Early carbonation for hollow-core concrete slab curing and carbon dioxide recycling

摘要

Early carbonation curing was developed for hollow-core concrete slab production to partially replace heat curing and recycle carbon dioxide recovered from the cement kiln. The cavities in hollow core slab were utilized as a CO_2 gas chamber to facilitate a carbonation curing at a low gas pressure. Concrete performance was evaluated by carbon dioxide uptake, compressive strength, pH values and resistance to air permeation. The microstructure was examined by X-ray diffraction patterns, thermogravimetric analysis and scanning electron microscope. It was found that early carbonation curing could reduce the conventional heat curing duration and produce concrete with higher strength and lower permeability due to the precipitation of calcium carbonates on surface. The pH value of the carbonated concrete at the reinforcement could be kept above the corrosion threshold through a subsequent hydration and the delayed ettringite formation owing to heat curing was totally eliminated by early carbonation. The process offers economical, technical and environmental benefits.