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Bentonite mostly exists in many counties and studies reported employment of activated bentonite in the concrete improves concrete performance more than using raw bentonite. However, it is not well-known which range of bentonite activation temperature and employment dose gives the best concrete performance for the sustainability of activated bentonite in construction materials. Therefore, the present study detail reviewed the effect of activated bentonite at different heating temperatures and replacement doses of bentonite on the durability, physical, mechanical, and microstructural properties of concrete. Also, environmental and economic beneficiary of employing activated bentonite in concrete is evaluated. As the review of various studies reveals, activation of bentonite between 201 and 800°C increases the pozzolanic reactivity of bentonite. Hence, the activated pozzolana can easily consume free calcium hydroxide to form a secondary C–S–H gel that can improve the mechanical, microstructural, and durability properties of activated bentonite blended concrete in addition to lessening energy consumption compared to conventional concrete. Besides these, adding 15%–20% of activated bentonite in concrete significantly improves the mechanical properties; specifically, most studies found the optimum activated bentonite dose is 15% by weight of cement in concrete. This replacement indicates lessened energy consumption by around 45% compared to the total employment of ordinary Portland cement in concrete production.

Cement plays a crucial role in mortar composition, and its particles exhibit a strong tendency to flocculate when mixed with water. This flocculation necessitates the addition of substantial water to improve the workability of mortar or concrete. However, this extra water does not contribute to the hydration reaction, potentially weakening the mechanical properties of the mortar. The introduction of superplasticizers has addressed this issue by reducing the water demand. Nevertheless, a common practice in construction is to use a standard dosage of superplasticizers for the same type of cement, even when sourced from different cement factories, which may affect material performance. This study investigated the influence of varying superplasticizer dosages on Portland pozzolana cement from different Ethiopian cement factories, examining the morphological characteristics of masonry mortar. Specifically, it evaluated the impact on cracks, porosity, and surface structure across different curing ages, as well as assessed the mortar’s physical and mechanical properties. Mortar samples prepared using cement from three factories, labeled A, B, and C, with constant cement-to-sand ratios of 1:3 and water-to-cement ratios of 0.5. Superplasticizer added in varying amounts 0%, 0.6%, 0.8%, and 1%. The morphological analysis conducted using a 3D optical surface profiler microscope at 1, 7, 21, and 28 days. Besides these standard physical and mechanical tests also performed on all samples. The results demonstrated that addition of superplasticizers significantly influenced the surface morphology of mortar samples. Mortars A and B exhibited denser structures with superplasticizer dosages 0.8% and 1%, respectively, whereas mortar C displayed a denser structure in its control state (without superplasticizer). The flexural and compressive strength tests also revealed notable differences. Sample A2 (0.8%) from group A, sample B3 (1%) from group B, and sample C0 (0%) from group C achieved the highest strength within their respective groups at 28 days. The findings suggest that it is essential to evaluate the specific properties of cement before applying a standardized superplasticizer dosage, as variations in cement production can significantly influence the performance of the mortar.

Construction industries are rapidly growing, sacking high amounts of concrete which has a highly dense microstructure with excellent mechanical properties, more durable, and highly eco-friendly materials. Hence, many of the researchers are interested in solving this problem with replacing concrete by natural pozzolana (NP) which is a supplementary cementitious material mostly from volcanic sources having much active silica content that can improve the durability and mechanical properties of concrete. However, it is not well-known which common optimum replacement range can give the most desirable concrete properties. So, the present study sought to review the effects of replacing NP from volcanic sources on the durability, physical, mechanical, and microstructural properties of concrete, also, to identify the most common dose of a positive effect as a replacement in concrete. The review shows that many of NP used by different literature from different places satisfy ASTM replacement standard in concrete, especially, based on its chemical compositions. Also, the review observed that employing NP in concrete significantly improves concrete workability, lengthens setting time, and reduces bulk density, porosity, water absorption, and chloride ion migration by making denser concrete microstructure. In general, adding 5%–20% of NP in concrete significantly improves compressive strength, split tensile strength, and flexural strength. Specifically, most of the studies found 15% replacement of NP having volcanic sources can give optimum strength. Besides these, most of the studies indicated that the improvement of the strength was more visible at the concrete age of 7–28 days.