Frost dilation measurements on concrete cores from a dam with ASR

Abstract

In order to evaluate length change measurements to determine damage in concrete due to both ASR and internal frost attack, concrete cores drilled from a 25 year old dam with slight ASR and some surface frost damage were used. Critical dilation was measured during a single freezing and thawing cycle of moisture conditioned and -sealed specimens using LVDT and invar steel frame. The effects of varying degree of capillary saturation (DCS), pre-drying, specimen size and length of freezing period on unrestrained freezing dilation were studied. Critical freezing dilation testing is well suited to determine durability against internal frost damage. The existence of critical dilation, the deleterious effect of severe drying compared to the frost damage observed in specimens with mild drying and the mechanisms causing detectable frost damage were similar to what is found in the literature on laboratory cast concrete without ASR. The experiments also illustrate the useful information from the PF-method for determination of DCS and porosity including protective pore factor (PF). Critical dilation was found to be around 0.08 – 0.1 o/oo based on observations of freezing- and residual dilation on the 25 year old cores with DCS = 92 – 100 %. Finally we propose a method of determining the interaction mechanism between ASR and frost damage based on the same criterion; namely strain.