Study on the freeze–thaw cycles and carbonization of ultra-high molecular weight polyethylene fiber reinforced engineered cementitious composite for link slab

Abstract

To explore the mechanical properties of ultra-high molecular weight polyethylene fiber reinforced engineered cementitious composite (UHMWPE-ECC) used as link slabs in Northeast and South China, experimental schemes of freeze–thaw cycles and carbonation were designed based on the service life of link slabs replacement expansion joints. Scanning Electron Microscopy (SEM) was used to analyze the microscopic morphology of UHMWPE-ECC after undergoing freeze–thaw cycles and carbonization. The carbonization front of UHMWPE-ECC was determined by X-ray diffractometer (XRD). Results indicate that freeze–thaw cycles cause minor surface damage, gradual mass loss, and a decrease in the relative dynamic elastic modulus. Furthermore, the compressive strength of the simulated link slabs is reduced by 9.8%, the tensile strain is reduced by 24.5%, and the ultimate load of three-point bending is reduced by 35.4% after 15 years of service in the Northeast. After 15 years of service in the Southern region, the compressive strength increased by 24.2%, the tensile strain increased by 45.1%, and the ultimate load of three-point bending increased by 61.4%. SEM reveals that carbonization roughens the fibers surface, enhancing bonding between the fiber and cement matrix. Additionally, freeze–thaw cycles cause cracks of less than 1 µm to appear in the matrix, which loosens the matrix and weakens the adhesion between the fiber and cement matrix. The carbonization fronts of link slabs in Southern China for 5, 10, and 15 years were 3–4 mm, 5–6 mm, and 6–7 mm. The tensile strain of UHMWPE-ECC after 15 years of service in the Northeast and Southern regions is 3.38 and 6.29 times what is required for the link slab in that region, and the compressive strengths all meet the requirements of the Chinese Bridge Code.