Construction practices in the country have accepted very well the blended Cements or Blended concrete as the means of achieving durable concrete with increased resistance to environmental deteriorating effects. While PPC and PSC are being separately used by site mix as well as ready Mix concrete segments. There was no serious attempt to look at a Cement or Concrete product with benefits of using GGBS and Fly ash complementing each other, as there were no specified standards in India allowing the manufacture of such fly ash – slag, multi-blend Composite Cement.
Presently the Indian standards on Fly ash – Slag Composite cements are being considered with the allowable limits, Portland cement clinker / Ordinary Portland Cement (35 – 65%), Fly Ash (15 – 35%) & Granulated slag (25 – 50%). At the ACC – Q&PD Thane Labs, substantial experimentation has been conducted on such multi blend cements with different combinations of Fly ash & Slag to compare these cements with PPC & PSC in terms of the Cement Mortar properties, fresh and hardened Concrete properties and Concrete performance in terms of the resistance to aggressive environments and environmental deterioration, the observations are discussed in the paper.
The paper also presents a comparison of the hydration characteristics of the OPC,PPC,PSC and composite cements, along with the free calcium hydroxide contents of the hydrated cement pastes , extent of formation of hydrates and assessment of the % reaction of the blending material at different ages of hydration of these cements .
The paper was published and presented at 14th NB Int Seminar on Cement,Concrete & Building Materials