The object of the present study is to prepare the cement suitable for particularly urgent construction work. This is “blended cement” consisting of aluminous cement-lime system. Our experiment showed that setting time could be controlled by using some kind of setting retarder. We found the suitable proportion of the mixture and the most effective setting retarder. In this paper, we dealt with the blended cements that set during from several ten seconds to a few minutes, and developed high compressive strength.
The results are summarized as follows:
(1) When lime is added to aluminous cement, it comes to flash setting which makes the cement useless practically.
(2) Under the condition of high alkalinity, the setting time can be retarded when about 1% of the setting retarder that formed coordination compounds with Ca
2+ is added into the cement. The most effective setting retarder is Ca-2 keto gluconate.
(3) Composition of the mixture to develop desirable high compressive strength is as follows;
aluminous cement, 100g and Ca(OH)
2, 20g, or dolomite plaster, 25g. Water cement ratio is 35%.
(4) Setting time can be also a little retarded by means of addition of portland cement or CaSO
4⋅2H
2O to aluminous cement-lime system.
In addition to this experiment, we discussed the mechanism of hydration and hardening reaction on the basis of the results on X-ray diffraction and differential thermal analysis.
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