Synthesis and characterization of green composites: Focus on accelerated strength,ductility and durability

High strength green composite material has been developed by this project by addition of lime sludge in stabilized class F fly ash with commercial lime and gypsum. The green composite material was shown to have high UCS (unconfined compressive strength) and good California Bearing Ratio (CBR) values to provide sufficient factor of safety as required by the standard code of practice for use in road construction. The good strength is attributed to calcium carbonate in lime sludge, which reacts with pozzolanic products of lime–gypsum stabilized fly ash. X-ray diffraction and scanning electron microscopy have illustrated the interaction/reaction between lime sludge and fly ash and development of additional calcium aluminium oxide carbonate hydrate that has improved the strength of the green composite. The addition of 0.1%, 0.2% and 0.3% (by weight) of short polypropylene (PP) fibre (30 mm size) in the mix has imparted ductility to reduce brittle behaviour. The UCS of 8.1 MPa was achieved with 0.3% fibre in the mix, which is well above the standard requirement. Moreover, durability tests were performed to determine long-term performance. Our overall findings have indicated that the new green composite developed would have good strength, ductility and durability, for construction of flexible pavements. Further research is needed on the long-term field performance for at least one monsoon period before the material can be used with confidence.