Saturated Lightweight Aggregate for Internal Curing in Low w/c Mixtures: Monitoring Water Movement Using X‐ray Absorption

Abstract

The susceptibility for early‐age shrinkage cracking in low w/c concrete has led to the development of new technologies that can reduce the risk of cracking. Internal curing, one of these new technologies, uses saturated lightweight aggregate to supply ‘curing water’ to low w/c pastes as they hydrate. While significant research has been performed to determine the effects of internal curing on shrinkage and stress development, relatively little detailed information exists on movement of water from the LWA to the paste. The details of when water moves and how far it travels has implications on the volume of aggregate and the aggregate gradation that should be used in mixture proportioning with internal curing. This study examines the timing of the release of water from saturated lightweight aggregate (LWA) and the distance that water can travel. X‐ray absorption is used to determine the time at which water is drawn out of the lightweight aggregate and the loss of water is traced over time. Further, it examines the travel distance of the water into the paste. Experimental details associated with the X‐ray technique are provided to describe the importance of specimen alignment. Further, in sealed specimens, the results indicate little water movement prior to set. After set however, the distance of water movement was as much as 2 mm. The importance of water movement is discussed in terms of mixture proportioning and its influence on shrinkage and stress development.

Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration

“…Thus, water is physically required 2.5 to 3 h after paste preparation as well. Even after the percolation threshold in low-W/C systems, internal curing water moves as far as up to some millimeters until 72 h [9,39]. With this in sight, the entire paste volume of the samples used in the present study is reached by internal curing water at any point of time, where it continues to influence autogenous shrinkage (cf.…”

Evaluation of the Techniques to Mitigate Early Shrinkage Cracking through an Image Analysis Methodology

“…In these cases, strain is usually limited by supports, adjacent structures and bonded reinforcements, among others. Consequently, the mix design and curing conditions become a very important part of good concrete technology practice . However, there are applications where curing is not enough to prevent cracking, that is, when severe environmental conditions are combined with large surface‐to‐volume ratios and restraints.…”

The influence of expanded perlite aggregate on compressive strength, linear autogenous shrinkage, restrained shrinkage, heat of hydration of cement‐based materials

“…Because of low strength of EPA, the strain values of EPA samples are lower than C samples. Henkensiefken et al stated that if saturated lightweight aggregates are used and the lightweight aggregate rate is increased, the crack time increases and maximum strains decrease. This situation can be clarified because of the tendency of EPA to retain water within the internal pores and hence, the effect of self‐desiccation is reduced by this water available in the lightweight aggregate pores.…”