Study On Shrinkage And Mechanical Properties Of Internal Curing High Performance Concrete With Fiber Reinforced

With the increasing application of low water cement ratio concrete,the cracking problem caused by shrinkage deformation has been paid more and more attention by scholars at home and abroad.Considering the traditional curing do not work effectively and need a lot of manpower and material resources,researchers put forward mix internal water sources in concreting,curing inside the concrete,is called internal curing.Because of its excellent mechanical properties,fiber concrete has been used more and more in engineering structures.There are a lot of scholars have studied internal curing technology and fiber reinforced concrete,and made some achievements,but there is less research on lightweight aggregate(LWA)ceramsite and fiber are added to high performance concrete together.In this paper,the mechanical properties,autogenous shrinkage and early crack resistance of internal curing high performance concrete with steel and polypropylene fiber are studied.The results showed that the water absorption rate of the LWA was 24.2%,and the water release rate reached 87% at 94% relative humidity,which had a significant water-absorbing ability,the crushing strength of LWA was 2.7MPa,was lower than that of ordinary aggregate.The particle size distribution is 1-5mm continuous grading,replacing part of fine aggregate can ensure the overall distribution is good.In order to ensure the internal curing used LWA high performance concrete still has enough strength,there are three kinds of replacement rate,10%,15%,20% volume fraction sand is replaced by LWA.With the increase of replacement fraction,the compressive strength,axial compressive strength,splitting tensile strength increases first and then,three respectively in the replacement rate of 10%,15%,10% reach the maximum,increasing 8.1%,9%,20.9% compared to ordinary unincorporated LWA concrete.The elastic modulus gradually decreases with the increase of the replacement rate but the amplitude is not large.With the increase of LWA incorporation,the autogenous shrinkage gradually decreased,the nominal area of cracks in mortar 24 h gradually decreased,and the cracking time was delayed.This shows that internal curing can limit the self-shrinkage of C60 high-performance concrete and enhance early crack resistance.Based on the LWA substitution rate of 20%,0.1% polypropylene fiber,1% steel fiber,and 0.1% polypropylene-1% steel fiber were blended respectively.The results show that 1% steel fiber can enhance the compressive strength of C60 inner curing high performance concrete.,Axial compressive strength,greatly improve the splitting tensile strength.0.1% polypropylene fiber has little effect on the compressive strength and axial compressive strength,and it has improved the split tensile strength.The influence of hybrid fibers is similar to that of single-doped steel fibers,but it has not been further improved compared to single-doped steel fibers.The three modes of incorporation can increase the elastic modulus,but the increase in the elastic modulus of the steel fiber is greater than that of the polypropylene fiber.The mortar crack resistance test results show that the incorporation of fibers can reduce the nominal area of cracks and delay the cracking time.The incorporation of fiber reduces the self-shrinkage of the HPC within 28 ?,but the effect is not obvious.Compare the mass loss rate of each group of high performance concrete to compare the relative internal curing efficiency of each group of concrete.The replacement rate is between 0% and 15%,and the quality loss rate increases.When the replacement rate of LWA is 20%,the mass loss rate is between 10% and 15%.The incorporation of fiber can reduce the quality loss rate of the internal curing concrete,but the impact is not significant.