• Durability and Smart Condition Assessment of Ultra-High Performance Concrete in Cold Climates

      Qiao, Pizhong; Zhou, Zhidong; Allena, Srinivas (Center for Environmentally Sustainable Transportation in Cold Climates, 2016-12-31)
      The goals of this study were to develop ecological ultra-high performance concrete (UHPC) with local materials and supplementary cementitious materials and to evaluate the long-term performance of UHPC in cold climates using effective mechanical test methods, such as “smart aggregate” technology and microstructure imaging analysis. The optimal UHPC mixture approximately exhibited compressive strength of 15 ksi, elastic modulus of 5,000 ksi, direct tensile strength of 1.27 ksi, and shrinkage of 630  at 28 days, which are characteristics comparable to those of commercial products and other studies. The tensile strength and modulus of elasticity in tension, dynamic modulus, and wave modulus show slight increases from the original values after 300 freeze-thaw (F-T) cycles, indicating that UHPC has excellent frost resistance in cold climates. Although porosity deterioration was observed in the F-T cyclic conditioning process, no internal damage (cracks or fractures) was found during imaging analysis up to 300 cycles. Since structures for which UHPC would be used are expected to have a longer service life, more F-T cycles are recommended to condition UHPC and investigate its mechanical performance over time. Moreover, continuum damage mechanic-based models have the potential to evaluate damage accumulation in UHPC and its failure mechanism under frost attack and to predict long-term material deterioration and service life.