Efficient heat curing of alkali-activated binder using self-heating cement composites

초록

This study examines the performance of electrically conductive cement composite (ECCC) heating blocks as an innovative method for indirect heat curing of alkali-activated fly ash (AAFA) binders. The heating performance of the ECCC heating blocks, powered by a 15 V DC voltage applied for 24 h, and the AAFA composites positioned between them for curing was assessed through thermal imaging, surface temperature measurements, and tunneling electrical resistivity analysis. The performance of one-day-cured AAFA using ECCC heating blocks was then compared to conventional steam curing at 90 degrees C and 99 % humidity, utilizing microstructural characterization techniques (TGA, XRD, MIP) and compressive strength testing. Results showed that smaller AAFA samples achieved superior average surface temperature due to their reduced size. ECCC blocks provided uniform heat distribution, with stable tunneling electrical resistivity during the first 5 h and subsequent increases due to thermal expansion and the disruption of conductive pathways. ECCC heat-cured composites exhibited higher total porosity (43.2 %), with 32.7 % attributed to transition pores (10-100 nm). In contrast, steam-cured composites had a comparable total porosity (41.7 %) but with 30.4 % comprising micropores (<10 nm). Despite these differences, compressive strength testing demonstrated promising performance, with cellulose microfibers (CMFs) enhancing strength by 13 % in steam-cured samples (46.3 to 52.2 MPa) and 12 % in ECCC heat-cured samples (36.1 to 40.3 MPa).These findings establish ECCC heating blocks as a sustainable and energy-efficient alternative to steam curing, offering consistent hydration and adaptability for diverse AAFA precast applications.

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