| The performances of the manufactured sand fair-faced concrete(MSFC) are studied by using the materials of Chongqing, and a new method that could recognize and and evaluate the quality of concrete apparent with digital image processing technology is also studied .The main research contents and achievements of this paper are:(1)Based on the preparation and performance tests, the effect of stone powder contained in sand,content of sand grading (both below 0.15mm and above 0.15mm), sand ratio, properties of machine-made sand, mineral admixture and different fineness nodulus of mixed sand on the workability and strength of MSFC is studied . It shows that the content of stone powder and optimal sand ratio with diverse sand grading is different, as far as the workability is concerned. The strength of concrete with bad workability is lower, and it's proved that the higher content of stone powder within the limit than 18%,the higher of the concrete strength. The strength of concrete made by machine-made sand with 12% and 18% stone powder is better than nature medium concrete. It is believed that the effects of occluding, lubricating, nuclei, activity, filling, sopping of machine-made sand would improve the performances of concrete through the acting mechanism analysis.The test results show that the the workability and strength of MSFC made by machine-made sand crashed from different rock has a little difference.The mineral admixture improvs the workability of concrete. Through the different mixed sand grading test, it's known that fair-face concrete with excellent performance could be made by using mixed sand as fine aggregate.(2) The volume stability and durability of MSFC made by manufactured sand instead of natural medium sand is studied in this part.It's proved that the higher content of stone powder within the limit than 24%, the better of impermeability. And the volume stability and durability of MSFC which is made by well grading sand is slim better than others. The performance of compressive modulus of elasticity, drying shrinkages, resistance to high temperature of MSFC is the same perfect as natural medium sand fair-faced concrete, part of then is better.(3)Principles for manufactured sand choice in fair-faced and the mix proportion disign mothods of MSFC are studied. Based on the tests in laboratory on the concrete composed of mixed sand,the relationship between the strength of concrete and the cement to water ratio is analyzed by the method of liner regression and the coeficient values ofαaandαbare determined respective,the result is:αa=0.43,αb=0.12 .(4)According to casting sample component test, the apparent quality and the defects of concrete apparent are discussed, and practical project that made by MSFC is successful with perfect performance and apparent quality.(5)A new method that could recognize and account the quantity of the defects and evaluate the quality of concrete apparent with digital image processing technology based on VB.NET software is studied. It is an impersonal, impartial and uniform remark system, and different repairing actions should be taken according to the assessing results.There are three innovative aspects in this paper: the first one is using MSFC in the practical project successful by studying the performance of MSFC made by different grading and different stone powder of manufactured sand. Secondly, coeficient values ofαaandαb in Bolomey formula of mixed face-faced concrete mix proportion design in Chongqing are studied. The last one is that digital image processing technology system could recognize and account the quantity of the defects, evaluate the apparent quality.
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