Leaching behaviour of calcium aluminate cement-based materials in water at 20°C and 60°C

Early performance modification of a waste-derived super-sulfated cement from arsenic-containing bio-oxidation waste via calcium aluminate and calcium sulfoaluminate cement

This study investigated the potential of liquid calcium aluminate cement (LCAC) as a sustainable substitute in the cement industry. The fluid form of LCAC effectively mitigates the rapid setting issues associated with traditional powdered calcium aluminate cement (CAC) and addresses logistical challenges related to transportation. Despite these advantages, challenges such as hydration conversion and subsequent compressive strength reduction, which can lead to self-degradation, have limited the application of LCAC. In addition, despite the fundamental similarity between LCAC and CAC, the significant differences in practical characteristics, including pH and reaction mechanisms, render traditional CAC methodologies less effective for LCAC. In this research, ground granulated blast-furnace slag (GGBS) was incorporated into LCAC mortar at various proportions to evaluate its potential as an auxiliary material. The findings demonstrated that the addition of GGBS noticeably enhanced the compressive strength and density of LCAC. The findings showed an optimal GGBS addition of 15% resulted in a 42.35% increase in compressive strength and a 31.23% reduction in water absorption. Microscopic structural analyses revealed that GGBS facilitated pozzolanic reactions, leading to the formation of stable Calcium-Aluminosilicate Hydrate (C-A-S-H) and Calcium Silicate Hydrate (C-S-H) gels, which mitigated self-degradation by reducing porosity. This study confirmed that LCAC can effectively address the challenges of hydration conversion and compressive strength reduction similar to CAC. The research highlighted the dual advantages of GGBS, which not only enhances the mechanical properties of LCAC but also fosters sustainability by lowering carbon emissions during both production and long-term application.

Polyphosphate-modified calcium aluminate cement under normal and elevated temperatures: Phase evolution, microstructure, and mechanical properties

Blast furnace slag is the most widely researched supplementary cementitious material (SCM) used to both reduce the carbon footprint of calcium aluminate cement (CAC) and inhibit conversion. Due to problems with the availability and cost of slag, there is a need to investigate other possible SCMs and their application potential in CAC. In this study, calcined clay with medium kaolin content (40% kaolinite) available in the region was used. The conversion process was accelerated by curing at an elevated temperature (38°C). The progress of conversion was evaluated by the development of compressive strength up to 56 days. At the same time, changes in the reaction products were analyzed by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) and the pore structure by mercury intrusion porosimetry (MIP). For the CAC samples cured at 38°C, TGA and XRD confirmed the conversion of metastable hydrates to stable hydrogarnet, resulting in the formation of new capillary pores, a significant increase in critical pore diameter, and a 60% loss of compressive strength. When slag or calcined clay was added to CAC, no decrease in compressive strength was observed after curing at elevated temperatures. When calcined clay was added to CAC, strätlingite hydrate was formed, which led to compaction of the structure and inhibition of conversion. This study has shown that the use of calcined clay instead of slag in CAC can effectively inhibit conversion, resulting in stable compressive strength regardless of the curing temperature.

This study investigates the effects of B 4 C, hBN, and SiC reinforcements on the mechanical, thermal, and tribological properties of calcium aluminate cement (CAC)-based composites. All composite samples were prepared by incorporating each reinforcement separately at varying weight fractions, followed by systematic evaluation of compressive strength, flexural strength, thermal shock resistance, and wear behaviour. The compressive strength of B 4 C-reinforced composites reached 339.1 ± 17.2 MPa, representing a 1208% increase compared to unreinforced CAC (25.93 ± 2.5 MPa). Flexural strength improved by 923%, and the residual compressive strength after thermal shock cycles reached 123.3 ± 9.3 MPa. For hBN-reinforced samples, compressive and flexural strengths increased by 804% and 213%, reaching 234.3 ± 12.1 MPa and 22.17 ± 3.2 MPa, respectively, with a post-thermal shock residual compressive strength of 81.2 ± 7.1 MPa. SiC-reinforced composites exhibited an 80% increase in compressive strength (46.48 ± 3.3 MPa) and a 23.9% improvement in flexural strength (5.45 ± 1 MPa). In terms of tribological performance, B 4 C-reinforced composites showed the most significant wear resistance, with a 98.3% reduction in wear rate and a 26.7% decrease in the friction coefficient. hBN and SiC reinforcements also contributed to notable reductions in wear rate by 96% and 86.6%, respectively. These findings demonstrate that the type and content of ceramic reinforcement significantly influence the performance of CAC-based composites. Among the tested reinforcements, B 4 C provided the highest overall improvements across mechanical, thermal, and tribological properties.

This paper highlights the essential tests for assessing the suitability of lime for stabilizing soils and typical changes in soil characteristics due to modification and stabilization processes with respect to mineralogical influences. The reasoning behind the mechanism of lime clay reaction on the compressive strength development of stabilized soils has been established. Clay with acidic origin exhibit less significant increase in compressive strength compared to clay with high intensity of kaolinite and with alkaline origin. In general, lime contents instituted, ranging from 3% to 6%, have contributed to a significant increase in unconfined compressive strength, from 2.5 to 11 times of the untreated soils. The formation of calcium aluminates silicate hydrate (CASH) observed from XRD test, after 14 days, indicates the early formation of new product, due to lime-soil reaction. The effectiveness of stabilization process has been found to be dependent on the quality of the lime, clay fraction, mineralogy and the alkalinity of the soil.

Hydration properties of portland cement plus calcium aluminate cement at 0∼20°C

Comparative Study on Impact of Rice Husk Ash and Fly Ash in Concrete Mix Design for Different Grades of Concrete

Influence of pre-wetting, non-shrink grout, and scaling on the compressive strength of grouted concrete masonry prisms

The biogenic corrosion of mortars adopted in sewage repair by sulfuric acid-producing bacteria was considered in this paper. Calcium aluminate cement (CAC) was known to resist microbiologically-induced corrosion significantly better than portland and blended portland cement.In this study, CAC as well portland cement mortars were tested as main binder to evaluate the corrosion resistance by the chemical immersion test. Replacement ratios of CAC were changed as 0, 20, 40, 50, 60% of OPC binder and 0, 2, 4, 6% of EVA(Ethylene Vinyl Acetate) were also adopted to increase properties of CAC repair mortars in sewage application. Setting time, compressive strength, acid resistance and adhesive strength were measured for various experiments. As a results of the experiments, the proper formulation of repair mortars was found at 40% of CAC and 4% of EVA. Finally, the CAC mortars adopted in field sewer pipe and were demonstrated to superior in adhesion and workability.

Calcium aluminate cements (CACs) are a group of rapid-hardening hydraulic binders with a higher aluminum composition and lower ecological footprint compared to their ordinary Portland cement (CEM) counterparts. CACs are commonly known to have higher thermo-durability properties but have previously been observed to experience a major strength loss over time when exposed to thermal and humidity conditions due to the chemical conversion of their natural hydrated products. To address this, in this study, silica fume is added to induce a different hydration phase path suggested by previous studies and utilized in conjunction with fiber-reinforced lightweight pumice to produce lightweight concrete. To closely evaluate the performance of the produced samples with CAC compared to CEM, two different types of cement (CEM and CAC) with different proportions of pumice and crushed stone aggregate at temperatures between 200 and 1000 °C were tested. In this context, sieve analysis, bulk density, flowability, compressive and flexural strength, ultrasonic pulse velocity and weight loss of the different mixes were determined. The results of this study point to the better mechanical properties of CAC samples produced with pumice aggregates (compared to crushed stone) when samples are exposed to high temperatures. As a result, it is found that CACs perform better than CEM samples with lightweight pumice at elevated temperatures, showing the suitability of producing lightweight thermal-resistant CAC-based concretes.

The influences of fibres originating from different waste materials on the fresh and hardened properties of self-compacting concrete (SCC) were investigated in this study. For this purpose, a total number of 13 mixes of wood (WF), polyvinyl chloride (PF), aluminium (AF), and iron filing (IF) fibres, with volume fractions (Vf) of 0.5%, 1.0%, and 1.5% were prepared. The investigated fresh properties of the prepared mixes were slump flow, T500, V-funnel as well as L-box tests, while the hardened properties were compressive strength, flexural strength, and ultrasonic pulse velocity (UPV). The findings indicated that although the majority of the prepared SCC mixes met the required self-compacting criteria, the inclusion of the waste fibres negatively affected the mix workability, particularly when Vf of 1.5% was used. Regarding the hardened properties, SCC mixes-containing IF exhibited a slight increase in both compressive and flexural strength compared with the reference mix without fibres, whereas mixes with AF fibres demonstrated a noticeable decrease in compressive strength, but with a comparable level of flexural strength. However, the flexural strength of WF and PF decreased as their Vf increased in the SCC mixes, although a slight increase in compressive strength was noted in the mixes with PF. Furthermore, there was no reliable relationship to be constructed between the compressive strength and UPV tests for all fibres used.

The compressive failure of nanoparticle silica and styrene‐butadiene rubber (SBR)‐filled epoxy composites has been investigated. Significant increase in compressive strength, compressive modulus, work of yielding, and work of fracture was noted for the cases of composites containing low weight fraction of silica and SBR. The compressive strength is about 4–10 times of the tensile strength for composite material containing different weight percent of SBR. Increase in compressive yield strength and decrease in compressive ultimate strength have been observed with crosshead speed 0.1–100 mm/s over all weight content of SBR and silica. The material shows increased elastic region with increasing crosshead speed. This indicates that the material is expected to behave more elastically and less plastically over all the crosshead speeds. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Utilization of aluminum sludge and aluminum slag (dross) for the manufacture of calcium aluminate cement

The purpose of this study was to Analyze the characteristics of theaggregates used in concrete mixtures and analyze how muchincrease in compressive strength of concrete with a variation ofnickel slag substitution 0%, 5%, 15%, 25% compared with normalconcrete. The characteristics of the material examined are watercontent, sludge content, specific gravity and absorption, volumeweight, abrasion with los angeles machines, and filter analysis.While the large increase in compressive strength of concrete can betested at the age of 7 days, 14 days, 28 days and 35 days. From the results of the analysis of the characteristics of nickel slagwaste in concrete mixes meet the test standards in concretemixtures, with a moisture content of 0.86%, sludge content of 0.44%,specific gravity of 2.94 gr / cm3, volume weight of 1.76 gr / cm3,abrasion 36.07%. And a large increase in compressive strength ofconcrete with a variation of nickel slag substitution of 0%, 5%, 15%,25% compared to normal concrete is increasing. The highestpercentage increase in concrete compressive strength is found inconcrete compressive strength between a variation of 15% with avariation of 25% at 14 days concrete age, with a percentage increasein value of 13.13%.