Study On Rheological Properties Of Concrete For Super Flat Floor

Super flat ground, namely "super flat floor", is made by high precision laser leveling machine for fresh concrete paving leveling and combined with a certain floor construction technology, to achieve particular use requirements of the floor. Using laser leveling machine rather than traditional manual type, can high precision control the levelness and flatness of the ground. In this way, the ground can achieve real super flat floor. Due to the short time of laser leveling floor technology imported in China, the construction process is carried out in accordance with the foreign method of construction. It is necessary to research the concrete for large area laser leveling machine paving floor which suitable for Chinese national conditions.This study was divided into two parts: the mortar part of concrete and coarse aggregate of concrete.We studied the influence of water cement ratio, cement sand ratio, water reducing agent on mortar liquidity, bleeding rate, the strength and shrinkage.on the basis of study the influence of VMA on mortar liquidity, bleeding rate and the shrinkage. In addition, we used the VISKOMAT XL concrete-mortar rheometer to measure mortar rheological parameter. This paper discussed the influence of water cement ratio, cement sand ratio, water reducing agent and VMA on mortar rheological properties. We regulated coarse aggregate gradation based on the theory of maximum density curve of aggregate and studied the influence of mortar extra coefficient on the slump,slump flow and compressive strength of concrete.The experimental results showed that under certain water cement ratio, choosed reasonable cement sand ratio and controlled cement mortar fluidity, which will greatly reduce the chance of mortar bleeding. When water cement ratio determined, mortar shrinkage ratio increased with the rise of the cement sand ratio. When cement sand ratio determined, mortar shrinkage ratio increased with the rise of cement sand ratio.The influence of water reducing agent on mortar shrinkage rate was not obvious. Adding VMA would not rise mortar shrinkage rate. Increased water cement ratio? cement sand ratio or adding water reducing agent, yield stress and plastic viscosity of mortar reduced. Adding VMA, yield stress and plastic viscosity increased. In this area, the g value in 50 ~ 200 Nmm and h value in 1.8 ~ 4.0 Nmm·min, mortar had suitable liquidity and less bleeding. This mortar can be used to make floor concrete.It is a feasible technology to adjusted coarse aggregate gradation by the aggregate maximum density curve, which would maximized the coarse aggregate packing density so as to reduce the dosage of mortar. The slump and slump flow of concrete increased with the rise of mortar extra coefficient. When water cement ratio is higher, the concrete strength would decrease along with the augment of mortar extra coefficient.