High performance mortars were microwave-cured for different times (45-780 min) at 80°C and their properties compared to those of samples wet-cured at the same temperature for 24 h. The composition was based on a CEM I 52.5 Portland cement, microsilica and fine quartz. The initial water to cement ratio was ~0.24 and an acrylic superfluidifier was used. The compressive strength after wet-cure was ~100 MPa; that after 780 min of microwave exposure varied from ~70 to ~110 MPa, depending on sample confinement during the treatment. A similar trend was found for the flexural strength (~16 MPa and 13-21 MPa, respectively). The sample weight either increased or decreased depending on whether water evaporated or was absorbed during the treatments; the strength was closely related to the water content variation. The bound water, evaluated by thermal analysis, linearly depended on log(time). Mercury intrusion porosimetry indicated that both the pore cumulative volume and the threshold size of microwave cured samples were substantially smaller than those of the wet-cured samples. Finally, DSC runs and SEM analysis suggested that the CSH of microwave treated samples was better structured than that of the samples matured in hot water.
Microwave treatment of high performance cement based materials
LEVITA, GIOVANNI;MARCHETTI, AUGUSTO;GALLONE, GIUSEPPE CARMINE;
2000-01-01
Abstract
High performance mortars were microwave-cured for different times (45-780 min) at 80°C and their properties compared to those of samples wet-cured at the same temperature for 24 h. The composition was based on a CEM I 52.5 Portland cement, microsilica and fine quartz. The initial water to cement ratio was ~0.24 and an acrylic superfluidifier was used. The compressive strength after wet-cure was ~100 MPa; that after 780 min of microwave exposure varied from ~70 to ~110 MPa, depending on sample confinement during the treatment. A similar trend was found for the flexural strength (~16 MPa and 13-21 MPa, respectively). The sample weight either increased or decreased depending on whether water evaporated or was absorbed during the treatments; the strength was closely related to the water content variation. The bound water, evaluated by thermal analysis, linearly depended on log(time). Mercury intrusion porosimetry indicated that both the pore cumulative volume and the threshold size of microwave cured samples were substantially smaller than those of the wet-cured samples. Finally, DSC runs and SEM analysis suggested that the CSH of microwave treated samples was better structured than that of the samples matured in hot water.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
