Alireza Boostani - Master Graduate, Highway and Transportation Engineering, School of Civil Engineering, Islamic AzadUniversity Tehran-North Branch, Tehran, Iran
Hanieh Motevali Kasmaee - Bachelor Graduate, Civil Engineering, School of Civil Engineering, Mazandaran-Pardisan University,Mazandaran, Iran
Seyed Javad Vaziri Kang Olyaei - Master Graduate, Highway and Transportation Engineering, Iran University of Science and Technology, Tehran,Iran

Plastic shrinkage cracking is one of the most common types of cracking in concrete structures. Usingdifferent fibres is one of the ways to control and reduce cracks in concrete. Examining the relationshipbetween the characteristics of Plastic shrinkage cracking in concrete structures containing fibres isimportant in better understanding this type of cracking and reducing it. The present research examines thechanges in the severity of plastic shrinkage cracking in concrete mixtures under influenced of the additionof macro synthetic fibres. After determining proportions of concrete mixtures, macro polypropylene fibreswere used in amounts of ۰, ۰.۹, ۱.۸ and ۲.۷ kg/m۳. Plastic shrinkage cracking was evaluated according tothe ASTM C۱۵۷۹ standard method, and the geometric characteristics of cracking, including average crackwidth, crack length, and crack area, were determined using digital image analysis. The results showed thatthe change of the average crack width causes a change in the behaviour of the cracking length and area.Cracking length and area change with the change of average cracking width up to ۱۵% and ۸۶%,respectively. It has been seen that the change of average crack width has a greater effect on the change ofthe cracking area. After the average crack width reaches a certain amount, the increasing trend of thecracking area decreases. Also, it was observed that the change in average crack width is greater than itslength.

Concrete structures, Plastic shrinkage cracking, Cracking severity, Macrosynesthetic fibres, Average cracking width, Cracking length, Cracking Area.