Early-age hydration of accelerated low-carbon cements for digital fabrication

Abstract

Digital fabrication processes with concrete offer several advantages compared to conventional processes, however, a major criticism with related concrete mixes has been with regard to their high cement paste content and consequent carbon footprint. One of the ways to address this is to reduce ordinary Portland cement (OPC) content in such mixes by using supplementary cementitious materials. This paper reports on such an approach for two different digital fabrication methods: digital casting system and 3D concrete printing. Results focus on the combined use of such low carbon blends with a calcium aluminate cement (CAC) based accelerator. Two such accelerators were studied: one being mainly crystalline based and the other mainly amorphous. Their performance is assessed at different temperatures. It is concluded that crystalline CAC is more suitable for applications above 20 °C while at temperature below 20 °C, amorphous CAC should be preferred. This paper also delves deeper into the effect of amorphous CAC on the hydration of tricalcium silicate present in OPC. It shows that the effect of amorphous CAC on that silicate depends on the OPC content of the system as well as on the type and amount of calcium sulfate used in the accelerator formulation.