| Lightweight aggregate concrete has many advantages such as light weight,high strength,good durability and good seismic resistance.The fiber can make up for the shortcomings of poor crack resistance of lightweight aggregate concrete.Steel Fiber Reinforced Expanded all-light Aggregate Concrete(SFRELAC)has become one of the hot research topics of new materials.With the continuous improvement of concrete performance,it is necessary to select high-strength steel bars with good performance.Considered concrete strength(LC30～LC40),steel bar diameter(14mm/16mm/20mm/25mm/28mm),steel fiber volume fraction(0,0.8%,1.2%,1.6%,2.0%),steel grade(HRB400/HRB500),the purpose of this topic is to study the bonding properties of high strength steel bars and SFRELAC.Through the experimental research on 130 center pull-out specimens,it is found that:(1)The failure modes of the pull-out specimens mainly include three types:splitting,splitting-shearing and shearing.The impact of the steel fiber is significant.(2)Under the same conditions,the ultimate bond strength increases with the increase of the concrete strength,which can be increased by 118%;(3)The influence of the steel grade on the bond strength needs to be considered to match the strength of different bases.At the strength of LC40,the ultimate bond strength increases with the increase of the steel grade;when the strength of LC30,the ultimate bond strength of the steel grade decreases.(4)The ultimate bond strength of LC30 strength specimens increases significantly with the increase of steel fiber volume fraction,but the corresponding peak slip change is not obvious.The ultimate bond strength of LC40 specimens increases with the increase of steel fiber volume fraction.Quite,but the peak slip changes without obvious rules.(5)Under the same conditions,the LC30 specimens with increasing diameter and the corresponding su are gradually reduced,and the LC40 specimens have no obvious regularity.(6)Comparative analysis of the bond-slip curve under different influencing factors,the test pieces with diameters of 14mm,16mm and fiber volume ratio of 0.8%matched well;diameters of 20mm,25mm,28mm and fiber volume ratio of 1.2 The%/1.6%matched test pieces have better bonding properties.Finally,combined with the experimental data and literature analysis,the bond-slip constitutive relation of HRB400/HRB500 steel and steel fiber lightweight aggregate concrete is proposed. |
