Method of producing and applying mortar

Details Method of producing and applying mortar Method of producing and applying mortar

1987-04-06

1989-05-16

Dixon, Jr., William R.

Compositions: coating or plastic

Coating or plastic compositions

Metal-depositing composition or substrate-sensitizing...

106 85, 106 86, 106 90, C04B 1402

Patent

active

048306690

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
This invention relates to a method of preparing, producing, molding and applying a cement-containing composition such as cement paste, mortar and concrete (hereinafter referred to as mortar), in which water necessary for a hydration reaction is obtained from small ice masses.
2. Background Art
To prepare mortar, cement and water, and also such aggregate as sand or gravel if necessary, are mixed and kneaded together. According to the water-cement ratio theory, the mechanical strength of the mortar after the solidification is higher when the quantity of water is lowe with respect to cement. Recently, it has been noted that with the solidification of such a composition with a water content in the neighborhood of the minimum quantity necessary for the hydration of cement, a very high mechanical strength can be obtained while also obtaining the necessary compression strength and the necessary tensile strength, bending strength and shearing strength.
The preparation of mortar also requires workability. More specifically, it is necessary to ensure adequate softness, fluidity, viscosity and plasticity, these factors being related to the difficulty or easiness of handling mortar or the like before solidification, i.e., during preparation, charging, molding, etc. Usually, a considerably greater amount of water than the amount necessary for the hydration of the cement is used to ensure workability. Also, various additives are used to reduce the amount of water. However, the minimum quantity of water necessary for the hydration is very small so that it is difficult to ensure workability with such small amount of water. Further, the mechanical strength after solidification depends not only on the water-cement ratio, but also on the homogeneity of the mixture of cement and aggregate, the agitation and kneading during the hydration reaction also being important factors which are difficult to carry out.
In a further aspect, since the hydration reaction proceeds as the mortar is agitated and kneaded with water, there are time restrictions on the transportation of raw mortar. Sometimes, a retarder is used. However, generally it is difficult to control the hydration reaction time.
In a still further aspect, in the preparation of mortar there are problems to be solved in connection with early release from a mold, i.e., early build-up of mechanical strength, facilitation of press molding and freedom from shrinkage. Various attempts have been made to solve these problems by using various additives. These attempts, however, have merits and demerits of their own.
Further, there have been attempts to reduce breeding of the mortar composition, suppress dispersion for underwater charging purposes and improve fluidity by incorporating water-soluble polymers such as cellulose derivatives, e.g., methylcellulose and hydroxyethylcellulose, or polyvinyl alcohol.
These water-soluble polymers (hereinafter referred to as polymers) are added in the form of powder or as aqueous solution to the composition before and after kneading and the admixture is then agitated and kneaded. However, when methylcellulose, for instance, is added in the form of powder, it is liable to be agglomerated into masses. When it is added as an aqueous solution, the viscosity of the composition being agitated is extremely increased. In either case, a great deal of labor and time are required for the kneading to obtain a homogeneous composition. Particularly, it is difficult to obtain a low water-cement ratio composition.
Further, in the case of heavy concrete used for the shields in atomic power generation facilities or the like, separation of aggregate from mortar portion is liable to result. The separation stems from the combination of the specific gravity difference, fluidity difference, size difference, etc. between the aggregate and mortar component. More specifically, the separation is pronounced when the specific gravity difference and slump are large while the viscosity of the mortar component is low. The separation is promoted

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