Abstract
Ground granulated blast furnace slag is widely used as a mineral admixture to replace partial Portland cement in the concrete industry. As the amount of slag increases, the late-age compressive strength of concrete mixtures increases. However, after an optimum point, any further increase in slag does not improve the late-age compressive strength. This optimum replacement ratio of slag is a crucial factor for its efficient use in the concrete industry. This paper proposes a numerical procedure to analyze the optimum usage of slag for the compressive strength of concrete. This numerical procedure starts with a blended hydration model that simulates cement hydration, slag reaction, and interactions between cement hydration and slag reaction. The amount of calcium silicate hydrate (CSH) is calculated considering the contributions from cement hydration and slag reaction. Then, by using the CSH contents, the compressive strength of the slag-blended concrete is evaluated. Finally, based on the parameter analysis of the compressive strength development of concrete with different slag inclusions, the optimum usage of slag in concrete mixtures is determined to be approximately 40% of the total binder content. The proposed model is verified through experimental results of the compressive strength of slag-blended concrete with different water-to-binder ratios and different slag inclusions.
Highlights
Slag is a by-product obtained during steel manufacturing and is commonly used in concrete because it improves durability and reduces porosity by improving the interface with the aggregate
To overcome the weaknesses of the current research [5,6,7,8,9,10], this paper presents a numerical procedure to simulate the cement hydration, slag reaction, microstructure and strength development of hardening slag-blended concrete
Content from 1 gram of reacted slag is higher than that from 1 gram of hydrated cement, at late age, for concrete containing 10%, 20%, and 40% slag, the compressive strength of slag-blended concrete can surpass that of the control concrete
Summary
Slag is a by-product obtained during steel manufacturing and is commonly used in concrete because it improves durability and reduces porosity by improving the interface with the aggregate. Using an artificial neural network, Bilim [10] evaluated the early-age strength and late-age strength of slag-blended concrete with different water-to-binder ratios and slag replacement ratios. To overcome the weaknesses of the current research [5,6,7,8,9,10], this paper presents a numerical procedure to simulate the cement hydration, slag reaction, microstructure and strength development of hardening slag-blended concrete. Evolutions of concrete properties are expressed as functions of reaction degrees of cement and slag; Third, the proposed numerical procedure evaluates the macro properties, such as the compressive strength of concrete, by using the microstructures of concrete such as the CSH content and phase volume fraction. The physical meanings of parameters in the proposed model are much clearer than those used in the artificial neural network model [10]
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