Pervious low-calcium fly ash geopolymer concrete using gap-graded limestone coarse aggregates in ambient curing

Abstract

This paper describes the research of pervious geopolymer concrete using limestone from Timor Island in Indonesia as coarse aggregate. No sand was used to make this pervious geopolymer concrete. Two types of crushed limestone aggregates used were coral limestone (organic limestone) and limestone (calcilutite). Abrasion losses of the aggregates using Los Angeles Machine test were 18.9% for limestone (calcilutite) and 34.98% for coral limestone. Those aggregates had many characteristics such as 10-20 mm of diameter length, angular shapes and apparent specific density 2.74-2.75. The mass ratios of aggregate to geopolymer paste were varied from 2.86 to 6.91. To make the geopolymer paste, it was used Class F or Low-Calcium Fly Ash from Bolok-Kupang Coal Fired Power Plant as a rich silica-alumina of precursor material. Meanwhile, the mass ratio of natrium silicate solution to natrium hydroxide solution 10 M was 1.0 and the mass ratio of fly ash to alkaline solution was 2.0. Ambient curing was applied to all specimens. Mechanical characteristics obtained at the age of 28 days of hardened pervious geopolymer concrete were: (1) compression strength, (2) splitting tensile strength, and (3) abrasion losses using Los Angeles Machine Test. Besides, density of hardened specimens were also obtained. In addition, the comparisons of mechanical properties of pervious geopolymer concretes using coral limestone and limestone (calcilutite) as coarse aggregate were also conducted. According to the results of this research, it is feasible to make pervious geopolymer concrete using Timor limestone as coarse aggregate due to its mechanical characteristics.