Contribution to the modeling of hydration and chemical shrinkage of slag-blended cement at early age

Abstract

This paper presents a contribution to the modeling of the chemical shrinkage of the slag-blended cement paste (binder) at early age. Assuming that the chemical shrinkage is a direct result of hydration, the hydration modeling of slag-blended cement was studied by considering the interaction between the hydrations of blast furnace slag (BFS) and ordinary Portland cement. The reaction of BFS in the presence of calcium hydroxide CH (Portlandite) produced from the hydration of the cement was investigated. The kinetic hydration of cement was developed, and the volume phases in the cementitious material during the hydration process were calculated. The chemical shrinkage, which is the negative volume balance between the reactants and the products formed, is then calculated. In parallel with this numerical modeling, an experimental study was conducted to investigate the effect of slag's addition (0%, 30%, 50% and 80%) on the heat of hydration and chemical shrinkage at early age (maturation up to 7 days). The proposed hydration model incorporates the effect of following variables; the chemical composition of the binder, the fineness, the water to binder ratio (w/b), the curing time and the temperature.

Early Hydration Kinetics of Cementitious Materials Containing Different Steel Slag Powder Contents

“…On this basis, the reaction rates of NG, I, and D, i.e., F1(α), F2(α), and F3(α), respectively,can be acquired using Equations (2) to (4). In reference to the handling of Group A, Groups b, c and d are processed to obtain the corresponding kinetic parameters.…”

“…Researchers should explore the chemical reactions via by kinetics to reveal its microscopic mechanism dynamically. Merzouki [4] used the Knudsen model to analyze the influence of slag content, water-binder ratio and other factors on the hydration heat emission quantity of composite cementitious materials and determined that the model can accurately predict the hydration heat emission rate of composite cementitious materials with a low slag content. However, the model fails to explain the hydration reaction mechanism.…”

Heat of hydration of low-clinker cements

“…Addition of fly ash more distinctly retards the acceleratory period of cement hydration than slag, this tendency is especially clear for the high substitution rate of fly ashes. This retarding effect of the mineral additions on the cement hydration has been already reported [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35].…”

“…The hydration heat of blended cements has been investigated by several authors . The hydration of blended cements with different substitution rates of GGBFS has been studied, inter alia, by Roy and Idorn [11], De Schutter [12,13], Escalante et al [14], Saeki and Monteiro [15], Pane and Hansen [16], Binici et al [17], Meinhard and Lackner [18], Ježo et al [19], Chen et al [20], Merzouki et al [21], Hana et al [22], Gruyaert et al [23] and Siler [24]. It has been observed in these tests that the evolved heat decreases as slag content increases, but at the same time the heat evolved increases with the fineness of the slag or clinker in the blended cements.…”

A new hydration kinetics model of composite cementitious materials, part 1: Hydration kinetic model of Portland cement

“…As presented in Figure , the cross section of the 30 years' hydrated cement particle shows an obvious hydration product layer and the schematic diagram of simplified concentric model is similar to that of the Jander's model, which is a classical mass continuity‐based diffusion model. Jander's model has been applied to describe the late hydration of cement in many complete hydration models, eg the Krstulovic‐Dabic model . The mathematical expression of the Jander's model is given in Equation .where is the reaction degree and D is the diffusion coefficient.…”