Reduction In Compressive Strength Research Articles

Preparation of a novel foamed concrete modified with carbon fiber and graphite: Mechanical, electro-magnetic and microstructural characteristics based on X-CT

In this paper, foam concrete is modified using graphite and carbon fiber as absorbents. The mechanical properties are analyzed in conjunction with hydration products, pore size distribution based on XCT test. Additionally, the resistivity, complex permittivity and complex permeability are tested. The results demonstrate that carbon fiber enhances the proportion of pores with diameters less than 200 μm in foam concrete, thereby significantly enhancing its flexural strength. Furthermore, incorporating graphite helps offset the initial retardation of sulfoaluminate cement hydration induced by carbon fibers, leading to an increase in the average pore size and a reduction in compressive strength. The incorporation of carbon fibers at a concentration of 0.6wt.% achieves the percolation threshold, akin to scenarios with singular fiber incorporation. Exceeding 2wt% graphite content results in negligible influence on the conductivity. The synergistic integration of graphite and carbon fibers significantly improves the electromagnetic wave absorption performance of the composite. At a thickness of 6 mm, the material exhibits an effective bandwidth where the reflection loss is less than -10 dB, extending up to 2.5 GHz, which constitutes 52.08% of the tested frequency spectrum.

Dispersion quality of aqueously dispersed MWCNT affected by step sonication process and its impact on mechanical strength of cement paste: A comparison between polycarboxylate based high range water reducers and air entraining agent

It has been widely reported that the application of high-level ultrasonic energy during dispersion process of carbon nanotube causes damage on the carbon nanotube and reduces its mechanical performance. However, if the amount of ultrasonic energy is insufficient, the quality of carbon nanotube dispersion becomes poorer so that the effect caused by carbon nanotube reinforcement is minimized. In this work, the step sonication process, which divides a prolonged sonication into a few separate cycles while maintaining the same level of ultrasonic energy, is applied since this process can improve dispersion of carbon nanotube without causing serious damage. Commercially available polycarboxylate ester, polycarboxylate, and air entraining agent were used as dispersing agents. The effect caused by step sonication and type of dispersing agent on dispersion quality of multi-walled carbon nanotube was evaluated, and their impacts on mechanical strength development of cement paste were analyzed. According to the experimental results, step sonication process improved the quality of multi-walled carbon nanotube dispersion when polycarboxylate ester and polycarboxylate were used. Step sonication process was found to be more effective for multi-walled carbon nanotube suspension with higher concentration. Among all dispersing agents, air entraining agent was found to be the best dispersing agent showing 2 times higher UV absorption peak than polycarboxylate and polycarboxylate ester, but the application of air entraining agent caused 40–65% reduction in compressive strength due to the air entrainment. It was also found that dispersion quality of multi-walled carbon nanotube affected flexural strength more significantly than compressive strength.

Mechanically suitable and osteoinductive 3D-printed composite scaffolds with hydroxyapatite nanoparticles having diverse morphologies for bone tissue engineering.

The challenge of integrating hydroxyapatite nanoparticles (nHAp) with polymers is hindered by the conflict between the hydrophilic and hygroscopic properties of nHAp and the hydrophobic properties of polymers. This conflict particularly affects the materials when calcium phosphates, including nHAp, are used as a filler in composites in thermal processing applications such as 3D printing with fused filament fabrication (FFF). To overcome this, we propose a one-step surface modification of nHAp with calcium stearate monolayer. Moreover, to build the scaffold with suitable mechanical strength, we tested the addition of nHAp with diverse morphology-spherical, plate- and rod-like nanoparticles. Our analysis showed that the composite of polycaprolactone (PCL) reinforced with nHAp with rod and plate morphologies modified with calcium stearate monolayer exhibited a significant increase in compressive strength. However, composites with spherical nHAp added to PCL showed a significant reduction in compressive modulus and compressive strength, but both parameters were within the applicability range of hard tissue scaffolds. None of the tested composite scaffolds showed cytotoxicity in L929 murine fibroblasts or MG-63 human osteoblast-like cells, supporting the proliferation of the latter. Additionally, PCL/nHAp scaffolds reinforced with spherical nHAp caused osteoactivation of bone marrow human mesenchymal stem cells, as indicated by alkaline phosphatase activity and COL1, RUNX2, and BGLAP expression. These results suggest that the calcium stearate monolayer on the surface of the nHAp particles allows the production of polymer/nHAp composites suitable for hard tissue engineering and personalized implant production in 3D printing using the FFF technique.

Effect of calcium stearate on cellulose acetate-based mortars

The purpose of this study is to investigate the properties of cellulose acetate-based mortars with the addition of calcium stearate (CS), superplasticizer (SP) and metakaolin (MK). Previous research has shown that cellulose acetate (CA) fibers from industrial cigarette butts (CB) treatment can be incorporated into standard mortars at a rate of 1.3 wt%. CS was added in various proportions by weight (0.5, 1, 1.5 wt%), and their influence on cement hydration and microstructure was studied using various investigative techniques. The addition of CS was found to be beneficial in reducing the amount of water absorbed by CA, despite the significant absorption of these fibers. Furthermore, a CS rate of 1 wt% decreased CA-based mortar shrinkage. Additionally, 1 wt% CS improved by 18% the compressive strength of CA-based mortars manufactured with SP compared to the reference CA-mortar. CA fibers and CS seem to modify mortar microstructure by creating a plurimodal pore size distribution and reducing capillary pores. The CS addition, however, resulted in more cracks and reduced workability due to the weakening of the bond between the cement paste components. MK-mortars showed a slight 15% reduction in compressive strength and 13% reduction in bending strength; along with a 20% increase in shrinkage. By incorporating CA fibers as an additive along with CS or MK, CA-based mortars can improve some properties, including shrinkage and mechanical strength. Further, this approach offers a potential solution to CB pollution by reducing the environmental impact of this waste.

Tensile and compressive properties of bamboo scrimber under different temperature conditions

AbstractBamboo scrimber demonstrates vulnerability to environmental temperature fluctuations, such as exposure to cold or fire, when deployed in structural applications. Consequently, its mechanical properties can substantially diverge from the intended design values under varying thermal conditions. This study aims to study the tensile and compressive properties of bamboo scrimber under different temperatures to provide data support for studying bamboo scrimber under low and high temperatures. The compressive properties of bamboo scrimber under temperatures ranging from −30°C to 250°C and the tensile properties under −20°C to 250°C were determined by a series of tests with a total of 125 specimens. The results show that the mass loss of bamboo scrimber increases gradually with the increase in temperature, and the increasing trend intensifies after 120°C. With the increase of temperature, the failure mode of the specimens under compression changes from the bottom compression cracking damage to the local destabilization of longitudinal fibers, while the tensile damage modes aren't influenced by temperature, and both “straight‐line” and “folded‐line” types of damage modes occur at different temperatures. The tensile and compressive strengths and elastic modulus of the specimens decreased with the increase in temperature, and the strength was more susceptible to the temperature than the elastic modulus: a rise in temperature from 20°C to 250°C resulted in a reduction of compressive strength and tensile strength by 80.80% and 84.11%, respectively, the compressive modulus and tensile modulus experienced decreases of 49.51% and 53.28%. Furthermore, equations of temperature influence coefficients of strength and elastic modulus were established based on the test results.Highlights Bamboo scrimber's mechanical properties under different temperatures are studied. Tendency and explanation of temperature influence coefficients are analyzed. Temperature coefficient equations for strength and elastic modulus are proposed.

Experimental study on the punching failure model of soft red rock subgrade by BPT-BVM methods and it’s assessment of the load bearing capacity

The recommended bearing capacity of medium weathering mudstone foundation is less than the capacity of the rock structure to withstand loads in Southwest China. A comprehensive failure characterization of medium weathering mudstone in Chengdu has been performed including bearing plate test (BPT), binocular vision measurement (BVM) test, uniaxial compressive strength test, trial trench test of shallow rock surface and 3D imaging in this paper. Failure behavior of rock has been modeled with 3D imaging algorithm that utilizes Zhang’s calibration method in BVM system combination with trial trench test of shallow rock surface. The bearing capacity of medium weathering mudstone foundation were extracted from uniaxial experiments and BPT-BVM test by fitting relevant material properties to the data. The results revealed that: Bearing capacity of medium weathering mudstone of layered isotropic in Chengdu is undervalued. Specifically, the characteristic load carrying value is in the range 1500–2500 kP, that is 50% higher than in the local standard system. Failure process is different from Hoek–Brown Failure Criterion, presenting a wave peak transfer phenomenon of the increment displacement into the distance. Thus, it can be reduced to that of punching failures for thin bedded structures of Moudstone foundations. Compressive strength of soft rock proves to be main factor limiting the bearing capacity, a clear correlation between the uniaxial compressive strength reduction coefficient and the bearing capacity has been used to establish, leading to the proposal of a load bearing capacity prediction model.

Mechanical characteristics of structural concrete using building rubbles as recycled coarse aggregate

Abstract The aim of this research is to investigate whether construction rubbles may be utilized as coarse aggregates in concrete. Experimentally, the slump, unit weight, compressive, tensile, and flexural strength tests were applied on concrete samples with varying percentages of recycled coarse aggregate (RCA) and compared with reference concrete produced with natural coarse aggregate. This research conducted 96 concrete samples with RCA replacement percentages of 0, 35, 65, and 100%, respectively. The control mixture produced with natural aggregate showed better results than the mixtures containing recycled aggregate; thus, compressive, tensile, and flexural strengths reduced as the amount of the recycled aggregate increased. Using 100% RCA, the compressive, tensile, and flexural strength reduction reached up to 64, 29, and 38%, respectively.

Phosphoric acid-activated metakaolin-based geopolymer: Optimizing P/A molar ratio to solidify Cs+ and Sr2+ in nuclear waste

Phosphoric Acid-activated Metakaolin-based Geopolymer (PAMG) is an efficient solidified material. This paper reports the effect of the H3PO4 to Al2O3 (P/A) molar ratio on the hydration, phase assemblage, morphology, and compressive strength of PAMG and the solidification of simulated radionuclides Sr and Cs by PAMG. The hydration behavior and microstructure of PAMG were investigated using isothermal calorimetry, X-ray diffraction (XRD), and scanning electron microscope (SEM). The impacts of Cs and Sr on the leaching behavior and microstructure of PAMG were assessed using atomic absorption spectrum (AAS), SEM, and energy dispersion spectrum (EDS). The results indicate that the compressive strength of PAMG increases and then decreases as the P/A ratio increases. The highest compressive strength reaching 98.1 MPa after 28 days of curing, was observed at a P/A molar ratio of 1.8. The addition of Cs and Sr resulted in a decrease in the compressive strength of PAMG, with Sr showing a more significant reduction in PAMG's compressive strength. However, PAMG still exhibited a high efficiency in solidifying simulated nuclides Cs and Sr, with 42 days leaching rates of 3.7 × 10−5 cm/d and 5.0 × 10−6 cm/d, respectively. These results indicate the huge potential of PAMG in solidifying nuclides.

Compressive failure analysis of composite honeycomb sandwich panels with impact damage and stepped-scarf repairs

Composite honeycomb sandwich panels (CHSPs) have been widely used in the aerospace industry owing to their lightweight and superior mechanical properties. However, these CHSPs are susceptible to impact damage, leading to a significant reduction in compressive strength and potentially jeopardize aircraft safety. It is crucial to investigate repair methods for CHSPs with impact damage. This paper aims to evaluate the repair performance of CHSPs with impact damage through an analysis of their compressive failure behaviors. To accomplish this, both experimental tests and advanced numerical models are employed. The numerical models for the intact, damaged and stepped-scarf repaired CHSPs are established using the progressive failure analysis model, cohesive zone model and sandwich plate theory. A good agreement is observed between the experimental results and numerical predictions of compressive failure behaviors. Moreover, the validated numerical models are successfully utilized for determining optimum repair parameters by parametric analysis of the repaired CHSPs. The establishment of these numerical models offers an accurate and cost-effective evaluation of repair performance for CHSPs with impact damage, highlighting the novelty and main contribution of this paper.

Effects of silica fume and rice husk ash contents on engineering properties and high-temperature resistance of slag-based prepacked geopolymers

Geopolymer slurries can be favored to achieve a sustainable approach in prepacked aggregate concretes. This study presented here investigated experimentally the effect of silica fume (SF) and rice husk ash (RHA) on the high-temperature resistance of slag-based sustainable prepacked geopolymers. In the production of prepacked aggregate geopolymers (PAGs), ground granulated blast furnace slag (GGBFS) was utilized as the main aluminosilicate-rich precursor material, and SF and RHA were replaced with GGBFS in various contents including 7.5% and 15%. The physical, mechanical and microstructural properties of specimens cured at 35°C and 70°C for 8 hours were determined comparatively. Residual compressive strength and mass loss of mixtures exposed to elevated temperatures (150°C, 300°C, and 600°C) were determined to observe high-temperature effects. The results revealed that the properties of PAGs were affected considerably by curing temperature and precursor type. The maximum oven-dry density of 2244 kg/m3 with RHA content of 7.5% was obtained at 70˚C curing temperature. Specimens produced with RHA tended to absorb more water under both heat curing conditions and the highest water absorption of 10.2% with RHA content of 7.5% was obtained at 35˚C curing temperature. The compressive strength of PAGs varied between 13.7 and 28.10 MPa, and flexural strengths varied between 1.48 and 2.74 MPa. Increasing curing temperature improved the strength properties of PAGs, and in general, the 8-hour compressive and flexural strength values of SF samples were relatively higher. The application of elevated temperature to the PAG mixtures caused a significant reduction in both compressive strength and mass loss. Among the specimens cured at 35°C, the specimens with RHA showed relatively better high-temperature performance in terms of compressive strength, while the specimens with SF cured at 70°C showed better performance. PAG specimens produced with RHA showed the best high-temperature performance against mass loss. According to the results obtained in the given study, these recycled wastes could be used to improve the physico-mechanical properties and high-temperature performance of slag-based PAGs.

Transformative innovations in nano-biochar-enhanced porous concrete: Elevating engineering performance and pollutant removal

This study addresses a significant gap in research by exploring the integration of nano-biochar (NBC) into porous concrete (PC) to enhance water purification capabilities while also evaluating its impact on the material's physical and mechanical properties. NBC was added in varying weights (0%–100%) to the binder material. Notably, beyond 10% NBC content, there was a significant reduction (p < 0.05) in porosity and compressive strength. Microstructural analyses using SEM, XRD, and FTIR revealed the incorporation of C–S–H within NBC pore structures. At 50% NBC content, substantial removal efficiencies (p < 0.05) were observed for manganese (Mn), nitrate (NO3−), total phosphorus (TP), and atrazine (AZ), reaching values of 97.4%, 93.9%, 97.3%, and 52.9%, respectively. Linear regression models revealed significant relationships between the degree of NBC enhancement and the efficiency of Mn and AZ removal. The logarithmic function provided the most accurate predictions for the quantity of NO3− and TP adsorbed by PC. These findings demonstrated that NBC-enhanced PC offers improved environmental remediation and provides guidelines for optimizing its composition for specific pollutants. Balancing mechanical and environmental performance, highlighting its potential as a sustainable construction material that meets both structural and pollution control needs is recommended.

Mechanical properties of recycled aggregate concrete reinforced with steel fibers under triaxial loading

The use of steel fiber reinforced recycled concrete (SFRAC) can help achieve resourceful reuse of construction waste and environmental sustainability. However, SFRAC structural members may experience complex stress states. Therefore, triaxial compression tests were conducted on 168 cylindrical SFRAC specimens to investigate their mechanical properties. The failure modes, stress-strain behavior, strength, and deformation of SFRAC under triaxial compression were observed. The effects of lateral confining pressure, steel fiber (SF) content, and recycled coarse aggregate (RA) replacement rate on these properties were analyzed. The internal micro-morphology of SFRAC was analyzed using SEM to better understand its failure mechanism under compression. The result shows that an increase in lateral confining pressure alters the failure mode of SFRAC specimens, resulting in a significant increase in peak strength and ductility. The enhancement of the elastic modulus by steel fibers decreases as the lateral confining pressure increases, suggesting a coupling effect between the two parameters. The inclusion of steel fibers in SFRAC did not have a significant impact on its failure mode or compressive strength. And yet, it did increase the ductility and toughness of the material, with an optimal steel fiber content of 1% (by volume). On the other hand, the addition of recycled coarse aggregate resulted in a significant reduction in the concrete's compressive strength, by almost 17%. Finally, several common material failure criteria for concrete were used to evaluate the impact of RA substitution rate and SF content on the strength of SFRAC. The Willam-Warnke failure criterion showed a higher strength. These findings provide a theoretical basis for future engineering applications of SFRAC.

Study on rock energy evolution and constitutive model under water–rock interaction

To explore the degradation in rock mechanical properties due to water–rock interactions and formulate a nonlinear damage constitutive model for the entire stress–strain curve of rocks, experiments involving saturated, dry-wet cycling, and uniaxial compression tests were conducted on granite and siltstone. Based on energy theory, the energy evolution of the rock throughout the testing process was scrutinized. The range of the compaction stage was identified through the analysis of the dissipation energy change curve. A nonlinear damage constitutive model for rocks subjected to water-rock interactions was then devised, drawing on concepts from statistical damage mechanics. The findings indicated a progressive reduction in uniaxial compressive strength and elastic modulus due to water–rock interactions, while the Poisson’s ratio was observed to increase. The energy density curve under these conditions delineated four distinct phases: compaction energy dissipation, linear energy accumulation, pre-peak gradient increase, and post-peak sudden change. The introduction of the unit elastic strain energy density metric underscored the deteriorating effects from an energy standpoint. A nonlinear damage constitutive model, incorporating the compaction stage based on a coupled damage variable, was formulated. The predictions of this model closely matched the empirical data, thereby affirming its validity. This model provides an enhanced depiction of rock deformation and failure mechanisms under the influence of water–rock interactions.

On the computational evaluation of carbon dioxide emissions of concrete mixes incorporating waste materials: A strength-based approach

In the last decades, the high emissions of carbon dioxide during concrete production have pushed the scientific community to develop innovative ways towards reductions of such carbon dioxide emissions. An effective way is to use waste materials replacing conventional concrete materials, but this may come at the cost of reduced concrete performance. Hence, there is a need to link the carbon dioxide emission of concrete with concrete strength (strength-carbon dioxide emission relationship). This study bridges this gap by investigating the possibility of reducing carbon dioxide emissions in concrete by incorporating waste brick powder (WBP) and waste tire rubber (WTR) using a strength-based approach. This resulted in the formulation of three concrete grades of 20MPa, 25MPa and 30MPa. It is shown that the impacts of including WBP and WTR on carbon dioxide emissions of concrete mixes are significant. Moreover, the compressive strength values corresponding to contents of 5% WBP and 20% WTR reduce dramatically by more than 32.57% in comparison with conventional concrete mixes. However, 5P0T and 5P10T concrete mixes reveal both the reductions in carbon dioxide emissions and reasonable concrete strength. The present research therefore shows that certain concrete mixes incorporating WBP and WTR can provide the driving force for reducing carbon dioxide emissions and preventing substantial compressive strength reductions.

Effects of ambient temperature and compaction delay time on the performance of cement-stabilised sand–gravel and the determination of allowable construction delay time

ABSTRACT Compaction delay time (t d) refers to the period from the mixing of inorganic binder–stabilised materials to the completion of compaction; this process is affected by ambient temperature (T a). To characterise the effects of T a and t d on the performance of cement-stabilised sand–gravel (CSG) during construction, the reliability of the vertical vibration compaction method (VVCM) is evaluated and the effects of T a and t d on the mechanical strength and freeze–thaw resistance of CSG are investigated. Next, a predictive model for the allowable construction delay time is developed based on a non-loss principle with respect to pavement performance. The results show that the correlation between the mechanical strength of CSG laboratory specimens subjected to VVCM and field core samples can reach ∼90%. Higher T a and longer t d significantly reduce the mechanical strength and freeze-thaw resistance of CSG. Notably, when t d exceeds the initial setting time of cement, the average reductions in compressive strength, splitting strength, and freeze-thaw resistance of CSG are ∼29.3%, 31.3%, and 20.4%, respectively. The allowable construction delay time decreases linearly with increasing T a, showing a correlation of up to 99%. The predictive model can effectively determine the allowable construction delay time at any temperature.

Effect of mix dosage on rubberized concrete mechanical performance: A multivariable prediction model towards design provisions

The accumulation of end-of-life tires generates significant environmental/economic/social problems worldwide; however, these tires can potentially be used in engineering applications when recycled as crumb rubber (CR). One possibility is to use CR as a replacement for river sand in concrete to reduce the disposal of CR and the use of sand as well as to improve some of concrete’s properties, such as thermal performance and carbon footprint at the expense of some compressive strength reduction. In this study, a novel and simple multivariable model was developed to predict the compressive strength reduction of rubberized concrete (RC) based on a dataset of 287 concrete mixtures from 38 different studies. The approach used in this study quantified the significance of the impact of 10 mix design variables on the evaluation of compressive strength reduction. The final model proposed in this paper considers six explanatory variables (i.e., volume replacement of sand by CR, CR quantity, fine aggregate quantity, coarse aggregate quantity, cement quantity, and water quantity) to predict the compressive strength reduction in which a logarithmic transformation was implemented to achieve a more precise model. The proposed model reached a coefficient of determination of 0.89, significantly better than other existing models with which the proposed model was compared, resulting in a highly accurate and yet easy-to-implement model. Finally, practical design considerations were provided to be used in concrete mix design or the design of minor structural elements.

A comprehensive study on mechanical properties, durability, and environmental impact of fiber-reinforced concrete incorporating ground granulated blast furnace slag

Concrete pavements are integral to sustainable infrastructure, offering longevity and resilience in construction and transportation. This study focuses on optimizing concrete pavements through the incorporation of steel and carbon fibers with Ground Granulated Blast Furnace Slag (GGBS) to enhance mechanical strength, reduce fracture development, and minimize carbon emissions. Utilizing 25 mixing designs with a consistent water-to-cement ratio of 0.40, varying ratios of GGBS, steel fibers, and carbon fibers (0.5 %, 1 %, and 1.5 % based on concrete volume) were explored. A comprehensive evaluation, including slump, compressive strength, flexural strength, split tensile strength, water absorption, abrasion resistance tests, carbon dioxide emissions, and cost analysis, was conducted at different curing stages. Results revealed a decline in compressive strength for all mix designs at 28 days, attributed to reduced cement strength with GGBS substitution. The 1.5 % steel fiber and 50 % GGBS mix demonstrated minimal compressive strength reduction (30.1 MPa, 5.5 % less than control), outperforming other mixtures. Steel fibers surpassed carbon fibers, likely due to \\erior distribution. Notably, 1.5 % steel fibers showed superior results, particularly with 50 % GGBS. Compressive strength generally increased with GGBS content, except for 1 % fibrous samples where 40 % GGBS produced optimal results. At 90 days, compressive strength increased for most designs, with G50S1.5 exhibiting over 38 % growth compared to the control. Steel fiber-containing samples outperformed carbon fiber-containing ones, showcasing the efficacy of steel fibers in enhancing compressive strength. Split tensile strength generally decreased, but steel fibers improved it, emphasizing their positive influence. Flexural strength increased in 28 and 90 days, with steel fiber-containing designs outperforming. G30S1.5 showed the most significant increase (33.3 %) at 28 days, and G30S1.5 exhibited the highest growth (32.22 %) at 90 days. Abrasion resistance tests indicated steel fibers and GGBS positively impacted abrasion reduction. G50S1.5 demonstrated the highest abrasion resistance (25 % increase over control). The environmental evaluation revealed lower CO2 emissions for GGBS-containing designs. G50S0.5 showed a 40.34 % reduction compared to the control sample. Cost analysis showed GGBS reduced costs, but fiber addition, particularly carbon fibers, increased costs. G30C1.5 had the highest cost increase (208.5 %), while G50S1.5 showed a marginal rise (3.9 %) compared to the control. Therefore, steel fibers in concrete pavements offer improved mechanical properties, durability, and reduced environmental impact, making them a viable choice despite a slight increase in cost. Conversely, carbon fibers are cautioned against due to their higher cost and inferior mechanical properties.

Enhancing concrete sustainability using crushed peanut shells: An analysis of thermophysical properties, durability, and application potential in construction

This study explored the integration of crushed peanut shells (PS) into concrete with an emphasis on sustainable construction. Uniquely, it examines the impact of PS morphologies at low incorporation rates (0–6%) on the thermophysical properties and durability of concrete through rigorous experimental analysis and computational simulations. Our findings reveal that PS significantly enhances insulation properties and reduces thermal metrics and density while maintaining structural viability despite a slight increase in water absorption and a reduction in compressive strength with higher PS content. This investigation not only highlights the potential of PS-concrete to improve the thermal efficiency of building envelopes but also introduces it as an innovative approach to using agricultural by-products in eco-friendly construction. The results indicate significant advancement in the development of sustainable building materials, contributing to enhanced construction practices with environmental benefits.

Study on Manufacturing of Bricks by Using Waste Foundry Sand

The main objective of this project is to utilize waste foundry sand (WFS) from foundry industry in manufacturing of bricks. The entire process of combining clay mixtures, forming of bricks, drying and firing was done with local conditions. With minimum process it was possible to introduce up to 30% WFS in clay bodies to produce bricks of desirable properties. The minimum average wet compression resistance of 5.54Mpa, and maximum average water absorption of 20.76% was obtained for bricks containing 30% WFS, when fired at 900 C. There was insignificant difference in apparent porosity, water absorption, and specific gravity of bricks containing WFS, when compared to commercial bricks. The addition of WFS reduced the bulk density of the bricks, which has also caused reduction in compressive strength. WFS bricks can be classified as class II bricks, based on recommendations of IS 1077 standard specification. These bricks can be used in single storied load bearing structures, and also in the construction of infill walls in multi-storied framed structures.

Carbonation of Recycled Concrete Aggregates for New Concrete and Concrete Fines to Make Cement-Free Hollow Blocks

Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, impedes their recycling in the concrete industry. The quality of coarse recycled concrete aggregates (RCA) can, however, be enhanced by carbonation. Even when starting with high-grade RCA obtained from a selective demolition process, the carbonation process can decrease the water absorption of the RCA to as low as 3.0%. Concrete with a 50% replacement rate of carbonated RCA can be produced without a significant compressive strength reduction. The research further shows that carbonation can be performed at atmospheric pressure and low CO2 concentrations (e.g., 10%). The recycled concrete fines (RCF, 0–4 mm) in combination with 25% stainless steel slag were used to make zero-cement hollow blocks (39 × 19 × 9 cm) by carbonation curing without using any hydraulic binder. The hollow blocks have a compressive strength of 15.4 MPa at the lab scale. Both technologies were demonstrated on a pilot scale. In both processes, CO2 is immobilized in the resulting construction product. The developed production processes use less primary raw materials and cause less greenhouse-gas emissions than the production of traditional concrete products.