Production of concrete pipes by carbonation curing in an inflatable enclosure

Production of concrete pipes using ambient pressure (AP) carbonation curing in an inflatable enclosure was studied. The process was developed to replace traditional steam curing in order to reduce energy consumption, improve concrete performance and sequester carbon dioxide in pipes. The ambient pressure carbonation was compared with high pressure (HP) carbonation at 5 bar and normal hydration references. A composite structure of calcium carbonate with C—S—H was found in concrete after AP carbonation. Multiple techniques including quantitative X-ray diffraction analysis (QXRD), thermogravimetry analysis (TGA), Raman spectroscopic analysis, and scanning electron microscopy (SEM) were applied to characterize the strength development and microstructural enhancement of such cementitious matrix. The results demonstrated that AP carbonated pipes had comparable CO₂ uptake, three-edge-bearing test (TEBT) strength, absorption, and resistance to internal-hydraulic pressure with HP carbonated ones. In addition, AP carbonation provided nucleating sites for C—S—H gel growth, thus contributing to the improved performance of concrete pipes while sequestrating CO₂ and reducing the overall carbon footprint. Lastly, the carbon sequestration cost is lower in AP than in HP carbonation, which confirms the economic benefits of using AP in early-age carbonation curing of cement-based products. © 2022 Elsevier Ltd.