7.3 : コンクリートの空隙率

As fresh cement paste sets, it transitions from a fluid state to a solid mass, entrapping water in various forms, such as gel water, capillary water, and combined water.

Gel water, which is trapped within the pores of the cement gel, typically constitutes approximately 28% of the total volume of the cement gel.

Around 23% of the mass of dry cement consists of the combined water that is associated with the various products resulting from the hydration process.

When the cement paste has more water than is needed for hydration, the excess water forms capillary pores, which constitute about 18.5% of the original cement volume and are often water-filled.

The ratio of the combined volume of gel and capillary pores to the overall volume of the cement paste determines the total porosity of the cement paste.

The water-to-cement ratio is a crucial factor, as excess water creates more capillary pores, leading to higher porosity and potentially weaker hardened cement paste.

Proper curing can reduce porosity by allowing continued hydration, which fills capillary pores with hydration products.