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Abstract Aim to assess and compare the effect of mid-root perforation repair using Biodentine and Portland cement in single-rooted endodontically treated mandibular premolars in terms of stress distribution using finite element analysis (FEA) and fracture resistance test. Methods In the FEA, an extracted human mandibular premolar tooth was scanned using cone beam computed tomography, and a 3-dimensional (3D) solid model was created. A sound tooth model (ST), an endodontically treated model (ET), an instrumented and mid-root perforated and repaired by Biodentine model (BM), and perforated and repaired by Portland cement model (PCM) were the 4 models simulated. A vertical force of 300 N on the occlusal plane was applied. Evaluation of von Mises stress distribution and maximum displacement were investigated. In the fracture resistance in vitro study, 28 extracted premolars were selected and randomized into 4 groups, (n = 7), (A) is the negative control intact group, (B) is the positive control of endodontically treated group, (C) is mid-root perforated and repaired by Biodentine group and (D) is mid-root perforated and repaired by Portland cement. All Teeth were instrumented except for group A, group B was obturated while groups C and D were instrumented, perforated, repaired, and obturated. All groups were restored coronally except group A. Fracture force was measured; subsequently, the fracture repairability was evaluated. Finally, the data were statistically evaluated using one-way analysis of variance (ANOVA); the significance level was set at P ≤ 0.05 and the repairability of teeth after fracture was correlated to the maximum loading using Pearson’s coefficient tests. Results In FEA, Maximum von Mises stress was descending assorted as 121.1 MPa for ET, 115.6 MPa for BM and PCM, and 109 MPa for ST, and in the mid-root area or perforation site were 20 MPa for PCM, 16.17 MPa for BM, 10.16 MPa for ET and 8.1 MPa for ST while the Maximum Displacement was descending assorted as 0.0179 mm for ET, 0.0169 mm for BM and PCM and 0.0151 mm for ST. In the fracture resistance test, Group A showed higher fracture resistance than other groups significantly. There was a non-significant difference between Groups B, C, and D. There was also an insignificant correlation between the maximum loading and the repairability of the tooth after fracture. Conclusion FEA and fracture resistance test showed that the 2 repair materials are acceptable and recommended in iatrogenic mid-root perforation.

The global production of furfural generates substantial amounts of furfural residue waste annually, which, if not properly managed, can lead to significant environmental pollution. However, the ash produced from the combustion of this biomass waste shows promise as a cement additive, offering an innovative solution for furfural residue management. In this study, ash obtained from the combustion of furfural residue in industrial boilers was used as an additive in both Portland cement and magnesium oxysulfate cement, with concentrations ranging from 5% to 20%. Mortar specimens were then prepared and tested for compressive and flexural strength at 3, 7, and 28 days. The results indicated that at a 10 wt% addition, the formation of cotton-like structures and ettringite needles was most pronounced, resulting in the highest compressive and flexural strengths in the Portland cement specimens. Similarly, in magnesium oxysulfate cement, a 10 wt% ash addition significantly promoted the formation of the 5·1·7 phase, leading to the highest compressive strength. In summary, under appropriate conditions, furfural residue ash can be effectively utilized as a cement additive, contributing to resource recovery and sustainable waste management.

Concrete is one of the most commonly used materials in civil engineering construction, and it continues to have increased production. This puts pressure on the consumption of its constituent materials, including Portland cement and aggregates. There are environmental consequences related to the increased emission of CO2 that are associated with the production process of Portland cement. This has led to the development and use of alternative cementitious materials, mainly in the form of condensed silica fume, pulverised fuel ash, and ground granulated blast furnace slag. All of these are by-products of the silicon, electrical power generation, and iron production industries, respectively. In recent years, attention has turned to the possible use of sustainable bio-waste materials that might contribute to the replacement of Portland cement in concrete. This research investigates the effects of using rice husk ash as cement replacement material on the 1 to 28-day concrete properties, including the compressive strength, workability, and durability of concrete. The findings indicate that including rice husk ash in concrete can improve its strength at 3–28 days for percentage replacements of 5% to 20% (ranging from 2.4% to 18.7% increase) and improvements from 1 day for 20% replacement (with 11.1% increase). Any percentage replacement with rice husk ash also reduced the air permeability by 21.4% and therefore improved the durability, while there was a small reduction in the workability with increased replacement.

Abstract The longevity of waste asphalt can be considerably improved through cold recycling techniques combined with various additives. This research investigates the cold regeneration of aged asphalt concrete using Reclaimed Asphalt Pavement (RAP), Portland cement, cationic bitumen emulsion, and additional aggregates. The primary goal is to evaluate the performance enhancements in terms of average density, compressive strength, water resistance, and swelling across different mix compositions. Three distinct mixtures were formulated and assessed. Mix No. 1, composed solely of RAP, showed the lowest average density and highest swelling, indicating poor performance due to the lack of binding agents. Mix No. 2, which incorporated RAP, Portland cement, and water, exhibited the highest density and compressive strength, highlighting the crucial role of Portland cement in improving structural integrity. Mix No. 3, a more complex mixture including RAP, aggregates, Portland cement, water, and bitumen emulsion, displayed balanced properties with enhanced moisture resistance and reduced swelling. The experimental findings emphasize the effectiveness of adding Portland cement and bitumen emulsion to improve the mechanical and durability characteristics of recycled asphalt mixtures. Specifically, Mix No. 2 and Mix No. 3 demonstrated significant performance improvements, making them suitable for road maintenance applications. This study advocates for the widespread use of cold recycling methods with additive integration to achieve sustainable and cost-effective pavement restoration solutions.

Sprayed fireproofing materials in underground coal mine roadways are limited due to their poor adhesion, easy-to-crack, easy-to-fall off and poor sealing effect. This study therefore develops a fireproofing spraying material with fly ash as aggregate, ordinary silicate cement, sulphur-aluminate cement and gypsum as base material, and re-dispersible latex powder(VAE)as additive. Specifically, we conducted the uniaxial compressive strength test and used coal rock multiphase multi-field triaxial dynamic seepage experimental system, and scanning electron microscopy to study the effects of dispersible latex powder on the adhesive, cementation, mechanical, and blocking properties of the spray material. The results show that adding dispersible latex powder could promote the formation of filamentary bonding bridges in the hydration product, and realize the riveting and bridging of the binder bridges with the hydration products to form a dense network structure. This improves the cracking resistance of the spray material and enhances the material's adhesion, sealing and cementing properties when combined with coal. Adding 1 % VAE spraying material can fully encapsulate the coal body, forming a dense coating on the surface of the coal body, effectively isolating the air from contact with the coal body, thus preventing spontaneous combustion of coal. The proposed materials are useful in preventing spontaneous combustion of coal at the top of the roadway.

Abstract The present study deals with two kaolins from Eseka and Dibamba‐Cameroon to determine their potential suitability as additive of CEM I 42.5R and to optimize the properties of cement in the sense to promote low‐carbon cement. X‐ray diffractometry was used to establish the mineralogical composition of two kaolins. X‐ray fluorescence was carried out to determine the chemical composition of kaolins and cement. Fine metakaolin powders obtained at 700°C were used as additive in CEM I 42.5R. Furthermore, consistency, setting time, water absorption, compressive and flexural test, and shrinkage test were evaluated. Scanning electron microscopy analysis was carried out to evaluate the microstructure variation. The substitution of CEM I with metakaolin resulted in a considerable increase in compressive and flexural strength from days 7 to 28 at optimum value. The compressive and flexural strengths at 28 days at optimum value of metakaolin increase to 52% and 44%, respectively, explaining the equilibrium oxides in the cement. The maximum values of strength with 20 wt.% MK1 and 30 wt.% MK2 at 7, 14, and 28 days appear in both cases when the ratio of SiO2/Al2O3 is between 2.8 and 2.9. The silica modulus and alumina modulus of cement–metakaolin improved when metakaolin was added. The properties of cement were optimized with a 52% increase in compressive strength at 28 days.

This study investigates the impact of fly ash on hydration and carbonation processes in carbonation-cured fly ash cements. Cement paste samples with fly ash replacement levels of 0 %, 5 %, 10 % and 30 % underwent carbonation curing for 28 days. Results reveal that the CaO content does not affect the final CO2 absorption capacity. Instead, optimal fly ash replacement of 10 % enhances CO2 uptake, yielding 52.9 g of CaCO3 on the surface after 28 days of curing, compared to 43.4, 43.1 and 48.4 g for 0 %, 5 % and 30 % replaced samples, respectively. Additionally, fly ash incorporation significantly enhances belite reaction and improved CO2 binding capacity. However, the reaction extent of alite was lower when exposed to CO2-curing conditions. These findings advance understanding of blended cements in carbonation-curing, facilitating the development of environmentally friendly and durable concrete structures.

This study investigated the potential of calcined clays from Nigerian deposits in the production of ternary blends of cement. Clay samples were obtained from three different locations namely: Ikpeshi, Okpilla and Uzebba. The raw clay samples were then calcined at 700°C and 800°C. Chemical and mineralogical compositions were determined for the raw and calcined clay samples using XRF and XRD respectively. The chemical composition confirmed these clays as potential pozzolans with SiO2, Al2O3, and Fe2O3 collectively exceeding 70%. XRD analysis identified kaolinite and quartz as major mineral phases in the raw clays, which transformed into metakaolin upon calcination. Compressive strength tests on mortar samples prepared with 50% substitution of Portland cement with the calcined clay and limestone, showed that Ikpeshi clay at 800°C had the best strength performance, with a strength activity index of 0.92 at 28 days, demonstrating superior pozzolanic potential. Strength development was more significant between 7 and 28 days, indicating the pozzolanic reaction's contribution to long-term strength. However, the initial strength at 3 days was lower than the reference cement due to a delayed pozzolanic reaction. XRD analysis of blended pastes revealed typical hydration phases like portlandite, C-S-H, Strätlingite, and ettringite, with the ternary blends showing reduced portlandite content, indicating absorption by the pozzolan's alumina phase. Durability assessments revealed that the ternary blends exhibited improved resistance to water and chloride ion ingress. These findings highlight the effectiveness of Nigerian calcined clays in producing durable and sustainable concrete, supporting their use as supplementary cementitious materials to reduce the environmental impact of concrete production.

The heat of hydration is fundamental in understanding the hydration mechanism of cementitious materials, and temperature can significantly affect the heat of hydration. A recent study has shown that coal-derived char can be used as a green additive for improving the engineering properties of conventional cement grout. However, the impact of temperature on heat of hydration of char-cement grout is currently unknown. In this study, the heat of hydration (with degree of hydration) of cement and char-cement grouts at 5, 23, and 35 °C are investigated. This study reveals that incorporating char into the cement grout enhances its degree of hydration at temperatures ranging from 5 to 35 °C, highlighting the potential advantages of using coal char in grouting applications, especially at low temperature.

Rice husk ash (RHA) is a promising pozzolanic alternative material for partial replacement of ordinary Portland cement to increase the durability and strength of concrete and, at the same time, to decrease the corrosion effect caused by the harsh environment conditions. In this study, the impact of adding RHA in different ratios (0%, 7%, and 14%) as a replacement of ordinary Portland cement with different water–cement ratios (0.3, 0.5, and 0.7) and cured in water for different periods (10, 20, and 30 days) both on the durability and strength of the concrete and on its corrosion was investigated. The prepared specimens were tested by flexural, compressive, and tensile strength tests, slump test, and Rapid Chloride Ion Penetration test to determine the suitability of the partial replacement of ordinary Portland cement by RHA in concrete. The most important findings of this work, which is considered novel in this field, are that adding fine (instead of more extensive) RHA particles enhances the flexural, compressive, and tensile strength values and limits the chloride ion penetration with time. An adverse impact was found to increase the water–cement ratio, which is assigned to the effect of water on RHA and as a result on the porosity of the concrete.

Objective. Study of the dependence of the compressive strength on the average density and the flexural strength on the compressive strength of vermiculite concrete composite. Determination of the expression for the coefficients of thermal conductivity and heat capacity of the resulting vermiculite concrete composites in the developed software for thermal engineering calculation of the fire resistance limit of reinforced cement structures with a fire retardant layer of vermiculite concrete.Method. Methods for reducing the consumption of cement binder in the developed fire-resistant concrete composites are considered. Experimental and theoretical methods for determining the fire-retardant properties of the developed vermiculite-concrete composites and expressions for determining their strength properties are proposed.Result. The dependences of the ultimate compressive strength on the average density and the ultimate bending strength on the ultimate compressive strength of vermiculite concrete for the concretes under study, the dependence of the coefficients of thermal conductivity and heat capacity during a fire on the type and average density of vermiculite concrete composites were obtained.Conclusion. Fiber-vermiculite-concrete composites with an average density of 470-560 kg/m3 have the best fire-retardant properties. Software has been developed for thermotechnical calculation using a numerical method of the fire resistance limit of two-layer reinforced-cement structures in a fire, ensuring at least 95% agreement with the experimental data of fire tests of two-layer reinforced-cement elements.

Introduction. Currently one of the focus areas for the development of construction material science is the creation of self-cleaning concretes characterized by polydisperse multicomponent composition with the presence of nanoscale photocatalytic additives, primarily based on TiO2 . These photoactive modifiers give the material a number of positive properties, including the ability to decompose atmospheric pollutants, to self-clean the surface, etc. The promising method for improving the functional characteristics of titanium oxide photocatalysts is the creation of nanostructured systems with ‘core (substrate) – shell (photocatalyst)’ architecture. Previous research results show that the final efficiency of the synthesized composite photocatalytic modifiers largely depends on the level of substrate reactivity in the cement system. The purpose of this study is to investigate the impact of three types of siliceous rocks (diatomite, trepel, and opoka) on cement stone formation processes and to identify the most effective raw materials for use as photocatalytic carriers in self-cleaning concrete compositions. Methods and materials. The methods of Kozeny-Karman, laser diffraction and X-ray fluorescence spectrometry were used to determine the specific surface area and parameters of granulometric and chemical compositions of silicite samples. The phase composition of siliceous rocks and modified cement systems was studied by X-ray powder diffractometry. Results and discussion. The main parameters of granulometric composition of diatomite, trepel and opoka were determined. The predominance of reactive modifications of free silica (47.6–78.0 wt. %), represented by amorphous opal-A or cryptocrystalline OCT-phase (opal-CT), were revealed in the structure of silicites. It was found that increasing the dosages of silica-containing additives from 0 to 10% resulted in decreased by 10–27% in the quantity of portlandite in the phase composition of cement stone aged 28 days, while the content of high-strength low-basic calcium hydrosilicates (C–S–H (I)) increased by 11–27%. Conclusion. The chemical and mineralogical composition peculiarities of silicites, as well as the nature of the impact of silica-containing modifiers on the structure formation processes of cement systems, determine the prospects of using opal-cristobalite rocks as dispersed photocatalyst carriers for self-cleaning concrete.

Current modern trends in road construction are the increase in traffic intensity and the carrying capacity of motor transport, as well as the expansion of the road network, including local roads. These trends put forward the task of not only increasing the durability of road structures, but also the use of local materials and soils in the construction of highways. Several methods have been developed to strengthen the soils of the road base. A variety of surfactants, modifiers and additives are also produced to strengthen the roadbed. Many of them have not shown their effectiveness in practice. Therefore, there is a need for plenty laboratory and field studies on this topic. Laboratory studies were carried out to investigate the effect of the modifier on the roadbed soil. The type of soil and its maximum density were determined at optimal humidity. Based on this, cement and a modifier were introduced into the soil composition, density and compressive strength were determined. The results of a scanning electron microscope (SEM) were obtained to study the effect of the modifier on the roadbed soil. Laboratory studies and SEM-analysis have shown that the addition of a modifier to the soil leads to an increase in its maximum density, a significant increase in compressive strength and that the modifier serves to improve the binding properties by forming a crystalline bond with cement.

Abstract One strategy to reduce CO2 emissions from cement production is to reduce the amount of Portland cement produced by replacing it with supplementary cementitious materials (SCMs). Biochar is a potential SCM that is an eco-friendly and stable porous pyrolytic material. However, the effects of biochar addition on the performances of Portland cement composites are not fully understood. This meta-analysis investigated the impact of biochar addition on the 7- and 28-day compressive strength of Portland cement composites based on 606 paired observations. Biochar feedstock type, pyrolysis conditions, pre-treatments and modifications, biochar dosage, and curing type all influenced the compressive strength of Portland cement composites. Biochars obtained from plant-based feedstocks (except rice and hardwood) improved the 28-day compressive strength of Portland cement composites by 3–13%. Biochars produced at pyrolysis temperatures higher than 450 °C, with a heating rate of around 10 C min-1, increased the 28-day compressive strength more effectively. Furthermore, the addition of biochar with small particle sizes increased the compressive strength of Portland cement composites by 2–7% compared to those without biochar addition. Biochar dosage of

Vegetation concrete is increasingly being used for slope stabilization in highways, green roofing in urban developments, and erosion control in coastal areas due to its sustainable solutions for enhancing landscape aesthetics, mitigating pollution, and protecting the environment. However, the environmental and economic impacts of different mix proportions, particularly concerning CO2 emissions, remain insufficiently explored. This study aimed to identify the optimal mix proportions of vegetation concrete through laboratory testing that minimize CO2 emissions while ensuring compatibility with plant growth and cost-effectiveness. The vegetation concrete mix were prepared using different quantities of biochar (5 %, 10 %, and 15 %) and cement content (4 %, 8 %, and 12 %) by weight to evaluate their impact on porosity, unconfined compressive strength (UCS), alkalinity, plant compatibility, cost-effectiveness, and CO2 emissions from raw materials. The results indicate that increasing the biochar content from 0 % to 15 % led to a 16 % reduction in porosity and a 92 % increase in UCS of vegetation concrete. Similarly, increasing the cement content from 0 % to 12 % resulted in an 11 % decrease in porosity and a substantial 200 % increase in the UCS of vegetation concrete. Moreover, the addition of 5 % biochar had a beneficial effect on plant growth, however, increasing the biochar content beyond this level adversely impacted plant development. Based on laboratory test results, the recommended optimal mix for vegetation concrete includes a mix of 5 % biochar, 8 % low-alkaline sulfoaluminate cement, 6 % sawdust, and 6 % ferrous sulfate. The analysis of CO2 emission of the materials studied showed that cement contributed the most to CO2 emissions, followed by biochar, sawdust, water, and soil. Notably, the utilization of sulfoaluminate cement led to a 31.8 % reduction in CO2 emissions compared to Portland cement, while also lowering the overall cost of vegetation concrete by 24.7–33.8 %. This research underscores the necessity of scientifically establishing relationships between the composition of plant-based concretes and their environmental and economic performance. In summary, this study identifies optimal mix proportions for vegetation concrete, leveraging low-alkaline sulfoaluminate cement and biochar to minimize CO2 emissions, enhance landscape aesthetics, and ensure compatibility with plant growth, thus emphasizing its potential as a sustainable and cost-effective construction material.

This work was undertaken to examine the compatibility of bamboo particles and their bonding with Portland cement for bamboo-reinforced cement-bonded particle board. Pozzolana Portland cement was used as a sizing agent. The amount of bamboo particles was taken on an air-dry basis of cement. Sodium silicate (Na2SiO3) and aluminium sulphate [Al2(So4)3] were used to prevent the heat of hydration and increase the rate of cement setting, respectively. Different ratios of cement and bamboo particles were used to study the properties of the particle board. The physical and mechanical properties of Bambusa bambos bamboo reinforced cement bonded particle boards were evaluated. The density of the boards varied between 1.28 g/cm3 to 1.36 g/cm3 in 2.0:1.0 and 3.0:1.0 cement: particle ratios, respectively. The moisture content of the boards was 9.96 %, 6.98 % and 6.62 % for 2.0:1.0, 2.5:1.0 and 3.0:1.0 ratios of cement: particle, respectively. The physical properties of the board, such as density, moisture content, water absorption and thickness swelling decreased with an increase in the cement: bamboo particle ratio. The maximum MOR and MOE were 9.17 N/mm2 and 4884 N/mm2, respectively in 3.0:1.0 cement: bamboo particle ratios. The mechanical properties of the boards such as tensile strength, modulus of rupture (MOR), modulus of elasticity (MOE) and screw withdrawal were increased with an increase in the cement: bamboo particle ratios. The 2.5:1.0 and 3.0:1.0 cement: bamboo particle ratios performed best for cement-bonded particle boards and also passed the IS: 14276 standard. These cement-bonded particle boards can be used for partitioning, wall cladding, flooring, false sealing, kitchen cabinets and other purposes.

To improve the resource utilization of chromium-containing solid waste in cement-based materials, the leaching rate, valence state, and microscopic morphology of hexavalent chromium in Portland cement-based materials were studied. The results indicate that the stabilization rate of hexavalent chromium in cement reaches 95% for specimens containing 0.5% potassium chromate by mass after 60 days. However, when the potassium chromate content is increased to 5%, the stabilization rate drops below 90%. Analysis through photoelectron spectroscopy elucidates that chromium mainly exists in two valence states within the cement paste: trivalent chromium, present as Cr(OH)3 and CrOOH, and hexavalent chromium, existing in the forms of CaCrO4 and K2CrO4. After curing for 28 days, the ratio of trivalent chromium to hexavalent chromium is approximately 7:13, with the main hexavalent chromium compound CaCrO4 constituting about 21.4% of the total chromium content. Microscopic phase tests further intricate interactions between calcium ions and hexavalent chromium ions in a low water-cement ratio matrix, resulting in the additional CaCrO4 whose quality steadily increased with age. The rise in ion content leads to a continuous augmentation in the diffraction peaks density of ettringite (AFt). This is attributed to the slightly larger spatial position of CrO42- compared to SO42-, facilitating its partial replacement in the columnar structure lattice of the ettringite hydration product.

The data provided is primary data related to cement production collected from the six different cement plants in India. This serves as the inventory for conducting material flow analysis, supply chain forecasting, and life cycle assessment of cement and concrete systems. The dataset is given in three data sheets with information relevant to the steps followed in line with the life cycle assessment (LCA) methodology, i.e., inventory, characterization factors and impacts (here, carbon footprint and energy consumed). The data includes the amounts of raw materials (type and source), the electricity (source and amount) used in the clinker and other products produced, such as OPC (Ordinary Portland Cement), PPC (Portland Pozzolana Cement), PSC (Portland Slag Cement) and GGBS (Ground Granulated Blast Furnace Slag). The data is presented (in Sheet A and C) for the relevant functional unit, i.e., one tonne of material produced in each plant. Sheet B gives one of its kind data related to electricity produced (1 kWh) in the thermal power plant associated with the cement plant, also called as captive power plant. As the cement production process contributes to 8% of the anthropogenic CO2 emissions, it is important to understand the environmental impacts associated with it, and primary data generated are essential for assessing the impacts and to modify the processes with higher contribution to reduce the impacts. This dataset can, therefore, serve as a basis to collect the data from similar plants in any part of the world and benchmarking.

Soft clayey soils present geotechnical engineering challenges with significant stability and settlement. Various methods are employed to enhance the geotechnical properties of these soils. Heating and grouting are the methods used to improve such soil. A new heating and cement grouting system using gas as a source of heating through boreholes and Portland cement for grouting was designed and manufactured to enhance the soft soil. Different parameters were investigated, including the shear strength and the angle of internal friction, as well as the water/cement ratio, W/C (0.5, 0.75, 1, 1.25, 1.5, and 1.75), and the period of curing (3, 14, and 28 days). The results showed the shear strength and angle of internal friction increased from 14 to 300 kPa and 0 to 50 degrees, respectively. If only the heating system is running, the strength and behavior of the soil will improve via heated and cement grouting with a water/cement ratio. If the w/c ratio increases from 0 to 1.25, the ultimate bearing capacity ratio (qu treated/qu untreated) increases from 6.5 to 14.3 at 15% settlement. However, when the water/cement ratio increases from 1.25 to 1.75, the ultimate bearing capacity ratio (qu treated/qu untreated) decreases from 14.3 to 11.4. The ultimate bearing capacity ratio improves with increasing curative time. It climbs from 14.3 to 19.6 during 3 to 28 days for cement grouting models, while the ultimate bearing capacity ratio grows from 6.5 to 7 during 3 to 28 days for heating process models only, at 15% settlement.

Statement of the Problem: Bond strength of furcation repair materials is an essential factor in clinical success. Studies on the effect of adding titanium dioxide (TiO2) nanoparticles on the push-out bond strength of commonly used endodontic cements for furcation perforation repair is limited.Purpose: This study aimed to evaluate the effect of adding TiO2 nanoparticles to white Portland cement (PC), white mineral trioxide aggregate (MTA), and calcium enriched mixture cement (CEM) on their push-out bond strengths.Materials and Method: In this in vitro study, 120 endodontically treated molars were assigned to six groups (n=20) based on the material used to repair the perforation. In three groups, the cements (white PC, white MTA, and CEM) were placed in pure form, and in the three remaining groups, 1 weight % of TiO2 was added. The push-out bond strength was measured using a universal testing machine at a strain rate of 0.5 mm/min. Data were analyzed using one-way ANOVA and post hoc Games-Howell test (p< 0.05).Results: One-way ANOVA showed significant differences in the mean bond strength values between the six groups (p= 0.002). The post hoc Games-Howell test showed that the bond strengths in MTA+TiO2 and PC+TiO2 groups were significantly higher than those in MTA and PC groups, respectively. However, there was no significant difference in the bond strength between CEM and CEM+ TiO2 groups.Conclusion: The incorporation of TiO2 into MTA and PC increased their push-out bond strength. However, it did not affect the push-out bond strength of CEM cement.

This research investigated the influence of using chemically treated glass microparticles as a partial replacement for cement in Portland cement pastes and mortars. The microparticles were obtained by grinding glass waste into three different particle size fractions (< 75 µm, < 45 µm, and < 25 µm), treated with calcium hydroxide (CH), and characterized using SEM/EDS and a laser particle size analyzer. Samples prepared with the incorporation of glass were characterized using XRD, TGA/DTG, and SEM/EDS. The pretreatment with calcium hydroxide induced the formation of C-S-H with different morphologies on the surface of the particles, in addition to causing changes in particle size distribution due to the formation of agglomerates. The pastes prepared with treated particles had lower amounts of CH and higher levels of hydrated silicates. However, when indirectly measuring the pozzolanicity of treated particles through the compressive strength of mortars, no significant differences were observed in the strengths of mortars made with treated and untreated particles.

Abstract This research evaluated the use of industrial ash from eucalyptus chips in the biosorption of sodium dipyrone with the subsequent, study of its potential in Portland cement matrix. The biosorbent was characterized by the point of zero charge and the surface area. For comparison, before and after the biosorption process, scanning electron microscopy, energy dispersive x-ray spectroscopy, and Fourier transform infrared spectrometry were performed. Regarding the study of the potential of industrial ash after biosorption (AAB), it was characterized by analyzing specific mass, moisture, loss on fire, and X-ray fluorescence, as well as by X-ray diffraction, modified Chapelle, pozzolanic activity index with lime, and performance index with cement, compressive strength, and tensile strength by diametral compression. The biosorption tests were carried out in batch, it being possible to observe that at 298.15 K, 130 rpm, without pH adjustment approximately 93% of commercial dipyrone was removed. The pseudo-second-order kinetic model fitted better with the experimental data and the process was characterized as exothermic and spontaneous. The chemical composition of ash and AAB showed a predominance of CaO followed by MgO, without the presence of an amorphous halo. In the study of the filer effect, using cement pastes, both materials showed favorable results. Thus, it is concluded that the industrial ash studied has the potential to be applied as an alternative material in the removal of sodium dipyrone and for the replacement of cement in the composition of cement matrices, due to the filer effect they presented.

Cement mortar without fibers might crack due to shrinkage or volume changes. Cracking in cement mortar leads to elastic deformation. The development of these cracks causes elastic deformation of cement mortar. This study examined the influence of two steel fibers' geometrical forms (crimped and hooked with just one end) in different amounts by volume (Volume fraction = 0.25%, 0.5%, and 0.75%) on the cement mortar's mechanical features. Among the characteristics were splitting, compressive as well as flexural strength. The samples were prepared, poured into cubic molds for compressive strength testing cylindrical molds used for splitting strength testing, and prismatic molds for flexural strength testing, and processed at various times 3, 14, and 28 days before the tests. According to the findings, the highest increase was obtained after adding 0.75% of crimped fibers, the compressive strength increased by 13.3 %21.29%, and 44.8%, for 3,14.28 days respectively, and split tensile strength increased by 66.17%,68.9%, and 79.48% for 3.14 and 28 days respectively and flexural strength increased by 72 %,91% and 92% for 3.14 and 28 days, respectively.

Recently, many enterprising attempts have been made to create more sustainable cement mortar mixes using modern technologies. Modified mixtures are a promising part of green infrastructure, which contributes to reducing environmental impact and cost. Determining the properties of modified cement mortar using Al Juss binder (JB) is the focus of this study. JB is a locally made binder from heated white stone (gypsum stone) near the Deir Ezzor region, Syria. The cement, which is the main element in the cement mortar, is replaced with different JB ratios of 0%, 10%, 25%, 50 and 75% of total cement weight. The results revealed that the compressive strength at 28 days of age of 10% JB-mortar was 26.5 MPa, matches type M-mortar (20 MPa), and 25% JB can be used in type S-mortar. As a result, it has been confirmed that cement-JB mixture mortars containing 10% or 25% of JB do not meet the properties achieved by control cement mortars. However, they possess acceptable properties such as compressive and flexural strength, initial and final setting time, and expansion value of the cement.

The study explores the potential of recycling construction and demolition waste into recycled coarse aggregates (RCA) to decrease waste generation and carbon footprint, using a standard compacting effort to calculate compressive strength and particle packing density in a specific cylindrical volume. This study investigates the impact of RCA on concrete’s workability, compressive strength, flexural, split tensile, drying shrinkage, electrical resistivity, rapid chloride penetration, and microstructural characteristics using XRD, SEM, and EDAX. Test findings showed that increasing the replacement percentage beyond the optimum value (RCA 25) had detrimental effects on the strength and microstructure of the concrete. RCA 25 has a higher compressive, flexural, and split tensile strength in the order of 11.56%, 3.06%, and 5.17% respectively compared to reference concrete, as well as 5.23% increase in drying shrinkage, 8.79% higher electrical resistivity, and 4.68% higher resistance to chloride penetration than reference concrete.

The dry stacking of filtered tailings is an option to deal with safety-related issues involving traditional slurry disposition in impoundments. Filtered tailings can be compacted to pre-define design specifications, which minimizes structural instability problems, such as those related to liquefaction. Yet, comprehending the tailing’s response under various stress states is essential to designing any dry stacking facility properly. Thus, the present research evaluated the mechanical response of cemented and uncemented compacted filtered iron ore tailings, considering different molding characteristics related to compaction degree and molding moisture content. Therefore, a series of one-dimensional compression tests and consolidated isotropically drained triaxial tests (CID), using 300 kPa and 3000 kPa effective confining pressures, were carried out for different specimens compacted at various molding characteristics. In addition, changes in gradation owing to both compression and shearing were evaluated using sedimentation with scanning electron microscope tests. The overall results have indicated that the 3% Portland cement addition enhanced the strength and stiffness of the compacted iron ore tailings, considering the lower confining pressure. Nevertheless, the same was not evidenced for the higher confining stress. Moreover, the dry-side molded specimens were initially stiffer, and significant particle breakage did not occur owing to one-dimensional compression but only due to shearing (triaxial condition).

In this study, the effect of limestone content on the mechanical performance and the heat of hydration of ordinary Portland cement (OPC) was investigated. Changes in the phase assemblage were analyzed through XRD and thermodynamic modeling. The purpose of the study was to identify the optimal limestone content in OPC. As a result of the experiment, all samples were found to have equal fluidity. Increasing the limestone content accelerated the hydration of the cement before approximately 13 h and shortened the setting time due to the acceleration of the initial hydration reaction. The compressive strength of the cement mortar showed a dilution effect, with lower compressive strength compared to the reference sample at an early age, but it gradually recovered at a later age. This is because, as shown in the XRD and thermodynamic modeling results, the carboaluminate phases formed due to the chemical effect of limestone contributed to the development of compressive strength. As a result, within the scope of this study, it is believed that maintaining the limestone content in OPC within 10% is optimal to minimize quality degradation.

Escalating global surface temperatures are highlighting the urgent need for energy-saving solutions. Phase-change materials (PCMs) have emerged as a promising avenue for enhancing thermal comfort in the construction sector. This study assessed the impact of incorporating PCMs ranging from 1% to 10% by mass into composite Portland cement partially replaced by fly ash (FA) and nanosilica particles (NS). Mechanical and electrochemical techniques were utilized to evaluate composite cements. The results indicate that the presence of PCMs delayed cement hydration, acting as a filler without chemically interacting within the composite. The combination of FA and PCMs reduced compressive strength at early ages, while thermal conductivity decreased after 90 days due to the melting point and the latent heat of PCMs. Samples with FA and NS showed a significant reduction in the CO2 penetration, attributed to their pozzolanic and microfiller effects, as well as reduced water absorption due to the non-absorptive nature of PCMs. Nitrogen physisorption confirmed structural changes in the cement matrix. Additionally, electrical resistivity and thermal behavior assessments revealed that PCM-containing samples could reduce temperatures by an average of 4 °C. This suggested that PCMs could be a viable alternative for materials with thermal insulation capacity, thereby contributing to energy efficiency in the construction sector.

This article discusses the impact of the aggressive environment on the pattern of pore distribution, strength, and mass absorption of investigated samples. For this purpose, a physical and numerical research model has been developed based on Fick’s second law and Zhurcov’s theory. Consequently, computer tomography research revealed that pore redistribution was revealed in test samples due to exposure. The degradation model is proposed assuming that in the first stage of interaction between concrete constructions and aggressive medium, the product of interaction is accumulated in the surface of structures and pores. Interaction products in the form of needle-shaped crystals grow in time and create additional stress in the body of the structure, resulting in partial distribution of the surface of the structure due to the growth. In this state, the excretion of dissolved substances (in the form of citrate and calcium acetate), leaching of Ca(OH)2, and decalcination of CSH lead to a decrease in the strength of cement stone. Based on the developed numerical models, the dependences of aggressive environment impact on the on the parameters of the structure of cement composites at different exposure times were obtained. For the samples obtained during the activation of Portland cement in the electromagnetic mill, energy parameters of the destruction process are 1.85–2.2 times heavier than the control compositions. The samples obtained by activating Portland cement in the electromagnetic mill have a higher susceptibility to an aggressive environment (they absorb 1.8 times more energy per unit of time for structure transformation). However, the higher U-energy barrier (1.85 times greater than the control composition) provides both a longer term of exploitation and a lower kinetics of the change in the strength of the material.

One of the promising raw materials for the synthesis of geopolymers is perlite, which is a natural low-calcium aluminosilicate. This research studied the physical, mechanical and microstructural characteristics of perlite-based geopolymers modified with different mineral additives that were prepared using different methods of introducing the alkali components and curing conditions. The experimental results of the consolidated perlite-based geopolymer pastes showed that curing conditions and the method of introducing the alkali component into the geopolymer matrix had a minimal effect on the average density while demonstrating a significant boost in compressive strength. So, after thermal treatment, the compressive strength increased by 0.63 to 11.4 times for the mixes when fresh alkali solution was used and by 0.72 to 12.8 times for the mixes with the 24 h conditioned alkali solution. Maximum-strength spikes from 1.1 MPa to 13.2 MPa and from 0.7 MPa to 9.7 MPa were observed for the mixes with kaolin when prepared with fresh and conditioned alkali solutions, respectively. It was also observed that thermal treatment facilitates the compaction of the matrix structure by 18% and 1% for the non-modified mix and the mix modified with Portland cement. Perlite-based geopolymers modified with Portland cement and citrogypsum demonstrated a significant reduction in the initial and final setting times with both methods of introducing the alkali solution. On the surface of mixes modified with citrogypsum, regardless of the curing conditions and method of introducing the alkali component, an efflorescence substance was observed. The microstructural analysis of the consolidated geopolymer perlite-based pastes containing citrogypsum demonstrated a loose structure and the presence of efflorescence, which can be associated with a retardation in interaction processes between alkali cations and the aluminosilicate component. EDS analysis demonstrated that the presence of such elements as oxygen, sodium and sulfur may indicate the efflorescence of unreacted sodium hydroxide (NaOH), citrogypsum (CaSO4) and the products of their interaction in the form of crystalline hydrates of sodium sulfate (Na2SO4).

Currently, the cement sector has become aware of the economic and environmental advantages of replacing clinker with other supplementary cementitious materials that have a lower carbon footprint in the design of eco-cements. In this study, hydrotalcite, a natural as well as synthetic clay, which can be fabricated at the cement plant site, was used as such an addition. The objective of this work was to evaluate the behavior of its physical–mechanical properties and durability in pastes and mortars, using a magnesium-type commercial hydrotalcite, Mg6Al2(OH)16CO3·4H2O, as a substitute material for 10, 20 and 30% by weight of ordinary Portland cement (OPC). The mechanical strength was not affected by the substitution, the resistance to chlorides increased, as the hydrotalcite (HT) was able to bind chlorides, and the resistance to carbonation increased at 3 months but was almost the same as the reference specimen at 6 months, which indicates the need to have longer test durations.

A comprehensive experimental investigation of Portland cement hydration kinetics in a wide temperature range from 35 °C to 150 °C with pressure up to 50 MPa was performed by heat of hydration, chemical shrinkage and ultrasonic measurements. Increasing curing temperature was found to have a stronger acceleration effect during the main hydration period while increasing curing pressure had a stronger acceleration effect during the pre-induction period of cement hydration. By comparing chemical shrinkage test results with other methods of estimating cement degree of hydration, such as quantitative X-ray diffraction, non-evaporable water content measured by thermogravimetric analysis, as well as heat of hydration, it was observed that total chemical shrinkage of cement at complete hydration decreased with curing temperature from 35 °C to 75 °C and then stayed stable between 75 °C and 150 °C. Similarly, the P-wave velocity of cement (which is an indicator of physical and mechanical properties) as a function of hydration degree decreased with increasing curing temperature in the range between 35 °C to 75 °C, then remained relatively stable between 75 °C and 130 °C. The reduction of gel water content in C–S–H from 35 °C to 75 °C is believed to be the primary cause of these observed phenomena.

Alternative substitutes to convectional building and construction materials which pose environmental challenges, will be a bonus to the construction industries. This research investigates the suitability of calcined termite mound as partial substitute for cement and recycled concrete aggregate as aggregates substitute in the production of concrete. Termite mound clay in its natural state was obtained, calcined, and pulverized to the fineness of 75 µm. Various concrete mixes were formulated in which Ordinary Portland cement was partially replaced with Calcined Termite Mound (CTM) from 0% to 25% replacement at a step size of 5%, and recycled concrete aggregates (RCA) was also used as a partial replacement of the coarse natural aggregate (NA) at 20%, 40%, 60%, 80% and 100% by weight replacement. Compressive strength test, setting time test, slump test, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), were used to characterize the test materials and the concrete specimens. The results show that addition of either RCA or CTM will lead to reduction in the compressive strength. However, when RCA is combined with CTM, the optimum combinations suitable for structural load bearing members were found to be 60% RCA, 40% NA with 5% CTM. Other comparable mixes were also discovered.

Life Cycle Assessment (LCA) quantifies the environmental impacts associated with products throughout their life cycle. LCA also assists in the interpretation of impact assessment results, enabling improvements in a product or process. This paper applied the LCA methodology to quantify and compare the greenhouse gas emissions associated with different types of concrete: with a traditional binder (Portland cement) and with alkali-activated materials (Metakaolin, Lateritic Soil, and Lateritic Concretion) as precursors. The environmental impact was evaluated using greenhouse gas emissions (kg CO2-eq/m³), considering 1 m³ of each binder and resistance of approximately 30 MPa, obtained by a recommended mix ratio. The main objective is to evaluate whether alkali-activated binders present lower emissions than Portland cement. The results demonstrated that Portland cement is responsible for over 92% of the emissions associated with traditional concrete production. The use of alternative materials in civil construction, such as laterite soil, reduces carbon dioxide emissions by 79% compared to traditional concrete.

The possibility of using materials in radiation protection shields when designing new and extending the service life of existing nuclear energy facilities requires knowledge or the ability to predict their radiation changes. The studies were carried out due to the lack of data sufficient to predict radiation changes in hardened Portland cement paste (HPCP) and concrete under the influence of gamma radiation when used as radiation shield materials for nuclear energy facilities. The research is based on published data on the effect of gamma radiation on concrete at irradiation temperatures of 20–30 °C and on HPCP at 70–375 °C. The author carried out computational and analytical studies to assess and establish the possibility of predicting radiation changes in HPCP under the influence of gamma radiation. The studies were conducted using the previously developed and tested method of analytical determination of radiation changes in concretes according to data on changes in their components. The formulas used in this method made it possible to determine (restore) the radiation changes of the HPCP from experimental data on radiation changes in concretes and aggregates. According to the available results of concrete irradiation, changes in linear dimensions and strength during compression of HPCP under the action of only gamma radiation were calculated (restored). The dependences of radiation changes in HPCP on the magnitude of the absorbed dose in the range from 3.8104 to 4.7108 Gy after irradiation at 20–30 °C were established. According to the available data on the irradiation of HPCP with gamma radiation at temperatures from 70 °C to 375 °C, the effect of the irradiation temperature on radiation changes in the HPCP was revealed. Mathematical expressions that approximate the established dependencies are selected. On the basis of the obtained mathematical expressions, radiation changes in the linear dimensions and strength of HPCP for compression, caused only by the action of gamma radiation, after irradiation to the values of absorbed doses from 3104 Gy to 11010 Gy were calculated. The calculations of radiation-thermal changes in the linear dimensions and strength of HPCP under the action of gamma radiation and heating after irradiation to the values of absorbed doses from 3104 Gy to 11010 Gy and the accompanying heating at temperatures from 20 °C to 500 °C were estimated.

This article presents an investigation into the potential use of ground granulated blast-furnace slag (addressed as Slag cement or ‘SC’) as a replacement to Ordinary Portland Cement (OPC) in hybrid (carbonation and hydration) cured cement-based materials. To investigate the effects of carbonation on mechanical performances and microstructures, 0 %–100 % OPC was replaced with slag cement (SC). Thermogravimetric analysis (TGA) and Fourier transformed infrared (FTIR) spectra were utilized to investigate the carbonation reaction extent, rate, and microstructural phase formations. Slag cement was found to improve the efficiency and rate of carbonation. This study revealed that a minimum of 72 h of carbonation in a CO2-containing environment yields better mechanical performance compared to the traditional curing method. Specifically, the incorporation of 72 h of carbonation curing was observed to increase the strength of concrete up to 30 % after 28 days of total curing duration (carbonation and hydration). The chloride permeability of the carbonation cured samples was observed to reduce by 80 % due to the addition of SC. Finally, it was observed that, the carbonated concrete sample with slag has nearly 60 % lower global warming potential compared to the carbonated and non-carbonated concrete sample with 100 % OPC binder.

Monazite contains natural radionuclides belonging to the natural radioactive series of uranium and thorium. The aim of the present investigation is to determine whether variations in monazite content can cause variations in naturally occurring radioactive material in ordinary Portland cement. Include a study on the feasibility of monazite as a building material. For this research, six cement–monazite mixtures were experimentally tested for radiological content with an HPGe gamma spectrometer. Radium equivalent, hazard indices, gamma index, and annual effective dose were all calculated from the measured gamma-ray spectra. With the samples' radium equivalents ranged from 33.51 Bq kg−1 to 796.81 Bq kg−1. The external and internal hazard indices varied from 0.57 to 0.91 Bq kg−1 and 0.64–1.13 Bq kg−1, respectively. The gamma index exceeded unity for samples with monazite concentration less than or equal to 0.016 % by mass when mixed and sand in mortar cement. The external and internal hazard indices varied from 0.57 to 0.91 Bq kg−1 and 0.64–1.13 Bq kg−1, respectively. The gamma index exceeded unity for samples with monazite concentration less than or equal to 0.016 % by mass when mixed and sand in mortar cement. The average annual effective dose rate from different cement–monazite mixtures varied from 19.35 to 441.41 mSv y−1 for cement and C-1-C-6 samples. The study demonstrated that as the concentration of monazite increased in the cement, the concentration of uranium, thorium series and 40K also increased for all practical purposes. As a result, monazite may only be utilized as a performance enhancer and not as a complete replacement or mixed for sand.

Objective. Development of compositions of vermiculite concrete and fibro vermiculite concrete with volcanic pumice. Investigation of the construction and technical properties of the developed compositions of vermiculite concrete and fibrovermiculite concrete with volcanic pumice under the influence of elevated temperatures.Method. Methods of increasing the fire resistance of reinforced concrete structures are considered. The research is aimed at the development of vermiculite concrete and fibro vermiculite concrete with volcanic pumice for fire protection of building structures and the manufacture of heat-resistant products and structures. To reduce the cost of vermiculite concrete, its partial replacement with volcanic pumice is proposed. For the study of vermiculite concrete with volcanic pumice reinforced with basalt fiber, a rotatable plan of the second order of the regular hexagon type was used.Result. Replacing a part of an expensive aggregate (expanded vermiculite) with pumice leads to a slight increase in the average density of the composite, while the bending and compressive strength increases. In addition, the heat-resistant properties of vermiculite concrete with pumice are increased. This is due to the fact that volcanic pumice, being a hydraulically active additive, is able to react hydration with cement components, eliminating the harmful effect of secondary hydration of free calcium oxide. The influence of the heating temperature on the change in the construction and technical properties of vermiculite concrete and fibrovermiculic concrete, including with the addition of pumice, has been studied. It was found that dispersed reinforcement with basalt fibers reduces shrinkage deformations, when heated to t = 800, the shrinkage decreases from 0.7 to 0.5% compared to the original concrete matrix.Conclusion. The dependence "compressive strength = f (average concrete density)" significantly depends on the presence and ratio of pumice in the composition of vermiculite concrete, while an increase in the holding temperature to 600 oC or 800 oC leads to a decrease in the compressive strength from 15 to 25%, and the main decrease occurs when heated to 600 oC, further the increase in temperature has a negligible effect. The dependence of the bending strength on the compressive strength is generally maintained regardless of the heating temperature, and the heating of concrete does not reduce the relative bending strength, i.e. the ratio of bending strength / compressive strength is not reduced. Dispersed fiber reinforcement increases the relative bending strength by about 70% regardless of the heating temperature.

Analysis of the use of reinforced concrete structures confirmed the destruction of reinforced products based on Portland cement due to stray currents, which makes it impossible to achieve the required durability and reliability of structures. The present work shows the results of a study on the diffusion permeability of samples with different degrees of electrical conductivity. The relative value of the electrode potential was measured by the open circuit potential method. The novelty of this work is its analysis of the quantitative and qualitative characteristics of the structure of the mineral matrix with specified electrical properties after long-term exposure to electrochemical corrosion. In this work, an assessment was carried out, for the first time, on the effects of electrochemical corrosion on modified composites with predominantly electrically conductive and electrically insulating properties. An increase in the electrical conductivity of the composite was found to reduce the potential difference. The use of such composites helped protect the reinforcement from electrochemical corrosion.

Introduction. Mixing of dry components in mixers is one of the most important stages of any technological process in the manufacture of a composite material. To date, various technologies use a wide variety of mixing equipment, which is characterized by different principles of mixing and design solutions. Of particular interest for the preparation of high-quality and homogeneous mixtures for heat-insulating purposes is a pneumatic mixer with a spiral energycarrying tube. The article presents the results of studies using the method of mathematical planning of the fullfactor ПФЭЦКРП24 experiment, which makes it possible to most adequately assess the ongoing processes while minimizing systematic errors.Materials and methods. In the work, ЦЕМ 0 42,5Н ГОСТ 31108–2020 Portland cement with a specific surface area of 308 m2 / kg, sand of the Volsky deposit were used as raw materials for testing. Expanded vermiculite obtained as a result of heat treatment of natural vermiculite at a temperature of about 700°C was used as a light filler.Results. Heat-insulating mixtures prepared in a pneumatic mixer with a spiral energy-carrying tube ensure the production of heat-insulating mortars with stable density values of 1420 kg/m3, having sufficient compressive strength of 3.3 MPa, and guarantee high heat-shielding properties in building structures.Conclusion. The developed design and the conducted studies made it possible to establish the high efficiency of the proposed mixer, which provides a uniform distribution of the particles to be mixed, high homogenization and the creation of conditions for accelerating the physicochemical interactions in the created mixture with subsequent mixing of the prepared mixture with water and the formation of the required internal structure of the created composites.

In response to the environmental implications of the massive quantities of excavation soil generated by global urbanization and infrastructure development, recent research efforts have explored the repurposing of calcined excavation soils as sustainable supplementary cementitious materials (SCMs). As it is still at an early stage, current research lacks systematic analysis across diverse soil deposits regarding their reactivity and mechanical properties within cementitious binders, despite recognized geographical variability in kaolinite content. Through comprehensive experimentation with soils sourced from four major southern Chinese cities, this study presents a pioneering assessment of the compressive strength, pozzolanic reactivity (X-ray diffraction, Fourier-transform infrared spectroscopy, solid-state nuclear magnetic resonance), and microstructural development (mercury intrusion porosimetry, scanning electron microscopy) of mortars modified by various calcined excavation soils (up to 28 days curing). The experimental data suggest that soils with a kaolinite content above 53.39% produce mortars of equal or superior quality to plain cement mixes, primarily due to their refined pore structures, microstructural densification, and enhanced hydration reactions. The findings highlight kaolinite—specifically, aluminum content—as the principal indicator of excavation soil viability for SCM application, suggesting a promising avenue for sustainable construction practices.

Over the last 20 years, flue gas desulfurization gypsum (FGD gypsum) has become a valuable and widely used substitute for a natural raw material to produce plasters, mortars, and many other construction products. The essential advantages of FGD gypsum include its high purity and stability, which allow for better technical parameters compared to natural gypsum, and, until recently, its low price and easy availability. This FGD gypsum is obtained in the process of desulfurization of flue gases and waste gases in power plants, thermal power plants, refineries, etc., using fossil fuels such as coal or oil. The gradual reduction in energy production from fossil raw materials implemented by European Union countries until its complete cessation in 2049 in favor of renewable energy sources significantly affects the availability of synthetic gypsum, and forces producers of mortars and other construction products to look for new solutions. The gypsum content in commonly used light plaster mortars is usually from 50 to 60% by mass. This work presents the results of tests on mortars wherein the authors reduced the amount of gypsum to 30%, and, to meet the strength requirements specified in the EN 13279-1:2008 standard, added Portland cement in the amount of 6–12% by mass. Such a significant reduction in the content of synthetic gypsum will reduce this raw material’s consumption, thus extending its availability and developing other solutions. The study presented the test results on strength, density, porosity, pore size distribution, and changes in the microstructure of mortars during up to 180 days of maturation in conditions of increased relative humidity. The results show that decreased porosity and increased mechanical strength occur due to the densification of the microstructure caused by the formation of hydration products, such as C-S-H, ettringite, and thaumasite.

Rapid urbanization in many cities has produced massive amounts of problematic excavation soil. The direct disposal of untreated excavation soil often leads to significant land use and severe environmental concerns. A sustainable solution is to transform the soil waste into high-quality nano-calcined excavation soil (NCES) for application as a substitute for cement in construction. However, research in this area is very limited. This study presents a systematic investigation of the nano-sized calcined soil materials from preparation to application in cementitious material. The influence of milling parameters, including the rotational speed, milling duration, ball diameter, and milling strategy, was investigated to produce NCES with various specific surface areas. The effect of NCES substitution (15 wt% of Portland cement) in cementitious materials was then examined for mechanical performance, hydration dynamics, hydration products, and microstructure. A cement mix with very fine NCES (specific surface area of 108.76 m2/g) showed a 29.7% enhancement in mechanical strength and refined pore structure while a cement mix with un-grounded calcined soil showed a mechanical loss in comparison to the Control specimen. Delayed and reduced heat release at an early age was observed in a cement paste mixed with NCES. The underlying mechanism was investigated. The results of this work will contribute to the high-quality application of excavation soil waste.

Compositions of fine-grained concrete mixtures that provide the minimum required strength values in 1 day (7.5 MPa) have been developed. A comparison was made of the test results of the properties of samples printed on a 3D printer with samples made according to the same recipes on a vibrating platform. A laboratory printer was designed and constructed to study the properties of extruded mixtures. The method was also proposed for measuring concrete mixes’ structural strength. Analysis of experimental data allowed the establishment of the features of the influence of the mineral additives and slag–alkaline binders for a comparison of basic physical and mechanical properties of concretes for 3D printing. It has been experimentally shown that possible undercompaction of the fine-grained mixtures formed on a 3D printer and decrease of properties are compensated by the introduction of hardening activator and superplasticizer additives. The novelty of this work lies in determining the comparative effect of various products of technogenic origin on the properties of mixtures for 3D printing.

Three-dimensional printing allows accurate geometries to be obtained across a wide range of applications and it is now also moving into the architecture and construction industry. In the present work, a unique binary mix composed of ordinary Portland cement (OPC) and quick-setting cement (QSC) was combined with silica sand aggregate in different proportions for a customized binder jetting 3D printing (BJ3DP) process. Specimens were printed using the blended dry powders and deionized water to determine the impact of the processing variables on the properties of the realized specimens. The results show that the properties are influenced by the binary mix proportions and the layer thickness. The investigation found significant improvement in mechanical performance on increasing the proportion of OPC and optimal conditions were identified with proportions of 35 wt% OPC and 5 wt% QSC. Notable enhancements were also observed as the layer thickness was reduced.

Cement-based composites, as primary construction materials, have undergone significant advancements over the years, yet researchers still face challenges in terms of their durability and impact on the environment. The goal of this research is to develop environmentally friendly cementitious composites blended with sugarcane bagasse ash (SCBA) and reinforce them with multi-walled carbon nanotubes and polypropylene (PP) fibers. Because of the high cost associated with carbon nanotubes (CNTs) and PP fibers, as well as CO2 emission, which affect the economic and environmental aspects of this field, an agricultural waste such as SCBA was introduced in the current study that is both economically and environmentally viable. For this purpose, five mixes were designed by varying the CNTs content whilst keeping the PP fibers and SCBA contents constant at 1.5% and 15% by weight of the binder (ordinary Portland cement + SCBA), respectively. The developed blends were tested for various mechanical and durability properties, i.e., compressive strength, flexural strength, impact strength, water absorption, and ultrasonic pulse velocity. Moreover, the microstructures of the newly developed low-carbon SCBA-based composites reinforced with PP fibers and CNTs were studied through scanning electron microscopy and energy dispersive spectroscopy. The results showed that the developed blends incorporating 15% SCBA, 1.5% PP fibers, and 0.08% CNTs, by weight of the binder, demonstrated the compressive, flexural, and impact strengths as 15.30 MPa, 0.98 MPa, and 0.11 MPa, respectively. The investigated blends proved to be cost-effective and environmentally beneficial, rendering them suitable for utilization in general construction and maintenance works.

Sulfate attack on concrete induces volumetric changes resulting in a severe damage to the structure. The structural deterioration can be coupled with carbonation in practice, while such coupled effect is relatively unknown. Herein, thermodynamic calculations are used to study the combined effect of sulfate attack and carbonation on slag-blended Portland cement. The results show that the resultant product of sulfate attack varies according to the cations being used. Gypsum and M-S-H are the major products when Mg2+ is present in the sulfate solution, while ettringite and gypsum are predominant in the presence of Na+. Higher levels of carbonation are found to accelerate the effects of sulfate attack, while slag replacement tends to lower the carbonation degree required for destabilization and precipitation of certain phases.

A theoretical model for cement hydration was proposed to study multi-mineral reactive transport processes under various mineral compositions and determine the effect of multi-mineral reactions and interactions on cement hydration kinetics shifting from silicate to aluminate dominance. The reaction rates of each mineral dissolution, product precipitation, ionic diffusion, and adsorption were calculated individually through the degrees of undersaturation and supersaturation associated with the ionic concentration, all of which were coupled in the modified Poisson–Nernst–Planck equation. The hydration heat flow was then theoretically calculated by the superposition of the reaction rates of silicate and aluminate phases, which was derived from the calculated ionic concentration. The model was validated by comparison with experimental data obtained under various conditions, showing consistency. The combined effect of multi-mineral reactions and interactions on hydration kinetics was investigated using the model, and the results indicated that (1) faster dissolution of gypsum or a higher ratio of tricalcium aluminate to tricalcium silicate leads to a larger time interval between silicate and aluminate peaks; (2) faster precipitation of calcium silicate hydrate results in a more significant difference between silicate and aluminate peaks; and (3) the sulfate ion retards cement hydration kinetics shifting from silicate to aluminate dominance.

The article discusses the effect of calcined clays on the properties of Portland cement. An optimal method for calcining clays is proposed, which makes it possible to reduce the proportion of Portland cement clinker in cement to 60% and increase the strength characteristics from 55 MPa to 79 MPa. The study of the composition and structure of clays made it possible to select the optimal heat treatment parameters, at which the calcination products are characterized by the highest pozzolanic activity. It is shown that the use of alkali-activated calcined clays significantly increases the strength and durability of hardened cement binders compared to the composition without additives. In addition, calcined clays increase the frost resistance of cement in a 5% NaCl solution. The obtained experimental data are confirmed by thermodynamic calculations and the results of scanning electron microscopy.

Recent investigations proposed alternatives for utilization of Açaí (Euterpe oleracea Mart.) fruit wastes, seeds, and lignocellulosic fibers. However, Açaí leaves may also be obtained without harvesting the palms and could be used in higher value-added products. Alkali reaction (1% and 5% of NaOH), different temperatures (70°C, 80°C, and 100°C), and bleaching were combined to produce fibres from the Açaí leaves. Scanning electron microscopy, X-ray diffraction, and thermogravimetry were used to evaluate the effect of treatments on fibers, whereas X-ray diffraction and calorimetry were employed to characterize Portland cement pastes containing fibers. Results indicated that Açaí leaves could be transformed into short-length fibers with improved degrading temperature. Alkali treatment at 5% sodium hydroxide (90°C) and bleaching increased fibers’ crystallinity and showed efficiency in removing non-cellulosic components. Cement paste evaluation also indicated that fibers treated at 5% NaOH solution caused fewer changes in calorimetric profile and therefore present a greater potential for cement-based composites.