Effects for partial replacement of Portland cement by low water absorption porcelain insulator

Abstract

The side effects caused by the low water absorption capacity of ground electrical porcelain insulator (GEPI) as a partial substitute for ordinary Portland cement (OPC) was evaluated. Despite the wide use of alternative eco-friendly materials in order to minimize the carbon footprint of the cement industry, the complex chemistry of cement hydration requires deeper studies to comprehend the influence of such admixtures. GEPI was characterized by granulometric analysis, as well as by XRF, PXRD and SEM. Its pozzolanic activity was determined by the Modified Chapelle assay, and the mechanical tests were performed in order to measure the compressive and flexural strengths of the specimens. For this reason, prismatic specimens were prepared by the replacement of 5.0, 10.0 and 20.0 wt.% of OPC by GEPI. The specimen strength showed a dependence on the level of substitution and a delay in the strength gain was observed over time. PXRD allowed the analysis of the variation in the quartz peaks intensities and to monitor the role played by the low water absorption of porcelain in the ettringite decomposition. A crystalline phase of γ-Al2O3, which was formed by the dehydration of the gel-like Al2O3, was identified. SEM images allowed us to indicate a fibre bundle-shaped C-H-S massive phase embedded in the mortar, as well as portlandite plates and angular crystallites of quartz. GEPI influenced the OPC hydration process and did not drastically compromise the strength of the mortar; therefore, it may be further investigated as a support material to prevent early OPC stiffening.