Numerical simulation of the hydration process and the development of microstructure of self-compacting cement paste containing limestone as filler

Abstract

This paper presents a numerical model for the simulation of the hydration process and the development of the microstructure on Selfcompacting cement paste (SCC) containing limestone powder as filler. Based on a series of experimental results, e.g. thermometric isothermal conduction calorimetry tests, environmental scanning electron microscopy (ESEM) image analysis, thermogravimetric analysis (TGA) and the derivative thermogravimetric analysis (DTG) measurements, the hydration process, the solid phase distribution, total porosity and pore size distribution have been determined at different hydration stages.Based on the hydration chemistry, the stoichiometry and the hydration kinetics of cement with limestone, an analytical hydration model and a microstructural model of self-compacting cement paste are proposed. Two SCC mixtures with w/c 0.41 and w/c 0.48, both with water/ powder ratio (w/p) 0.27, were simulated and compared to a traditional cement paste (TC) with w/c 0.48. The simulation results were discussed and validated against experimental measurements.Ré sumé Cet article présente un modèle numéri-que qui réalise une simulation du processus d'hydratation et le développement de la microstructure de la pâte de ciment auto-compactante (SCC) contenant comme filler de la poudre calcaire. Sur base d'une série de résultats expérimentaux-par exemple~: tests de calorimétrie par conduction thermométrique isotherme, analyse d'images par microscopie électronique environnementale (ESEM), analyse thermogravimétrique (TGA), analyse thermogravimétrique dérivée (DTG)-, le processus d'hydratation, la distribution de la phase solide, la porosité totale et la distribution de la taille des pores ont été déterminés à différentes étapes de l'hydratation.Sur base de la chimie et de la stoechiométrie de l'hydratation et de la cinétique de l'hydratation du ciment en présence de calcaire, un modèle analytique d'hydratation ainsi qu'un modèle de la microstructure de la pâte de ciment auto-compactante sont proposés. Des simulations concernant deux mélanges de SCC avec un rapport E/C de, respectivement, 0,41 et 0,48 et un rapport eau / poudre (W/P) de 0,27 ont été menées. Les résultats ont été comparés avec ceux d'une pâte de ciment traditionnelle (TC) dont le rapport E/C vaut 0,48. Les résultats de la simulation ont été discutés et validés en les comparant avec des mesures expérimentales.

Kinetic Hydration Heat Modeling for High-Performance Concrete Containing Limestone Powder

“…When cement is partially replaced by limestone, the value of the second peak of hydration heat increases, and the time corresponding to the second peak becomes much earlier. This trend agrees with experimental results about the rate of heat evolution of limestone blended cement paste [11]. When the surface area of Blaine surface of limestone increases, the nucleation effect becomes more significant, and the value of the second peak of hydration heat also increases.…”

“…On the other hand, because the reactivity of limestone is very weak compared with other supplementary cementitious materials, limestone can be approximately regarded as chemical inert filler [1,11]. Hence in this study, the chemical effect of limestone is not considered.…”

“…The hydration heat is scarcely simulated in their studies. Poppe and Schutter [10] and Ye et al [11] proposed models to analyze heat evolution of limestone blended selfcompacting concrete. But their study mainly focuses on the isothermal condition or adiabatic temperature rise.…”

“…For concrete structures in construction sites, the heat release from hydration and heat transfer to ambient environments occurs simultaneously. Poppe and Schutter [10] and Ye et al 's [11] studies do not consider semiadiabatic temperature rise in real construction sites.…”

“…To overcome the shortcomings in current models [7][8][9][10][11], we proposed an integrated numerical procedure to analyze the temperature history and temperature distribution of hardening limestone blended concrete. The hydration model is combined with finite element method.…”