ABSTRACT
The introduction of newly developed blended cements into the mass market is essential to ensure an effective reduction of the carbon footprint related to cement production. To facilitate this process, formulating mix proportions using pastes and/or mortars rather than concrete can be a great advantage. However, for the upscaling towards industrial concrete it is then essential to maintain the target rheological and mechanical properties, something that is all too often challenging. In this work, a procedure facilitating such an upscaling was illustrated in the form of a flow chart. Specifically, best practices to obtain a good correlation between concrete prepared in a laboratory and one prepared in a plant were presented. This includes new data showing how to accommodate for possible differences in temperature and/or water content between both situations. The dataset of state-of-the-art correlations between mechanical performance and heat of hydration, considering w/b ratios relevant to practice, were expanded. This greatly facilitates the mix design of concrete with particularly low clinker contents, which in this work were illustrated with a blended cement containing only 50% clinker. Supplementary Information: The online version contains supplementary material available at 10.1617/s11527-022-02040-5.
ABSTRACT
Digital fabrication with concrete is considered to potentially revolutionize the construction sector and is often presented as a means to reduce its environmental footprint. However, at least in the case of concrete, it encounters significant challenges in terms of material design, since high paste volumes and Portland cement contents are normally used due to process requirements. In this article, the application to layered extrusion of a recently developed low clinker cement containing 50% Portland cement and 50% supplementary cementitious materials, such as limestone, burnt oil shale, and fly ash, is presented. It is found that an accelerator paste composed by Calcium Aluminate Cement (CAC) and anhydrite provides the required hydration and structural build-up for 3D printing, while not compromising the early and long-term compressive strength. Such a low clinker mortar can be successfully retarded, processed, pumped, and extruded just after mixing it in line with the accelerator paste. This accelerated mortar formulation contains only 303 kg/m3 of Portland cement, which is roughly half the amount used in current accelerated formulations used for digital fabrication with concrete.
