In order to examine the surface hardening characteristics of sulfated slag cement,
i.e. influencing 16 different factors and 15 interactions on it, an orthogonal array experiment was carried out with results as follows:
The main cause of the failure of the surface hardness of this type of cement may be due to the existence of CO
2 in air, which lowers the pH value of liquid phase and disturbs the hydration of the surface of hardened body. The factors relating with the carbonation, especially the interactions between some of them and CO
2 are generally found to be efficacious.
The following conditions are favorable for the surface hardening of this type of cement: (1) making the cement from slag having higher basic degree and finer particle size, (2) making the mortar of coarser sand, and rich mix and low water cement ratio, (3) curing in lime solution instead of water, and (4) storaging in the atmosphere with high humidity after above curing.
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