Development of In-Situ Sensing Method for the Monitoring of Water-Cement (W/C) Values and the Effectiveness of Curing Concrete

US Transportation Collectionhttps://doi.org/10.5703/12882843173772022PDFTech ReportHe, RuiLu, Na (Luna)Olek, JanPurdue University. Joint Transportation Research ProgramIndiana Department of TransportationUnited States. Department of Transportation. Federal Highway AdministrationPurdue University. Joint Transportation Research ProgramUnited StatesIndianaConcrete curingMonitoringWater cement ratioTestingGround penetrating radarnon-destructive testingFHWA/IN/JTRP-2022/14SPR-4418Final reportAs the most widely used construction material, concrete is very durable and can provide long service life without extensive maintenance. The strength and durability of concrete are primarily influenced by the initial water-cement ratio value (w/c), and the curing condition during the hardening process also influences its performance. The w/c value is defined as the total mass of free water that can be consumed by hydration divided by the total mass of cement and any additional pozzolanic material such as fly ash, slag, silica fume. Once placed, field concrete pavements are routinely cured with liquid membrane-forming compounds. For laboratory study, concrete samples are usually cured in saturated lime water or a curing room with a relative humidity (RH) value higher than 95%. Thus, the effectiveness of curing compounds for field concrete needs to be studied. In this study, the dielectric constant value of plastic concrete was measured by ground penetrating radar (GPR). The w/c value of the plastic concrete was calculated by a mathematical model from the measured dielectric constant value. The calculated w/c value was compared with the microwave oven drying measurement determined result in AASHTO T318. A modified coarse aggregate correction factor was proposed and applied in microwave oven drying measurement to determine the w/c value of plastic concrete in AASHTO T318. The effectiveness of curing compound was evaluated by field concrete slabs by GPR measurement. It was found that GPR can be a promising NDT method for w/c determination of plastic concrete and can be a promising curing effectiveness evaluation method for hardened concrete.143