Speaker
Description
This study presents a novel strategy to enhance CO₂ uptake in cement systems by incorporating 1,6-hexamethylenediamine (HMDA) as a water-soluble additive. Conventional CO₂ curing approaches are constrained by the low solubility of CO₂ in cement pore solutions and the associated reduction in alkalinity, which can hinder cement hydration. To overcome these limitations, HMDA was introduced into CO₂-saturated water to chemically bind dissolved CO₂ via carbamate formation while maintaining a pH favorable for hydration.
Cement pastes were prepared using four mixing solutions: tap water (W1), carbonated water (W2), and carbonated water containing 0.1% and 0.6% HMDA (W3 and W4). A comprehensive characterization program was employed, including total inorganic carbon (TIC) measurements, pH analysis, X-ray diffraction (XRD), micro-computed tomography (μCT), Fourier-transform infrared spectroscopy (FTIR), mechanical testing, and pore structure analysis.
The results demonstrate that HMDA markedly increased CO₂ uptake, rising from 0.74 g/L in carbonated water (W2) to 8.2 g/L in the HMDA-rich system (W4) at a water-to-cement ratio of 0.5. While HMDA-modified samples exhibited reduced early-age strength, they achieved superior long-term mechanical performance. At 28 days, W3 showed the highest compressive strength of 113.8 MPa at a water-to-cement ratio of 0.3, along with increased stiffness and elastic modulus.
XRD and FTIR analyses confirmed enhanced calcite formation and reduced portlandite content, indicating deeper and more controlled carbonation. μCT and pore size distribution analyses revealed decreased total porosity and refined pore structures, particularly in W3 and W4. These microstructural improvements underpin the observed gains in long-term mechanical properties.
Overall, the HMDA-based approach provides a dual benefit of significantly enhanced CO₂ sequestration and improved cement performance. This method offers a scalable and cost-effective pathway for carbon utilization in cement production, contributing to the development of high-performance, low-carbon construction materials.
| Country | Saudi Arabia |
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