The influence of NaOh solution on the efflorescence of geopolymer mortar

Fly ash Nagan Raya (FANR) is an alternative material from power plantation in Nagan Raya, Aceh, Indonesia. The material of FANR was considered as a novelty material in the pozzolanic material due to have the chemical content of Si, Al, and Ca, respectively. However, the shape of the FANR particle was a misty surface that absorbed the water or alkaline solution from the fresh geopolymer mortar and impacted the workability. The previous investigation described the use of the ratio of AS/FANR of 1.1 with the concentration of 8M NaOH in the alkaline solution. However, the efflorescence was a presence on the surface of geopolymer mortar. This study aimed to reduce the presence of efflorescence on the surface of geopolymer mortar. The samples were prepared by mortar cubes 50mm x 50mm x 50mm with the ratio of AS/FANR of 1.0 and 1.1, the ratio of Na2SiO3/NaOH of 2.0, 2.5, 3.0, and 3.5, the concentration of NaOH solution of 6M and 8M, respectively. The results showed that the reduction of efflorescence was affected by the reduction of NaOH concentration, AS/FANR ratio, and Na2SiO3/NaOH, respectively. This study described that the ratio of AS/FANR of 1.0, the ratio of Na2SiO3/NaOH of 3.0, and the concentration of 6M NaOH reduced the efflorescence on the surface of geopolymer mortar and maintain the characteristic of geopolymer mortar.