Lei Liu’s scientific contributions

This paper investigates the cracking prevention and control of concrete engineering in ultra-high altitude areas. Combined with the hydration-temperature-humidity-constraint coupling model, the cracking risk assessment of bridge piers under extreme environment was carried out. The effect of deformation compensation crack control in concrete cracking risk control was revealed. Finally, the concrete cracking risk was assessed after long-term temperature changes. The results show that wind speed, air temperature, light, humidity and freeze–thaw greatly affect the cracking control of concrete. The cracking risk in the surface layer of the bridge piers is maximum around 2–4 days. The maximum cracking risk coefficient is between 0.6 and 0.95. And the risk of core cracking increases progressively after 14 days. When the HME-V ® crack-resistant product is added, the unit expansion deformation of concrete increases during the temperature rise phase. Furthermore, the unit volume shrinkage is decreased during the temperature drop phase. A significant deformation compensation is produced. The risk of early and long-term cracking in the core and surface layers of the concrete structure is significantly reduced. The effect of crack control is remarkable. In summary, pre-cracking control in the surface layer of bridge piers is crucial. The risk of long-term cracking in the core is significantly higher than that in the early stage, and long-term cracking control should also be emphasized.

Concrete structures in high-altitude environments face many challenges. Establishing concrete crack control methods in high-altitude environments is crucial for enhancing the service capacity of concrete structures. In this study, a multi-field (hydration-temperature–humidity-constraint) coupling model was used to quantitatively assess the cracking risk of pier bodies at high altitude. On-site crack control tests were conducted on pier bodies using a micro-expansion anti-cracking agent to demonstrate the effectiveness of deformation shrinkage compensation in crack control at high altitudes. The results indicated that there was a risk of cracking in the pier body at high-altitude conditions, especially within 0.3 m from the pile cap and ±2.5 m from the center of the pier side surface. Compared with conventional piers, the micro-expansion anti-cracking agent approximately doubled the unit expansion deflection of piers at high temperatures while reducing the unit shrinkage deflection of piers by 11% to 12% at low temperatures. The concrete in conventional pier bodies was in a tension state after long-term hardening, while the concrete treated with the micro-expansive anti-cracking agent was in compression. Therefore, the deformation compensation effect of the micro-expansive anti-cracking agent was significant and reduced the risk of concrete cracking. In addition, early freezing had a significant impact on concrete strength, underscoring the importance of effective temperature control during the early stages of concrete placement in high-altitude environments.