Effect of hydrated lime (Ca(OH)2) to compressive strength of geopolymer concrete

Abstract

The development of the Portland cement concrete industry is expanding globally until now. The demand for concrete or mortar as a construction material continues to increase due to the increase in infrastructure development. This increase causes environmental problems, namely carbon dioxide gas emissions. Recently cement has become a concern among environmentalists in the world. This is because carbon dioxide (CO2) is produced from cement production which has an impact on global warming and environmental pollution. Therefore, various studies have been conducted to find environmentally friendly alternatives to cement. One way is to develop a geopolymer. The purpose of this study was to measure the compressive strength of geopolymer concrete with the addition of hydrated lime (Ca(OH)2). This experimental test was carried out using a cube-shaped specimen measuring 15 × 15 × 15 cm. Cement substitute binders are class C fly ash and alkaline activator (NaOH 8M+Na2SiO3) and quenched lime as a substitute for 20% of fine aggregate. The characteristics of the concrete tested were the compressive strength of the concrete at the age of 7, 14 and 28 days with curing oven at 60°C for 24 hours and air curing, the total number was 6 of specimens. The results showed that the maximum compressive strength of the sample at 28 days reached 19.92 MPa. This result is not in accordance with the planned compressive strength of concrete, namely 20.75 MPa (K250). In addition, the addition of quenched lime to geopolymer concrete can complicate the workability process because the slump test value is very small, which is only 6 cm.

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