Research On High Strength Semi-Lightweight Concrete

High strength semi lightweight concrete (HSSLC) refers to the coarse aggregates compounded with normal weight aggregate and lightweight aggregate, whose dry apparent density is between 1950 kg/m3 and 2300kg/m3 and the compressive strength is higher than 50MPa. HSSLC has many merits such as high compressive strength, small dead load, good volume stability, etc. So it is economic to use HSSLC in high-rise buildings and long-span bridges, and the prospect of its application is very extensive. The main defect of semi lightweight concrete is that it easily occurs lamination and segregation phenomena before concrete curdle, which will affect the mechanical property and durability of the concrete. In order to meet the need of modern architectures using lightweight, high strength and durable concrete, it is necessary to research the working performance, mechanical property and durability of the semi lightweight concrete.On the basis of analyzing the active property of coarse aggregate in HSSLC mix, the author of this article established the active equation of the coarse aggregate of HSSLC. Raised the separation divisor of the coarse aggregate to determine the main factors and the key technical measures of the uniformity of HSSLC. Exploited a new apparatus to detect the uniformity of HSSLC. Raised the evaluation method of uniformity of HSSLC. Established the evaluation system of the working performance of HSSLC, and disclosed the technique parameters of the uniformity of HSSLC, which include grain size and gradation of coarse aggregate, mineral admixture, fiber, viscosity increasing and water reducing agent, and vibration time.The rule how ingredients affect the mechanical property of HSSLC was studied systematically in this article. Based on this, HSSLC was yield, which possessed many merits such as good workability and uniformity, dry apparent density between 1950 kg/m3 and 2200kg/m3, elastic modulus larger than 32GPa, small shrinkage and compressive strength higher than 60MPa. A calculation formula to evaluate the elastic modulus of HSSLC was raised in this article.The volume distortion property and durability of HSSLC were also studied systematically in this article. The results indicated that compared with high strength lightweight aggregate concrete and high strength normal weight aggregate concrete,the dry shrinkage and autogenous shrinkage of HSSLC were smaller, and the period of shrinkage to become stable was shorter. Compared with normal weight aggregate concrete in the same strength class, the creep value of HSSLC was lager while the creep coefficient was approximately proximity when applied load at 3 days. It was found that the durability of HSSLC was good, mixing with proper dosage of mineral admixture could increase the durability of semi lightweight concrete obviously.