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Limestone calcined clay cement (LC3) has considerable potential for large-scale implementation. We investigated three selected kaolinitic clays at different locations in South Africa. LC3 mortars were compared to Portland cement mortar as control, particularly the hydration phase mineralogy/content, microstructure, compressive strength, and 3D void structure. The investigation indicated that similar pozzolanic oxide (SiO2 + Al2O3) could be obtained from calcined clay of varied kaolinite content. While kaolinite content improves the pozzolanic activity, consistency, and compressive strength of the mortar, the void refinement at the microscale depends on the degree of limestone filling/hydration. The hydration phase contents, microstructure, mineralogy, and porosity of the processed kaolinitic clays were determined to be adequate. However, it is noted that the intrinsic content of limestone (and gypsum) in commercially available Portland cement should be considered for equivalent clinker, limestone, and gypsum contents of 50%, 15%, and 5%, respectively. [ABSTRACT FROM AUTHOR]

Admixtures are an integral part of modern cementitious materials, as they significantly enhance the rheological, mechanical, and durability properties of the material. Though manufactured admixtures are mainly used in concrete production, they are expensive. Therefore, this research investigated the effect of sugarcane juice (SCJ), as a natural admixture, on the properties of concrete. Various percentages of SCJs were used to investigate the initial and final setting time, workability, compressive strength, and splitting tensile strength of concrete. Furthermore, the effect of different cement-sand ratios (c/s) and water-cement ratios (w/c) on the setting time of different cement mortar mixes was studied. Experimental results have shown that the setting time measured by the Vicat's apparatus reduces significantly, up to a certain percentage of SCJ in the mortar mixes. Setting time is also reduced as the c/s and w/c ratios are reduced in the mortar mix. From the results, it was found that, based on the c/s ratio, with the addition of 20% SCJ in the mix, the initial setting time of mortar can be reduced to 10% from 79%. In the case of mechanical strength, compared to the control mix (0% SCJ), more than 29% higher compressive strength in concrete was achieved by adding 10% SCJ to the mix. For the splitting strength, this increment was more than 4%. The ANOVA analysis also proved that the higher percentages of SCJ produced a compressive strength that was not statistically different from the control concrete mix. Finally, the research outcome showed that the dosages of SCJ can greatly alter the setting time and mechanical strength of cementitious materials. [ABSTRACT FROM AUTHOR]

The massive amount of plastic waste in our natural environment is a global concern. In this study, recycling plastic waste to partially replace natural sand in concrete is investigated. The performance of Resin8, a unique combination of all types of plastics and Polyethylene Terephthalate (PET) in concrete, has also been investigated. Replacement contents of 5%, 10%, and 15% for sand by volume were performed. The concrete mixes incorporating recycled plastic waste were tested against a reference concrete mix without plastic. The workability, compressive strength, tensile strength, oxygen permeability index (OPI), and effect of temperature were assessed. Scanning Electron Microscopy (SEM) analysis was conducted on the plastics and plastic concretes, pre- and post-temperature exposure. PET at a replacement content of 10% slightly increased the compressive strength by 2.4%. Regarding the OPI test, all the mixes incorporating recycled plastic waste are classified as "good". When exposed to a temperature of 250 °C, no significant change in compressive strength was observed for the concrete mixes incorporating Resin8 at a replacement content of 15%, and the mixes incorporating PET at a replacement content of 5%, 10%, and 15%. It was clear from the results that both Resin8 and PET are suitable as a partial replacement for sand in concrete. [ABSTRACT FROM AUTHOR]

This study evaluates the mechanical, durability, and residual compressive strength (after being exposed to 20, 120, 250, 400 and 600 °C) of mortar that uses recycled iron powder (RIP) as a fine aggregate. Within this context, mechanical strength, shrinkage, durability, and residual strength tests were performed on mortar made with seven different percentages (0%, 5%, 10%, 15%, 20%, 30% and 50%) of replacement of natural sand (NS) by RIP. It was found that the mechanical strength of mortar increased when replaced with up to 30% NS by RIP. In addition, the increase was 30% for compressive, 18% for tensile, and 47% for flexural strength at 28 days, respectively, compared to the reference mortar (mortar made with 100% NS). Shrinkage was observed for the mortar made with 100% NS, while both shrinkage and expansion occurred in the mortar made with RIP, especially for RIP higher than 5%. Furthermore, significantly lower porosity and capillary water absorption were observed for mortar made with up to 30% RIP, compared to that made with 100% NS, which decreased by 36% for porosity and 48% for water absorption. As the temperature increased, the strength decreased for all mixes, and the drop was more pronounced for the temperatures above 250 °C and 50% RIP. This study demonstrates that up to 30% RIP can be utilized as a fine aggregate in mortar due to its better mechanical and durability performances. [ABSTRACT FROM AUTHOR]