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Concrete production consumes enormous amounts of fossil fuels, raw materials, and is energy intensive. Therefore, scientific research is being conducted worldwide regarding the possibility of using by-products in the production of concrete. The objective is not only to identify substitutes for cement clinker, but also to identify materials that can be used as aggregate in mortar and concrete productions. Among the potential alternative materials that can be used in cement composite production is rock dust of different geological origin. However, some adversarial effects may be encountered when using rock dust regarding the properties and durability of mortars and concrete. Therefore, comprehensive research is needed to evaluate the adequacy of rock dust use in cementitious composite production. This paper presents a comprehensive review of the scientific findings from past studies concerning the use of various geological origins of rock dust in the production of mortars and concrete. The influence of rock dust as a replacement of fine aggregates on cementitious composites was analyzed and evaluated. In this assessment and review, fresh concrete and mortar properties, i.e., workability, segregation, and bleeding, mechanical properties, and the durability of hardened concrete and mortar were considered.

The increasing demand in cement has inspired researchers in both developed and developing countries around the world to explore and consider alternative materials as partial replacement of cement both in concrete and in mortar. In this study, the influence of agricultural waste, particularly corn cob ash, (CCA) as pozzolanic material or supplementary cementitious material (SCM) on the physical properties and compressive strength of cement mortar was investigated. CCA was used as partial replacement of cement ranging from 0% to 20% by weight at water-cementitious ratio of 0.6 and mix proportion of 1 cementitious: 3 fillers. The physical properties evaluated for the mortar paste were setting time and consistency; and compressive strength of hardened mortar cube. The chemical analysis of CCA was conducted, and results indicated that the CCA used in this study is classified as Class C pozzolana with combined SiO2 + Al2O3 + Fe2O3 of 55.86%. The addition of CCA increases the initial and final setting time. The study also revealed that the addition of CCA in the mortar mix reduces the plasticity or fluidity of the paste. Further, the result indicated that the compressive strength of mortars with CCA decreased as the amount of CCA replacements increased in the mixture. The mortar pastes with varying amount of cement replacements, however, are superior for use as mortar for masonry construction.

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The continuous demands for stringent environmental regulation and increased interests in the preservation of natural resources have motivated industries and research institutions to examine and consider alternative approaches on the use of renewable resources and waste by-products. This study was conducted using one of the most available natural fiber types worldwide, the Phoenix Dactylifera L. Fibers, commonly known as Date Palm Fibers (DPF). Limited researches and inconsistencies in results obtained have been reported in literature on the use of DPF in concrete. Thus, there is a need of further evaluation and study on the structural behavior of fiber reinforced concrete with DPF. The present study used DPF as a natural reinforcement in concrete at varying content of 0%, 0.6%, 1.0%, and 1.4%; and different fiber lengths of 0 mm, 15 mm, 30 mm, and 45 mm. The results indicated that integration of DPF affects the physical properties particularly the workability and density of fresh concrete. Generally, the mechanical properties such as compressive strength, tensile strength, and flexural strength of DPF reinforced concrete decreases as the amount of DPF increases in content and fiber lengths. Scanning Electron Microscopy (SEM) analysis was carried out to examine the internal behavior and effect of DPF in the hardened concrete. Matrix deboning, fiber fractures, and voids due to the pull-out effect were observed as failure modes that contributed to lower compressive strength, tensile strength, flexural strength, and deflection as compared to control specimen.