Crushed Rock Geopolymer as a Future Road Construction Material: An Evaluation of Compaction and Strength Characteristics

Abstract

To be more sustainable in the road construction industry, the rock-based geopolymer concept should be applied with an aim to create a geopolymer-based road structural layer. This research episode concentrated on the primary study of compaction characteristics of crushed rock geopolymer (CR-GP) in conjunction with its unconfined compressive strength (UCS) and micro-observations through XRF and XRD. The new grain size distribution curve, namely practical grading, was produced for use as a prime material in CR-GP. Especially, CR-GP is a mixture of CR practical grading (B) and liquid alkaline activator (L) of Na2SiO3 (SS) and NaOH (SH) with a concentration value of five molar. The SS/SH ratio of 0.67 was also used. Test results showed that the compaction curves of CR-GP can be established as the bell curve with a peak point. The modified compaction curve showed higher maximum dry density (MDD) of 2210 kg/m3 and optimum liquid alkaline activator content (OLC) of 11%. It was found that higher compactive efforts of the modified compaction, higher densification than that of the standard compaction, corresponding to the compaction theory in soil mechanics. CR-GP having practical grading achieved higher UCS up to the minimum requirement of the normal cement-stabilized road base as a benchmark material. Based on the micro-observation of this research, an applicable level of alkaline solution concentration could dissolve silica (Si), alumina (Al), and calcium (Ca) from crushed rock with the practical crushed rock grading characteristics, leading to an increase in strength up to an appropriate level for the road construction material.