Investigation of Comparative Effect of Macro and Micro Polypropylene Fibers on Controlling or Mitigation of Plastic Shrinkage Cracking in Concrete Pavements in High-Temperature Conditions

Plastic shrinkage cracking in concrete pavement is a place for ingression of water and corrosive substances to the pavement, which reduces its durability and ultimately leads to failure of the pavement slab. The use of fibers is one way to control these cracks. This study investigates the effect of the addition of macro polymer fibers in comparison with micro polymer fibers on plastic shrinkage cracking in concrete pavements. For this purpose, one type of micro polypropylene fibers and two types of macro polypropylene fibers in a volume of 0.1% were used to make the samples. Mechanical tests including compressive, tensile and flexural strengths and evaluation of plastic shrinkage cracking according to ASTM C 1579 in climate conditions including relative humidity of 20%, wind speed of 30 km/h and at temperatures of 35 and 40 Celsius degrees, were performed. The results showed that concrete samples containing both macro and micro fibers had better performance in controlling cracks than control samples. Meanwhile, micro fibers performed better in controlling crack width at both temperatures conditions. In contrast, macro fibers showed a better effect in reducing the length of cracking, especially at higher temperatures. The use of macro fibers can significantly reduce the length and area of plastic shrinkage cracking in concrete pavements.