The results indicate that the slag cement mortar shows the best corrosion behavior since the alive powder in it produces hydration reaction together with water, which prevents SO42− permeation and slows down the formation of CaSO4⋅2H2O and AFt.
Here, in relation to the assumption made by Yaniamoto et al. about their model, we note that for a hydration product produced by hydration, a mixed layer containing pores of calcium hydroxide and ettringite is formed on the particle surface of the expansive additive.
Calcium hydroxide released from red mud and Calcium hydroxide produced from hydration reaction of Portland cement, could react with the alumina left in red mud to produce calcium aluminates (CA and possibly C3A5).
The concrete with 40% fly ash dosage under the cuing temperature of 50 °C also produced more hydration products, but the specific creep of which increases significantly and is 119.5% of the reference concrete.
On the other hand, because all of the cement particles are the same size, Katsura et al. (1996) defined the strength of a cube of cement paste as the cement's original strength, where the strength of the hydrated cement paste could be expressed in terms of the contact between the cement particles within the cube produced by hydration.
Compared with the concrete with 20% fly ash dosage under the curing temperature of 20 °C, the concrete cured under the temperature of 50 °C produced more hydration products, with a slight decrease of Ca(OH 2, and the specific creep of which is close to the reference concrete.
Therefore, in this study, the volume of the hydration product layer produced by the hydration of only the expansive additive was acquired by considering the volume ratio of each of the assumed hydration products (calcium hydroxide and ettringite) that were expanded as a result of the expansive additive.
This can be attributed to the pozzolanic effect of UFS resulting in enhancing the chemical reaction between free lime in cement and silica producing more hydration products that makes the paste more homogeneous and dense.
For the purpose of simplicity in the present study, it is assumed that the calcium silicate hydrate [C S H(S)] was produced from the hydration reaction of slag which is equivalent to 'weak' cement due to its latent hydraulic property.
Superfine ettringite (S-ettringite) synthesized in this research presents same structure with the ettringite produced by the hydration of cement, which is expected to promote the hydration of sulphoaluminate cement-based materials.
