Ultrasonic and X-CT measurement methods for concrete deterioration of segmental lining under wetting-drying cycles and sulfate attack

Accurately assess the concrete deterioration of segmental lining under sulfate attack environment is important for tunnel construction and operation. Ultrasonic testing of concrete samples is generally used to determine the sulfate resistance of concrete materials. However, concrete is a porous medium material, and the internal coarse aggregate and pores will affect the sulfate attack velocity, so the ultrasonic velocity cannot directly assess the local deterioration of concrete structure under sulfate attack. In this study, the durability of concrete samples exposed to sulfate attack and wetting-drying test was studied by using the comprehensive assessment method of X-ray computed tomography (X-CT) scanning and ultrasonic testing. The ultrasonic attenuation velocity and internal pore change of deteriorated concrete were measured, and the sulfate attack depth was calculated. Test results indicate that the newly defined ultrasonic velocity after removing coarse aggregate and pores through X -CT results is a suitable index to describe the non-uniform deterioration behavior of sulfate-attacked concrete. A local deterioration assessment method of concrete structural based on X-CT, ultrasonic velocity and sulfate attack model is proposed, which provides a potential application for the deterioration assessment of sulfate-attacked tunnel segmental lining based on laboratory accelerated test results.

Automated summary

Accurately assessing the deterioration of segmental lining concrete under sulfate attack is crucial for tunnel construction and operation. This study used X-ray computed tomography (X-CT) scanning and ultrasonic testing to study the durability of concrete samples exposed to sulfate attack and wetting-drying test. The results indicate that the newly defined ultrasonic velocity after removing coarse aggregate and pores is a suitable index to describe the non-uniform deterioration behavior of sulfate-attacked concrete. A local deterioration assessment method for concrete structures based on X-CT, ultrasonic velocity, and sulfate attack model is proposed, which can be applied to the assessment of sulfate-attacked tunnel segmental lining based on laboratory accelerated tests.