Toward net zero carbon for concrete and mortar: Clinker substitution with ground calcium carbonate

The industry is responsible for 65% of greenhouse emissions, contributing to dramatic and irreversible climate changes. Among all the industries, construction is the most carbon and material demanding. Therefore, short- and long-term solutions should be quickly found to reduce both materials needed and their carbon footprint. With more than 20 GT produced per year, concrete and mortar are the most used construction materials. Even if they have a low carbon footprint compared to steel, glass, or wood, their massive volume consumption generates more than 3 GT of carbon dioxide annually. This paper exposes how to reduce the carbon-intensive clinker by up to 75% by substituting two different grades of Ground Calcium Carbonate (GCC), reaching the 50% carbon emission reduction target of the Paris climate agreement. As an alternative to the still limited resources of conventional Supplementary Cementitious Materials (SCMs), using different grades of GCC reduces the water needed and, therefore, the clinker required for a specific strength. We demonstrate that this reduces the carbon footprint by up to 50% for concrete and mortar with similar mechanical properties. A theory is proposed, linking materials' strength and relative porosity, giving an excellent relation and explaining the impact of the clinker substitution with GCC. Ecological concretes and mortars with improved performances could then be obtained, demonstrating a possibility of reducing in the short term 50% of the carbon emission of concrete and mortar by using broadly available grades of low carbon footprint Ground Calcium Carbonate.