The Durability of Lightweight Geopolymer Concrete (LGC) on Chloride Resistance

Abstract

Lightweight geopolymer concrete is an innovative concrete from a combination of environmental-friendly geopolymer concrete and lightweight concrete which has a density of less than 2,400 kg/m³. This concrete does not use Ordinary Portland Cement (OPC) but uses type F fly ash which has the same main composition as OPC namely silica and aluminum. Reducing the use of OPC aims to reduce the production of CO₂ gas emissions which are the main contributors to global warming. This study aims to provide the information needed to develop lightweight geopolymer concrete to reduce carbon emissions and create environmental-friendly concrete materials. The constituent materials of lightweight geopolymer concrete include type F fly ash as precursors, Na₂SiO₃ and NaOH 14 M as activators, fine aggregates in the form of sand as concrete fillers, superplasticizers, and foam. The use of foam helps in reducing the density of lightweight geopolymer concrete. The ratio used in this study is 1:2 for activators and precursors, 1:2 for precursors and fine aggregates, 2.5:1 for Na₂SiO₃ and 14 M NaOH, and 1:40 for foam agents and water with a percentage of foam that is 50% of test object volume. The amount of plasticizer used is 3% of the weight of the precursor. Treatment of the lightweight geopolymer concrete using an oven with a temperature of 60°C for 24 hours and then the specimen coated with plastic wrap for 28 days to achieve maximum compressive strength. Curing for 28 days, the specimen has a compressive strength of 27.9 MPa with a specific gravity of 1,702.5 kg/m³. This research focuses on the durability of lightweight geopolymer concrete using 5% HCl acid solution under different conditions, which are left at room temperature, fully immersed in 5% HCl acid solution, and cyclic conditions. Tests were carried out on days 28 and 56 with observations of changes in compressive strength, density, visual conditions, Scanning Electron Microscope, and XRD. The results showed that acid solutions' long duration and soaking conditions, especially hydrochloric acid, affect lightweight geopolymer concrete.