The Assessment Of Concrete Workability And Key Control Techniques

The evaluation of concrete workability often limited to slump test, and is accompanied by subjective judgement as well as large deviation. Here the research is deploied on ordinary concrete with the slump from120mm to220mm and SCC, which is taken C50 as example.The homogeneity of mechanical properties and durability is fully studied so as to establish contract with workability. The workability of cement paste and slurry is also studied for the same reason.Have the impacts of W/C, mineral admixture, water reducing agent on paste workability fully examined, it turns out to have positive impact on flowability and negative influence on cohesiveness and water retention ability with the addition of W/C, slag and water reducing agent increased, while the impact of first class fly ash is otherwise. The cohensiveness of cement paste and slurry is similar under different circumstance, witch can be hopeful to the control of concrete workability, and it does work.With the relationship of homogeneity and workability builit, it comes out that the degradation of workability often impliy the increase of unhomogeneity. Specifically, the deviation of compressive strength, dynamic elastic modulus, chloride migration, gas migration, drying shrinkage is enlarged.In view of that, the workability assessment system is builit.The image processing method is introduced to make precise assessment. The final expansion, bubuule content, ultimate shape, and expansion time are obtained, which can be the first step to have the workability assessment intelligentized.By means of microscopic analysis, the deviation of pore structure, hydration products and microstructure with different workability is discovered, which confirmed the differences in micro scale.