Durability of concrete with high cement replacement

The durability of concrete made from various non-reactive waste materials, i.e. carbon black, silts and clays, and with various water contents were investigated. The compressive strength, workability, sorptivity, and water permeability of the concrete were studied to assess the durability. Further, the resulting change in the microstructure and cement hydration in these concrete were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. It was found that the critical problem of maintaining or increasing the designed workability could be solved by using high specific surface area material and with the superplasticizer admixture. The present study also indicated that an alternative durable concrete could also be made with 25 vol.% of cement replaced with silts and clay using a water/cement (w/c) ratio of 0.5. That is, the cement and water contents were less than those in OPC. Also, the cost of concrete will be lowered. (C) 2000 Elsevier Science Ltd. All rights reserved.