Surface treatments are able to modify the fibre/concrete interface by roughening the fibre surface, altering surface polarity. The modification of the surface chemistry and morphology of polymers increase the interfacial strength compared to untreated Polypropylene fibres (Buendía et al., 2013, Rokade etal., 2014). Polypropylene fibres have been reported to reduce unrestrained plastic and drying shrinkage of concrete at fibre contents of 0.1 to 0.2% by volume of concrete (IS, 2013).
2.3.3 Properties of SPFRC
Workability is the property of SPFRC which determines the ease and homogeneity with which it can be mixed, placed, compacted and finished. Major factors affecting the workability are water content, cement content, aggregate content, fibre type & their content, air content, temperature, mixing conditions, chemical admixtures etc. After the addition of fibres significant reduction in fresh properties of concrete (IS 2013, Yap et al., 2013, Chang et al., 1995, Kumar et al., 2014, Rokade etal., 2014). The reduction in workability due to strong fibre matrix bond in the concrete mix. Due to this bond viscosity of concrete increases and the distribution of the cement matrix is restricted; thus significant reduction in the workability was observed. The addition of super-plasticiser, plasticizer or mineral admixtures can improves the workability by dispersing the fibres in mix uniformly and reducing the viscosity of cement paste (Kaikea et al., 2014, Rokade etal., 2014). Temperature plays an importance role for the workability behaviour. As temperature varies the loss of workability and hence change in the admixture dosing. At the time of pouring of concrete its temperature should not be exceed 30 0C as per IS-15. Temperature of concrete in the batch mix plant will normally be around 25 0C (IS, 2013).
(ii) Compressive Strength
The determination of compressive strength for the various grades of concrete has received a large amount of attention as concrete is primarily meant to withstand compressive stresses. The addition of fibres enhances the compressive strength of concrete (Parveen et al., 2013, Qureshi et al., 2013, Rokade etal., 2014). The compressive strength is significantly influenced by steel fibres and increases by increasing quantity of steel fibre (Chang et al., 1995, Kumar et al., 2014, Girish et al., 2012, Li et al., 2010, Soutsos et al., 2012). From the previous studies, it was concluded that, steel fibre provides the ductility to concrete, as they have high strength & high modulus of elasticity thus have more ability to arrest the macro cracks.