Comparative study on early strength of sodium hydroxide (NaOH) activated fly ash based geopolymer

Abstract

Abstract. The urge to reduce carbon dioxide (CO2) emission has encourage researchers to introduce environmental friendly binder or known as geopolymer. This new binder was produced by mixing source materials rich in silica and alumina with alkaline liquids. For this study, class F fly ash was used as source material with two different types of alkaline activator; sodium hydroxide (NaOH) only and a combination of water glass with NaOH. The different concentration of the NaOH solutions (8M, 10M, 12M and 14M) is used in the production of geopolymer. The parameters such as curing regime, solid/liquid ratio, and water glass/NaOH ratio are controlled in the study. The samples with combination of NaOH and water glass as alkaline activator were prepared by mixing these two solution and stirred for 2 minutes. Then this solution were mixed together with fly ash for 3 minutes and casted in the mould. The performance of the fly ash based geopolymer are evaluated by the compressive strength, water absorption and density at the early age of 1th, 3th and 7th days. Based on the study, at a concentration of 14M on 7th days had achieved the maximum compressive strength of 7.1 MPa for samples activated with NaOH only. Meanwhile, for geopolymer samples activated with a combination of the water glass and NaOH, the maximum strength of 33.33 MPa was recorded on 7th days of testing with NaOH concentration of 12 M. The water absorption for all geopolymer samples were ranging from 2.04 % to 2.78%, which are below the limit (3%). While the density of the geopolymer paste were in the range of 1552 kg/m3 to 1680 kg/m3, which are below the limit (2400 kg/m3). From the standpoint of strength of hardened geopolymer samples, the most effective alkaline activator in geopolymer is the combination of NaOH and water glass.

Mechanical and microstructural properties of high calcium fly ash one-part geopolymer cement made with granular activator

“…Accordingly, it can be deduced from these findings that at the initial stages the reaction process is faster. These findings are quite the opposite of [44]. Fig.…”

Waste-Based One-Part Alkali Activated Materials

“…The mortars MCA0.35 and MCT0.33 exhibit slightly higher absorption values (1.36 and 1.37%), due to the greater water content. Nevertheless, all the one-part AAMs prepared show suitable water absorption values (<5%), above which their compressive strength can be compromised [ 39 ]. In addition, the typical water absorption values for mortars with OPC vary between 15 and 18% [ 40 ], while for traditional AAMs they are slightly lower, from 5 to 11% [ 41 , 42 ].…”

“…The authors observed that the workability and setting time of the AMMs mixtures prepared with sodium silicate did not fill the requirements, even when additives were used, and a decrease of the compressive strength was observed. On the contrary, in the mixtures prepared with anhydrous sodium metasilicate, it was possible to adjust the pastes' workability and the setting time leading to interesting mechanical properties (37)(38)(39)(40)(41)(42)(43)(44)(45).…”

Produção De Cimento Geopolimérico a Partir De Cinza Volante E Soluções Ativadoras Simples E Compostas

“…O processo de geopolimerização necessita de um menor consumo energético pode ser realizado pelo uso de subprodutos industriais (NATH et al, 2016). Em relação ao consumo de energia e a emissão de gases de estufa, o cimento geopolimérico emite 80% menos de CO2 e consome 30-40% menos de energia do que o cimento Portland, em sua produção (YAHYA et al, 2017).…”

“…O desenvolvimento da microestrutura geopolimérica é dependente das características das matérias-primas e de parâmetros do processo, especialmente da concentração alcalina da solução ativadora utilizada e da temperatura de cura (YAHYA et al, 2017). Estudos têm demonstrado que a temperatura de cura é um parâmetro que tem papel importante no processo geopolimerização (NATH et al, 2016).…”