A Microstructure Based Strength Model for Slag Blended Concrete with Various Curing Temperatures

Li-Na Zhang,Wang Xiao-Yong,Kyung-Taek Koh

doi:10.1155/2016/1738417

Abstract

Ground granulated blast furnace slag, which is a byproduct obtained during steel manufacture, has been widely used for concrete structures in order to reduce carbon dioxide emissions and improve durability. This paper presents a numerical model to evaluate compressive strength development of slag blended concrete at isothermal curing temperatures and time varying curing temperatures. First, the numerical model starts with a cement-slag blended hydration model which simulates both cement hydration and slag reaction. The accelerations of cement hydration and slag reaction at elevated temperatures are modeled by Arrhenius law. Second, the gel-space ratios of hardening concrete are calculated using reaction degrees of cement and slag. Using a modified Powers’ gel-space ratio strength theory, the strength of slag blended concrete is evaluated considering both strengthening factors and weakening factors involved in strength development process. The proposed model is verified using experimental results of strength development of slag blended concrete with different slag contents and different curing temperatures.

Highlights

Granulated slag from metal industries is a steel industrial byproduct and can be used as a mineral admixture to produce normal and high strength concrete
Where RCHCE is the mass of produced calcium hydroxide from cement hydration and RCHSG is the mass of reacted calcium hydroxide in slag reaction
This paper presents a numerical procedure to simulate cement hydration, slag reaction, microstructure development, and strength development of slag blended concrete

Summary

Introduction

Granulated slag from metal industries is a steel industrial byproduct and can be used as a mineral admixture to produce normal and high strength concrete. The compressive strength of slag blended concrete generally relates to materials properties, such as water to binder ratios and slag replacement ratios, and curing conditions, such as curing temperatures. The strength development is evaluated using reaction degrees of cement and slag This kinetic model is valid for concrete with larger slag contents (60% slag of total binder contents). Brooks and AlKaisi [9] and Barnett et al [10] proposed maturity functions to model the strength development of slag blended concrete at elevated temperatures. To overcome the weak points of current models [6,7,8,9,10], this paper puts forward a numerical procedure to simulate cement hydration, slag reaction, microstructure development, and strength development of slag blended concrete. The proposed model is valid for slag blended concrete with different slag contents, different isothermal curing temperatures, and time varying curing temperatures

Modeling of Hydration of Cement-Slag Blends

Experimental results

Conclusions