PSI - Issue 67

Dan Huang et al. / Procedia Structural Integrity 67 (2025) 61–79 Huang, D., Velay-Lizancos, M., Olek, J./ Structural Integrity Procedia 00 (2024) 000–000

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conditioned. The first phase of the preconditioning procedure involves placing specimens in a 50°C/80% relative humidity (RH) oven for 3 days. Subsequently, the specimens undergo a 15-day long “equilibration period”, during which they are placed in a sealed container kept at 23°C and 50% RH. After the sample conditioning procedure was completed, the side surface of each specimen was sealed with electrical tape, and the end of the specimen that was not intended to be exposed to water was sealed with a loosely attached plastic sheet. The other end of the specimen is exposed to room temperature water, and the increase in the mass of the specimen ( � ) was recorded at predetermined time intervals specified by ASTM C1585-20 (ASTM C1585, 2013). The recorded changes in the mass of the specimen � were then used to calculate the absorption values using equation 5: � � � ����� (5) where is the absorption, � is the change in the mass of concrete samples (in grams) at time t, is the cross section area of the sample exposed to the water (mm 2 ), and is the density of the water (g/mm 3 ). Following this, the absorption values (I) were plotted against the square root of time. The initial rate of water absorption was determined from the slope of the line that best fitted all data points gathered between 1 minute and 6 hours of testing. Similarly, the secondary rate of water absorption was derived from the slope of the line that best fitted the data points collected from 1 day to 7 days of testing. Considering the significant influence of initial water content on the water absorption of concrete samples, as reported in previous studies (Hall & Hall, 1989; Nokken & Hooton, 2002; Zhutovsky & Douglas Hooton, 2019), this research implemented a modified sample conditioning procedure to enhance the linearity of the initial water absorption rate results. This modified procedure, guided by recommendations outlined in (Zhutovsky & Douglas Hooton, 2019) and affected only the first phase of the previously described specimens conditioning process. Specifically, it involved replacing drying of specimens at 50°C for 3 days with drying at 60°C oven until constant mass was achieved (defined as when the difference between two consecutive mass measurements was less than 0.2%). 3.5. Scaling resistance test Concrete slabs (3 in. x 8 in. x 11in. (76 mm x 203 mm x 279 mm)) were fabricated to be tested for scaling resistance according to ASTM C672-03 (ASTM C672/C672M-12, 2012). The sample conditioning involved a 14 day curing period in saturated lime water, followed by an additional 14-day air drying. Prior to the initiation of exposure to deicers, small dikes were installed around the perimeter of the top surface of the slabs. These dikes served to contain the deicing solution to which the concrete specimens would be subjected throughout the scaling test. The scaling resistance test was performed in the programmable environmental chamber, which lowered the temperature of the specimens to -18±3°C within one hour and maintained it with a full load of specimens for 16 hours. At the end of the freezing cycle, the chamber was programmed to start increasing the temperature to 23±3°C (within a period of about one hour) and maintaining it for an additional 6 hours. Thus, the length of one testing cycle was 24 hrs. Qualitative and qualitative assessments were conducted every 5 cycles throughout the entire 50-cycle testing duration. These assessments involved thorough flushing of the surface of the slab, followed by visual examination and collection (with subsequent weighing) of any spalled flakes of concrete. In accordance with the criterion established by the Ontario Ministry of Transportation (MTO) (Transportation, 2022), the cumulative mass loss should not exceed 0.8 kg/m 2 after 50 freeze-thaw cycles for the concrete to be considered scaling resistant.