Dataset Information

Optimizing a Test Method to Evaluate Resistance of Pervious Concrete to Cycles of Freezing and Thawing in the Presence of Different Deicing Salts.

ABSTRACT: The lack of a standard test method for evaluating the resistance of pervious concrete to cycles of freezing and thawing in the presence of deicing salts is the motive behind this study. Different sample size and geometry, cycle duration, and level of submersion in brine solutions were investigated to achieve an optimized test method. The optimized test method was able to produce different levels of damage when different types of deicing salts were used. The optimized duration of one cycle was found to be 24 h with twelve hours of freezing at -18 °C and twelve hours of thawing at +21 °C, with the bottom 10 mm of the sample submerged in the brine solution. Cylinder samples with a diameter of 100 mm and height of 150 mm were used and found to produce similar results to 150 mm-cubes. Based on the obtained results a mass loss of 3%-5% is proposed as a failure criterion of cylindrical samples. For the materials and within the cycles of freezing/thawing investigated here, the deicers that caused the most damage were NaCl, CaCl 2 and urea, followed by MgCl 2 , potassium acetate, sodium acetate and calcium-magnesium acetate. More testing is needed to validate the effects of different deicers under long term exposures and different temperature ranges.

SUBMITTER: Tsang C

PROVIDER: S-EPMC5457218 | biostudies-other | 2016 Oct

REPOSITORIES: biostudies-other

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Project description:Lucerne (Medicago sativa L.) is a major component of the crops used in dry-land farming systems in China and its management is associated with notable nitrous oxide (N2O) emissions. A high proportion of these emissions is more likely to occur during periods when the soil undergoes freezing and thawing cycles. In this study, the effects of freeze/thaw cycles on N2O emissions and related factors were investigated in lucerne grasslands. The hypothesis was tested whether increased emissions resulted from a disruption of nitrification or denitrification caused by variations in soil temperatures and water contents. Three days (3 × 24 h) were chosen, where conditions represented freezing and thawing cycles. N2O emissions were measured for a fallow control (F) and two grasslands where lucerne had been cultivated for 4 and 11 years. Soil temperature, soil water content, soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), soil ammonium nitrogen (NH4 +-N), and soil nitrate nitrogen (NO3 --N) contents were measured. Moreover, the quantities of soil nitrification and denitrification microbes were assessed. Variations in N2O emissions were strongly affected by freeze/thaw cycles, and emissions of 0.0287 ± 0.0009, 0.0230 ± 0.0019, and 0.3522 ± 0.0029 mg m-2 h-1 were found for fallow, 4-year-old, and 11-year-old grasslands, respectively. Pearson correlation analyses indicated that N2O emissions were significantly correlated with the soil water content, temperature, NH4 +-N content, and the number of nitrosobacteria and denitrifying bacteria at a soil depth of 0-100 mm. The numbers of nitrosobacteria and denitrifying bacteria correlated significantly with soil temperature at this soil depth. MBN and soil NH4 +-N contents correlated significantly with soil water content at this depth. Principal component analysis highlighted the positive effects of the number of denitrifying bacteria on N2O emissions during the freeze/thaw period. Furthermore, soil temperature and the number of nitrosobacteria at the tested soil depth (0-100 mm) also played a significant role. This shows that soil freeze/thaw cycles strongly impacted both N2O emissions and the diurnal range, and the number of denitrifying bacteria was mainly influenced by soil temperature and soil NH4 +-N content. The number of denitrifying bacteria was the dominant variable affecting N2O emissions from lucerne grasslands during the assessed soil freeze/thaw period on the Loess Plateau, China.

Dataset Information

Optimizing a Test Method to Evaluate Resistance of Pervious Concrete to Cycles of Freezing and Thawing in the Presence of Different Deicing Salts.

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