Eco-cements containing Belite, Alite and Ye’elimite. Hydration and mechanical properties.

Abstract

Cement industry is one of the major contributors for greenhouse gases emissions, releasing about one ton of carbon dioxide per ton of ordinary portland cement (OPC) fabricated. For these reasons, there is a growing interest in the development, characterization, and implementation of alternatives. The term “alternative eco-friendly cement” refers to a man-made mineral material that, reacts with water to produce a hardened mass which can be used in concrete or mortar. This is the case belite-rich cements. The major problem of these cements is the space between the extremely fast reaction of ye'elimite and the slow reaction of β-belite. A possible solution is the activation of belite clinkers by the production of cements that jointly content alite and ye’elimite, known as belite – alite – ye’elimite (BAY) cements. This PhD Thesis is focused on the design, synthesis and characterization of a BAY cement, with and without fly ash addition; as well as the deep understanding of the joint hydration mechanism of alite with ye'elimite. In addition, for the sake of comparison, a blended of two commercial cements (belite and calcium sulfoaluminate) was prepared, which mineralogy was similar to BAY. One of the objectives of this thesis has been to obtain a BAY clinker with the major jointly content of alite and ye’elimite from natural raw materials. The maximum obtained percentages of alite with ye’elimite were 16.0 and 12.1 wt% respectively, presenting an alite/ye’elimite ratio of ~1.3. These phases were associated with 60.3 wt% C2S, 2.3 wt% C12A7, 7.0 wt% C4AF and 2.3 wt% C3A in the clinker.Another objective has been to understand the water-to-cement (w/c) ratio effect, the superplasticizer content and the addition of fly ash (FA) in the hydration mechanism and mechanical properties of BAY.