15322Composition of Ultrahigh Strength Concrete

To illustrate the composition of ultrahigh-strength concrete, two examples are given in Table 15.6. The key characteristics of ultrahigh-strength concrete can be summarized as

• A large quantity of silica fume (or other fine mineral powder).

• Aggregates containing only fine sand.

• A high dosage of superplasticizers. Depending on the level of compressive strength, postset heat treatment, and application of pressure before or during setting may be necessary.

TABLE 15.5 Characteristics of Ultrahigh-Strength Concrete

Compressive strength (MPa) Water-binder ratio Chemical admixture Mineral admixture

Fibers

Air entrainment Processing Steady-state chloride diffusion (x10-12m2/s)

Conventional concrete

Not necessary Not necessary

Beneficial Necessary Conventional 1.0

High-strength concrete

WRA/HRWRA necessary Fly ash (and/or) silica fume commonly used Beneficial Necessary Conventional 0.6

Ultrahigh-strength concrete

HRWRA essential Silica fume (and/or) fine powder essential Essential Not necessary

Heat treatment and pressure 0.02

TABLE 15.6 The Two Mix Proportions of Ultrahigh-Strength Concrete

Cement Water Superplasticizers Silica fume Fine sand Quartz flour

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