CO2 Curing for Surface Hardening of Flowable Fill with By-Product Material and Air-Foam: A Sustainable Approach

The impact of CO2 curing on the surface hardening of flowable fill material containing by-product material and air foam is investigated in this study. The utilization of air foaming technology resulted in the poor surface quality of the hardened specimens due to high air voids in the mortar skin. To address this issue, CO2 curing was employed to enhance the durability of the specimens. The mix design involved using low-strength materials with dredged soil (50% replacement of normal sand) and bottom ash (30% substitution of cement) to promote sustainable construction practices. Air-foaming was introduced to the fresh slurry at a 10% volume content to improve workability. Unconfined compressive strength and the CIP (Chloride Ion Penetration) test were conducted at various ages (3 days, 7 days, 14 days, and 28 days). The test results revealed that CO2 curing significantly enhanced the strength of the CLSM (Controlled Low-Strength Material), particularly at early ages, with improvement percentages of 21%. The CIP test results further confirmed the effectiveness of CO2 curing, as all mixtures demonstrated promising increases in CIP resistance. Overall, CO2 curing shows great potential as a technique to enhance the quality of CLSM incorporating by-product materials, particularly in the challenging climate conditions of the Mekong Delta.