ITZ properties of LWA surroundings in high strength mortar according to LWA/sand with relative humidity

Abstract

The internal moisture content significantly influences the quality and durability of cement-based composite materials. However, reliable methods to analyze the moisture retention of concrete and mortar are lacking, particularly in relation to internal curing with lightweight aggregates (LWA). In this study, the internal moisture retention of mortar with different lightweight aggregate/sand (L/S) ratios was investigated while considering the absorption characteristics of LWA. Furthermore, the impact of internal moisture retention on the development of the interface transition zone (ITZ) between the LWA and cement matrix was analyzed. Additionally, compressive strength development was evaluated over different curing periods (3, 7, 28, 56, and 90 days) under internal curing conditions. The results showed that the L/S ratio, which is directly proportional to the amount of moisture absorbed, enhanced the compressive strength and plastic hardness, contributing to the development of depletion of internal moisture in the mortar was could be observed. The moisture consumption for different types of LWA was analyzed using CT scanning. XRD and SEM-EDS analyses confirmed the abundant presence of hydration products in the ITZ. This study demonstrates that the L/S ratio that considers the LWA absorption characteristics, can serve as a critical parameter for precisely correlating the curing time and compressive strength in internally cured mortars.