A new admixture has been introduced to the market that reportedly gives a higher, more dependable degree of control of hydration of the portland cement during setting and hardening of concrete. The product was developed and introduced by the Construction Products Division of W. R. Grace. In the past, one of the problems with the use of admixtures has been that the amount needed has been likely to change if there is a change in brand of cement or even sometimes, a change in the lot of the same brand. When such changes are made it has been necessary to redesign the mix with respect to the amount of admixture used. The reason for this is related to the fact that Portland cement is a mixture of four major chemical components which react at different times and rates: one component reacts as soon as water is added, another three to four hours later, and another in 18 to 20 days. No two cements or lots have exactly the same proportions of these components, even if they are made in the same plant with the same raw materials. Admixtures are used to affect hydration one way or another, normally by the simple physical dispersion of the cement particles . They can either delay or accelerate the reaction. The problem is that the hydration reaction of cement particles. They can either delay or accelerate the reaction. The problem is that the hydration reaction of cement has not been completely predictable. The new admixture is said to compensate for possible variations in ingredients and help assure more uniform portland cement concrete. This makes it possible to predict the rate of hydration more accurately.