Compositions: coating or plastic – Coating or plastic compositions – Metal-depositing composition or substrate-sensitizing...
Patent
1986-10-03
1989-05-09
Dixon, Jr., William R.
Compositions: coating or plastic
Coating or plastic compositions
Metal-depositing composition or substrate-sensitizing...
106 93, 106 99, C04B 2204, C04B 1438, C04B 1602
Patent
active
048286184
DESCRIPTION:
BRIEF SUMMARY
PRESENT STATE OF THE ART
It is known that absorption of air by concrete, and its expansion by formation of macrovoids, provides considerable advantages such as greater lightness, increased resistance to frost, better heat insulation and protection from noise, dehumidification of brickwork helped by aerated plastering, lower retention of humidity in new buildings.
It is also known that the percentage of air to absorb will vary according to the purposes to be fulfilled.
Distribution of the macrovoids throughout the concrete must however be as uniform and regular as possible so that the benefits brought by their function shall be equally effective at all points.
Various additives are used to form macrovoids, such as: resinous acids and their salts, fatty acids and their salts, alkyl-aryl sulphonates, alkyl sulphates, phenol-ethoxylates, ionic and non-ionic surface-active agents generally; reducing metal powders able to develop gaseous hydrogen in basic aqueous environments (aluminum in most cases).
Use is made of different processes. During mixing, the following are put into the mixer:
(a) surface-active or reactive additives, or both,
(b) mixtures in powder form consisting of aggregates and additives,
(c) an aqueous dispersion, in foamy form, of surface-active and reactive substances.
It is clear however that these processes will not alone ensure perfectly uniform dispersion of the additives throughout the whole mixture and consequently uniform distribution of the macrovoids.
If additives are put into the mixer singly, quantities are in fact usually limited so that they can be uniformly distributed.
Further, reaction times are negative in their effects partly because these reactions tend to develop in the mixer itself while it is intended that they should mainly occur when the concrete is in place so that the resulting microvoids form when the concrete will be no longer disturbed.
When mixtures of aggregates and powdered additives are used the differing specific gravities of the component materials tend to impede achievement of uniformity from the time when preparation of the mixing begins.
In the same way the problem of uniform distribution of the macrovoids cannot be solved by prior transformation of a dispersion of additives in foam because the foam itself is insubstantial.
If, according to the purpose for which the concrete is made, differing degrees of aereation (and different sizes of macrovoids) are required, the systems considered do not facilitate the making up of various proportions, even if always limited and therefore difficult to measure or weigh out. Where mixtures contain various types of additives problems arise of homogenizing and stabilizing it if it is fluid.
If the mixture consists of powders, the larger particles of materials will inevitably sift down to the bottom in time. This present invention eliminates or lessens the above drawbacks and, further, offers considerable advantages as will be explained below.
DESCRIPTION OF THE INVENTION
Subject of the invention is a process for making aerated concrete in accordance with which a solution of a hydro-soluble cellulose derivate is prepared in water and to this is added a surface-active agent and a metal powder reactive in a basic environment.
The dispersion so obtained is mixed into, and evenly absorbed by inert materials such as sand, fibers or whatever else is to be mixed with the cement or other binders and the water.
A drying process is then carried out by mixing under heat so as to achieve actual modification of the above aggregates by absorption or piling together.
The aggregates thus treated are put into the cement mixer together with the cement or other building material and the whole is mixed dry for as long as necessary for a perfectly uniform distribution of the ingredients, water being added during the movement and mixing done for the length of time needed for them all to be completely wetted.
Production of gas, during mixing, generated by the reactive powder will cause formation of air bubbles, practically grain by grain or
REFERENCES:
patent: 3236925 (1966-02-01), Urmston
patent: 3926650 (1975-12-01), Lange et al.
patent: 4058405 (1977-11-01), Snyder et al.
De Chiffre Chiara
De Chiffre Enrica
Dixon Jr. William R.
Knab Ann M.
Striker Michael J.
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