Rice husk ash (RHA) based geopolymer mortar incorporating sewage sludge ash (SSA)

Abstract

Geopolymer based cementitious materials were produced to reduce or completely eliminate the use of cement in concrete in which could be incorporated with waste materials. In this study, rice husk ash (RHA) which is a waste having rich in silica content after burnt was intended to be used as based geopolymer. Besides, sewage sludge ash (SSA) was incorporated with RHA producing geopolymer mortar in which also having pozzolanic element of Si and Al. Geopolymerisation requires Si and Al elements to react with highly alkaline solution to produce geopolymeric material. Therefore, combination of RHA and SSA will be possible solution as base geopolymer mortar in order to provide Si and Al. The effect of SSA inclusion was investigated under different sodium hydroxide (NaOH) molarity and curing conditions to the strength development. NaOH and sodium silicate were used as activator with ratio of 1:1 and the solution to ashes ratio of 1:1 was used. Compressive strength was tested at 7, 14 and 28 days. The results showed that the geopolymer mortar made of SSA replacement exhibited higher compressive strength with reference to those made of RHA (control sample). In addition, the results showed that geopolymer mortar specimen containing 15% of SSA replacement activated with 8M NaOH solution gave the highest strength recorded 15.0MPa in oven curing condition (60°C for 24 hours). As conclusion, SSA up to 20% replacement has potential to be used in producing geopolymer as replacement alternative to RHA.