Browsing by Author "Pour Ghaz, Mohammad"

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    Characterizing Lightweight Aggregate Desorption at High Relative Humidities Using a Pressure Plate Apparatus
    (ASCE-AMER SOC CIVIL ENGINEERS, 2012) Pour Ghaz, Mohammad; Castro, Javier; Kladivko, Eileen J.; Weiss, Jason
    This paper describes the results of an experimental study that was performed to obtain desorption isotherms for a wide range of fine lightweight aggregates that are used commercially in North America. The desorption isotherms were determined for the entire gradation of the fine lightweight aggregates (as received). To obtain the desorption isotherms a pressure plate apparatus (porous plate) was used. The pressure plate enables the desorption isotherm to be measured at high relative humidities (beginning at 100%). In addition to providing experimental results obtained with the pressure plate method, desorption results obtained by gravimetric desorption and dynamic vapor desorption methods are also provided. The gravimetric desorption and dynamic vapor desorption methods are generally used at lower relative humidities (98% and 0% relative humidity). The results indicate that water leaves the fine lightweight aggregates at relative humidities as high as 99.9%. This suggests that internal curing water is available to the cement matrix even at relatively high water-to-cement ratio mixtures when the suction forces exerted by cement paste are small. The results of this work are helpful for the development of mixture proportioning techniques and numerical simulation for internally cured concrete mixtures. DOI: 10.1061/(ASCE)MT.1943-5533.0000422. (C) 2012 American Society of Civil Engineers.
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    Water Absorption and Critical Degree of Saturation Relating to Freeze-Thaw Damage in Concrete Pavement Joints
    (ASCE-AMER SOC CIVIL ENGINEERS, 2012) Li, Wenting; Pour Ghaz, Mohammad; Castro, Javier; Weiss, Jason
    Fluid ingress is a primary factor that influences freeze-thaw damage in concrete. This paper discusses the influence of fluid ingress on freeze-thaw damage development. Specifically, this paper examines the influence of entrained air content on the rate of water absorption, the degree of saturation, and the relationship between the saturation level and freeze-thaw damage. The results indicate that whereas air content delays the time it takes for concrete to reach a critical degree of saturation it will not prevent the freeze-thaw damage from occurring. The results of the experiments show that when the degree of saturation exceeds 86-88%, freeze-thaw damage is inevitable with or without entrained air even with very few freeze-thaw cycles. DOI: 10.1061/(ASCE)MT.1943-5533.0000383. (C) 2012 American Society of Civil Engineers.