Method for production of expansive cement

Details Method for production of expansive cement Method for production of expansive cement

1976-12-17

1978-02-28

Poer, J.

Compositions: coating or plastic

Coating or plastic compositions

Metal-depositing composition or substrate-sensitizing...

106314, C04B 735

Patent

active

040765466

ABSTRACT:
A method for the production of an expanding cement which includes the steps n which so-called "Portland cement" is dry-mixed with an expanding additive which comprises 6 to 30% of the total weight of the cement. The expanding additive contains 2 to 8% dialuminium pentahydroxychloride, 4% to 15% gypsum, and optionally, a small amount up to about 7% lime. All percentages are by weight.
The dialuminium pentahydroxychloride (Al.sub.2 (OH).sub.5 Cl 2.5 H.sub.2 O) is a source of aluminium ions, which are necessary to form an increased (expanded) quantity of ettringite. It has high solubility, forming a solution having a concentration above 50%, and has a high content of active dialuminium trioxide (approximately 46%), a low content of chlorine and is not hygroscopic. The lime component is not critical and its addition depends on the desirability for greater expansion (without lime) or lesser expansion and higher strength (with lime). With Portland cement of higher activity (mark 450 or more), the expansion is less but the strength is greater; with Portland cement of lower activity (marks 350 and 250), greater expansion is obtained but there is less strength.
The dry mixing of the compounds is done either by grinding them together at the same time as the Portland cement or by first grinding the cement and the ingredients separately, then mixing them, and finally, homogenization. The expansion of the cement stone is thus controlled with precision and occurs in the first 1 to 2 days after hardening either in water or in the air and thereafter the volume stabilizes permanently; meanwhile the strength increases with time.

REFERENCES:
patent: 2465278 (1949-03-01), Schenker et al.

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