INFLUENCE OF AUTOCLAVING PROCESS ON THE FRACTURE-BEHAVIOR OF ALC

The fracture behavior was investigated on autoclaved lightweight concrete (ALC) block samples, which were prepared from lime, cement and quartz sand at 180-degrees-C under the saturated steam pressure for 1 to 16h. After 1h autoclaving, the samples gave C-S-H as an initial product, which further reacted with quartz sand to form 1.1-nm tobermorite. The compressive strength increased from 2.0 to 5.7 MPa with the formation of tobermorite, while the fracture energy G(F) increased from 5.1 to 6.4 N/m. The fracture behavior interpreted from the tension softening curves was strongly affected by the formation of tobermorite. Extended autoclaving increased the energy for the initial microcrack formation but resulted in brittle crack growth behavior.