The Effect of Different Types of Internal Curing Liquid on the Properties of Alkali-Activated Slag (AAS) Mortar

Guang-Zhu Zhang,Yi Han,Xiao-Yong Wang,Tae-Wan Kim,Jong-Yeon Lim

doi:10.3390/su13042407

Guang-Zhu Zhang, Yi Han + Show 3 more

Open Access

https://doi.org/10.3390/su13042407

Copy DOI

Abstract

This study shows the effect of different types of internal curing liquid on the properties of alkali-activated slag (AAS) mortar. NaOH solution and deionized water were used as the liquid internal curing agents and zeolite sand was the internal curing agent that replaced the standard sand at 15% and 30%, respectively. Experiments on the mechanical properties, hydration kinetics, autogenous shrinkage (AS), internal temperature, internal relative humidity, surface electrical resistivity, ultrasonic pulse velocity (UPV), and setting time were performed. The conclusions are as follows: (1) the setting times of AAS mortars with internal curing by water were longer than those of internal curing by NaOH solution. (2) NaOH solution more effectively reduces the AS of AAS mortars than water when used as an internal curing liquid. (3) The cumulative heat of the AAS mortar when using water for internal curing is substantially reduced compared to the control group. (4) For the AAS mortars with NaOH solution as an internal curing liquid, compared with the control specimen, the compressive strength results are increased. However, a decrease in compressive strength values occurs when water is used as an internal curing liquid in the AAS mortar. (5) The UPV decreases as the content of zeolite sand that replaces the standard sand increases. (6) When internal curing is carried out with water as the internal curing liquid, the surface resistivity values of the AAS mortar are higher than when the alkali solution is used as the internal curing liquid. To sum up, both NaOH and deionized water are effective as internal curing liquids, but the NaOH solution shows a better performance in terms of reducing shrinkage and improving mechanical properties than deionized water.

Highlights

Alkali-activated slag (AAS) requires less energy than ordinary Portland cement (OPC)in the manufacturing process [1,2] and has gained widespread interest in the construction manufacturing sector
Both NaOH and deionized water are effective as internal curing liquids, but the NaOH solution shows a better performance in terms of reducing shrinkage and improving mechanical properties than deionized water
The purpose of this study is to investigate the effect of different internal curing liquids on the heat of hydration of AAS mortars

Summary

Introduction

Alkali-activated slag (AAS) requires less energy than ordinary Portland cement (OPC)in the manufacturing process [1,2] and has gained widespread interest in the construction manufacturing sector. Alkali-activated slag (AAS) requires less energy than ordinary Portland cement (OPC). The use of alkali-activated slag can effectively reduce carbon emissions [3]. The materials required to make AAS concrete usually include slag, aggregate (fine or coarse aggregates), and various alkali activators [4]. Some related studies reported that the influencing factors affecting the autogenous shrinkage of AAS concrete mainly include the slag fineness [6,7], the type and amount of alkali activators [8], and the curing conditions [9]. It is well known that internal curing is proven to reduce autogenous shrinkage in concrete [10,11]. The autogenous shrinkage of concrete is most closely related to cement hydration [12].

Objectives

Methods

Results

Conclusion