The inclusion of high specific surface materials such as calcined clays in cementitious systems enhances the hydration of clinker products at very early ages, but it may also increase water demand; thus, the pursuit of a flowing concrete may demand an increase in the dosage of superplasticizers. The grinding regime can have a major influence on the properties of the cementitious system and could help mitigate the problem of water demand. This paper discusses the impact of grinding alternatives for the production of a binder consisting of clinker, calcined clay, limestone and gypsum. Two main target products will be discussed: (i) LC3, a binder with a formulation of 50% clinker, 30% calcined clay, 15% limestone and 5% gypsum, co-ground all together, and (ii) LC2, a mineral addition with a formulation of 60% calcined clay, 35% limestone and 5% gypsum, ground separately and further blended with Portland cement on a 1:1 basis (mass). The experimental program is carried out in several stages: (i) the binder, (ii) cement pastes and (iii) standard mortars, and concrete grinding aids from the family TEA are used to enhance grinding, and their impact is also be assessed.

Early age cracking in concrete is caused by a combination of the chemical and autogenous shrinkage caused by the exhaustion of the water in the pores during the hydration of cement phases. Generally, this process takes place in the first 72 h of concrete casting. The use of supplementary cementitious materials (SCMs) can mitigate cracking due to several factors, among them: dilution effect, provision of extra nucleation sites due to the high specific surface of the SCMs, and the increased water retention associated with the presence of fine SCMs. This paper compares the impact of two SCMs systems on early age cracking of the following concretes: (i) pozzolanic cement with natural pozzolan (zeolite) and (ii) a ternary binder limestone-calcined clay cement (LC3). The study was Carried out on cement paste and concrete. The addition of calcined clay and limestone decreases early age cracking better than in any other system, including the Portland-pozzolan system. It is related to a lower clinker factor and improved hydration of the system, and a better-developed microstructure at early ages due to the energetic reaction of the alumina phase C₃A, enhanced by the extra alumina (Al₂O₃) provided by the calcined clay.

Replacing clinker with mixtures of calcined clay and limestone is one of the most sustainable strategies for decarbonizing the cement industry. However, the kinetic patterns governing the grinding behavior of these materials are not yet fully understood. This study developed a kinetic model based on particle population balance to simulate this process. Experiments were conducted using a standard Bond ball mill, and the samples were characterized by X-ray diffraction. The results show that the grinding of calcined clay and its mixtures with limestone follows first-order kinetics. The proposed model simulates the process with a high degree of accuracy, with residual errors below 1.5% and a coefficient of determination exceeding 99%.