High early strength concrete (HES) or fast track concrete is a type of concrete that develops its compressive strength at an early age, compared to ordinary concrete. HES is developed by using ordinary concrete constituents, special admixtures, and certain concreting practices. It is used in many applications including rapid form reuse, precast concrete for fast production of elements, high-speed cast-in-place construction, cold-weather construction, quick repair of pavements to reduce traffic downtime, and fast-track paving.

Accelerating admixtures

In order to develop the early strength of concrete, accelerating admixtures such as calcium chloride are used. They are added to the concrete mixture and increase the rate of hydration, which results in higher early strength development.

Improved cements

The improvement in the quality of Portland cement and other components have resulted in an increase in concrete strengths to values above 6,000 psi. This increased strength is achieved by the use of improved cements, admixtures, and technology in proportioning and batch control.

Aggregates and other additives

The addition of aggregates to concrete has a major effect on the early strength of the concrete. Some aggregates have better binding with cement paste than others. The type of aggregate that is used has an important effect on the overall performance of the concrete, including its strength, durability, and workability.

A number of studies have been performed to determine the influence of aggregates on the strength of concrete at different ages. For example, Kim et al. (1998, 2001) found that the use of fine aggregates increases the tensile strength of concrete, while the addition of coarse aggregates decreases the tensile strength of concrete. Moreover, the effects of these aggregates on the drying shrinkage and compressive creep of concrete were also studied.