ABSTRACT
This paper deals with the contribution of fibres to the reduction of shrinkage cracks during the initial setting stage of concrete. The fibres were either polymeric fibres or steel fibres. In the case of polymeric fibres, the fibres were made of nylon6, polypropylene and polyester. The fibre length was 19 mm in all cases except in one case when a mix of different fibre lengths was used. Nylon6 and polyester fibres were single filament type whereas polypropylene was a fibrillated type. The fibre content varied from 0.02 to 0.1 volume percent. In the case of steel fibres, low-carbon hooked steel fibres were used. Three fibre lengths of 30 mm, 50 mm, and 60 mm, and two fibre contents of 45 kg/m3 and 60 kg/m3 were evaluated. The tests were conducted by using 600 × 900-mm rectangular slabs that were 19 mm thick. The slabs were subjected to rapid drying right after casting.
The contribution of fibres was evaluated using the crack area. In all cases, the crack area of unreinforced matrix is compared with the crack area of reinforced matrix. The test results show that: fibres with higher modulus of elasticity are less effective for 19 mm-long fibres, fibre count (number of fibres/kg) plays a role in the reduction of cracking, and fibres are more effective when the cracking in plain matrix is extensive.
