Applied Research On The Self- Compacting Concrete In Structure Reinforcement Project

The use of self-compacting concrete (SCC) is becoming more and more popular in construction filed. Many researches are also conducting on SCC, including workability, mechanical properties, deformation performance, durability, constructability and cost-effective construction, etc. This paper carried out researches on the development of SCC which is suitable for concrete stucture strengthening application. The research includes: 1) raw materials, to determine appropriate water reducer and the proportion of cementing materials; 2) mix design of SCC which is especially for concrete stucture strengthening application, to propose a fast, simple and applicable design method based on the commonly used design method; 3) to propose a fast, simple and applicable test method for the workability of the fresh SCC; 4) the performance of hardened strengthening SCC including the bonding strengthen between new and old concretes, elastic modulus, expansion properties, the development of early strength. The main achievements obtained in this study are as follows:(1) The selection of raw materials and optimization of the binder of SCC used in strengthening applicationFluidity test showed that polycarboxylate superplasticizer Fox-80 has some obvious advantages: low level of addition, 0.3% (by the mass of binder); high initial flowability, 310mm; low loss of fluidity, there is no loss of fluidity after 60 min. Thus, Fox-80 was selected as the water reducer in this study. The mix proportion of cementing materials was: Cement: silica fume∶fly∶slag∶expansion admixture = 66∶4∶10∶10∶10.(2) The mix design method of SCC used in strengthening applicationBased on the requirements of SCC for strengthening application, the ranges of there important parameters were determined: the absolute volume of coarse aggregate (VG), 280 ~ 350L; water (W), 155 ~ 180L, water powder ratio (W/P), 0.291 ~ 0.393; powder content (VB), 160 ~ 230L; slurry content (VB + W + Va), 320 ~ 400L.(3) Test methods for the workability of fresh SCC used in strengthening applicationThe test methods have to be simple, fast and applicable on site. Slump test was employed, and the slump flow, height difference and visual stability were measured. Slump flow of concrete structure strengthening SCC for was 650±50mm, height difference was lower than 20mm.(4) Properties of hardened SCC used in strengthening applicationInterface bonding strength between SCC with good workability and old existing concrete was high; the elastic modulus of strengthening SCC was equal to that of normal concrete with one lower strength grade. 3d longitudinal expansion of strengthening SCC was 0.023%; the early strength development of strengthening is rapid, 1d cubic compressive strength of SCC with strength grade of C55 was 29.3MPa, which is 45% of 28d cubic compressive strength.