Method for determining temperature process curve of mass concrete with ultrahigh volume of fly ash

Abstract

The invention discloses a method for determining a temperature process curve of a mass concrete with ultrahigh volume of fly ash. Through adoption of a reference concrete and a concrete with ultrahigh volume of admixture, adiabatic temperature rise tests are carried out; a big cubic test block with side lengths of 1.2m is manufactured for carrying out a temperature measurement test; through combination of the actual measurement temperature records of the internal points of a certain hyperbolic high arch dam A constructed through adoption of the reference concrete, the adiabatic temperature rise models of the two concretes are provided; ANSYS finite element software is improved for carrying out temperature field simulating calculation; verification is carried through utilizing the actual measurement temperature curves of the big test block manufactured by the concrete with ultrahigh volume of admixture and the entity dam of the reference concrete; therefore, the temperature process curve of the dam manufactured by the concrete with ultrahigh volume of admixture is simulated and determined, and there is no construction precedent of the temperature process curve; and the temperature process curve can be used for a temperature-stress test and evaluation of the early-age crack resistance of the mass concrete with ultrahigh volume of fly ash.

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 results show that: the adiabatic mode overestimates the initial cooling point and underestimates the crack resistance of concrete; the constant temperature mode cannot reflect the influence of precompression stress caused by temperature rise, and the cracking temperature of concrete is low; only the temperature matching mode can objectively reflect the temperature history Influence on actual structural stress and cracking temperature

[0004] However, the normal dam concrete with ultra-high content of fly ash (hereinafter referred to as "ultra-high content concrete") has not been used in actual dam engineering, so it is difficult to use the measured temperature history curve of dam concrete as the temperature matching of temperature-stress test Conditions to study and evaluate its early age crack resistance

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