The Experiment And Performance Calculation Method Of Hybrid Fibers Reinforced Recycled Brick Aggregates Concrete

With the development of economy,China has gradually accelerated the urbanization process and infrastructure construction,and the demand for concrete is increasing.Meanwhile,the demolition of existing buildings inevitably resulted in a large number of sintered clay bricks and other construction wastes.The waste clay bricks could be produced recycled brick aggregate(RBA)by crushing,sieving and cleaning.Then it would be partly or totally instead of natural coarse aggregates to produce the recycled brick aggregates concrete(RBAC).It is an effective way to realize the utilization of sintered clay bricks in resources and high efficiency.Because of low strength,poor property of anti-crack and poor durability of RBAC,in this thesis,the steel-polyolefin hybrid fibers were mixed with RBAC to produce the hybrid fibers reinforced recycled brick aggregates concrete(HFRBAC).The mixture design method,basic mechanical performance,axial compression performance,axial compressive stress-strain curves,flexural performance and durable performance of HFRBAC were studied.The main contents as follows:(1)The effects of water-cement ratio,sand ratio,replacement rate of RBA,hybrid fibers volume content and fiber types on slump of HFRBAC was investigaed by 15 group mixture proportions.With consideration of the characteristics of RBA and hybrid fibers and,according to the material characteristics and the thickness of paste layer enveloping the aggregates and fibers,a new mix design method of HFRBAC was put forward.(2)The compressive test,splitting performance test,shear performance test and flexural performance test were conducted.The effects of water-cement ratio,sand ratio,replacement rate of RBA,hybrid fibers volume content and fiber types on the compressive strength and deformation,splitting tensile strength and deformation,shear strength and deformation,flexural strength and deformation,and axial compressive stress-strain curves of HFRBAC were investigated.With the consideration of above effects,the strength calculation formula,equation of axial compressive stress-strain curve,as well as the calculation and evaluation methods of flexural toughness of HFRBAC was proposed.(3)Based on the cooperation of meso-scopic and micro-cosmic anlysis method,the chemical composition and volcano activity of RBA,surface morphology of RBA and natural coarse aggregate(NA),pore distribution of RBA and NA,surface morphology of steel and polyolefin fibers,interface morphology between steel fiber,polyolefin fiber and mortar,and interface morphology between RBA,NA and mortar were investigated.The damage mechanism of HFRBAC and mechanism of fibers reinforcement were studied.(4)The tests of carbonation,freeze-thaw,sulfate corrosion and chloride penetration were conducted.The effects of water-cement ratio,sand ratio,replacement rate of RBA,hybrid fibers volume content and fiber types on the carbonation depth,freeze-thaw mass loss ratio,relative dynamic elastic modulus,sulfate erosion coefficient and chloridepenetration depth of HFRBAC were investigated.Based on the test data of durability,calculated formulas of carbonation depth and corrosion resistance coefficient of sulphate compression strength were put forward.