| Sand is the most commonly material used in the construction industry. With theincreasing development of the construction industry, the demand for sand willinevitably continue to increase. At present most natural sand is used in theconstruction. However, natural sand is a non-renewable resource, which isincreasingly reduced and can not meet the needs of the construction sand. Therefore,pressing for exploiting artificial sand in instead of natural sand in the application ofthe engineering is becoming an important topic. Artificial sand’ sources are mostfrom the rock crushers and the characteristics are determined by its parentrocks.Currently the limestone machine-made sand is commonly applied in theengineering, which is deeply researched and have more successful cases inengineering. In China the reserves of the granite are also very rich, but the researchon granite machine-made sand is less and is not much used in engineering. There arerich granite rocks in Quanzhou which is located in South Region of Fujian.Exploiting granite rocks provides a great deal of machine-made sand for SouthRegion of Fujian and meets the demand of the construction sand in this Region. Thispaper bases on the granite machine-made sand in South Region of Fujian for rawmaterials. The experimental studies contain the three main parts that are on theproperties comparison of machine-made sand concrete and natural sand concrete, theeffects of the different micro-fines content on the properties of concrete andestablishment and analysis on Rebound Method and Ultrasonic-rebound CombinedMethod Strength-measuring Curve. It will provide valuable references for the regionthat the granite machine-made sand applied in the construction.By experiment machine-made sand concrete for workability, cube compressivestrength, drying shrinkage deformation and resistance to chloride ion penetration arerespectively test research, and compared with the natural sand concrete in the relatedproperties. The research results show that（:1）the concrete prepared by machine-madesand has better workability, without occurrence of segregation and bleeding; Keeping in the same slump of concrete, the concrete prepared by machine-made sand hasobviously better workability than that by natural sand.（2）In the same slump, theconcrete28d compressive strength value prepared by machine-made sand issignificantly higher than that by natural sand.（3）Early shrinkage rates in the24h to92h, the early shrinkage rates of low-strength concrete and strong-strength concreteare greater than the early shrinkage rates of high-strength concrete, but this time theearly shrinkage rates of the concrete have tended to be a stable state; Compared withthe natural sand concrete, the early shrinkage rates of the machine-made sandconcrete are higher in the24h to92h.（4）In terms of the impermeability, the higherthe concrete strength level, the better the resistance to chloride ion penetration is. Inview of strong-strength concrete for comparison, the resistance to chloride ionpenetration of the natural sand concrete is better.Keep the machine-made sand concrete mixing ratio unchanged, by experimentstudying the effects of the different micro-fines content on concrete for workability,compressive strength, drying shrinkage deformation and resistance to chloride ionpenetration. The research results show that（:1）low-strength concrete workability andstrong-strength concrete workability gradually become better with the increase of themicro-fines content,and high-strength concrete workability gradually becomes poorwith the increase of the micro-fines content（.2）In the right amount of the micro-finescontent range, the concrete28d compressive strength value increases with theincrease of the micro-fines content.The effects of the different micro-fines content onlow-strength concrete strength are bigger, and the effects of that on strong-strengthconcrete strength and high-strength concrete strength are smaller（.3）In the24h to92h,the early shrinkage rates changes of the micro-fines content of different strengthlevels are certain regularity.（4）The micro-fines content is helpful to improve theimpermeabilities of the low-strength concrete and the strong-strength concrete, butinhibition from the impermeability of the high-strength concrete.The impermeabilitiesof the low-strength concrete and the strong-strength concrete improve with theincrease of the micro-fines content, and the impermeability of the high-strengthconcrete basically decreases with the increase of the micro-fines content, but themagnitude of decrease is smaller.（5）A combination of the experimental research obtains different strength levels concrete on a reasonable content of micro-fines inmachine-made sand: low-strength concrete and strong-strength concrete are within11%~14%, high-strength concrete is within6%~9%.This paper adopts gravel and machine-made sand broken by the granite in SouthRegion of Fujian as raw materials, making non-pumped concrete briquettes andpumped concrete briquettes, and the concrete briquettes’ sound velocity value,rebound value, carbonation depth value and damaged strength value are respectivelytested by14d，28d，60d，90d，180d，360d.The specified power function model isselected to play a regression analysis of the experimental data, establishing on14d~360d Rebound Method and Ultrasonic-rebound Combined Methodstrength-measuring curves of the granite machine-made sand concrete in SouthRegion of Fujian, and further using the curves established by experiment to verify theactual engineering concrete specimens. In addition, in the system analysis of differentstrength levels of concrete’s rebound value, carbonation depth value and actualstrength value changing rule with age on the basis, the influence of age on using ofthe rebound method strength-measuring curve is further analyzed, and the erroneouscorrected value of presumed28d strength in the actual projects is put forward. It willprovide reliable inferences basis for nondamaged Inspection and Evaluation of thegranite machine-made sand concrete strength in South Region of Fujian. |
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