Internal curing (IC) of concrete by pre-wetted lightweight aggregate (LWA) is an established technology to assist cement hydration and reduce shrinkage and cracking in concrete. However, the current understanding in what makes a certain LWA effective for IC gives opportunities to improve the technique. The aim of this article is to identify the moisture transport mechanisms within an LWA that govern IC performance. Results on LWA of different internal structures (natural, manufactured), and different size distributions (fine, coarse), pre-soaked with either pure water or water containing shrinkage reducing admixtures (SRA), indicate that there are different mechanisms involved in water uptake and release: one controlled by capillary action, and one controlled by air diffusion into the pore water. It is concluded that it is the internal structure, geometry, and particle size distribution of the LWA that determine the effect of SRA and the overall LWA impact on the IC performance. By using 3D micro-CT images LWAs are studied in order to determine which characteristics (pore size, pore connectivity, pore distribution) are better suited for improving IC. This contribution to understanding water transport in LWAs may help to engineer the characteristics of LWA optimized for IC applications.
Bibliographical noteFunding Information:
The work included in this article is supported by the National Agency of Research and Development (ANID) under grants Fondecyt No. 11060341, Fondecyt No. 11170432 and Fondef ID19I10031. Authors also acknowledge the support of CEDEUS, CONICYT/FONDAP 15110020. Authors would also like to acknowledge the assistance of John Sharman, undergrad student at Universidad de los Andes, Chile, during image processing and analysis.
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- CT scan
- Internal curing
- Lightweight aggregate