Method for determining temperature process curve of ultrahigh fly-ash content hydraulic massive concrete

Abstract

The invention discloses a method for determining a temperature process curve of ultrahigh fly-ash content hydraulic massive concrete. The method comprises: using normal concrete and ultrahigh mixture concrete to perform an adiabatic temperature rise test, manufacturing an ultrahigh mixture concrete cubic large test block with side length of 1.2 m to carry out a temperature measuring test, combined with an internal point actual measured temperature record of a certain double-curvature arch dam which is established by using the normal concrete, providing an ultrahigh mixture concrete adiabatic temperature rise model, to improve temperature simulation calculation program, so as to simulate a temperature process curve of an ultrahigh mixture concrete dam which has no construction precedent. The method can be used for temperature-stress test evaluation and early-age crack resistance.

Description

technical field [0001] The invention belongs to a new method necessary for the temperature-stress test of early age crack resistance evaluation of green high-performance hydraulic mass concrete. Background technique [0002] Concrete with a large amount of mineral admixture can save a lot of cement, turn waste into treasure, reduce environmental pollution, reduce the temperature rise of heat of hydration and improve its performance. At present, fly ash is still the main admixture of hydraulic mass concrete. As far as the normal dam concrete dams (non-roller compacted concrete dams) that have been built at home and abroad, the maximum amount of fly ash is within 70%. The external dosage of American dams is 25%, and the internal ratio is 50%; the highest dosage in Japan is 30%; the Three Gorges Dam in my country is 20%-50%; my country's "Technical Specifications for the Use of Fly Ash in Hydraulic Concrete" ( DL / T5055-2007) stipulates that its dosage shall not exceed 55%. In...

AI Technical Summary

Problems solved by technology

However, Malhotra et al. did not study the effect of temperature on its performance

From the existing HVFC research at home and abroad, there are still the following deficiencies: (1) Class I and Class II ash are widely used in engineering, but a large amount of low-grade ash cannot be utilized

(2) Due to the high water-to-cement ratio, the amount of fly ash cannot be increased

(3) Due to the lack of correct test techniques and evaluation standards for "HVFC", the effect of temperature cannot be accurately estimated, and the amount of fly ash is also limited

The research results show that: under the adiabatic curing mode, the stress development of concrete is faster, the cracking temperature is higher, and the crack resistance of the two concretes is significantly different; under the other two modes, the crack resistance of the two concretes is equivalent; The initial cooling point underestimates the crack resistance of concrete. The constant temperature mode cannot reflect the influence of the precompressive stress caused by temperature rise, and the cracking temperature of concrete is low. Only the temperature matching mode can objectively reflect the influence of the temperature history on the actual structural stress and cracking temperature. influences

[0004] However, ultra-high-volume fly ash hydraulic mass concrete (abbreviated as "ultra-high-concrete") has not been used in actual dam projects, so it is difficult to use the measured temperature history curve of dam concrete as the temperature matching condition for temperature-stress tests

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