Freeze-thaw damage is among the most detrimental factors on concrete durability. In the current practice winter construction measures. i.e. heating, are applied to fresh concrete with a duration estimated based on experience. The uncertainty tends to either cause high construction cost or concrete subject to freeze-thaw damages. This paper describes the study that aims at determining a criterion based on instrumentation data to optimize the concrete curing during winter construction activities. The rationale ofthis research lies in the fact that the volume of pore water expands while freezing; unless there is sufficient pore space to accommodate such volume expansion, the chemical bonding among concrete constituents will be broken by ice. The likelihood of freezing damage to concrete is extremely high at the early stage due to the relatively weak bonding strength development. A sound criterion to prevent freezing damage of early stage concrete needs to be set upon accurately measuring the amount of free water (and consequently the amount of volume expansion) and the volume of air void. An innovative instrument based on Time Domain Reflectometry (TDR) principles is evaluated to measure the physical properties of curing concrete. A preliminary framework to apply this technology to prevent freeze-thaw damage of early stage concrete is developed. This method will help to ensure the long term durability of concrete.
Abstract