Non-OPC binder based on a hybrid material concept for sustainable road base construction towards a low-carbon society

Abstract

In this study, a non-OPC binder as a cementless material for a road base stabilizer was established based on a hybrid material concept between the pozzolanic and the alkali-activated materials. Solid sodium hydroxide (NaOH) was used as an alkali additive in a dry mixing process to compensate for the early strength in a pozzolanic-based material matrix with its intrinsic property of delaying the strength gain. Effects of varied NaOH concentrations on the fly ash (FA) and hydrated lime (HL) mixes to generate such a non-OPC binder were investigated through the mechanical properties and microstructure observations. The selected non-OPC binders were then mixed with the road base aggregate to evaluate non-OPC-based mixtures' properties against the road base material specifications. The results revealed that the non-OPC binder, the FA–HL mix (FA:HL = 90:10 by weight) with the NaOH content of 3.5% wt by dry aggregate mass, provided the most effective mechanical properties an entire network of gel and needles-sharp cementitious products. Based on the pavement design conducted in this study, the flexible pavement with the non-OPC base layer provided a significantly lower cost and GHG emission than those of the OPC-based material as a benchmark. This non-OPC binder with a hybrid material concept reveals a great potential to be a cleaner product in road construction and rehabilitation for a new era of our low-carbon society.