INFLUENCE OF AUTOCLAVING PROCESS ON THE F RACTURE-BEHAVIOR OF ALC

The fracture behavior was investigated on autoclaved lightweight concr ete (ALC) block samples, which were prepared from lime, cement and qua rtz 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 produc t, 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 format ion of tobermorite, while the fracture energy G(F) increased from 5.1 to 6.4 N/m. The fracture behavior interpreted from the tension softeni ng curves was strongly affected by the formation of tobermorite. Exten ded autoclaving increased the energy for the initial microcrack format ion but resulted in brittle crack growth behavior.