STRENGTH AND DEFORMATION PROPERTIES OF HIGH PERFORMANCE STEEL FIBER REINFORCED LIGHTWEIGHT CONCRETE UNDER MULTIAXIAL COMPRESSION

To investigate the influence of triaxial stress ratio and steel fiber content on the failure criterion and constitutive relationship of high-performance lightweight concrete (HPLWC), the strength and deformation of steel fiber reinforced all lightweight concrete and steel fiber reinforced semi-lightweight concrete subjected to multiaxial compression were studied experimentally. Considering the loading capacity of the testing machine and the workability requirements of fresh HPLWC, the selected loading paths consisted of uniaxial compression and tension, equal biaxial compression and truly triaxial compression. The fiber volumetric ratios were 0%, 0.5%, 1.0% and 1.5%. Results indicate that under the condition of uniaxial loading or lower stress ratios, the addition of steel fiber was beneficial to crack inhibition, strength and toughness improvement. Especially the fiber volume fraction has an obvious effect on the descending branch of the stress-strain curve. With the increase in the steel fiber content, the intermediate principal stress has a greater influence on the peak stress and peak strain. Under the condition of higher stress ratios, the steel fiber content had no obvious effect on the peak strength, peak strain and the descending branch of the stress-strain curve, but had a great effect on the plastic flow plateau of the stress-strain curve of lightweight concrete. Finally, based on the Kotsovos' strength criterion for conventional concrete and test results, a novel failure criterion was proposed for steel fiber reinforced lightweight concrete materials which considers the influence of steel fiber content parameter.