Research on the formation of M1-type alite doped with MgO and SO3—A route to improve the quality of cement clinker with a high content of MgO

Abstract

This paper discusses the effect of SO3 dopants on the M1 polymorph formation and mechanical properties of alite containing a high content of MgO. The structure of the M1 alite is identified by XRD, high-temperature XRD and TEM analysis. A characteristic XRD pattern of M1 alite doped with MgO and SO3 is determined, and TEM results show that M1 alite has an incommensurate modulated structure feature with 2.4 times the subcell dimension along [2¯10]H∗ and could be expressed as ha∗ + kb∗ + lc∗ + m/[2.4(−2a∗ + b∗)], where m = ±1. The First-Principles method is used to simulate the structure of M1 alite, and the calculated Delta Cohesive Energy is approximately 11–12 eV between the M1 and M3 alite. Quantitative analysis is performed by the Rietveld method. The SO3/MgO (mass ratio from SO3 to MgO) and M1% in alite M1-C3S%M1-C3S%+M3-C3S%×100% are shown to have a strong linear relationship, which can be defined as M1-C3S%M1-C3S%+M3-C3S%×100% = 24.73 + 108.11 * SO3/MgO (%). Mechanical properties results show that appropriate SO3 dopant can improve the compressive strength of alite containing high MgO while over dosed SO3 will lead to a contrary effect because of the decomposition of alite. The relationship between M1% in the alite and the compressive strengths at different ages is also given. The optimal M1% in alite is approximately 68% and the best SO3/MgO ratio is approximately 0.43 because the compressive strength could be maximized at each age.