An effect of NaOH molarity on fly ash—Metakaolin-based self-compacting geopolymer concrete

Abstract

The study aims to investigate the workability and mechanical properties of fly ash- and metakaolin-based self-compacting geopolymer concrete (SCGC) on different NaOH molarities. The mix proportion of SCGC was arrived by trial and error method. Workability properties like slump flow, T50 slump flow, V-funnel, and L-box and mechanical properties such as compressive, split tensile, and flexural strength were tested at 7, 28, and 56 days. The specimens were cured at 70 °C for 24 h in oven followed by ambient curing till the respective days of testing. The experiments were carried out by varying the mass fraction of fly ash with metakaolin by 0, 10, 20, and 30% by mass for all the molarities like 8, 10, and 12 M, for a constant binder content of 400 kg/m3. The fluid-to-binder (F/B) ratio of 0.47 by mass and superplasticizer (S.P) dosage of 3% was used for all the molarities, and extra water content was varied accordingly. The experimental result revealed that workability parameters like slump flow, L-box ratios were decreased, and V-funnel flow time and T50 cm flow time increased with the increase of metakaolin replacement level and as well with increase in molarities, and the entire test was done as prescribed by EFNARC guidelines. The results of compressive, split tensile, flexural strength reduced with addition of metakaolin in fly ash content, and however, it increased with increase in morality.