Engineering properties of mortar and concrete using eco-processed pozzolan as partial cement replacement material / Lin Ying

Lin , Ying (2024) Engineering properties of mortar and concrete using eco-processed pozzolan as partial cement replacement material / Lin Ying. PhD thesis, Universiti Malaya.

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Abstract

This research aims to develop sustainable and structural-grade mortar and concrete by partially replacing conventional cement with two palm oil-based by-products namely, unprocessed eco-minerals (UEM), and ground and unground eco-processed pozzolan (GEPP and EPP). This study characterized the physical, chemical, morphological, and mineralogical properties of UEM, EPP, and GEPP. In addition, this research assessed the effect of cement replaced by UEM, EPP, and GEPP at various levels on workability, hardened properties, microstructural characteristics, and sustainability aspects of mortar. Additionally, this research examined the effect of varying EPP replacement levels on fresh and hardened properties, microstructure characteristics, and sustainability aspects of granite, electric arc furnace steel slag (SS), and palm oil clinker (POC) coarse aggregates concrete. The effect of EPP on selected durability properties of concrete was examined. The research findings demonstrate that incorporating UEM, EPP, and GEPP as SCMs has some effect on the flow, density, ultrasonic pulse velocity (UPV), and compressive strength compared to the control mortar. Based on the UPV test results, the quality of mortar containing up to 30% UEM and 70% EPP was classified as good. The compressive strengths of mortars with 30% UEM, 50% EPP, and 50% GEPP show that these can be classified as structural grade mortar. Based on the FESEM images, the control mortar exhibited a denser matrix compared to UEM, EPP, and GEPP mortars. Furthermore, the XRD test results depict that the GEPP consumed the highest amount of Ca(OH)2, followed by EPP and UEM. Incorporating UEM and EPP significantly reduces CO2 emissions and energy consumption of mortar. The inclusion of a higher volume of EPP, ranging from 30 to 50%, influenced the fresh and hardened properties of the concrete. On the concrete incorporating the EPP in granite and SS-based mixes, the UPV results show that the quality of granite and SS concrete with EPP generally was outstanding, while the quality of POC concrete with 0-50% EPP was good. The mixes with 0–50% EPP in concrete with granite, SS, and POC were classified as a structural-grade, especially POC concrete, which was classified as a lightweight structural-grade. The Ca(OH)2 peak intensity was high in the control concrete relative to 10% EPP concrete. Incorporating EPP prominently reduced CO2 emission and energy consumption of concrete. Regarding concrete durability, incorporating EPP rises water absorption, porosity, and electrical resistivity of granite, SS, and POC concrete. The HCl resistance of granite concrete increased with the improvement in the EPP replacement level. Notably, the FESEM images and XRD pattern of the control and 30% EPP concrete exposed to HCl solution showed an absence of CH and ettringite. However, when exposed to MgSO4 solution, there was a decrease in the compressive strength improvement of granite concrete as the EPP replacement level increased. Furthermore, the FESEM images demonstrated that the control concrete displayed a denser microstructure compared to the 30% EPP concrete when the concrete was exposed in MgSO4 solution. The XRD pattern revealed higher peak intensities of ettringite and gypsum in the control concrete exposed to MgSO4 solution.

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