Laboratory Testing Material Property and FE Modeling Structural Response of PAM-Modified Concrete Overlay on Bridges

Portland cement concrete overlay on bridge deck is subjected to distresses of cracking and interface debonding under the effects of repeated vehicle loading and temperature cycling. In order to improve the overlay performance, this research used the polyacrylamide (PAM) polymer to modify the mechanical properties of concrete. The direct shear and impact resistance tests were designed to measure the interface bonding strength and dynamic performance, respectively. The comprehensive and flexural strength and three-point bending fatigue tests were conducted following the standards. Meanwhile, the three-dimensional finite-element (FE) models of the T-girder and box-girder bridges under the moving traffic loadings were built to analyze the stress response and improve the structural design. An analytical model of flexural stress was developed and validated the FE modeling results. A rubber cushion was designed in the FE model to “absorb” the flexural stress. Laboratory testing results indicate that PAM can significantly improve the flexural strength, bonding strength, impact resistance, and fatigue life of concrete. The modified concrete with 8% PAM by mass of cement poses higher flexural strength and impact resistance than concretes with other PAM percentages. FE simulation results indicate that there exists a critical overlay thickness inducing the maximum interface shear stress, which should be avoided in the structural design. The rubber cushion can effectively relieve the flexural stress.

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