The influence of aluminium dross residue and coal fly ash on the properties of geopolymers

In this research, aluminium dross residue (AD) and coal fly ash (FA) were used for the production of geopolymers. The illegal dumping of AD and the high cost for AD waste disposal have been problems for long time in Thailand. Therefore, the feasibility of using AD (0 wt% to 100 wt%) in the geopolymer production had been carried out to find the alternative way to resolve these problems. The alkaline solution of NaOH 7 M and Na2SiO3 with the ratio of 1:3 was used for the geopolymerization reaction. It was found that the addition of AD caused the ammonia gas during the process, which resulted in high porosity of the samples. The low compressive strength, low density and low thermal conductivity were observed in the samples with higher AD contents. The results indicated that the sample with 50 wt% AD and 50 wt% FA gave the reasonable properties for lightweight concrete block with the density of 1.56 g∙cm‒3, the compressive strength of 6.32 MPa, and the water absorption of 4.26%. In addition, the phase structure, microstructure and the structure change of the geopolymer samples were investigated using XRD, SEM and FTIR techniques, respectively.