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2.4 HYDRATION OF CEMENT

2.4 HYDRATION OF CEMENT . 2.4.1 The Hydration Reaction 2.4.2 Volume products of hydration . Progress of cement hydration. Hydration of PFA …. PFA reacts with the lime produced by the hydration of cement to give more hydration products - reducing the voids and lowering the permeability.

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2.4 HYDRATION OF CEMENT

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  1. 2.4 HYDRATION OF CEMENT • 2.4.1 The Hydration Reaction • 2.4.2 Volume products of hydration

  2. Progress ofcement hydration

  3. Hydration of PFA … PFA reacts with the lime produced by the hydration of cement to give more hydration products - reducing the voids and lowering the permeability.

  4. Cement HydrationGel pores 0.005 nm Capillary pores 10 nm

  5. The need for Gypsum If pure C3A is mixed with water the reaction leads to uncontrolled setting. To prevent this Gypsum (Calcium Sulphate CaSO4.2H2O) is added to the cement clinker. This reacts with the C3A to form insoluble calcium sulphoaluminate, but eventually tricalcium aluminate hydrate is formed.

  6. Heat of Hydration

  7. Definitions (conventions for cement and concrete) Bulk volume: The overall volume defined by the outer dimensions of the sample Net volume: The volume of solids (excluding pores) Density: The mass divided by the bulk volume Specific Gravity: The mass divided by the net volume Porosity: Volume of Pores Bulk Volume = Bulk Volume - Net Volume Bulk Volume Units: 1m3 = 1000 litres (l)

  8. Effect of w/c on permeability

  9. Pore size distribution

  10. 2.4 HYDRATION OF CEMENT • 2.4.1 The Hydration Reaction • 2.4.2 Volume products of hydration

  11. Section 2.4 Question 1 Volumes in litres NOTE THAT THE TOTAL VOLUME IS CONSTANT When mixed Part Hydrated More Hydrated Cement 0.063 Cement 0.127 Cement 0.317 Hydrated cement 0.465 Hydrated cement 0.35 Water 0.4 Pores 0.24 Pores 0.19

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