Experiment Research On Expansive Deformation And Crack Resistance Of Ready-mixed Shrinkage-compensating Concrete

Traditionally, the agitation in site was undertaken in the course of underground construction of coalmine roadway. However, this construction method will definitely be replaced by the "ready-mixed concrete" due to the great attention on environment protection. In addition, the concrete displayed relatively weak tensile strength and tend to cracking, which will weaken the overall performance of concrete. To extend the service performance of concrete, this paper produced ready-mixed concrete shrinkage-compensating on the basis of ready-mixed concrete and ready-mixed concrete shrinkage-compensating. Setting the moisture content, the storage period of dry mixed materials and Admixture as variable, this work focused on the impact of the moisture content, the storage period of dry mixed materials and admixture on the performance of preventing from deforming, fracture and cracking of ready-mixed concrete shrinkage-compensating.The deforming assays include the performance test of free expansion (125repeats) and Expansion performance test limit (14repeats). Ideal "effective expansion" was achieved when the amount of expander was6%. However, effective expansion increased slowly when the expander continued to increase. Meantime, the free expansion rate and limited expansion ratio were enhanced with increase of moisture content of the sand and the storage time.The anti-fracture assay show that Ready-mixed concrete shrinkage-compensating exhibited the best performance to prevent from fracture when the amount of expander was6%. When the amount of expander was kept increasing to more than6%, it did not increase but decreased the strength. Flexural strength decreased little when the moisture of sand was below1%. However, when the moisture of sand was above1%, the anti-fracture ability of concrete was significantly decreased. When the moisture of sand was constant, the anti-fracture ability was significantly decreased when the storage time was short.According to the expansion test and bending test,6%was determined as the optimized amount of expander. Based on this result, anti-cracking assay was conducted on Plain concrete, the shrinkage compensating concrete and ready-mixed concrete shrinkage-compensating. The shrinkage compensating concrete crack limiting grade, fracture reduction coefficient was as high as94.4%. With the increase of storage time and moisture of sand, the nominal cracking area of the shrinkage compensating concrete was increased. The crack limiting grade of ready-mixed concrete shrinkage-compensating was the first class standard when the amount of moisture of sand was not more than1%andstorage time was in30days. When the moisture of sand was1.5%and storage time was in7days, the crack limiting grade was still the first class standard. To sum up, ready-mixed concrete shrinkage-compensating displayed better anti-cracking performance.