Properties and Microstructure of Roller Compacted Concrete with High Volume Low Quality Fly Ash

The properties of roller compacted concrete (RCC) with high volume low quality fly ash are investigated, including strength, elastic modulus, impermeability and frost resistance, meanwhile the microstructure of the cement paste containing low quality fly ash and ground low quality fly ash are also studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA) and Mercury Intrusion Porosimetry (MIP). The results indicate that the properties of RCC containing 60 % or more ground fly ash meet the design requirement. When incorporated with high volume (60 %) ground fly ash, the effect of the pozzolanic reaction was observed at 7 days by consumption of portlandite. At the hydration age of 90 days, a drastic pozzolanic reaction was observed by the depletion of CH and the formation of substantial secondary products. Moreover, the property development of the cement containing 60 % ground fly ash is much faster and enhanced than that compound with same content of raw fly ash. The incorporation of high volume (60 %) ground low quality FA not only refine the pore size but also ameliorate the pore size distribution of cement pastes, which greatly promotes the development of microstructure and the consequent strength and durability of RRCs