Under the sponsorship of the New Jersey Department of Transportation a unique concrete mix was developed. This concrete mix attains a significant strength in a period of six to nine hours for use on pavement repair in high-traffic areas. It is not a “rapid setting” formulation, but is Portland cement based, relying on chemical admixtures and insulated coverings to attain very high temperature levels, very quickly.

The mix, which is designated as “fast track mix”, has been shown to be effective in reaching its target compressive and flexural strengths of 3000 and 350 psi, respectively in as little as six hours. Several full-scale demonstration slabs have been completed both in the laboratory and in the field with satisfactory results.

The strength gain is primarily dependent on its temperature history, over time. All other factors being equal, higher curing temperatures result in concrete of greater maturity, at any point in time. One application of this is the maturity method. The maturity method is a means of estimating the in-place strength of concrete, based on its temperature history. Two different types of maturity functions are in current use: the equivalent age and the temperature-time factor. A correlation between either strength and equivalent age or between strength and temperature-time factor must be established experimentally. Once the correlation has been established thermoprobes are embedded in freshly placed concrete and connected to specially designed field computers for continual maturity determination. Knowing the maturity; in terms of either the equivalent age or the temperature-time factor, the strength of in-place concrete is estimated.