Effect of the Carbonate Source on the Carbonation Performance of Blended Binders Containing Calcined Clays

There is a burgeoning interest in determining the feasibility of using different clay types as potential supplementary cementitious materials (SCMs), for the production of more sustainable concretes. Given the connection between sustainability and longevity of construction materials, attention needs to be paid to the potential threats new SCM-containing cements might undergo. This will enable the design of materials accounting for environmental savings during production and improved resilience and longevity. This research is part of the collaborative USA-UK project ‘RENACEM’ aiming to understand the response to CO2 exposure of sustainable cements containing calcined clays as SCMs. The present study reports the outcomes of the carbonation performance studied in selected Portland blended specimens exposed to accelerated or natural carbonation evaluating the influence of limestone or dolomite addition. Compressive strength development, carbonation depth and microstructural changes induced by CO2 exposure were determined. Clinker content governs the carbonation rate of both binary and ternary formulations in accelerated carbonation. Natural carbonation samples exhibited similar carbonation depths independently of the carbonate type used, conversely to those exposed to accelerated carbonation testing.