Study on strength development and strength management method of high strength concrete in structure

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The high-strength concrete which the design strength exceeds 120 MPa is the one of which binders are made of low-heat Portland cement and silica fumes, and water-binder ratio is about 15-25%, is a low water-binder ratio concrete. Generally, the concrete subjected to high-temperature history in early ages shows the early-age strength development is high, but the long-term strength development is stagnant, and it would be outstripped by the concrete subjected to standard curing. However, it was also said that the concrete with a water-binder ratio of 20% or less and subjected to high-temperature history in early ages shows a remarkable early-age strength development, and the long-term strength development would not be outstripped by the concrete which is subjected to standard curing.In this study, we propose to clarify the mechanism of strength development of the low water-binder ratio concrete using silica fumes with which the water-binder ratio is 20% or less, and the design strength is over 120 MPa. Upon investigation, the following results are made:(1) It can be said that the strength of the concrete with 17% or less of water-binder ratio, and heated to 60ーC in early stages of the setting period has exceeded the standard curing concrete strength at 91 days.(2) The mortar from the matrix of the concrete with 17% of water-binder ratio, and heated to 60ーC in early stages of the setting period shows there is nearly the same distribution of micro pores and nearly the same value of combined water and consumed calcium hydrate at 91 days to the one from the concrete which did not subjected to high-temperature history