Durability performance of Geopolymer Mortar Synthesized from ternary blend of cassava peel ash, rice husk ash, and metakaolin

Abstract

Geopolymer technology involves production of cementless, environmental-friendly concrete which is synthesized from agriculture by-products such as Rice Husk Ash (RHA), Cassava Peel Ash (CPA) and earth explore product like Metakaolin (MK) with merits to decrease the enormous amount of agricultural waste and earth explore materials as well as the contribution in carbon footprint annually. The study therefore explored the development of alkali-activated CPA-SHA-MK ternary blended geopolymer mortar (GPM) using sodium silicate (Na2Si3) and sodium hydroxide (NAOH) solution with 9M constant concentration as alkaline activators under both the aggressive and ambient-temperature curing media. The mass ratio of sodium silicate to sodium hydroxide (NS:NH) and as well as the binder to fine aggregate were fixed to 2.5 and 0.8 respectively It also analyse the extent to which the Supplementary Cementitious Materials (SCMs) improves the durability performance of the product. The durability of the ternary blended geopolymer mortar was examined through water absorption test, acid resistance test and sulphate resistance test using 50 mm cubes after 28, 56 and 90 days of curing. The results revealed that the setting time prolonged as the replacement levels of RHA-MK increased at a decrease in replacement levels of CPA. The results also showed that the mortar cured in sulphate solution as well as the sulphuric acid showed white precipitate on the reference specimen (PCM) with rounded edges and the GPM incorporated SCMs and activators (C90M7R3, C70M20R10, C50M33R17, C30M47R23 and C10M60R30) showed a little dark colour at all ages. The GPM discovered to be more resistance to water absorption as compared to PCM while it was observed that the absorption increases as the hydration periods increases. Furthermore, both the PCM and GPM samples studied suffered mass and strength losses in both the acid and sulphate solution and the loss increases at an increase in the hydration periods while the loss as caused by sulphuric acid is more pronounced. The losses were observed to be higher in PCM as compared to the GPMs while the mix incorporated 50% CPA, 33% MK and 17% RHA (C50M33R17) was observed to be better compared to other mixes in durability behaviour and the study therefore recommends C50M33R17 for good durability performance.