Experimental Study On The Performance Of Shrinkage-compensating Concrete With Fly Ash

Ordinary concrete due to shrinkage, dry shrinkage and other reasons, often lead tocracking and deterioration. Coordinated expansion properties, strength properties and thedevelopment of shrinkage compensation concrete of fly ash from the material point of view,has a certain practical value. Were swelling mortar expansion properties of fly ash, fly ashcompensation strength properties and shrinkage of concrete expansion properties, strengthperformance tests. And the whole calculation of shrinkage compensation concrete ratio designmethod is applied in the fly ash on the mixture ratio design. Through the work done in thispaper, we can draw the following main conclusions:(1) Experimental study of the fly ash mortar expansion shows that: when fly ash contentis10%, the reasonable expansion additive weight in the range of10%~12%; when the fly ashcontent is30%, the reasonable expansion additive weight in the range of8%~10%. In order tomake cement, expansive agent and fly ash is the three element composite cementitiousmaterial system with ideal expansion and strength properties.(2) Study the performance of shrinkage compensating concrete with fly ash shows that:ensure that key performance and the use of shrinkage compensating concrete with fly ash isthe expansion and strength coordinate development. If the expansion agent hydration reactionfaster mainly concentrated in the early, so most of the expansion can be consumed in theconcrete has not yet hardened plastic stage, will greatly reduce the effective expansion; on thecontrary, if the expansion agent hydration occurs in the concrete system has been formed inconcrete strength, high early strength will inhibit concrete expansion, so that there is "selfrestraining effect" in the concrete, even extended to the expansion of the system into full playthe strength of late, which causes delayed expansion of destruction, has been formed tostabilize the structure of the system will be more negative..(3) In the practical engineering for the expansion of strength grade C40concrete shouldbe controlled the coordination dosage of expansion agent and fly ash. When the dosage ofexpansive agent (greater than12%), high dosage of fly ash should be reduced, generally no more than10%; When the dosage of expansive agent is low (<12%), dosage of fly ash canimprove the appropriately, is generally not less than10%. So to reduce early hydration heat ofconcrete, concrete strength, enhance the expansion performance is very good.(4) Paste-aggregate ratio also has some influence on the expansive concrete coordinationand strength for development. No matter how expansive ash, fly ash as low (10%),paste-aggregate ratio is relatively large (37.5/62.5), the more favorable the coordinateddevelopment of the system expansion and strength; when compared with fly ash high (30%),paste-aggregate ratio decreases, the more favorable the coordinated development of thesystem expansion and strength. So not all the concrete optimal paste aggregate ratio weredetermined as35/65this experience, it is in a certain range for different types of concrete.The article also combined with chemical mechanism of ettringite formation, with thewidespread use of sulpho aluminate expansive agent as an example, through the analysis ofchemical composition of cement gives the main chemical composition of the expandedproduct of the theoretical value, the swelling agent products matching techniques,expectations for the new expansion model to the research and development of agent up.