Low Carbon Cements for Construction and Encapsulation

Background: The buildings & construction sector accounts for 37% of global carbon dioxide emissions, with concrete production accounting for approximately 6-8% of global emissions, significantly impacting global climate and the environment. As highlighted at COP27, to meet climate targets, embodied carbon in new builds must be reduced by at least 40% by 2030 and eliminated by 2050. The manufacture of traditional Portland cement involves large amounts of thermal energy and emits CO₂ during the chemical conversion of calcium carbonate to calcium oxide. The chemical conversion process alone is a significant CO₂ emitter (accounting for ~50% of the emissions associated with cement manufacture) along with the emission of other harmful gases (NOx, SOx and mercury). Reducing and capturing emissions from cement production using low-carbon Supplementary Cementous Materials (SCM) and carbon-capturing processes are vital if the construction industry is to meet global climate targets.

Project Summary: The PhD project will explore whether crushed silicate-based rock (e.g. basalt or granite) can be mechanochemically treated to form a partial cement replacement, reducing the embodied carbon content in cement for waste encapsulation. Current low-carbon cements use replacement products, such as pulverised fly ash (PFA) or ground granulated blast furnace slag (GGBS). PFA and GGBS derive from very high-carbon industries (coal-fired power stations and steel production) which will be phased-out by 2050, hence, they do not provide a long-term solution. As a consequence, there is a need to find alternative low-carbon cement replacement products.  

The project will explore mechanochemical treatment of excavated rock to produce an entirely new cement replacement product that can significantly reduce the carbon footprint of cement. Mechanochemical treatment involves mechanically damaging the excavated rock and reacting it with a gas or liquid to generate a rock powder with pozzolanic properties. We have previously found that mechanochemical reactions between CO2 and silicate rocks can be used to trap CO2 (Stillings et al. 2023) into rock powders. This project provides an exciting opportunity for the successful applicant to join a research group that is pioneering the application of mechanochemistry to solve industrial decarbonisation challenges alongside industry partners.

The PhD project is funded by the nuclear decommissioning authority and will develop and characterise cement replacement powders of interest for waste encapsulation. The researcher will identify the cement minerals created and characterise the carbon reduction, the final cement strength, the cement porosity and the sorption capacity for different radionuclide species.

Eligibility: Applicants should have a first-class or upper-second-class bachelor's degree and/or Master’s degree in an appropriate science or engineering discipline (e.g. Chemistry, Physics, Biology, Geoscience, Civil Engineering, Chemical Engineering, Material Science, Environmental Science). Knowledge and basic laboratory skills would be beneficial. However, theoretical and hands-on training will be provided through the aligned SATURN Nuclear Centre for Doctoral Training and at the University of Strathclyde.

Applicants must be able to demonstrate enthusiasm, creativity, resourcefulness and a passion for problem solving. Independent and critical thinking will be encouraged.

Research Hypothesis: We hypothesise that mechanochemically treated rock powders can be used as an alternative cement replacement product to PFA and GGBS, producing low-carbon cement for construction and nuclear waste encapsulation.

The PhD project will build on our pilot mechanochemical experiments to develop a low-carbon cement for construction and waste encapsulation. Specific objectives are:

1.    To understand how the structural and mineralogical variability of mechanochemically treated rock powders affect the mechanical strength of the final cement product;

2.    To determine the composition of cement minerals which form when mechanochemically treated rock powders are mixed with Portland cement;

3.    To quantify the carbon credential of the final cement through life cycle analysis;

4.    To characterize the porosity and sorption capacity of the cement produced for different radionuclide species;

The candidate is not expected to have any prior knowledge of mechanochemistry. Applicants with a first degree in materials science, chemistry, physics, biology, geoscience, civil/chemical engineering or environmental engineering are encouraged to apply.

This project is part of the SATURN CDT: https://www.saturn-nuclear-cdt.manchester.ac.uk/