Study And Application Of High-Performance Rapid Repair Concrete

In this paper, a series of ultra-fine fly ash composite powder (CUFA II)products for rapid repair are researched and developed successly with the ultra-fine fly ash as matrix . CUFA II can replace cement equivalently more than 30%. High performance rapid repair concrete(HPRRC) in which CUFA II replaces cement equivalently more than 30% can meet the requirements of opening traffic within 12~48h,which solves the problem of opening traffic as soon as possible after damaged Portland cement concrete pavement are repaired for a whole plate, and the engineering cost is lowered greatly. CUFA II is a kind of new environmental friendly green building material.The main achievements in this paper are as following:1 Based on the systematical study about physical properties, particle morphologies and micro-mechanism of ultra-fine fly ash, CUFA II products are successly developed by means of optimizing the particle gradation and activation technique. HPRRC composed of CUFA II products and with the strength grade no less than 32.5R ordinary Portland cement can meet the minimum strength index demands. At present , CUFA II has been produced commercially and applied to engineering . The fact that CUFA II based on fly ash is applied to whole plate Portland cement concrete pavement rapid repair engineering has not been reported at home and abroad.2 By extensive experiments and research, in consideration of the requirements of durability to chemical composition, referring to "high strength high performance concrete mineral admixture " (draft report) and correlating standards in abroad, the first Technical Specification (Q/DBAA001-2002) of ultra-fine fly ash mineral admixture in china has been put forward.3 By finite element method, the stress of New-Old concrete is simulated in condition of standard axis loading .The critical bond strength of new-old concrete interface is obtained. According to Chinese standard and referring to foreign research results, the key parameters forrepaired concrete to open traffic are put forward.4 By means of multiple regression analytical method, the significant correlation factors with the flexural strength at the age of 12hours, 24hours and 28days are analysed. At the same time, the factors affecting dry shrinkage and durability are also analysed .The mix proportion parameters of HPRRC are determined, while HPRRC is good in workability (slump 30mm), and can meet the needs of opening traffic within 12~48h.5 . The experiment test results of mechanical properties and durability of HPRRC show: no matter at early age or later age, the ration of flexural strength to the cubic compression strength of HPRRC is higher than ordinary concrete, and the brittleness of HPRRC is reduced ;the bond performance of new-old concrete interface and chloride permeability are good; its resistance to freeze and thaw, permeability are all excellent; its volume stability is improved ,and its cracking resistance is good.6 With the optimization of the mix proportion of HPRRC and with the old concrete was repaired with HPRRC whose strength is close with that of the old concrete, the stress-strain curves of new-old concrete is tested on ordinary testing machine and MTS .The results show that under equal stress conditions, the ratios of the strain of old concrete ,HPRRC to new -old concrete are 82.4-105% on ordinary testing machine and 90-121.3% on MTS respectively. These demonstrate that the deformation of three kinds of concrete is basically similar. The stress-strain curve of new-old concrete and HPRRC, are suggested to be modeled by two sections: the ascending section of the stress-strain curve is simulated by cubic parabola equation and the descending section is simulated by rational fraction, where the theoretical value is in good agreement with the test value .The research results also provide a theoretical basis of earlier stage for improving crack resistance of new-old concrete interface.7 A fractional dimension testing instrument...