of columns with UHPC jacket. Abstract This paper firstly performed compressive tests on 18 stub concrete columns with externally confined ultra-high performance concrete (UHPC) jacket. The studied parameters in this testing programme were the thickness of UHPC jacket and the shapes of specimens. The influences of these parameters on the compressive behaviour of stub concrete columns confined by UHPC jacket were reported and discussed. The test results revealed that increasing the thickness of confining UHPC jacket significantly improved the compressive behaviours of concrete stub columns for cylindrical shaped column. However, this influence on that of square shaped stub columns was less significant. An analytical model was proposed to predict the compressive stress-strain behaviour of stub concrete columns with externally strengthening UHPC jacket. The validations of the predictions against the reported test results confirmed the accuracy of the analytical model. The compressive behaviour of stub concrete columns with UHPC jacket was also simulated by 3D nonlinear finite element model (FEM). Validations against the reported test data proved that the FEM simulated well compressive behaviour of concrete stub columns with UHPC jacket. [ABSTRACT FROM AUTHOR]

Full understanding on the characteristic and behavior of manufactured sand (MS) is very crucial to its application. The particle shape, surface texture and behavior of MS are characterized in this paper. Results indicate that MS has higher roundness and Length-width ratio, and wider distribution ranges of those parameters compared with river sand (RS), in the micro scale, most MS has lower surface roughness than RS unexpectedly. To obtain the similar workability, most MS concretes require higher water reducer dosage than RS concrete, and MSs with less stone powder and clay lump content require even lower water reducer. Nearly all MS concrete has higher strength than RS concrete with same paste composition. The particle shape and surface texture of MS has less significant effect on its behavior in concrete than the stone powder, clay lump content and the gradation of MS, so MS with suitable production process may have better behavior in concrete than RS. [ABSTRACT FROM AUTHOR]

Airport flexible pavements are subjected during their use to continuous stresses from mainly dynamic repeated aircraft loads, environmental climatic conditions and hence the risk of fatigue and deterioration. Geosynthetics, such as geogrids, improve the performance of pavements and increase its bearing capacity and its life expectancy as the reduce cracking and damage of different layers. Few experimental and numerical studies are available in the literature to predict the behavior of pavement over time. In this paper, a case study for the application of geogrids in an airport runway is presented. An evaluation of the static behavior by measurement of deformations and stresses in different sections of runways are presented as well as non-destructive testing by heavy weight deflectometer (HWD), before and after geogrids reinforcement. A finite element numerical study on the behavior of these geogrids reinforced runway is also presented and compared to the experimental results. [ABSTRACT FROM AUTHOR]

• WEO grafted on the surface of kapok fiber after milling. • Under the same aging state, the effect of delaying aging OKFA was optimum. • OKF improved the anti-aging performance of asphalt significantly. The aging of asphalt binder is one of the vital factors to shorten the service life of asphalt pavement. The researches on delaying the aging of asphalt binder by different fibers are extremely valuable. The recycled kapok fiber (KF) mixed into the asphalt improves the properties of the matrix microscopically and achieves the effect of delaying aging. It still needs to modify KF because of its hygroscopicity and water absorption. It results in the lack of adhesion with the asphalt interface. This paper studies a liquid-phase ball-milling technology for KF with waste engine oil (WEO) as a grinding medium. Through the mechanical force activation, it optimizes the size and surface properties of KF and finally prepares the oil-grinded kapok fiber modified asphalt binder (OKFA). After scanning electron microscope (SEM), X-ray diffractometer (XRD), nitrogen adsorption–desorption method (BET) and Fourier transform infrared spectroscopy (FTIR) tests, the structure of KF and OKF was characterized. It showed that the crystallinity of oil-grinded kapok fiber (OKF) increased by 11.5% compared with KF, and the specific surface area and pore volume increased by 74.3% and 62.5%, respectively. Through the accelerated aging test, nanoindentation and viscosity and other correlation tests were used to evaluate the mechanical properties and aging performance of the modified asphalt. It showed that OKFA performed good aging resistance and potential low-temperature resistance enhancement of asphalt. This research not only solves the resource recycling and reuse of textile fiber waste and follows the new development of energy-saving and environmental protection, but also provides a new direction for improving the performance of asphalt. [ABSTRACT FROM AUTHOR]

• The tensile test is widely used for the characterization of FRCM systems. • The tensile behavior of FRCM involves different phenomena interacting among them. • A theoretical model for studying the tensile behavior of FRCM is proposed. • The reliability of the model is assessed with reference to experimental cases. • The proposed model is a valid support for understanding the experimental outcomes. Fabric Reinforced Cementitious Matrix (FRCM) systems have been recently introduced for repairing or strengthening interventions of reinforced concrete and masonry structures. Thanks to the combination of a dry grid of fibers and a cement-based material (matrix), they present a good strength and numerous advantages with respect to traditional Fiber Reinforced Polymer (FRP) systems. The tensile and bond behavior of FRCM reinforcement systems is characterized by specific phenomena influencing their performance, which are generally not observed in the case of FRP, and that are still object of experimental and numerical studies. Aim of the present paper is the proposal of a theoretical model for numerically studying the tensile behavior of FRCM systems, able to consider the different phenomena characterizing the response of FRCM in tension. The model is carried out on the basis of equilibrium considerations by introducing both linear and nonlinear laws for schematizing the local behavior at the level of the matrix, reinforcement and reinforcement/matrix interface. The model is presented in detail in the first part of the paper and, in the second part, it is applied to an experimental case study derived from literature. [ABSTRACT FROM AUTHOR]

• The axial behaviours of FRP-confined regular and rubberised concrete are investigated. • Effects of rubber content, section shape, FRP type and number of layers are assessed. • Confinement effectiveness enhances by increasing rubber content & FRP rupture strain. • Efficiency of confinement models for rubberised square and circular concrete examined. • Existing models fail to predict the behaviour of confined square rubberised concrete. This paper investigates the axial behaviour of square and circular concrete specimens confined by externally bonded Fibre Reinforced Polymer (FRP) jackets. Axial compression tests were performed on 96 regular and rubberised concrete specimens. The parameters considered were rubber content (0% and 60%), section shape (circular and square), FRP type (Carbon or Aramid) and the number of FRP layer (1, 2 and 3). The behaviour of the specimens in both axial and lateral directions, as well as their dilation characteristics, were investigated. The test results indicate that the confinement effectiveness of Aramid-FRP is better than that of Carbon-FRP. It is also shown that the detrimental effect of sharp corner on confinement effectiveness is less critical when using high rubber content as the element can develop large lateral expansion at unprecedented axial deformation. Large axial deformations can enable the development of highly ductile concrete elements. Existing design-oriented models fail to predict the behaviour of confined rubberised concrete with rectangular cross-section, indicating the need for developing more refined confinement models. [ABSTRACT FROM AUTHOR]

• Variation of impedance with drying depends on presence and volume fraction of carbon fibers. • Water loss during drying increases impedance for non-fibrous mortar. • In the presence of fibers, behavior tends towards a resistive behavior over drying time. • Coupling fibers with a specific monitoring frequency limits sensing uncertainty caused by drying. • Uncertainty related to drying is equal to 84,14% in case of non-fibrous mortar. • Uncertainty drops to 1.12% in case of high carbon fiber presence with a 40 kHz measurement frequency. The addition of conductive fibers to a cementitious material reduces its electrical impedance, for monitoring purposes, based on the relationship between external stresses (mechanical or thermal) and changes in electrical properties. In this context, variations in the electrical properties due to drying prevent the application of this technique, unless such variations are negligible or precisely predictable. The aim of this paper, therefore, is to study the variation of the complex electrical impedance during drying, for measurement frequencies between 4 Hz and 1 MHz. Shrinkage, weight loss and electrical impedance spectrum were measured on three mortars with carbon fiber volume fractions (FVF) of 0, 0.1 and 0.5%. The results show that in the absence of conductive fibers, the real and imaginary parts of the impedance increase due to water loss. On the other hand, in the presence of a percolated carbon fiber network, the real impedance of the material decreases at low frequencies and increases at high frequencies during drying; for intermediate frequency ranges, quasi-constant values can be observed. In addition, as the material dries, the capacitive behavior of the material wanes, and the imaginary impedance values tend towards 0. The electrical behavior then approaches ideal resistive behavior with a real impedance value independent of the measurement frequency. Blind frequencies have been identified for fibrous mortars around 1 kHz and 40 kHz for 0.1% and 0.5% FVF, respectively. For monitoring purposes, coupling the presence of fibers with an appropriate measurement frequency would minimize the effects related to the variation of impedance as a function of time – i.e., allowing more precise monitoring of mechanical loads with time. [ABSTRACT FROM AUTHOR]

• Proposed a modelling approach to predict the in-plane behavior of confined arches. • Proposed a model to predict the compressive strength of actively confined concrete. • Proposed-model can well capture the eccentric-loading behavior of confined members. • Parameters study of confined arches is carried out with the proposed methodology. Numerical modelling approaches are favoured in studying the instability failures of concrete-filled steel tube arches (CFSTAs) due to the complexity and high cost of experimental testing of such structural members. While some of the existing numerical models are able to capture the constitutive behaviour of the materials in CFSTAs accurately, they are computationally expensive to be used for studying the effect of key parameters affecting the CFSTA behaviour. This paper presents a simple yet accurate numerical modelling approach to predict the behaviour of CFSTAs considering in-plane instability failures. Numerical modelling was carried out using open-source finite element (FE) software OpenSees. CFSTAs were modelled using fibre section beam-column elements available in OpenSees. A modified stress–strain model was used to capture the constitutive behaviour of both confined normal and high strength concrete. Bi-axial stress state of steel tube was considered for failure modelling of steel. Proposed FE model for CFSTA was verified using existing experimental results of CFSTAs. Consideration of the bi-axial stress state of the steel tube was shown to increase the accuracy of the predictions. FE results showed that when a CFSTA is failing due to instability, geometric imperfection will significantly influence CFSTA behaviour. Both percentages of steel content and unconfined concrete strength was found to affect the ultimate load of the CFSTAs, but the effect was found to be dependent on the loading conditions. Rise-to-span ratio as well as the shape of the arch was also found to significantly influence the behaviour of CFSTAs, with the parabolic arch shape being found to be the best. [ABSTRACT FROM AUTHOR]

This paper aims to develop a robust homogenization scheme for the viscoelastic behavior of early age and hardened cement pastes. The short-term creep of early age cement and the short- and long-term creeps of hardened cement are modeled by the non-ageing viscoelastic behavior. The ageing creep at early age is modeled by considering the evolution of the microstructure during the hydration process. This model offers a practical technique to predict the ageing creep at early age from data of non-ageing creep at the hardened state, and vice versa. It is also able to describe the creep behavior of a paste with certain water to cement ratio from data of a paste with another water to cement ratio. It is well validated against a large variety of the most relevant data available in literature and provides a great potential of application in practice. [ABSTRACT FROM AUTHOR]

• Bond behavior for deformed steel bars in cementitious grout were tested. • Peak bond stress models for deformed steel bars in cementitious grout were proposed. • Bond stress-slip models for deformed steel bars in cementitious grout were proposed. • Agreement between proposed models and test data from different sources was achieved. The bond behavior between deformed steel bars and four types of cementitious grout under monotonic loading was investigated in a series of experiments. The effects of testing age and confinement ratio on the bond behavior of the deformed steel bar in the four types of cementitious grout were discussed. The results indicated that the peak bond stress was linearly increased with the increase of time–dependent tensile splitting strength and confinement ratio. The slip at peak bond stress decreased linearly accompanied with the increasing time–dependent tensile splitting strength, and does not seem to be confinement ratio dependent. Moreover, accompanied by the increase of time–dependent tensile splitting strength, the shape parameter of ascending branches of bond stress–slip curves exhibited a linear decrease, whereas the shape parameter of descending branches increased linearly. In addition, with the increasing confinement ratio (1.25 ≤ c / d ≤ 2.5), these two shape parameters stays at a relatively similar values. According to an analysis of the bond behavior of the bond specimens with different test ages and confinement ratios, a peak bond stress model and bond stress–slip constitutive relationships between the deformed steel bars and four types of cementitious grout were proposed. Subsequently, the accuracy of the models proposed in this paper was verified by comparing their results with test results obtained from different sources. [ABSTRACT FROM AUTHOR]

• FRCM composite bond behavior is affected by the presence of interface normal stress. • In modified beam tests the normal stress is directed against the matrix internal layer. • The normal stress increases the bond capacity of modified beam tests. • The effect of the normal stress is related to the specific FRCM composite. In the last decades, the increasing need for strengthening and retrofitting of existing masonry members has led the scientific community toward the development of innovative strengthening systems. Among these systems, inorganic-matrix composite materials have been gaining increasing popularity due to their effectiveness, relatively low cost, ease of the application, and reversibility of the intervention. Inorganic-matrix composites, usually referred to as fiber- (or fabric-) reinforced cementitious matrix (FRCM) composites, were successfully used as externally bonded reinforcement (EBR) of masonry members subjected to various load combinations. However, their effectiveness is strictly related to the FRCM-substrate bond behavior. Therefore, numerous set-ups were employed to investigate the bond properties of FRCM composites. Among them, single-lap direct shear test set-ups were the most commonly employed and are now recommended by available design guidelines for FRCM composites. In this paper, a modified beam (MB) test set-up is used to study the bond behavior of two different FRCM composites: a polyparaphenylene benzobisoxazole (PBO) FRCM and a carbon FRCM. The parameters studied are the dimensions of the blocks used in the MB tests and the presence of bare or embedded fibers at the gap between the blocks. The bond behavior observed is compared with that of single-lap direct shear tests of the same FRCM composites. The results obtained provide an insight on the influence of normal stress components at the matrix-fiber interface on the FRCM bond behavior, which may play an important role in the capacity of FRCM strengthened curved members. [ABSTRACT FROM AUTHOR]

• Flatwise behavior of Integral Mechanical Attachments is experimentally studied. • Small differences are observed between the yield and peak strengths. • A brittle failure is observed in fiber- perpendicular specimens. • The joints are mainly classified as having low ductility. This paper aims to characterize the force–deformation response of through-tenon wood-wood connections subjected to out-of-plane (flatwise) loads. Six beech LVL timber specimen groups with variations in the fiber orientation (parallel and perpendicular) and tab insertion angle (45°, 60°, and 90°) are tested. Minimal replicate-to-replicate variability for each specimen group was observed. Overall, the specimens reached their maximum capacity soon after yielding. Furthermore, the joints are classified as having low ductility. For the specimens where the main fibers are oriented perpendicular to the loading direction, low strength and brittle failure were observed. The yield and maximum strengths and the slip modulus were not affected by the tab insertion angle and therefore remained almost constant among these specimens. For the specimens where the main fibers are oriented parallel to the loading direction, higher strength and more ductile behavior was observed. The following mechanisms contributed to the load-deformation response of these specimens: inter-fiber layer resistance, tension–compression, flexural, shear and torsional resistance of the fibers, and the embedment compression resistance. Furthermore, the damage propagation was not concentrated in a specific location/surface. The notch size was found to have a strong influence on the yield and maximum strengths, as well as the slip modulus of the 45°-angled specimens. [ABSTRACT FROM AUTHOR]

• Characterization of the mechanical behaviour of grey clay brick (GCB) masonry. • Numerical models based on experimental result are setup. • Safety level of a traditional Chinese building is obtained. Grey clay bricks (GCBs) are a traditional and unique masonry material for Chinese buildings, and their application is especially prevalent in traditional Chinese architectures. Despite that structural analyses of historical constructions have been a popular area of focus in recent studies, information on the behaviour of GCB masonry structures is still lacking. In this paper, a comprehensive characterization of the mechanical behaviour of GCB masonry by using experimental and numerical methods is presented and discussed. Characterization tests were primarily carried out to determine the mechanical strengths of GCB, cement-based and lime-based mortar, and the bond behaviour between them. Then, a series of tests was performed on GCB masonry prisms and panels to evaluate the compressive, flexure and shear behaviours of GCB masonry, respectively. Finally, numerical models based on the experimental results were setup and further implemented for analysing the nonlinear response of a historical unreinforced masonry building in Macau to obtain the safety level. The combined experimental and numerical investigation evaluates important parameters for the mechanical behaviour of GCB masonry and delivers updated understandings of the structural behaviour of existing GCB masonry buildings in China. [ABSTRACT FROM AUTHOR]

• Comparison of the behaviour of three integral water-repellents (WRs) on lime mortars. • The studied WRs were based on sodium oleate, silane and silicone resin. • Sodium oleate effectively reduced water absorption without hindering vapour permeability, but decreased mechanical strength. • Silicone resin had the lowest impact on porous structure and water absorption, but increased mechanical strength. • Silane had a performance between that of the other two substances. The paper compares the behaviour of three types of integral water-repellents (WRs) on air lime mortars. These were based on sodium oleate, silane and silicone resin. Results demonstrated that sodium oleate was the most effective in reducing water absorption without compromising water vapour permeability, but decreased mechanical strength. Conversely, silicone resin had the lowest impact on porosity and water absorption, but it was the only WR that increased mechanical strength, even at early ages. These trends were intensified with increasing WR dosage. Silane had a performance between that of the other two substances. Based on the results, silicone resin has the highest potential to be used in lime mortars for restoration purposes. [ABSTRACT FROM AUTHOR]

• Sustainable way of ground treatment was investigated using CSA cement. • CSA cement showed significant and rapid strength improvement for expansive soils. • Key phases of stabilization mechanism of CSA cement for expansive soils are unveiled. • Stabilization follows cationic exchange and flocculation and agglomeration. • Subsequently, cementitious hydration form space filling ettringite needles. Expansive soils are a common problem to overlying geotechnical structures risking for distress and damage caused by moisture induced ground movements. Calcium-based stabilization is readily adopted to improve and enhance the problematic expansive subgrade increasing strength and the volume change behaviour. For ground improvement, the use of lime and Ordinary Portland Cement (OPC) to treat expansive soil has been in common practice; however, Calcium Sulfoaluminate (CSA) cement can be an effective alternative due to the reduced environmental impact. To date, limited literature surrounds the understanding of CSA cement in expansive soil, but largely focussed its applications on concrete infrastructure. This paper investigates the stabilization mechanism of CSA treated expansive soils by identifying the major hydration products and microstructural characteristics with respect to CSA cement dosage and curing rate. The study reveals CSA cement stabilization directly affects mechanical properties and microstructural characteristics due to three key phases of cationic exchange, flocculation and agglomeration between the clay sheets and cementitious hydration. The addition of CSA cement in the ground stabilization serves to shift towards a sustainable approach in reducing the carbon impact of traditional stabilization techniques. [ABSTRACT FROM AUTHOR]

• Properties and structure of alkali-activated slag grouting material were studied. • The samples presented a slight expansion. • The samples presented a small increase in mass. • The main gel products were C-A-S-H gels. • The samples presented a good resistance to sulfate corrosion. In this paper, according to the alkalinity of 4 wt%, 5 wt%, and 6 wt%, alkali-activated slag grouting material (AASGM) specimens were prepared by mixing waterglass (sodium silicate) with a modulus of 2.0 and slag. The specimens were immersed in pure water and sodium sulfate solutions with a concentration of 1–4 wt% for 90 days. The linear expansion, mass change, mechanical properties, and microstructure of the specimens were measured and analyzed. The results indicate that the main gel products were C-A-S-H gel in this process. The AASGM samples presented slight expansion, a small increase in mass, essentially unchanged compressive strength, and good anti-sulfate corrosion performance. [ABSTRACT FROM AUTHOR]

• The behaviour of BFRP tendon systems is investigated by cyclic tensile tests. • The regression formula of the anchor colloidal deformation is established based on the tests. • The rheological model that can consider the pretension loss is established. • The influence of the anchor colloidal deformation on the performance of SC-BRB is studied. Basalt fibre-reinforced polymer (BFRP) is an excellent pretensioned tendon material due to its high elongation, and it has been used in the self-centering buckling-restrained brace (SC-BRB). During previous experiments on SC-BRBs, although the BFRP tendon did not cause anchorage slip failure, pretension loss occurred. To determine the cause of the pretension loss, in this paper, cyclic tensile tests were conducted on multiple sets of BFRP tendon systems. Based on the experimental results, the pretension loss of the SC-BRB was due to the deformation of the colloid in the anchor under cyclic loading, and the regression formula of the colloidal deformation of the anchor was established. According to the results of a quasi-static experiment on a SC-BRB, the BFRP tendon can provide a reliable self-centering restoring force for the brace, and the accuracy of estimating the pretension loss based on the regression formula is demonstrated. Finally, a rheological model that can accurately describe the hysteresis performance of the SC-BRB and consider the pretension loss is established. Based on this model, the influence of the pretension loss on the brace performance is studied. [ABSTRACT FROM AUTHOR]

• A FE model of veneer-based timber CHS beams is developed. • The model accurately reproduces all failure modes observed experimentally. • The mechanisms leading to an compressive sudden failure mode are explained. • Design rules which capture all experimentally observed failure modes are proposed. Various forms of timber hollow structural profiles have either been proposed in the literature or are already commercially available. Tests performed on Circular Hollow Section (CHS) beams showed failure modes not usually encountered in timber structures. For relatively thin-walled profiles, a sudden failure in the compression zone, with the opening of the cross-section, was observed. To confidently use and market CHS timber products, design rules considering all possible failure modes must be developed. This paper presents a Finite Element (FE) model of CHS timber beams which captures all experimentally observed failure modes. Cohesive zone elements were used to model the quasi-brittle failure modes of the timber material. The model was validated against ten experimental tests performed on CHS of three different cross-sectional slenderness and manufactured from juvenile hardwood Gympie messmate (Eucalyptus cloeziana) rotary peeled veneers. The model was found to accurately capture the measured structural behaviour and resulted in an average experimental-to-predicted bending capacity ratio of 1.02. The model was also used to explain the mechanisms leading to the sudden compressive failure mode. A parametric study was finally performed on 72 CHS beams of different cross-sectional slenderness. Results showed a strong correlation between the cross-sectional slenderness ratio and section capacity. Design rules are proposed and discussed. [ABSTRACT FROM AUTHOR]

• A study on slender FRP-confined concrete-encased steel columns (FCCSCs) is presented. • The test variables include column slenderness, load eccentricity and FRP thickness. • The excellent structural performance of slender FCCSCs was demonstrated. • The confinement effects are remarkable for slender FCCSCs under compression. Fibre-reinforced polymer (FRP)-confined concrete-encased cross-shaped steel columns (FCCSCs) consist of a square FRP outer tube with round corners, a cross-shaped inner steel section and concrete filled in the between. The unique configuration of FCCSCs ensures that the concrete in the columns is well confined despite the square column shape, as demonstrated by the relevant existing research. The existing work on FCCSCs, however, has been limited to the behavior of short FCCSCs under axial compression. With their optimal configuration, the use of FCCSCs means that considerably reduced section dimensions may be adopted for the same load demand, leading to relatively slender columns in practice. In addition, the load eccentricity is an important parameter to consider in the column design. This paper presents the first-ever experimental study on the behaviour of slender FCCSCs. The test variables in this study included the load eccentricity, the slenderness ratio of the column and the thickness of FRP tube. The test results confirm the excellent structural performance of slender FCCSCs, and show that the load capacity of FCCSCs decreases with the slenderness ratio and the load eccentricity. Nevertheless, the confinement effects on the behavior of FCCSCs were found to be remarkable even when the column slenderness ratio and load eccentricity are large. [ABSTRACT FROM AUTHOR]

• A hybrid structural connection system has been investigated for its suitability to offer increased bearing capacity for timber structures. • SDS were used in forming the STC connections to check SDS' suitability as a new connecting element in this type of application. • SDS connectors offer higher stiffness and more ductility to STC connections. • Test results for key connection parameters were compared against those predicted using GB/T 50005–2017, NDS-2018 and Eurocode 5. • Foschi formula was used to predict the nonlinear load-slip behaviour of considered specimens and analytical predictions showed reasonable agreement with test results. This paper presents an experimental investigation on a Steel Timber Composite (STC) connection system composed of steel H-section and engineered timber, glulam produced from Larix gmelinii. Static push-out tests were conducted on this new composite connection type to investigate its yield characteristics as well as relevant failure modes. Effects of the type, diameter and spacing of shear connectors, and thickness of glulam on the mechanical response of this STC connection were carefully analysed. For all considered specimens, "two-hinge" yield mode was observed but the failure of joints were characterized by the simultaneous occurrence of embedding strength failure of glulam flanges and bending failure of bolts used as shear connectors. The ultimate load carrying capacities as well as yielding of joints were directly proportional to the bolt diameter but inversely proportional to bolt spacing. As the thickness of glulam was increased, both the ultimate load and the yield load of joints initially increased but then decreased. Self-drilling screw connected joints performed better than the bolt connected joints both in terms of stiffness and ductility. Experimentally obtained key design parameters were compared against those predicted using GB/T 50005–2017, NDS-2018 and Eurocode 5. It is worth noting that the code predictions are not suitable for design application due to significant conservatism or over-prediction of connection response; this shows a clear gap in the existing knowledge on STC connections. Foschi formula was used to predict the nonlinear load-slip behaviour of considered specimens and analytical predictions showed reasonable agreement with test results. [ABSTRACT FROM AUTHOR]

• Development of an innovative steel-to-CLT strengthened nailed connection. • Use of FRP composites for realizing lightweight and hyper-resistant connections. • Experimental study of monotonic and cyclic behavior of steel-to-CLT nailed joints. • Quantitative evaluation of the reinforcement effect by means of linearization methods. • Proposal of a design-oriented analytical capacity method based on adjusted density values. Connections play a key role in timber structures because they are the parts devoted to energy dissipation during an earthquake or, when specific hysteretic devices are introduced, their hyper-resistant design allows for a rigid fastening of those devices, thus assuring an elastic behavior of the structure under seismic loads. A promising technique to improve both the load-bearing capacity and the stiffness of joints with dowel-type fasteners, consists in increasing the embedment strength of the wood-based materials, usually by applying a superficial reinforcing layer to the timber-connection shear plane interface. In this framework, results of an experimental campaign carried out on steel-to-CLT panel nailed joints strengthened with a carbon fiber ply glued to the shear plane interface are presented and discussed in this paper. Two different load configurations (perpendicular and parallel to grain) and two different loading protocols (monotonic and cyclic) have been considered, analyzing the results in order to evaluate the effectiveness of the reinforcement technique in terms of load-bearing capacity and stiffness, with respect to the reference unreinforced configuration. Finally, the applicability of the current design method is verified together with the proposal of a simplified design procedure. [ABSTRACT FROM AUTHOR]

• The thermoelectric behaviours of fly ash and metakaolin based geopolymer paste were investigated. • The effects of alkali activator concentration, curing temperature and slag substitution ratio were discussed. • Geopolymer, especially metakaolin based geopolymer, was found to be a more promising thermoelectrical material. In this paper, the thermoelectric behaviors of fly ash and metakaolin based geopolymer were investigated. It was found that the seebeck coefficient of geopolymer paste is much higher than that of cement paste, indicating geopolymer may be a promising thermoelectrical material. The influences of different parameters were discussed. The seebeck coefficient for both fly ash and metakaolin based geopolymers were found to increase with the increase of alkali concentration. The curing temperature has a more significant influence on the thermoelectric behavior of fly ash based geopolymers. Meanwhile, the increase of slag replacement ratio would result in a decreased seebeck coefficient for fly ash based geopolymer. [ABSTRACT FROM AUTHOR]

• 4 Timber-to-timber composite floor specimens were tested over a period of 1.5 years. • Each specimen was pre-cambered and pre-stressed using only inclined screws. • 2 Type of screws were adopted: double threaded (DT) and single threaded (ST). • The Toratti rheological model was used for the theoretical comparisons. • Specimens assembled with DT screws exhibited the best long-term performance. The paper presents the outcomes of an experimental investigation on the long-term behaviour of timber-to-timber composite (TTC) floors assembled using a cambering-prestressing (CP) procedure previously proposed by the authors. The short-term effectiveness of such technique has been demonstrated in previous literature where it is shown that by exploiting the capability of the screw connectors to apply a compression force on the joining timber members, it is possible to obtain a camber and a prestressed condition without any use of other external devices or propping. To prove the applicability of the aforementioned CP procedure to real life design-scenarios, the long-term efficacy should be investigated. With such aim, four TTC floor specimens of 5.0 m of span and different connection layouts, were loaded in flexure under controlled environmental conditions for a period up to almost 1.5 years. One of the main results from the long-term monitoring of the specimens is that the floors uplift achieved by applying the CP procedure was found to be persistent over time with minimal camber losses. [ABSTRACT FROM AUTHOR]

• It is vital to explore new strategies of preserving freshwater in concrete production. • The GFRP rods use in RC structures produced with seawater is a promising solution. • Concrete compositions with seawater were developed and evaluated. • Bond behaviour between GFRP rods and the developed concrete was assessed. • Seawater had no severe effects on neither concrete properties nor bond behaviour. Freshwater is an increasingly scarce resource. Its use in the production of concrete is one important contributor to its fast depletion. Alternatively, the use of seawater for reinforced concrete production, combined with the use of glass fibre reinforced polymers (GFRP) as reinforcement, may represent an interesting solution to increase concrete sustainability. The objective of this paper is to explore this promising solution through the development of concrete compositions with seawater. Additionally, it is also an objective to assess the bond behaviour between GFRP rods and concrete, in a design perspective. The influence of concrete age, rod diameter and anchorage length were also investigated. An analytical model capable of determining the local bond stress-slip laws was used. Results demonstrated that the use of seawater had no relevant effects on neither concrete mechanical properties nor bond behaviour. [ABSTRACT FROM AUTHOR]

• Zero shear viscosity values of mastics increase remarkably in response to ageing. • Finer filler particles improve fatigue behavior, regardless of mastic age. • Addition of fine filler particles to a mastic reduces its sensitivity to fatigue. • Fatigue response is related to the morphological characteristics of mastic surface. Fatigue cracking is caused by repeated traffic loads and environmental conditions (temperature, ageing, etc.); it predominantly initiates within the mastic phase in the form of micro-cracks. In this sense, bituminous mastics (comprised of a binder, filler and entrapped air) play a significant role in the anti-fatigue performance of asphalt mixes. In this paper, the effects of filler particle size and ageing on the fatigue behaviour of bituminous mastics were evaluated. Prior to this, the rheological properties of the studied samples were evaluated using physical tests and frequency sweep tests. Moreover, the mastic morphology and filler distribution inside a bituminous matrix were characterized by Scan Electronic Microscope (SEM). The results revealed that ageing had a greater effect than filler particle size on the rheological behaviour of SBS-modified bituminous mastics, especially for mastics containing coarse filler particles. According to the ageing responses derived from log-log fatigue law plots, aged mastics containing coarse filler particles had higher slopes (represented by coefficient B) and lower intercepts (identified by coefficient A) than un-aged mastics. However, opposite fatigue behaviour was observed with fine filler granules, where coefficient B slightly decreased while coefficient A slightly increased after ageing. In addition, mastic morphology and filler dispersion inside a bituminous matrix were characterized by SEM, providing insight to possible relationships between morphological characteristics and fatigue performance. [ABSTRACT FROM AUTHOR]

• Textile-to-mortar bond behaviour in lime-based textile reinforced mortars is experimentally and analytically investigated. • 160 pull-out tests are performed on two TRM composite types. • The role of test setup, loading rate, mortar age, fabric configuration and embedded length are discussed. • The results contribute to standardization of test methods and fundamental understanding of the bond behaviour in TRM composites. • The results contribute to development and design of TRM composites with enhanced properties. Lime-based textile-reinforced mortars (TRM) have recently found a growing interest for repair and strengthening of masonry and historical structures. Despite extensive experimental and numerical investigations performed in the last years on the performance of these composites, there is still a lack of fundamental understanding of the fabric-to-mortar bond behaviour (as one of the main mechanisms affecting the cracking and nonlinear response of these composites) and the parameters affecting that. This paper, aimed at addressing this gap, presents a comprehensive experimental and analytical investigation on how the test setup, embedded length, load rate, mortar age and fabric configuration affect the bond behaviour in lime-based TRMs. In total 160 pull-out tests are performed on a glass-based and a steel-based TRM commonly used for strengthening of masonry structures. The results contribute to standardization of the test procedures for characterization of the fabric-to-mortar bond behaviour, to fundamental understanding of this mechanism and to optimization of the design of these composites for enhancing their mechanical response. [ABSTRACT FROM AUTHOR]