Potential Use of Lightweight Aggregate (LWA) Produced from Bottom Coal Ash for Internal Curing of Concrete Systems

Published

October 1, 2019

Author(s)

Mohammad Balapour, Weijin Zhao, Edward Garboczi, Nay Ye Oo, Sabrina Spatari, Grace Hsuan, Peter Billen, Yaghoob Farnam

Abstract

This study evaluates the potential use of a novel lightweight aggregate (LWA), spherical porous reactive aggregate (SPoRA), which is produced from waste coal bottom ash, for internal curing of concrete. Engineering properties of SPoRA required for concrete internal curing were assessed including specific gravity, porosity, sphericity, water absorption, and water desorption. SPoRA showed a low oven dry specific gravity, ranging from 0.83 to 1.43, accompanied by high porosity which makes it capable of storing the amount of water needed for concrete internal curing. Through X-ray computed tomography (XCT), the high porosity of SPoRA (39.6 % to 57.8 %, by volume) was confirmed, and the sphericity of SPoRA, which influences the workability of concrete, was evaluated. XCT evaluation also showed that the pore structure of SPoRA is well connected, allowing stored water to move through the SPoRA pore structure to the outer surface of SPoRA during the self-desiccation of concrete. SPoRA's 72 h water absorption not only passed the requirements of ASTM C1761 for internal curing (water absorption > 5 % and minimum of 85 % water desorption at 94 % relative humidity, RH), but also showed a superior performance in comparison to traditional LWAs, which were also evaluated in this study. Moreover, the SPoRA desorption isotherms showed its capability for releasing a favorable amount of absorbed water as the internal RH decreases during concrete self-desiccation, thereby providing a promising desorption behavior for concrete internal curing. In conclusion, the observations found in this study show that SPoRA can be considered as an ideal LWA for internal curing of concrete.

Citation

Cement and Concrete Composites

Volume

105

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.cemconcomp.2019.103428

Local Download

Keywords

Concrete, Lightweight Aggregate, Internal Curing, Pore structure, Sintering, Sorption Properties

Citation

Balapour, M. , Zhao, W. , Garboczi, E. , Oo, N. , Spatari, S. , Hsuan, G. , Billen, P. and Farnam, Y. (2019), Potential Use of Lightweight Aggregate (LWA) Produced from Bottom Coal Ash for Internal Curing of Concrete Systems, Cement and Concrete Composites, [online], https://doi.org/10.1016/j.cemconcomp.2019.103428, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=927249 (Accessed November 23, 2025)