Off-spec fly ash-based lightweight aggregate properties and their influence on the fresh, mechanical, and hydration properties of lightweight concrete: A comparative study

Published

August 1, 2022

Author(s)

Edward Garboczi, Mohammad Balapour, Mohammad Khaneghahi, Yick Hsuan, Diana Hun, Yaghoob Farnam

Abstract

In this study, an off-spec fly ash-based spherical lightweight aggregate (LWA), designated SPoRA, was manufactured through a pilot-scale production and its engineering properties, including specific gravity, dry rodded unit weight, water absorption, mechanical performance, and pore structure, were evaluated. Using the characterized SPoRA, lightweight concrete (LWC) samples were made and fresh, mechanical, and hydration properties of the LWC were assessed and compared with samples made using two commerical LWA types available in the US market. The results indicated that fine and coarse SPoRA had 72 h water absorption capacities of 16.4 % and 20.9 %, respectively, which were higher than that of the two commercial LWAs. SPoRA had a saturated surface dry (SSD) specific gravity higher than the commercial LWAs, thus leading to a higher fresh density for the corresponding LWC. Using X-ray computed tomography, large spherical type pores were found in SPoRA similar to those in the commercial slate-based LWA. The pore size distribution of SPoRA, characterized using a dynamic vapor sorption analyzer, indicated that more than 97 % of the pores had pore diameters greater than 50 nm. The crushing strength of SPoRA was lower than the commercial LWAs, which was attributed to the differences in manufacturing processes. On the other hand, LWC made using SPoRA passed the ASTM C330 requirement (28 d compressive strength greater than 21 MPa) and had compressive strength comparable to LWC prepared with the commercial LWAs. SPoRA LWC had lower workability and degree of hydration compared to LWC prepared with commerical LWAs, which was most probably related to the fluxing agent used in the SPoRA production. Overall, SPoRA was found to be a promising construction LWA for use in structural LWC.

Citation

Construction and Building Materials

Volume

342, Part B

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.conbuildmat.2022.128013

Local Download

Keywords

Waste fly ash, lightweight aggregate, pore size distribution, lightweight concrete, X-ray computed tomography, SPoRA

Citation

Garboczi, E. , Balapour, M. , Khaneghahi, M. , Hsuan, Y. , Hun, D. and Farnam, Y. (2022), Off-spec fly ash-based lightweight aggregate properties and their influence on the fresh, mechanical, and hydration properties of lightweight concrete: A comparative study, Construction and Building Materials, [online], https://doi.org/10.1016/j.conbuildmat.2022.128013, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933926 (Accessed May 19, 2024)