Study on durability of face slab concrete under freeze-thaw cycle and carbonation

Abstract

[Objective] According to the actual service environment of the face slab of rockfill dam in northern China, the failure of carbonation durability under freeze-thaw conditions is the main problem leading to the deterioration of the durability of face slab concrete in cold areas. In order to explore the influence law and mechanism of freeze-thaw cycles on carbonation durability of face slab concrete, [Methods]the rapid freeze-thaw test, accelerated carbonation test, scanning electron microscope and nuclear magnetic resonance analysis technology were used to conduct freeze-thaw cycles on concrete specimens for 0, 50, 100, 150 and 200 times, and then accelerate carbonation for 0, 7, 14 and 28 days. By testing the macro indexes of concrete such as carbonation depth, relative dynamic elastic modulus, ultrasonic wave velocity, splitting tensile strength and compressive strength, and micro indexes such as porosity and pore size distribution, the influence of freeze-thaw cycle and carbonation on the micro-pore structure and durability of concrete is analyzed. [Results] The results show that the carbonation depth of concrete after carbonation is greater than that under the condition of freeze-thaw damage. Carbonization improves the relative dynamic elastic modulus, ultrasonic wave velocity, splitting tensile strength and compressive strength of concrete face slab. After 200 freeze-thaw cycles, the most probable pore size of carbonization for 28 days decreased from 59.35 nm to 41.94 nm, a decrease of 29.33%. [Conclusion] The damage caused by freeze-thaw cycle to concrete reduces the carbonation resistance of concrete; Carbonization reaction reduces the porosity and the most probable pore size of face slab concrete, and alleviates the damage to concrete caused by freeze-thaw cycle. Controlling the pore content in the range of concrete internal pore diameter d>1 000 nm and increasing the pore content in the range of 10 nm≤d<100 nm can improve the carbonation resistance of face slab concrete under freezing and thawing conditions.

Keywords

freeze-thaw cycle / face slab concrete / carbonization depth / compressive strength / microstructure / mechanical properties / influencing factors / durability