Title: Effect of Initial Curing on Carbonation of Lightweight Concrete Masonry Units

Author(s): Hilal El-Hassan, Yixin Shao, and Zaid Ghouleh

Publication: Materials Journal

Volume: 110

Issue: 4

Appears on pages(s): 441-450

Keywords: carbon uptake; carbonation; compressive strength; concrete masonry unit; curing.

DOI: 10.14359/51685791

Date: 7/1/2013

Abstract:
The effect of initial curing on carbonation curing of lightweight concrete masonry units (CMUs) was examined. Initial curing was performed from 4 to 18 hours at a relative humidity (RH) of 50% and temperature of 25°C (77°F). Based on cement content, 4-hour carbonation curing allowed concretes to uptake 22 to 24% CO2 with initial curing and 8.5% without initial curing, while prolonged 4-day carbonation recorded an uptake of 35%. Carbonated CMUs exhibited higher early strength but lower 28-day strength due to water loss by initial curing in comparison to hydrated and steam-cured references. A water-spray mechanism was thus devised to compensate the water loss and, ultimately, made the late strength of carbonated CMUs comparable to references. Carbonation curing can replace steam in CMU production to accelerate hydration, improve durability, and recycle cement kiln CO2 in a beneficial manner.