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Three-dimensional (3D) printing with earth-based mortar is still under development and faces challenges. Optimising the mortar mixture, improving structural strength, determining the relationship between the printing speed and the amount of extruded material, and ensuring long-term durability are areas that are being refined. Additionally, regulatory and certification issues must also be considered to ensure the safety and compliance of 3D printed structures. This paper presents for discussion the records, analyses, studies, and considerations regarding initial initiatives involving 3D printing with the extrusion of earth-based mortar developed at the Faculty of Engineering of the University of Porto (FEUP). Through this work, it was possible to strengthen and reaffirm that 3D printing with earth-based mortar has significant potential in the construction industry and that the incorporation of dispersed kraft paper fibres from the recycling of cement bags is an excellent resource to achieve good constructability in 3D printing with earth-based mortar. [ABSTRACT FROM AUTHOR]

This paper explores the new potential strategy of using fine recycled aggregates (fRA) derived from waste 3D printed concrete (3DPC) as a substitute for cement in additive manufacturing. This study hypothesizes that fRA can optimize mixture design, reduce cement content, and contribute to sustainable construction practices. Experimental programs were conducted to evaluate the fresh and hardened properties, printability window, and buildability of 3DPC mixes containing fRA. Mixes with replacement rates of cement with fRA by 10 vol%, 20 vol%, 30 vol%, 40 vol%, and 50 vol% were produced. A comprehensive experimental protocol consisting of rheological studies (static and dynamic yield stress), dynamic elastic modulus determination (first 24 h of hydration), flexural and compressive strengths (2 d and 28 d), and an open porosity test was performed. The obtained results were verified by printing tests. In addition, an economic and environmental life cycle assessment (LCA) of the mixes was performed. The results indicate that up to 50 vol% cement replacement with fRA is feasible, albeit with some technical drawbacks. While fRA incorporation enhances sustainability by reducing CO2 emissions and material costs, it adversely affects the printability window, green strength, setting time, and mechanical properties, particularly in the initial curing stages. Therefore, with higher replacement rates (above 20 vol%), potential optimization efforts are needed to mitigate drawbacks such as reduced green strength and buildability. Notably, replacement rates of up to 20 vol% can be successfully used without compromising the overall material properties or altering the mixture design. The LCA analysis shows that reducing the cement content and increasing the fRA addition results in a significant reduction in mix cost (up to 24%) and a substantial decrease in equivalent CO2 emissions (up to 48%). In conclusion, this study underscores the potential of fRA as a sustainable alternative to cement in 3D printed concrete. [ABSTRACT FROM AUTHOR]

Chemical shrinkage (CS) is an intrinsic parameter that may affect the early age cracking of paste, mortar and concrete. It is well known as the driving force of self-desiccation, autogenous shrinkage (AGS) and drying shrinkage. During the first stage of cement hydration (at the initial setting time), the CS and AGS are equal. In the hardened stages, there is a difference in values between the two shrinkage parameters. This paper is a comprehensive review on CS and AGS, measurement techniques, modeling and prediction of different cementitious systems. Based on the various experimental studies, chemical shrinkage depends on the water to binder ratio (w/b) and is proportional to the degree of hydration. A low w/b ratio leads to high CS and AGS. The composition of cement has an effect on both CS and AGS. Also, incorporating supplementary cementitious materials (SCMs) affects both shrinkage parameters. It is concluded that adding fly ash (FA) to concrete contributes to CS and AGS reductions. However, this is not the case when concrete contains slag. More than 170 references were consulted including 35 which were published after 2020. According to the authors knowledge, there is no published work on the effect of fibers, especially bio-fibers, on the chemical shrinkage of cement-based composites. Therefore, in addition to traditional chemical shrinkage of cementitious systems, this review includes a section on recent papers conducted by the authors on the effect of bio-fibers on the chemical shrinkage of cement composites. [ABSTRACT FROM AUTHOR]

In this paper, we present the structural, mechanical and electrical properties of composite cement materials that can be widely used as substituent for cement. We start with the characterization of a composite cement sample using an analysis of X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectra. The measurements of the Vickers hardness, cyclic and sweep linear voltammetry and electrochemical impedance spectroscopy (EIS) of composite cement materials were also recorded. This study compared the effect of the different nanocomposites added to cement on the mitigation of the alkali–silica reaction, which is responsible for the swelling, cracking and deleterious behavior of the material. The enhancement in Vickers hardness was more pronounced for composite cement materials. In contrast, the values of Vickers hardness decreased for the composite cement containing mortar and the control sample, suggesting that the long-term performance of cement was compromised. In order to obtain information about the bulk resistance of the composite cement material, electrochemical impedance spectroscopy (EIS) data were employed. The results suggest that for composite cement materials, there is an improvement in bulk electrical resistance, which can be attributed to the lower amounts of cracks and swelling due to lower expansion. In the control sample, a reduction in the bulk resistance suggests the formation of microcracks, which cause the aging and degradation of the material. The intersection of arcs in the EIS spectrum of the mixed composite cement sample gradually increased by an alkaline exposure of up to 21 days and finally shifted towards a low value of high frequency with an increase in alkaline exposure of up to 28 days. [ABSTRACT FROM AUTHOR]

With the development of UHV transmission technology, large-tonnage disc-type suspension porcelain insulators have been widely used. Insulators with cylindrical heads have the advantages of light weight and high strength compared with traditional insulators with conical heads. Cement is an important part of disc-type suspension porcelain insulators. The drying shrinkage of cement can lead to sliding between cement and porcelain. It can also transform the stress distribution of the porcelain, thus influencing the overall long-term mechanical performance of the insulators. In this paper, the effect of the shrinkage of cement on the stress distribution of porcelain insulators was studied by simulation. In addition, the effect of the drying shrinkage rates of cement on insulators with cylindrical and conical heads were compared. The simulation results show that cylindrical-head insulators can better resist the stress change caused by cement shrinkage than the conical-head insulators, which was beneficial to the long-term performance of the insulators. Based on the tensile stress of porcelain parts, the recommended range of the drying shrinkage rate of cement for insulators with cylindrical heads was presented. The research results are of practical value for the selection of cement. [ABSTRACT FROM AUTHOR]

For the first time, this paper explores the role of hydration kinetics on microcrack development in cement mortars using the μ-CT technique with a resolution of 2.2 µm. Three binders were tested: fine-grained ordinary Portland cement (OPC) with Blaine fineness of 391 m2/kg, coarse-grained OPC made from the same clinker with Blaine fineness of 273 m2/kg, and H-cement as a representative of the alkali-activated binder. It was found that most microcracks have a width in the range of 5–10 µm, increasing their occurrence with the progress of sealed hydration. While H-cement and coarse-grained OPC showed a comparable number of microcracks, fine-grained OPC exhibited more than twice the number of microcracks. In this sense, high hydration kinetics induce more microcracks, promoting later coalescence into visible cracks and disintegration of concrete at the end. Therefore, durable concrete with minimum microcracks should be derived from slow hydration kinetics or alkali-activation processes. [ABSTRACT FROM AUTHOR]

The risk of the releasing of nanometric particles from construction materials with nanometric components might be one of the biggest threats to further development of them. One of the possible ingress routes to human organisms is the respiratory system. Therefore, it is crucial to determine the risk of emission of nanometric particles during material usage. In the presented paper, abrasion of mortar samples with nanometric TiO2 was investigated. A special abrasion test setup was developed to reflect everyday abrasion of the concrete surface of pavements. In the study, three TiO2-modifed mortar series (and respective reference series) underwent the developed test protocol and the grains were mobilized from their surface due to the applied load analyzed (granulation, morphology, and chemical composition). For a comparative analysis, an abrasion parameter was developed. Based on the obtained results, the modification of cementitious composites with nanometric TiO2 contributed to a reduction in the emission of aerosols and, therefore, confirmed the compatibility between TiO2 and cement matrix. [ABSTRACT FROM AUTHOR]

Soil concrete is a material produced by mixing the soil at the site with a hydraulic binder. This paper aims to study the influence of the nature of binder on the physical and mechanical properties of soil concrete. For the mixtures, three types of soil were chosen and studied: sandy clay with a granular class of 0/5 (SA5), laterite with a granular class of 0/5 (LA5), and laterite with a granular class of 0/10 (LA10). Three different cements were used: CEM I 52.5, CEM II 42.5, and CEM III 32.5, with cement contents of 150 and 250 kg/m3. The soil concretes were designed for a constant spread of 32–33 cm measured on a mini-slump. The results showed that LA5-based soil concrete has a higher water content of about 8.8% more than SA5 and LA10-based soil concretes. For all the mixtures, the lowest porosity values were obtained with CEM III 32.5, followed by CEM I 52.5, and finally CEM II 42.5. For the three types of cement and the same soil granular size, the compressive strength, static, and dynamic modulus of SA5-based soil concretes are higher than LA5. It was noted that the mechanical properties of soil concretes made with CEM III 32.5 are higher than those made with CEM I 52.5 and CEM II 42.5. Regardless of the type of cement used, the mechanical properties obtained on LA10-based soil concrete are higher than those on LA5-based soil concrete. [ABSTRACT FROM AUTHOR]

Desert areas contain abundant desert sand (DS) resources, and high-volume recycling of DS resources as components of cement-based materials can achieve high-value applications. In this paper, DS was processed into desert sand powder (DSP) and replaced with cement in high volumes (20 wt.%–60 wt.%) to produce cement pastes. The mechanical properties, heat evolution, nanomechanical characteristics, microstructure, and economic and environmental impact of cement pastes were studied. The results show that adding 20 wt.% DSP increases the compressive strength of pastes and accelerates cement hydration, compared with the control group (0 wt.% DSP). Meanwhile, incorporating an appropriate amount of DSP (20 wt.%) effectively reduces porosity, increases the proportion of harmless and less harmful pores, and reduces the proportion of more harmful pores. From the perspective of nanoscopic properties, the addition of 20 wt.% DSP increases the C-S-H volume fraction, especially enhancing the transformation of low-density C-S-H to high-density C-S-H. Notably, the sample incorporating 60 wt.% DSP exhibits the lowest values for CI coefficients (13.02 kg/MPa·m3) and Cp coefficients (2.29 USD/MPa·m3), thereby validating the application of high-volume DSP feasibility in cement-based materials. [ABSTRACT FROM AUTHOR]

Cement-based materials encompass a broad spectrum of construction materials that utilize cement as the primary binding agent. Among these materials, concrete stands out as the most commonly employed. The cement, which is the principal constituent of these materials, undergoes a hydration reaction with water, playing a crucial role in the formation of the hardened composite. However, the exothermic nature of this reaction leads to significant temperature rise within the concrete elements, particularly during the early stages of hardening and in structures of substantial thickness. This temperature rise underscores the critical importance of predictive modeling in this domain. This paper presents a review of modeling approaches designed to predict temperature and accompanying moisture fields during concrete hardening, examining different levels of modeling accuracy and essential input parameters. While modern commercial finite element method (FEM) software programs are available for simulating thermal and moisture fields in concrete, they are accompanied by inherent limitations that engineers must know. The authors further evaluate effective commercial software tools tailored for predicting these effects, intending to provide construction engineers and stakeholders with guidance on managing temperature and moisture impacts in early-age concrete. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the effect of calcium nitrite (CN) on improving the mechanical properties and microstructures of early-frozen cement paste. Cement pastes containing 1%, 1.5%, 2%, 2.5%, and 3% CN were prepared. One batch of samples was frozen at −6 °C for 7 days and then cured at 20 °C, and the other batch of samples was directly cured at 20 °C as a control. The compressive strength, ultrasonic pulse velocity, and resistivity of all specimens at different target ages were measured under these two curing conditions. The hydration products and microstructures of typical samples were observed using XRD and scanning SEM. The results showed that the addition of 1.5% CN could promote cement hydration and enhance slurry densification, thereby increasing the compressive strength, ultrasonic pulse velocity, and electrical resistivity of the slurry, and positively affecting the early freezing resistance of the slurry. However, when the CN dosage exceeded 1.5%, the internal structure of the slurry was loose and porous due to the generation of a large amount of nitrite–AFm, which negatively affects the properties of the cement paste. In addition, the effectiveness of CN is only limited to temperature environments above −6 °C. Concrete antifreeze suitable for lower temperatures still requires further research. [ABSTRACT FROM AUTHOR]

Magnesium oxychloride cement (MOC), an alternative to ordinary Portland cement (OPC), has attracted increasing research interest for its excellent mechanical properties and its green and sustainable attributes. The poor water resistance of MOC limited its usage mainly to indoor applications; nevertheless, recent advances in water-resistant MOC have expanded the material's potential applications from indoor to outdoor. This review aims to showcase recent advances in MOC, including water-resistant MOC and ductile fiber-reinforced MOC (FRMOC), exploring their potential applications including in sustainable construction for future generations. The mechanism under different curing procedures such as normal and CO2 curing and the effect of different inorganic and organic additives on the water resistance of MOC composites are discussed. In particular, the review highlights the recent developments in achieving over 100% strength retention under water at 28 days as well as advancements in FRMOC, where tensile strength has surpassed 10 MPa with a remarkable strain capacity ranging from 4–8%. This paper also sheds light on the potential applications of MOC as a fire-resistant coating material, green-wood-MOC composite building material, and in reducing solid waste industrial byproduct accumulations. Finally, this study suggests future research directions to enhance the practical application of MOC. [ABSTRACT FROM AUTHOR]

The utilization of bio-fiber materials in building components has become imperative for improving sustainability, controlling global warming, addressing environmental concerns, and enhancing concrete properties. This study is part of a wide-range investigation on the use of Phragmites-Australis (PhA) fibers in construction and building materials. In this paper, the volume stability and mechanical properties of paste containing PhA fibers and exposed to high temperatures were investigated. Four mixes were made with 0, 0.5, 1, and 2% fibers by volume. To evaluate the volume stability and mechanical properties, the chemical shrinkage, autogenous shrinkage, drying shrinkage, expansion, ultrasonic pulse velocity, compressive strength, and flexural strength were tested. The curing duration and temperature were 180 days and 45 °C, respectively. The results indicated that an addition of PhA fibers of up to 2% resulted in a reduction in all the shrinkage parameters at 180 days. The presence of PhA fibers in the paste tended to reduce the compressive strength, with the lowest value observed at 2%. Apart from the values at 90 days, the optimal flexural strength seemed to be achieved by the paste with 1% PhA fibers. To further elucidate the experimental results, a hyperbolic model was employed to predict the variation in the length change as a function of the curing age with a high accuracy. Based on the results obtained, PhA fibers can play a crucial role in mitigating the shrinkage parameters and enhancing the mechanical properties of cement paste. [ABSTRACT FROM AUTHOR]

Additives such as nano-silica and fly ash are widely used in cement and concrete materials to improve the rheology of fresh cement and concrete and the performance of hardened materials and increase the sustainability of the cement and concrete industry by reducing the usage of Portland cement. Therefore, it is important to study the effect of these additives on the rheological behavior of fresh cement. In this paper, we study the pulsating Poiseuille flow of fresh cement in a horizontal pipe by considering two different additives and when they are combined (nano-silica, fly ash, combined nano-silica, and fly ash). To model the fresh cement suspension, we used a modified form of the power-law model to demonstrate the dependency of the cement viscosity on the shear rate and volume fraction of cement and the additive particles. The convection–diffusion equation was used to solve for the volume fraction. After solving the equations in the dimensionless forms, we conducted a parametric study to analyze the effects of nano-silica, fly ash, and combined nano-silica and fly ash additives on the velocity and volume fraction profiles of the cement suspension. According to the parametric study presented here, larger nano-silica content results in lower centerline velocity of the cement suspension and larger non-uniformity of the volume fraction. Compared to nano-silica, fly ash exhibits an opposite effect on the velocity. Larger fly ash content results in higher centerline velocity, while the effect of the fly ash on the volume fraction is not obvious. For cement suspension containing combined nano-silica and fly ash additives, nano-silica plays a dominant role in the flow behavior of the suspension. The findings of the study can help the design and operation of the pulsating flow of fresh cement mortars and concrete in the 3D printing industry. [ABSTRACT FROM AUTHOR]

Nowadays, the sustainable development of the construction industry has become a focus of attention. Crushing and grinding waste seashells originating from the fishery industry, such as oyster shells, cockle shells, mussel shells, and scallop shells, into different particle sizes for usage as aggregate and cement in concrete or mortar provides an effective and sustainable solution to environmental problems by reducing natural resource dependence. Numerous studies have attempted to analyze the suitability of waste seashell as a possible alternative to natural aggregates and cement in concrete or mortar. This paper presents an up-to-date review of the characteristics of different types of waste seashell, as well as the physical, mechanical, durability, and other notable functional properties of seashell concrete or mortar. From the outcome of the research, waste seashell could be an inert material, and it is important to conduct a series of proper treatment for a better-quality material. It is also seen from the results that although the mechanical properties of seashell concrete have been reduced, they all meet the required criteria set by various international standards and codes. Therefore, it is recommended that the replacement of seashells as aggregate and cement should not exceed 20% and 5%, respectively. Seashell concrete or mortar would then have sufficient workability and strength for non-structural purposes. However, there is still a lack of investigation concerning the different properties of reinforced concrete members using seashells as the replacement of aggregate or cement. Further innovative research can solidify its utilization towards sustainable development. [ABSTRACT FROM AUTHOR]

The Intergovernmental Panel on Climate Change (IPCC), which is the United Nations body for assessing the science related to climate change, has recently recognized the natural carbonation process as a way of carbon offsetting with mortar and concrete. Accordingly, this activity could be recognized as a carbon removal process for which certification should be granted. The aim of the certification of carbon removal is to promote the development of adequate and efficient new carbon removal processes. Therefore, the main objective of this study is to provide reliable results on carbon dioxide uptake by cement-based materials in Spain. Yearly, greenhouse gas emissions are reported to the United Nations Framework Convention on Climate Change (UNFCCC) by each country, and the natural carbonation should be added up to the carbon accounting. Therefore, natural carbonation should be included in the IPCC Guidelines for National Greenhouse Gas Inventories, and such accounting information should be made available promptly to the national regulatory authorities. This paper provides the results of carbon dioxide uptake by Spanish cement-based materials from 1990 to 2020 by using an easy method of estimating the net carbon dioxide emissions (simplified method) considering the carbon dioxide released by the calcination during clinker production (process emissions). The outcome of this study reveals that there was 93,556,000 tons of carbon dioxide uptake by the mortar and concrete manufactured in Spain from 1990 to 2020. [ABSTRACT FROM AUTHOR]

Calcined mixed clays are one of the most promising alternative supplementary cementitious materials. However, their standardized use is difficult due to the wide range of compositions of the raw materials. The reactivity potential of different clays can hardly be estimated on the basis of simple characteristics so far. This review aims to identify and compile the factors that determine reactivity. At first, an overview of the methods to evaluate reactivity is presented in order to provide a definition of this term. Subsequently, the reactivity-determining factors are compiled and subdivided into the characteristics of the raw material (chemical and mineralogical composition), the parameters of calcination (furnace type, temperature, grain size, retention time, and cooling), and the characteristics of the calcined material (physical properties and amorphous phase). Interrelations are discussed qualitatively. In the second step, a quantitative literature analysis was conducted to quantify correlations between the different factors and reactivity. However, since the characterization methods in the literature are very different, the data can hardly be analyzed quantitatively. Consequently, this paper points out what information is needed to conduct profound, comparable studies to evaluate the reactivity potential of clays. [ABSTRACT FROM AUTHOR]

The current derivation and application of traditional culture lack a scientific procedural method, and the existing processes are overly cumbersome and complex. The transformation of flat patterns requires manual modeling by professional product designers, resulting in low efficiency, especially when dealing with intricate patterns. To address these issues, this paper takes Xiamen cement encaustic tiles as an example and establishes a standardized process from the extraction of cultural elements to the 3D printing of physical products. Additionally, a one-click transformation plugin from flat patterns to three-dimensional models is developed based on the QT framework and Grasshopper platform. This plugin utilizes an edge recognition algorithm to identify the transformed patterns as editable NURBS curves. The curves are then converted into surfaces using the plugin's modeling functionality before being encapsulated. With the encapsulated plugin, users only need to input a PNG image of the desired pattern and the basic model of the desired product to obtain a product with the structural features of the specified pattern. This research aids product designers in quickly extracting the most distinctive features, significantly accelerating the development speed of cultural and creative product transformations, improving production efficiency. The simplified operational process enables more people to participate in the design of cultural and creative products, promoting the dissemination and integration of traditional culture with modern technology. [ABSTRACT FROM AUTHOR]

Recycling of multi-source solid waste is of great benefit to energy conservation and environmental governance. In this paper, a new type of environmental protection concrete for railway accessory facilities was prepared from silicon-manganese slag, steel slag, fly ash and recycled macadam. Seven kinds of concrete with different mix proportions were designed. Through unconfined compressive strength, splitting, drying shrinkage and temperature shrinkage tests, the multivariate changing trends of steel slag content, cement dosage and age on the anti-interference ability of concrete were investigated. The main mechanisms of the development of mechanical and dry shrinkage properties were revealed by the hydration process of 3SR-60. The results show that 3SR-60 had better mechanical strength under the same cement dosage. The temperature shrinkage strain decreased and then increased with the rise of the proportion of waste residue, increased with the addition of cement dosage and decreased first and then increased with the descent in the temperature. The temperature shrinkage coefficient reached the lowest value at 0–10 °C. The drying shrinkage coefficient decreases with the increase in the proportion of waste residue and increases with the increase in cement dosage. The dry shrinkage strain increased rapidly during the first 8 days and became almost constant after 30 days. Cementation of calcium silicate hydrate (C-S-H) and ettringite (AFt) developed continuously and filled the internal pores of the structure, interlocking and cementing with each other, which made the microstructure develop from a three-dimensional network to a dense complex, and the macro dimension was reflected in the enhancement of the power to resist external interference. The conclusion of the test summarized that SR-60 had preferable mechanical and shrinkage performance. [ABSTRACT FROM AUTHOR]

The slag generated as a by-product of the steelmaking process can be used to manufacture cement, reducing the generated waste and contributing to the circular economy. Currently, steelmaking companies promote long-term bilateral deals with one or few cement companies where the price is fixed, and the slag is a treated as commodity. We propose a new solution, which promotes slag reuse through its differentiation with a composition-based grouping and an auction. This process is carried out in a blockchain network, which increases trust in the system, provides guarantees about the slag composition to cement companies and helps external regulators to reliably extract circularity indicators. [ABSTRACT FROM AUTHOR]

In this study, the characteristics of grout mixed with charcoal as an expansive agent were examined to reduce the pre-hardening shrinkage of cementitious materials. This study compared and reviewed the application of CSA, a conventional expansive agent, to grout. The setting time, fluidity, compressive strength, and pre-hardening shrinkage/expansion were evaluated to explore the usability of charcoal as an expansive agent. The test results confirmed that, as the incorporation rate of charcoal increased, the pre-hardening expansion rate of the grout also increased, making it more effective for pre-hardening expansion than the conventional expansive agent CSA. However, when charcoal was used as an expansive agent, the compressive strength decreased after hardening, indicating the need for caution regarding the amount of charcoal used. Furthermore, the pre-hardening shrinkage and expansion rates of the various types of charcoal used in this study showed some differences, suggesting the need for further research on the internal pore volume and pore size of the charcoal. [ABSTRACT FROM AUTHOR]

This study investigates the post-liquefaction monotonic undrained shearing behavior of cemented sand at the macro- and microscales, using the discrete element method. A series of cyclic undrained triaxial tests with different stress amplitudes and post-liquefaction monotonic undrained triaxial tests were simulated on cemented sand with diverse cement contents (CCs). For comparison, a series of monotonic undrained triaxial tests on cemented sand without liquefaction (virgin cemented sand) were also modeled. The macroscopic behavior was analyzed in conjunction with the microscopic characteristics of the assembly, such as the deviator fabric of contact normal orientation, mechanical coordination number, energy components, and bond breakage. The results show that the DEM model can capture the effect of CC and cyclic stress ratio (CSR) on the undrained shear strength, stiffness, and pore pressure observed in laboratory experiments. Referring to the virgin specimen, with an increase in CC, the mechanical coordination number and the input work increment increase, while the deviator fabric for total contacts changes irregularly, leading to a greater initial stiffness and shear strength. In the case of the liquefied specimen, the smaller initial mechanical coordination number results in a very low initial stiffness regardless of CC. Contrary to the uncemented sand, both the mechanical coordination number and the input work increment decrease with an increasing CSR for the cemented sand. The microstructure evolution governs the effect of cementation level and liquefaction history on the macroscopic post-liquefaction behavior. [ABSTRACT FROM AUTHOR]

Assessing the sustainability of material-based products now encompasses social sustainability, a vital aspect often overlooked. Even though the existing frameworks provide a starting point, they do not often differentiate between the assessment criteria when making comparisons within one specific material category, which has made sustainability assessments more focused on environmental and economic aspects. This study addresses this critical gap by pioneering a social assessment framework curated to help practitioners to choose the most sustainable cement type out of the standard cement types used in the industry. Utilizing the Fuzzy Analytic Hierarchy Process (FAHP) and linear-scoring method, criteria weights were systematically assigned based on scoring by industry and academic experts. The findings highlight the importance of integrating social sustainability with environmental and economic factors in cement selection. Unlike traditional material selection, which primarily considers cost and performance, green material selection emphasizes the holistic impact of materials, including social factors. Variations in weightage decisions among experts highlight the influence of practical experience, research interests, and context. Functionality emerges as a crucial criterion. The ranking of cement types based on social scores places CEM II/B-M at the top, followed by CEM IV/A, CEM II/A-S, CEM II/A-V, CEM I, and CEM II/A-LL. The evolving nature of sustainability necessitates ongoing research to refine and expand existing frameworks for a more sustainable construction industry. [ABSTRACT FROM AUTHOR]

This study aimed to compare the biological properties of newly synthesized cements based on calcium phosphate with a commercially used cement, mineral trioxide aggregate (MTA). Strontium (Sr)-, Copper (Cu)-, and Zinc (Zn)-doped hydroxyapatite (miHAp) powder was obtained through hydrothermal synthesis and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDX). Calcium phosphate cement (CPC) was produced by mixing miHAp powder with a 20 wt.% citric acid solution, followed by the assessment of its compressive strength, setting time, and in vitro bioactivity. Acetylsalicylic acid (ASA) was added to the CPC, resulting in CPCA. Biological tests were conducted on CPC, CPCA, and MTA. The biocompatibility of the cement extracts was evaluated in vitro using human dental pulp stem cells (hDPSCs) and in vivo using a zebrafish model. Antibiofilm and antimicrobial effect (quantified by CFUs/mL) were assessed against Streptococcus mutans and Lactobacillus rhamnosus. None of the tested materials showed toxicity, while CPCA even increased hDPSCs proliferation. CPCA showed a better safety profile than MTA and CPC, and no toxic or immunomodulatory effects on the zebrafish model. CPCA exhibited similar antibiofilm effects against S. mutans and L. rhamnosus to MTA. [ABSTRACT FROM AUTHOR]

The present work analyses the physical characteristics of aggregates recovered with the waterjigging process from comminuted concrete. In this work, conventional concrete (C16/20) was crushed to a top size of 20 mm with a jaw crusher and classified in a size range of 5 to 20 mm. The densimetric distribution analysis was carried out in a densimetric range of 2.4 to 2.8 g/cm3, and the cement paste was dissolved from all granulometric ranges to analyze the composition (sand, cement paste, and aggregates) of each part and define the possibilities of materials to recover. A two-stage water jig concentration process was used, generating a cleaner material in the first stage and a re-cleaner material in the second jigging stage. The physical properties of the material inserted in the feed and the material generated in the first and second stages were analyzed to compare them with natural aggregates. The results indicate the viability of recovering 47.8% of the coarse aggregates present in the concrete feed in the re-cleaner material, with 84% of particles having a density higher than 2.6 g/cm3. These characteristics are similar to those found in natural aggregates. [ABSTRACT FROM AUTHOR]

In China, airports predominantly utilize airport cement concrete pavement, which inevitably undergoes deterioration in service. To uphold pavement durability and functionality, and ensure aircraft operational safety, prompt repairs of affected areas are imperative. Therefore, ordinary Portland cement mortars were used as the control group to compare and analyze the bonding performances of two common airport pavement repair materials: modified Portland cement mortars and phosphate cement mortars. Meanwhile, through microscopic experiments, the microscopic characteristics of the interfacial transition zone (ITZ) were studied, and the interface bonding mechanism was analyzed. The research results indicate that the interface bonding strength between phosphate cement mortar and old concrete pavement is the highest. This was because the elements in phosphate cement penetrated the old concrete pavement through hydration reactions, forming van der Waals forces and chemical bonding forces. In addition, the research results indicated that the presence of old concrete pavement made the three repair materials produce similar sidewall effects with the old concrete pavement, leading to a low hydration degree of the repair materials. However, the chemical bonding and penetrating structure of phosphate cement compensated for the weakening effect of the ITZ in the repair materials. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between the molecular structure and foaming of poly(ethylene glycol) and poly(propylene glycol) triblock copolymers in Portland cement pastes. Four copolymers with different molecular structures were studied at varying concentrations. All copolymers showed a reduction in surface tension of the cement pore solution; however, only some of them demonstrated foaming and air entraining in cement paste. The results indicated that the molecular structure parameter, hydrophilic-to-lipophilic balance (HLB), has a direct relationship with the foaming and air-entraining performance of the copolymers. The total organic carbon measurements showed very small adsorption of these non-ionic copolymers on hydrating cement particles due to the lack of surface charge needed to interact with the heterogeneously charged surface of hydrating cement. In addition, these copolymers did not seem to affect the flow of cement paste due to a lack of adsorption on cement particles. The cement paste modified with the copolymers showed increased water sorption compared to the control paste due to the increased capillary porosity and slight increase in pore surface hydrophilicity. However, the freeze-thaw resistance was shown to improve with an increase in the number of air voids in the modified cement pastes. The findings establish the relationship between molecular properties of copolymers and their air-entraining performance in cement paste to mitigate the damages caused by freeze-thaw action. [ABSTRACT FROM AUTHOR]

This research employs response surface methodology (RSM) to optimize and model ultra-high-performance concrete (UHPC) formulations, integrating desert sand and varying proportions of supplementary cementitious materials (SCMs), specifically fly ash (FA) and ground granulated blast furnace slag (GGBS). By investigating the influence of desert sand and SCM contents, the study aims to discern their impact on the workability and 7-day compressive strength of UHPC. Employing a central composite design (CCD), thirteen separate mixes were formulated. Key responses, namely workability and compressive strength, were evaluated. The developed models underscore the enhancement in UHPC performance through the partial replacement of cement with SCMs. Notably, an optimal combination of 75% desert sand and 30% SCMs resulted in a workability of 69.4 mm and a 7-day compressive strength of 46.01 MPa. The findings emphasize the potential for eco-friendly concrete in the construction industry, also prompting further exploration into long-term strength and higher SCM concentrations. [ABSTRACT FROM AUTHOR]

Background and Objectives: Osteoporosis renders the use of traditional interbody cages potentially dangerous given the high risk of damage in the bone–implant interface. Instead, injected cement spacers can be applied as interbody devices; however, this technique has been mainly used in cervical spine surgery. This study aimed at investigating the biomechanical behavior of cement spacers versus traditional cages in lumbar spine surgery. Materials and Methods: Destructive monotonic axial compression testing was performed on 20 human cadaveric low-density lumbar segments from elderly donors (14 f/6 m, 70.3 ± 12.0 y) treated with either injected cement spacers (n = 10) or traditional cages (n = 10) without posterior instrumentation. Stiffness, failure load and displacement were compared. The effects of bone density, vertebral geometry and spacer contact area were evaluated. Results: Cement spacers demonstrated higher stiffness, significantly smaller displacement (p < 0.001) and a similar failure load compared to traditional cages. In the cage group, stiffness and failure load depended strongly on bone density and vertebral height, whereas failure displacement depended on vertebral anterior height. No such correlations were identified with cement spacers. Conclusions: Cement spacers used in lumbar interbody stabilization provided similar compression strength, significantly smaller failure displacement and a stiffer construct than traditional cages that provided benefits mainly for large and strong vertebrae. Cement stabilization was less sensitive to density and could be more beneficial also for segments with smaller and less dense vertebrae. In contrast to the injection of cement spacers, the optimal insertion of cages into the irregular intervertebral space is challenging and risks damaging bone. Further studies are required to corroborate these findings and the treatment selection thresholds. [ABSTRACT FROM AUTHOR]

Ultrahigh-performance fiber-reinforced cement-based composite (UHPFRC) made with waste derived from scrap tires and oil refineries was tested in this study. The UHPFRC sample exhibited a maximum compressive strength of about 189 MPa at the end of 28 days. Steel fibers were recovered from scrap tires and were added up to 3% by volume in the UHPFRC samples. Such additions reduced cement flow by 11% but improved compressive strength by 21%. The equilibrium catalyst particles (ECAT) disposed of by oil refineries were used in amounts of up to 15% by weight as a replacement for cement in such UHPFRC samples. These aluminosilicate materials are spherical in shape and have a porous microstructure, which was found to reduce the cement flow by absorbing more free water onto their surfaces. They also reduced the heat and strength developments at early stages. However, the total cost of the final cement-based mixture and associated CO2 emissions were reduced by up to 7% and 15% due to the inclusion of the ECAT particles. These findings help to optimize the ECAT and recovered steel fibers in the UHPFRC mix design, and such waste valorization strategies can help achieve the goal of becoming carbon neutral. [ABSTRACT FROM AUTHOR]

Globally, the demand for single-use plastics has increased due to the rising demand for food delivery and household goods. This has led to environmental challenges caused by indiscriminate dumping and disposal. To address this issue, non-degradable plastics are being replaced with biodegradable alternatives. Polylactic acid (PLA) is a type of biodegradable plastic that has excellent mechanical properties. However, its applications are limited due to its low crystallinity and brittleness. Studies have been conducted to combat these limitations using carbon or inorganic nucleating agents. In this study, waste cement and PLA were mixed to investigate the effect of the hybrid inorganic nucleating agent on the crystallinity and mechanical properties of PLA. Waste cement accelerated the lamellar growth of PLA and improved its crystallinity. The results indicate that the flexural and impact strengths increased by approximately 3.63% and 76.18%, respectively. [ABSTRACT FROM AUTHOR]

The concrete slurry waste (CSW) produced by concrete mixing plants is a type of hazardous waste that is difficult to handle. To better recycle the CSW separated from the aggregates, this study uses a variety of wet-grinding processes to refine the solid in it, replaces some of the cement with the solid particles in wet grinding concrete slurry waste (WCSW), and investigates the properties of WCSW and its effect on the hydration and hardening properties of cement. The results show that a suitable wet-grinding process can ensure that the particle size in WCSW is less than 10 μm, the particle morphology is more flat, and the degree of hydration is higher. The WCSW particles can promote early cement hydration; after adding WCSW, the heat release peak of cement hydration appears earlier and more early hydration products are produced, and with the increase in the substitution amount, the promoting effect on early cement hydration will be more significant. The WCSW particles have a great effect on improving the strength of mortar, especially in the early stage. At 1 d, when the substitution amount is 7.5 wt.%, the compressive and flexural strength is increased by 43.67% and 45.04%; this is related to the filling of matrix pores and the improvement of the interface transition zone by micro- and nanoparticles. After the wet grinding of CSW, fine WCSW particles are obtained, which can improve the performance of cement-based materials by replacing cement. [ABSTRACT FROM AUTHOR]

The hydrophilic and porous structure of cement-based concrete materials makes it vulnerable to various harmful ions dissolved in water in the environment or during the freeze–thaw cycle, resulting in a significant decline in durability. Therefore, the introduction of hydrophobic hydroxyl silicone oil with good chemical stability and excellent hydrophobic properties during the process of concrete preparation to achieve the hydrophobic modification of its internal holes has very positive significance in terms of improving its durability. In order to disperse the hydrophobic hydroxyl silicone oil evenly in the internal pores of the concrete, synthetic non-ionic polyether-modified silicone oil was used as an emulsifier to make it a water-soluble emulsion. The influences of the composition of the emulsifier on the dispersion, water contact angle, water absorption, porosity, and compressive strength of cement mortar were investigated. The results show that when the emulsion content is 0.5%, the pore volume of the cement mortar decreases by 15%, and the maximum contact angle reaches 128°, which is conducive to improving the anti-erosion and anti-freezing properties of concrete and provides a new solution for the preparation of high-durability concrete. However, the introduction of polyether-modified silicone oil increases the number of large holes in the cement mortar, and leads to an increase in water absorption and a decrease in compressive strength. It is necessary to further optimize the composition of emulsifier in future work. [ABSTRACT FROM AUTHOR]

South Africa is endowed with a wealth of coal-fired power stations that can produce extremely high volumes of fly ash per year exceeding 34 million tonnes. The use of high-volume fly ash (HVFA) binders in the construction sector has the capacity to significantly reduce greenhouse gas emissions associated with traditional cement production and offset the carbon footprint of Eskom. The excessive production of fly ash by Eskom warrants the need for developing ultra-high-volume fly ash binders (UHVFA, fly ash/binder > 60 wt%). Nonetheless, fly ash (FA) replacement of cement is still largely limited to 35% regardless of more ambitious research indicating the potential to surpass 60%. In view of the urgent need for South Africa to offset and reduce its carbon footprint, this work reviews and summarises the literature on the performance of HVFA binders with a focus on two specific areas: (i) strength and (ii) durability. On HVFA binder strength, the focus is drawn on work that analysed the compressive strength, flexural strength, and split tensile strength. This review focuses on the extant literature analysing the durability of HVFA binders using various tests, including sorptivity, resistivity, permeability, tortuosity, rapid chloride penetration tests, resistance to sulphate attack, and microstructural analysis. As the FA content increases towards optima, i.e., 50–80%, the most indicative composite characteristics of the strength and durability properties are UCS (30–90 MPa) and permeability (low). This review reveals the leading methodologies, instrumentation, findings, challenges, and contradictions. [ABSTRACT FROM AUTHOR]

Urbanization and demographic growth have led to increased global energy consumption in recent years. Furthermore, construction products and materials industries have contributed significantly to this increase in fossil fuel use, due to their significant energy requirements, and consequent environmental impact, during the extraction and processing of raw materials. To address this environmental problem, architectural design and civil engineering are trying to implement strategies that enable the use of high-performance materials while minimizing the usage of energy-intensive or toxic and dangerous building materials. These efforts also aim to make buildings less energy-consuming during their useful life. Using waste materials, such as Construction and Demolition Waste (CdW), is one of the most promising approaches to address this issue. In recent years, the European Union (EU) has supported recovery strategies focused on using CdW, as they account for more than 30% of the total waste production in the EU. In this regard, reuse techniques—such as incorporating concrete fragments and bricks as road floor fillers—have been the subject of targeted scientific research. This review will outline various strategies for producing green cement and concrete, particularly emphasizing the reuse of Construction and Demolition Waste (CdW). [ABSTRACT FROM AUTHOR]

Currently, oyster shell powder (OSP) is becoming more widely used in the production of cement-based materials. The purpose of this study is to propose a predictive model that can predict the properties of concrete materials incorporating oyster shell powder. The methods of this prediction model are given as follows. First, based on the measurement results of the heat of hydration in the first 7 days, the prediction parameters of the hydration model are obtained. Secondly, based on the hydration model, the measured results of the heat of hydration were extrapolated, and the heat of hydration from the start of stirring to day 28 was calculated. From the calculation results, the developments of compressive strength, ultrasonic velocity, and surface electrical resistivity were estimated. Finally, we evaluated the CO2 emissions of concrete incorporating oyster shell powder. The CO2 emissions corresponding to unit compressive strength and unit surface electrical resistivity were calculated. The important conclusions of the prediction model are given as follows. First, for different substitution amounts of oyster shell powder, the model result shows that the ultimate value of the heat of hydration corresponding to the unit cement mass is the same, i.e., 454.27 J/g. While the substitution amount of oyster shell powder increases from 0% to 30%, the model result shows that the cumulative 28-day hydration heat for 1 g cement increases the powder amount from 405.7 J/g to 419.3 J/g. Secondly, as the amount of substituted oyster shell powder increases from 0% to 30%, the model result shows that the cumulative 28-day heat of hydration per gram of cementitious material decreases this amount from 405.7 J/g to 293.4 J/g. Compressive strength, ultrasonic pulse velocity, and surface electrical resistivity can all be expressed as exponential functions of the heat of hydration. For compressive strength, ultrasonic pulse velocity, and surface electrical resistivity, the coefficients of determination for the simulation results and experimental results are 0.8396, 0.7195, and 0.9408, respectively. Finally, as the amount of substituted oyster shell powder increases from 0% to 30%, the model result shows that the CO2 emission per unit of compressive strength increases from 10.18 kg/MPa to 16.51 kg/MPa. As the amount increases from 0% to 30%, the model result shows that the CO2 emission corresponding to the unit surface electrical resistivity does not change significantly. In summary, the importance of this model is that it can predict various properties of concrete mixed with oyster shell powder, reduce the number of experiments, and promote the engineering application of oyster shell powder concrete. [ABSTRACT FROM AUTHOR]

Although quartz powder is a common concrete filling material, the importance and originality of this study lies in the development of a hydration model for quartz powder–cement binary mixtures and the adoption of this model to predict the development of concrete material properties. The purpose of this study is to use this model to promote the material design of environmentally friendly concrete and to elucidate the relationships in the development of the various properties of quartz powder concrete. The method used in this study was as follows: The parameters of the hydration model were obtained through seven days of hydration heat experiments. The hydration heat up to 28 days was also calculated, and the various properties of the concrete were predicted from the heat of hydration. The main findings of this study were as follows: (1) The ultimate hydration heat released per gram of cement for the different quartz powder substitution rates and quartz powder particle fineness was the same, at 390.145 J/g cement, as was the shape index of the hydration model at −1.003. (2) Moreover, through the model calculations, we found that, at the twenty-eighth day of the curing period for the quartz powder specimens with different quartz powder substitution amounts and different fineness, the reaction level of the cement was similar, at 0.963, as were the values of the cumulative heat of hydration, with both at 375.5 J/g cement. (3) The model showed that, in the late stage (28 days) of hydration for quartz powders of different fineness and when the substitution amount was the same, the cumulative heat of hydration over 28 days was similar. (4) The properties of concrete were evaluated using the calculated hydration heat. Overall, the predictive performance of the power and linear functions was similar, with no significant differences being found. [ABSTRACT FROM AUTHOR]

The following study presents the results of research in the field of the performance of geopolymers consisting of Class F fly ash with an alkaline activator solution consisting only of sodium metasilicate (Na2SiO3) and water. The performances of this geopolymer are compared to the those of American Petroleum Institute (API) Class G cement. This comparison is to evaluate the potential of the geopolymer as an alternative to cement in cementing hydrocarbon wells in the oil and gas industry. The gap in the research is determining the performance properties that restrict the use of fly ash in the oil and gas industry. Using only sodium metasilicate as an activator with water, the solution creates a strong binding gel for the geopolymer and activates the aluminosilicate properties of the fly ash. This geopolymer is compared with Class G cement without additives to determine their base performances in high pressure and high temperature conditions, as well as note any properties that are affected in the process. This commences by formulating recipes of these two materials from workable ratios and concentrations. The ratios are narrowed down to the best working models to proceed to comparative performance testing. The tests included exploring their vital performances in fluid loss and thickening time. The results produced suggest that Class G cement generally has less fluid loss at low temperature than the geopolymer but could not maintain its integrity and structure as temperatures increased. Class G cement exhibited stability, consistencies of 100 Bcs (Bearden Consistency Units), and a faster thickening time of 1 h and 48 min when placed under high temperature and high-pressure conditions, respectively. However, the geopolymer showed more consistency regarding fluid loss with respect to rising pressure and temperature, and smoother, less fractured samples emerging from both tests. Though the geopolymer showed stronger performances in thickening and water retention, the experiments showed that it is not a uniform and consistent material like Class G cement. Through the use of different additives and intricate design, the sample may show success, but may prove more difficult and complex to apply than the industry standard and uniform content of Class G cement. [ABSTRACT FROM AUTHOR]

In this research, the properties and cementitious performance of thermally activated cement pastes (referred to as DCPs) are investigated. Hydrated pastes prepared from Portland cement and slag blended cement were subjected to different thermal treatments: 350 °C for 2 h, 550 °C for 2 h, 550 °C for 24 h and 750 °C for 2 h. The properties and the reactivity as SCM of the DCPs were characterised as well as their effect on the mechanical performance and hydration of new blended cements incorporating the DCPs as supplementary cementitious materials (SCMs). It was observed that the temperature and duration of the thermal treatment increased the grindability and BET specific surface area of the DCP, as well as the formation of C2S phases and the reactivity as SCM. In contrast, the mechanical strength results for the blended cements indicated that thermal treatment at 350 °C for 2 h provided better performance. The hydration study results showed that highly reactive DCP interfered with the early hydration of the main clinker phases in Portland cement, leading to early setting and slow strength gain. The effect on blended cement hydration was most marked for binary Portland cement–DCP blends. In contrast, in the case of ternary slag cement–DCP blends the use of reactive DCP as SCM enabled to significantly increase early age strength. [ABSTRACT FROM AUTHOR]

The viability of incorporating agricultural by-products, such as oat husks, not yet explored in limestone-based composites, as more sustainable alternatives for use as novel aggregates may be improved through the adoption of well-known valorisation strategies applied to other plant-based resources. In this context, this work innovates by assessing how treatments on oat husk surfaces and the choice of limestone-based binders impact the mechanical performance of composites. The strategy adopted to achieve these objectives, in addition to carrying out the physical and geometric characterisation of the husks, consists of treating the husks' surface using washing cycles in water, cement/pozzolan binder, and linseed oil. Furthermore, matrices combining cement, calcium hydroxide Ca(OH)2, and microsilica (SiO2) were used. In conclusion, even though the effects of different binder combinations are inconsistent, coating oat husks—especially with linseed oil—works well in delaying particle degradation and improving mechanical strength compared to untreated particles. Furthermore, when aggregates are substituted with the longer and lamellar particles of oat husk, the impact of the water/cement ratio on mechanical performance and composite workability significantly decreases. [ABSTRACT FROM AUTHOR]

This study investigated the influences of ultrafine fly ash (UFA) and ultrafine slag powder (USL) on the compressive strengths, autogenous shrinkage, phase assemblage, and microstructure of magnesium potassium phosphate cement (MKPC). The findings indicate that the aluminosilicate fractions present in both ultrafine fly ash and ultrafine slag participate in the acid–base reaction of the MKPC system, resulting in a preferential formation of irregularly crystalline struvite-K incorporating Al and Si elements or amorphous aluminosilicate phosphate products. UFA addition mitigates early age autogenous shrinkage in MKPC-based materials, whereas USL exacerbates this shrinkage. In terms of the sustained mechanical strength development of the MKPC system, ultrafine fly ash is preferred over ultrafine slag powder. MKPC pastes with ultrafine fly ash show greater compressive strength compared to those with ultrafine slag powder at 180 days due to denser interfaces between the ultrafine fly ash particles and hydration products like struvite-K. The incorporation of 30 wt% ultrafine fly ash enhances compressive strengths across all testing ages. [ABSTRACT FROM AUTHOR]

In the production of cement, raw materials can be partially substituted by regenerable waste provided from glasses, construction and demolition waste in order to reduce the environmental problem and burden of landfills. In this study, limestone–silicate composites were synthesized using starting materials such as glass waste and lime, brick, autoclaved aerated concrete (ACC), mortar or plaster waste. The structure and mechanical properties of the nano-composite materials have been studied. The mean CaCO3 crystallite sizes are higher for composites containing ACC and brick than for doping with lime, mortar and plaster. Cement-based materials are formed by replacing 2.5% of the Portland cement with limestone–silicate composites. The results indicate new possibilities for introducing 2.5%of composites in cement paste because they promote the formation of the C-S-H network, which provides strength and long stability for the cement paste. The influence of varied types of mix composites in the expired cement on the initial cracking strain and stress, tensile strength and compressive strength were investigated. The compressive strength values of composite-expired cement specimens are situated between 11.8 and 15.7 MPa, respectively, which reflect an increase from 22.9 up to 63.54% over the compressive strength of expired cement matrix. [ABSTRACT FROM AUTHOR]

In the cement concrete manufacturing industry, mixers are critical pieces of equipment that play an essential role. Mixers ensure, by mechanically mixing the materials that make up the concrete, the homogeneity of the mixture. Since the active elements of the mixer in the concrete industry—the mixing blades—come into permanent contact with the mineral aggregates in the mixture formed by water and cement, they are permanently subjected to a strong abrasive–erosive wear process. The authors of this article were concerned with the establishment of tribological models for studying the wear of mixing blades, in order to identify the influence of their constructive parameters on the wear intensity. A complex model (Kraghelsky–Nepomnyashchi model) was adopted for the study. The modeling results revealed that the wear intensity decreases with an increasing blade angle of attack and increases linearly with increasing speed, as well as with an increasing friction coefficient. The modeling results confirm that the wear intensity is lowest when the mixing blade is inclined at a 60° angle, while the highest value is recorded for 30°. By identifying the angle at which the greatest wear of blades occurs, interventions can be made in the design of a more durable mixer (with the optimal installation angle of the mixer blades), thus requiring fewer corrective maintenance interventions. Based on these findings, we conclude that the complex model used in the experiment can provide a convenient and efficient tool for the study of erosive–abrasive phenomena. [ABSTRACT FROM AUTHOR]

The change in the corrosion activities of SS304 and the carbon steel A36 were studied during their exposure for 30 days to hybrid pumice-Portland cement extract (CE), to simulate the concrete–pore environment. The ionic composition and the initial pH (12.99) of the CE were influenced by the reduction of Portland cement (PC) content, volcanic pumice oxides and alkaline activators. Because of the air CO 2   dissolution, the pH decreased and maintained a constant value ≈ 9.10 (established dynamic ionic equilibrium). The CE promoted the passivation of both steels and their free corrosion potential (OCP) reached positive values. On the surfaces, Fe and Cr oxides were formed, according to the nature of the steel. Over the time of exposure, the presence of chloride ions in the pumice caused a localized pitting attack, and for carbon steel, this fact may indicate an intermediate risk of corrosion. The chloride effect was retarded by the accumulation of SO 4 2 − ions at the steel surfaces. Based on electrochemical impedance (EIS), the polarization resistance (Rp) and the thickness of the passive layers were calculated. Their values were compared with those previously reported for the steels exposed to CEs of Portland and supersulfated cements, and the hybrid cement was considered as a PC "green" alternative. [ABSTRACT FROM AUTHOR]

This study aims at the evaluation of different formulations of concrete made with calcined clays and limestone (LC3 cement) exposed to aggressive environments. The study includes the evaluation of fresh and hardened properties and a comprehensive evaluation of durability over 24 months. The inclusion of calcined clays in cement increases the specific surface area of the cements, and thus the water demand. However, the high reactivity of calcined clays compared to any other pozzolan, and the synergy that occurs with limestones, enables the use of cements with very low clinker content that achieve strengths similar to those of Portland. Comparisons of LC3 formulations with Portland cement and with concrete containing silica fume prove the superiority of calcined clays in terms of strength and durability. The best results are obtained with LC3-50 cement with 50% clinker produced through co-grinding. Results of concrete made with a blend of 70% Portland cement with 30% LC2 (60% calcined clay, 35% limestone, 5% gypsum, separate ground) are also promising. All concretes made with LC3 show good durability in terms of the results of effective porosity, chloride permeability, and resistivity tests. [ABSTRACT FROM AUTHOR]

The heat of hydration, mechanical properties, pozzolanic activity, and microscopic characteristics of cement pastes incorporating co-combusted fly ash (CCFA) were investigated, and the disparities between the CCFA/cement system and the coal fly ash (CFA) binding system were also compared. The results indicate a decrease in the heat of hydration for both CFA and CCFA samples, with a more pronounced trend observed as the fly ash content increased from 10% to 30%. The distinction in the early hydration between CFA and CCFA samples primarily manifested in the rate of heat release, potentially correlated with variations in the active Al2O3 content in the fly ash. Neither CFA nor CCFA samples exhibited significant cementitious activity at 3 days, functioning solely as inert fillers in the cement paste. By 3 and 28 days, the mechanical properties of both CFA and CCFA samples were inferior to those of pure cement paste. However, by 180 days of hydration, the compressive strength of CCFA-blended mortar notably increased, with the highest strength observed in the 10% CCFA-blended sample. Both CFA and CCFA samples produced the secondary hydration product C-A-S-H and demonstrated comparable consumption of calcium hydroxide (CH). These findings underscore the potential of CCFA as a supplementary cementitious material (SCM) and lay a foundation for its widespread adoption. [ABSTRACT FROM AUTHOR]

The interfacial bonding capacity between cement emulsified asphalt composite binder (CEACB) and reclaimed asphalt pavement (RAP) plays a critical role in improving the pavement performance of cold recycled asphalt emulsion mixtures (CRAEMs). This study aims to investigate the formation and development of the interfacial bonding capacity between CEACB and RAP. First, the dynamic wettability and the spreading behaviors of CEACB on RAP surfaces were explored according to the surface free energy theory. Second, digital image processing (DIP) technology was employed to recognize interfacial failure patterns. Lastly, the influence of internal and external factors on the interfacial bonding capacity between CEACB and RAP during the curing process was analyzed via grey relational analysis (GRA). The results indicate that a moderate cement content with a mass ratio of asphalt to cement equivalent to 1.0 can significantly enhance the wettability of CEACB on RAP surfaces. By appropriately prolonging the curing time and controlling the curing temperature, it is possible to increase the bonding strength between CEACB and RAP. Additionally, a strong correlation exists between initial wettability and ultimate bonding capacity during the bonding strength curing process. The good wettability that developed in the initial stage of interfacial strength formation relates to the decreased spalling rate of CEACB on the RAP surface. This study is not only devoted to understanding the mechanisms that can enhance CRAEM performance but also provides important guidance for practical engineering applications of cold recycled asphalt pavements. [ABSTRACT FROM AUTHOR]

As internal curing self-healing agents in concrete repair, the basic properties of superabsorbent polymers (SAPs), such as water absorption and release properties, are generally affected by several factors, including temperature and humidity solution properties and SAP particle size, which regulate the curing effect and the durability of cementitious composites. This study aimed to investigate the water retention capacities of SAPs in an alkaline environment over extended periods by incorporating liquid sodium silicate (SS) into SAP–water mixtures and examining the influence of temperature. The influence of SAP particle size on mortar's water absorption capacity and mechanical behavior was investigated. Two mixing techniques for SAPs (dry and pre-wetting) were employed to assess the influence of SAP on cement mortars' slump, mechanical properties, and cracking resistance. Four types of SAPs (SAP-a, SAP-b, SAP-c, and SAP-d), based on the molecular chains and particle size, were mixed with SS to study their water absorption over 30 days. The results showed that SAPs exhibit rapid water absorption within the first 30 min, exceeding 85% before reaching a saturation point, and the chemical and temperature variations in the water significantly affected water absorption and desorption. The filtration results revealed that SAP-d exhibited the slowest water release rate, retaining water for considerably longer than the other three types of SAPs. The mechanical properties of SAP mortar were reduced due to the addition of an SAP and the improved cracking resistance of the cement mortars. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive investigation into the mechanical properties of Basic Magnesium Sulfate Cement Concrete (BMSC) in comparison to Ordinary Portland Cement Concrete (OPC) within reinforced concrete components. The main objective is to evaluate BMSC's applicability for practical engineering purposes, with a focus on its with early high strength, improved toughness, and superior crack resistance compared to conventional concrete. Experimental procedures involved fabricating beam specimens using OPC concrete with a C40 strength grade, alongside BMSC beams with varying strength grades (C30, C40, and C50). These specimens underwent bending resistance tests to analyze crack patterns and mechanical characteristics. The findings reveal that BMSC beams demonstrate enhanced bending and tensile properties at equivalent strength grades compared to OPC beams. Particularly, cracking mainly occurred at the mid-span region of BMSC beams, characterized by narrower cracks, indicating superior crack resistance. However, it was noted that the toughness of BMSC beams decreases as the strength grade increases. The maximum mid-span deflection of the BMSC test beam was smaller than that of the OPC test beam, which was 3.8 mm and 2.6 mm, respectively. The maximum crack width of the OPC beam was 4.7 times that of the BMSC beam. To facilitate practical implementation, the study developed calculation models for estimating the crack bending distance and ultimate bending distance in BMSC beams, offering valuable tools for engineering design and optimization. Overall, this research provides significant insights into the mechanical behavior of BMSC, presenting potential advantages for structural engineering applications. [ABSTRACT FROM AUTHOR]

Soil stabilization problems like liquefaction, bearing capacity, permeability, excessive settlement and swelling can be solved by improving soil's engineering properties by using various methods. The use of fly ash as a stabilizer has become popular in recent years since it is eco-friendly and effective on soil stabilization, especially for fine-grained soils. This study investigated the reuse of fly ash as a stabilizer (5–25% by weight) and cement (constant 3% by weight) as an activator to enhance the geotechnical properties of poorly graded sand (SP). Standard proctor tests were conducted to determine optimum water content and maximum dry unit weight, followed by direct shear box, falling head permeability and CBR tests at the determined optimum water content. Direct shear box experiments were carried out at two relative densities (30% and 80%) and CBR experiments were performed after 7 and 28 days of curing time. The results demonstrated that the addition of fly ash and cement improved the geotechnical properties, including shear strength, permeability and bearing capacity of the fine sand soil. [ABSTRACT FROM AUTHOR]