High Performance Concrete (HPC) with small water/binder ratio has been widely used in the construction industry nowadays. However, HPC is found to be extremely delicate to the threat of early age cracking which vastly affect the concrete quality. Previous researchers have proposed self-curing technique as a solution to the problem. A self-curing concrete is able to absorb moisture from the surrounding for proper cement hydration. This paper study the environmental monitoring and material characterization of new and used diapers hydrogel polymer. In this study, diapers hydrogel polymer is proposed as a self-curing agent due to its amazing water absorption ability. Laboratory testing was done for environmental monitoring of both new and used diaper polymer, including turbidity test, colour test, pH test, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) test whilst for material characterization, Wavelength Dispersive X-Ray Fluorescence (WDXRF) test, X-Ray Diffraction (XRD) analysis and Fourier Transform Infrared (FTIR) analysis was conducted. As a result, addition of used diapers polymer with pH of 8.34 into high performance concrete mix has no significant effect of the alkalinity of concrete, which it is a crucial requirement to maintain the performance of concrete structure. Hence, it concluded that polymer source from used diaper has a good potential as self-curing agent in concrete.