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Natural pozzolan is a promising supplementary cementitious material for hydraulic concrete due to the pozzolanic effect, especially in the area where fly ash is scarce. In this paper, the physical properties of pozzolan were evaluated. The effects of pozzolan fineness and content on the microstructure, compressive strength, and early-age chemical shrinkage of pozzolan blended cement pastes were investigated. The results showed that the addition of pozzolan decreased the compressive strength of hardened cement pastes. The pozzolanic reactivity was closely related to the fineness of pozzolan, and higher pozzolan content led to lower strength. X-ray diffraction (XRD) and thermogravimetric (TG) analysis proved that Ca(OH)2 was consumed by reacting pozzolan, forming new calcium silicate hydrated (C-S-H). Besides, the addition of pozzolan caused the increase in porosity, which was reflected by the increase in macro-pores content. The chemical shrinkage of cement pastes was mainly determined by the hydration rate of cement, so the early-age chemical shrinkage was notably reduced after adding pozzolan due to its lower reactivity than cement clinker. In addition, finer pozzolan particles resulted in less macro-defects in the cement matrix, which enhanced the deformation resistance of hardened cement paste, and thus the chemical shrinkage was also decreased. [ABSTRACT FROM AUTHOR]

In the present investigation, a comparison of Graphene Oxide (GO) and Functionalized Multiwalled Carbon Nanotubes (FMWCNTs) incorporated in Pozzolana Portland Cement (PPC) mortar was carried out to find their influence on mechanical and durability properties. It has been observed that Pozzolana Portland Cement Carbon-Based Nano-Composites (PCCNCs) mortar has outstanding mechanical and durability properties. The finding shows that the PPC-1G (0.0015% of GO by weight % of cement) and the PPC-1C (0.0015% of FMWCNTs by weight % of cement) showed the greatest improvement in mechanical and durability performance over the curing period of 90 days (d). When PPC-1G and PPC-1C were compared with the reference (PPC-Control) sample, their compressive strengths increased by 11.67% and 8.73%, respectively. In terms of tensile splitting strength, PPC-1G and PPC-1C had shown a 26.35% and a 20.61% increment, respectively, as compared to PPC-Control. The C-S-H gel grows efficiently in the PCCNCs mortar, as per Powdered X-ray Diffraction (PXRD) data. It is possible to determine the carbonates present in the PCCNCs mortar by using Fourier Transform Infrared Spectroscopy (FT-IR). Furthermore, the microstructural behavior of PCCNCs mortar revealed by the Field Emission-Scanning Electron Microscope (FE-SEM) indicates that the production of ettringite and needle-shaped structures contributes to the enhancement of the mechanical strength and durability properties of the PCCNCs mortar. The research paves the way for incorporating GO and FMWCNTs in cement-based materials. This tremendous advancement holds enormous promise for the advancement of the building and infrastructure sectors. Implementing high-performance mortars has the potential to increase the strength, durability, and sustainability of structures, hence contributing to the development of safer and more resilient built environments. [ABSTRACT FROM AUTHOR]