CO2-Sequestered Cast-in-Place Engineered Cementitious Composites
Duo Zhang and Victor C. Li
Appears on pages(s):
carbonation; carbon mineralization; CO2 sequestration; durability; engineered cementitious composites; fly ash; lifecycle assessment; steel slag; sustainability
The built environment is facing an increasing challenge of emission reduction regarding both embodied and operational carbon. As an ultra-durable concrete, engineered cementitious composites (ECC) reduce the need for repair, thus resulting in a prominent reduction of lifecycle footprints. Here, a new version of low-carbon ECC was developed for cast-in-place applications by sequestering CO2 via mineralization. Two waste streams were pre-carbonated and incorporated into ECC as fine aggregate and supplementary cementitious material, respectively. At 28 d, the CO2-sequestered ECC exhibited a compressive strength of 32.2 MPa (4670 psi), a tensile strength of 3.5 MPa (508 psi), and a strain capacity of 2.9%. Multiple fine cracks were distinctly identified, with a residual crack width of 38 µm (0.0015 in.) and a self-healing behavior comparable to that of conventional ECC. The new ECC sequestered 97.7 kg/m3 (164.7 lb/yd3) CO2 (equivalent to 4.7 wt% of final mixture) and demonstrated a 42% reduction in cradle-to-gate emissions compared to conventional concrete at the same strength level. This study demonstrates the viability of turning waste CO2 gas into durable construction materials and proposes a potential path toward carbon neutrality.