Experimental Investigation On Flexural Performance Of HRB500 High Strength Steel ECC/Concrete Beam For The Purpose Of Crack-width Control

With the development of the times,high strength steel bars have been used more and more widely.As a kind of high strength,good ductility of steel bar,HRB500 reinforcement has been listed in our concrete structure design code(GB50010-2010).However,using HRB500 high strength steel bar as the design on the reinforcement can improve the bearing capacity of structure,reduce the dosage of steel,but structure or component may develop a big crack durning normal using stage and can’t meet the requirements of the applicability and durability of structure.This problem limits the use of HRB500 high strength steel bar in the practical engineering application.Recent years,some professors have introduced a new kind of high toughness cement matrix composites(Engineered Cementitious Composites,ECC)from Europe and America developed country.Compared with ordinary concrete materials or some fiber concrete,it showes metal tensile strain hardening characteristics and it’s ultimate tensile strain reaches 3%.Also it has significant nonlinear deformation ability,crack forms is multiple-cracking,crack width and spacing is generally descreased.In this paper,based on the mechanical properties of ECC,through experiments to explore whether ECC can help solving existing problems in the normal using period of HRB500 high strength steel.The main research contents as follows:1)The preparation of the ECC is not very perfect at present stage,There is no unified norms,different origin and content of components will affect the mechanical properties of ECC.So at first this paper studied the preparation method of ECC,finding suitable ratio for casting under the existing materials.2)Design a set of beams of three dimensions for b × h × l=150mm × 250 mm ×2700mm,using HRB500 high strength steel bars as mechanical reinforcement,one beam(FB1-1)casts only concrete and The other two cast h/4 ECC in the tension zone,cast concrete in the rest.PVA fibers used in ECC,one(FB1-2)is import fiber,the other(FB1-3)adopts domestic fiber.According to three equinoctial concentrated load test,research the addition of the ECC materials make what effect on the beam bending performance,emphatically observe whether crack width is under control effectively and whether HRB500 high strength steel stress can play full.At the same time,evaluate which kinds of PVA-ECC is better from the engineering cost,the toughening effect,etc and Providing a reference for practical engineering.3)Design a set of beams of three dimensions for b×h×l = 200 mm×300 mm×3300mm,using HRB500 high strength steel bars as mechanical reinforcements,respectively casting h/4、h/3、h/2 ECC in the tension area,casting concrete in the rest.According to three equinoctial concentrated load test,observing the influence of the beam bending performance with the different heights of ECC.Finding suitable ECC cast height through comparison and analysis of the results.4)By comparing two casting a quarter section height of ECC beam data results,researching the mechanism of the composite beams in bending by the change of the section size.