Properties of Geopolymer Paving Blocks Based On Fly Ash with Bottom Ash as A Sand Substitution
The waste material from coal production in the form of fly ash (FA) and bottom ash (BA) is increasing from time to time so efforts are needed to make the most of it, but until now the use of BA is still very less compared to FA. This research was conducted by combining FA and BA in the manufacture of geopolymer paving blocks. FA as a binder and BA as a substitute for sand. This study aims to examine the performance of geopolymer paving blocks with variations of BA on compressive strength, absorption, porosity, abrasion resistance, and sulfate resistance against wet-dry cycles. Geopolymer paving blocks were made with a composition of 10 M NaOH, a ratio of Na2SiO3/NaOH of 2.5, a ratio of alkaline activator/FA solution of 0.4 with BA variations of 0%, 25%, 50%, and 75% by weight of sand and curing at ambient temperature. The test results showed that paving blocks with a BA substitution of 25%-75% showed good performance according to SNI-03-0691-1996 including absorption, porosity, abrasion resistance, and sulfate resistance except for compressive strength. The nature, shape, and gradation of BA affect the performance of paving blocks. Paving blocks without BA meet the standard quality D paving used for parks and other uses.