Abstract

More undesirable wastes or by-products are generated from the coconut and coir industry as coir pith. The raw coir pith was fired up to 500 ºC inside a suitable oven to obtain Coir Pith Ash (CPA). The effect of CPA as a supplementary cementitious material on the various specific characteristics of Portland cement pastes was investigated. Results illustrated that the blaine fineness of the whole cement blend, water of consistency and setting times increased with the increase of CPA addition. The bound water content and bulk density as well as flexural and compressive strengths improved and enhanced with the addition of CPA only up to 12wt % CPA (CP4), and then sharply decreased suddenly with further increase of CPA content (CP5). The free lime content of the blended cement pastes containing different ratios of CPA decreased at all hydration times and were being lower than those of the blank (CP0). The apparent porosity also gradually reduced with cement pastes containing up to 12wt % CPA as in the cement blend CP4, but then increase with further increase of CPA content > 12wt% CPA as in the cement blend CP5. The Ultrasonic Pulse Velosity (USPV) test showed that the matrix conformities of the various hardened cement pastes with CPA are well sticky and good quality.

Keywords: Cement; CPA; Consistency; Setting; Free lime; Porosity; Strength