Experimental investigation of the effect of cassava starch as a natural retarding admixture on the setting time of cement paste

Abstract

The increasing demand for sustainable and environmentally friendly construction materials has encouraged research into the use of locally available agricultural products as alternatives to conventional chemical admixtures. This study investigated the effect of cassava starch as a natural retarding admixture on the setting time of cement paste. Cassava starch was incorporated into cement paste at dosage levels of 0%, 0.5%, 1%, 1.5%, 2% and 2.5% by weight of cement. Two commercially available cement brands, Dangote Cement and BUA Cement, were used to evaluate the influence of cement type on the performance of cassava starch. The initial and final setting times of the cement pastes were determined using the Vicat apparatus. The results showed that the incorporation of cassava starch generally delayed both the initial and final setting times of the cement paste. For Dangote Cement, the control paste recorded initial and final setting times of 160 and 250 minutes, respectively, while the 2% cassava starch paste recorded 300 and 410 minutes. For BUA Cement, the corresponding values increased from 202 and 253 minutes for the control to 313 and 423 minutes at 2% cassava starch. A slight reduction in setting time was observed at 2.5% dosage in both cement brands. The results demonstrate that cassava starch has significant potential as a locally available natural retarding admixture. The study recommends controlled dosage levels, particularly around 1–2%, depending on the cement type and the required delay in setting. Cassava starch may provide a low-cost and renewable alternative to some conventional chemical retarders, especially in regions where cassava is abundantly produced.