Title: Industrial Mineral Waste as an Alternative Pozzolan for the Design of Eco-Efficient Binary Cements: Impact on Physical Properties and Chloride Resistance

Author(s): Laura Caneda-Martínez, Moisés Frías, Mª Isabel Sánchez de Rojas, Javier Sánchez, and César Medina

Publication: Symposium Paper

Volume: 349

Issue:

Appears on pages(s): 301-320

Keywords: coal mining waste, supplementary cementitious materials, eco-efficient cements, chloride resistance, porosity, resistivity, chloride diffusion coefficient, critical chloride content

DOI: 10.14359/51732754

Date: 4/22/2021

Abstract:

The current exponential growth in cement demand and the gradual reduction in the availability of the supplementary cementitious materials (SCMs) conventionally employed in the cement sector (fly ash, blast furnace slag, etc.) have brought awareness over the need to find alternative sources of pozzolanic materials. Whereas the use of calcined kaolinitic clays (metakaolinite) could represent an excellent substitute for the traditional SCMs, the environmental and economic cost associated with kaolinite extraction thwarts the development of this course of action. Conversely, the clayey wastes obtained in the coal mining industry could represent an inexpensive and environmentally sound raw material for the production of recycled metakaolinite, promoting at the same time a Circular Economy model.

This work describes the physical and durable properties of binary mortars prepared with different substitution levels (20 % and 50 %) of thermally activated coal mining waste (600 ºC/2 hours), placing emphasis on their chloride resistance. The results show that the differences observed in the pore network and in the mineralogical composition of the blended matrices result in a superior resistance to chloride ingress and, therefore, in a decrease in the risk of corrosion of the subsequent structures and an increase in their service life.