15323Microstructure of Ultrahigh Strength Concrete

Based on the observations made by optical, SEM, TEM, x-ray diffraction, and mercury intrusion porosimetry, the microstructure of ultrahigh-strength concrete can be concluded to have the following properties:

1. On a millimeter scale, the material is more homogeneous.

2. Absence of a pronounced transition zone between sand and the paste.

3. Low or negligible presence of portlandite.

5. Proportional lower volume of capillary porosity (10% of total porosity).

6. Strong component of pores with diameter 2.5 nm.

The above-mentioned microstructural features lead to low water absorption, gas permeability, and chloride diffusivity.

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