Stress-strain Behaviors Of Steel Fiber Reinforced Full-lightweight Concrete Under Compression

Both containing the good tensile properties of steel fiber reinforced concrete and light weight properties of full-lightweight aggregate concrete,steel fiber reinforced full-lightweight aggregate concrete attracts a lot of attention and develops rapidly.Compressive stress-strain curve is an important element for estimating the mechanical properties of concrete.So far,researches about compressive stress-strain curves of steel fiber reinforced full-lightweight aggregate concrete(SFRFLAC)are still lacking.Therefore,experiments for compressive constitutive relation of SFRFLAC are conducted in this study.The absolute volume method of direct mix design was used to make SFRFLACs.Raw materials were P.O.42.5 and P.O.52.5 cements,class-II fly ash,high-strength ceramsite of sintering expanded shale,fine sintering expanded shale,steel fiber of thin-plate shearing type with indentations and polycarboxylic acid superplasticizer.The water-to-cement ratio is 0.25,0.3 and 0.35,where 0.3 is the benchmark water-to-cement ratio.The volume fraction of steel fiber is selected for 0%,0.4%,0.8%,1.2%,1.6%,and 2.0% when the water-to-cement ratio is 0.3.It includes 16 groups of specimens,where 64 specimens with size of 100mm×100mm×300mm for measuring the axial compressive stress-strain curves and 48 specimens with size of 150mm×150mm×150mm for measuring cubic compressive strength.The cubic compressive strength is conducted with the 2000 KN compression testing machine and the axial compressive stress-strain curves are gotten by 3000 kN SANS electro-hydraulic servo universal test machine with sufficient rigidity and higher loading control precision.Donghua Data Acquisition instrument was used to collecting test data as the compressive stress and strain at any point and then mapped the stress-strain curves.The characteristics of axial compressive stress-strain curves,compressive failure modes,compression energy absorption capability and the compression toughness ratio of SFRFLAC were analyzed.Formula and key point values for calculating uniaxial compression stress-strain curve of SFRFLAC were also recommended in this paper.As the results of the experiment,the addition of steel fiber significantly improves the ability to absorb the compressive energy and the compression toughness ratio of full-lightweight aggregate concrete.Therefore,the addition of steel fiber improves the compressive toughness of full-lightweight aggregate concrete,and with the increase of steel fiber volume fraction the improvement becomes higher.Meanwhile,as the increase of steel fiber volume fraction,the cubic compressive strength also has a little improvement,but not obviously.According to the calculation models of normal concrete,this paper suggests the calculation expressions and formulas of its parameters by means of analyzing testing results and then fitting stress-strain curves.