Mohsen Ben Haha is the team leader scientific coordination of the Global R&D department of Heidelberg Materials. His research is focusing on multi-phase materials interaction, Building materials’ physical chemistry, transport phenomena in porous materials, chemical attacks investigation, and their consequences on qualitative and quantitative levels. During his career, he had the chance to work in different departments and institutes covering complementary aspects of materials science which enables him to understand different disciplines and thus gives him the opportunity to look at problems from a broad perspective. His interest in cement and concrete technology is tightly linked to its importance to the development of humankind. The production of Portland cement clinker accounts for about 5-7% of the total manmade CO2 emissions, as the manufacturing of 1-tonne cement clinker generates about 800 kg of CO2. Thus, the themes underpinning his research are:
Low clinker systems: towards a rational use of SCMS for optimal performance
Clinker replacement by other SCMs is the second-largest contributor to reduced emissions, after carbon capture technologies, according to The GCCA roadmap. However, most producers are still far from the 60% clinker factor as of 2022. Optimizing SCM use and lowering the clinker factor below 60% will be far more cost effective than relying so heavily on carbon capture despite their importance in the roadmap. Each SCM type adds a different filler and chemical effect to the cement reaction and contributes differently to the development of performance. They influence C-S-H formation, morphology, and chemical composition, as well as cement and concrete properties at different ages.
An optimized use of the cement components through optimized PSD and content will avoid lasting with large amounts of unreacted particles that will not contribute to the concrete mechanical and durability performances when placed. Additionally, it can avoid excess of extremely fine materials that are very reactive but need in turn more water demand of concrete leading to larger voids and porosity. The reactivity of a cementitious material increases with fineness until a certain point where extra grinding cannot beneficiate strength development at later ages. Through the optimized particle packing density of composite cement, clinker may become the minor component in the cementitious mix. Addition of mineral and chemical performance enhancer can help to further reduce clinker from composite cements without harming the concrete performances. Looking at the fundamentals by enhancing the reactivity of the different particles allows us to further reduce clinker in cement use. Future approaches might be more technical than only grinding and blending.