How does Type III concrete compare to Type I concrete in terms of composition?

Type III concrete is specifically formulated to have a quicker strength gain than Type I concrete, which is the standard composition for common concrete. The key aspect that distinguishes Type III from Type I is its fineness; Type III has a similar basic composition in terms of the cement type, coarse aggregates, and overall ratios, but it is produced with a finer grinding process.

This finer grinding increases the surface area of the cement particles, allowing for better hydration and faster reaction with water. As a result, Type III concrete develops strength more rapidly, which is critical for projects requiring quicker formwork removal and sped-up construction schedules.

The other choices do not accurately capture the principal differences in composition between Type III and Type I concrete. For example, while Type III may involve varying the aggregates used to some extent in specific mixes, the defining characteristic of its composition is the fineness of the cement rather than an increase in coarse aggregate or the inclusion of admixtures that delay setting.