Investigation On The Composition, Structure And Performance Of High Performance Expansive Concrete (HPEC)

High performance concrete (HPC) is the direction of concrete technology in 21st century and a hot point of concrete materials research. In this dissertation, getting to know HPC deeper the author puts composition-property diagram forward. On this base, a more precise volume model of concrete is established and one conception of dry mortar volume is brought forward. At the same time the author absorbed the concept of the best ratio between paste and aggregates and used mathematical method to induce the formulas of water content and ratio between fine aggregate and coarse aggregate in concrete:Ratio between fine aggregate and coarse aggregate:If the two formulas are connected with the classical rule of water cementitious materials ratio (Bolmy formula), the contents of all materials in concrete can be determined completely by calculation and overall calculation proportioning is realized. This method can be applied for not only HPC, but also other types of concrete. So it is universal.In this dissertation the author puts forward the concept of high performance expansive concrete (HPEC), and deems that HPEC is a compound material of EC (expansive concrete) and HPC in which both sides can bring well play. The author investigated systematically the strength property - expansive property and coordination between expansion and strength of HPEC mortar and HPEC. The study on HPEC mortar shows that restricted expansive ratio (E2) increases in the curve of parabola with the increase of the dosage of calcium sulphoaluminate(CSA)expansive agent. So there is a suitable range of CSA dosage (generally 6%-12%). In this range, E2 of HPEC mortar can reach as high as (5 -10)10~4, and the strength is not decreased. This provides the probability to design the expansive concrete with different expansive energy levels and different strength grades. If blast furnace slag (BFS) or fly ash (FA) is added, e2 will decrease. The more the CSA, the larger the reducing percentage of E2 when adding BFS or FA. So to remain the E2 unchanged, CSA dosage should increase properly. When CSA dosage is very large, adding BFS or FA will restrain possible structure destroy which is caused by excess expansion. From the research on HPEC we can know that expansion property of high strength superplasticizedexpansive concrete shows obvious particularity compared with ordinary expansive concrete. When BFS is not put in, high strength superplasticized expansive concrete shows autogenous shrinkage in 1 day standard curing. And in 14 day's age E2 is less than half of middle strength superplasticized expansive concrete's with same CSA dosage , and this shows expansion effect is confined more. After BFS is put into high strength superplasticized expansive concrete (substituted for cement), autogenous shrinkage doesn't appear in 1 day standard curing, and E2 in 14 day's age is higher than that of high strength superplasticized expansive concrete without BFS in the same age. Inversely, E2 of middle strength superplasticized expansive concrete, which has high E2, will decrease after FA is put in. The higher the CSA dosage is, the bigger the reducing range is. This seemingly contrary phenomenon is rooted in the coordination of expansion and strength development: the high strength especially high early strength of high strength superplasticized expansive concrete confined expansion effect, and there is "self-restricted effect" in concrete. BFS can reduce the early strength of high strength superplasticized expansive concrete and make expansion effect develop fully. So high strength concrete with BFS shows higher E2. The expansion and strength of middle strength superplasticized expansive concrete develop more coordinately. FA reduces the early strength of middle strength superplasticized expansive concrete, and this make more expansion become invalid when the concrete is in plastic state. So E2 of the concrete will decrease. This research reveals a basic viewpoint: the strength development should coordinate with expansion increase. This still can be applied...