Performance of magnesia cements in pressed masonry units with natural aggregates: Production parameters optimisation

Although the manufacturing of masonry units by pressing dry concrete mixes is widespread, the information on how the process variables influence the resulting product is limited. This is partly because the process is operator controlled and partly because its details are usually confidential. The process variables are believed to be aggregates type and grading, manufacturing pressure, water to cement ratio and cement content. In this paper, the influence of the manufacturing pressure, water content and cement content on the density, porosity and strength of a number of pressed dry concrete mixes was studied. Natural aggregates and three types of binders were used: Portland cement, magnesium oxide and the combination of the two. Recently emerged magnesia cements, which are proposed as a more sustainable alternative to Portland cements, are used to assess their potential for their utilisation in the manufacturing of masonry units. Results are presented and recommendations are made to manufacturers of pressed masonry units and potential researchers conducting testing of novel materials for the utilisation of these binders in the manufacturing of construction products by pressing.