Asbestos-free building material plates and method of making same

Details Asbestos-free building material plates and method of making same Asbestos-free building material plates and method of making same

1985-11-15

1989-02-28

Dixon, Jr., William R.

Compositions: coating or plastic

Coating or plastic compositions

Metal-depositing composition or substrate-sensitizing...

106 93, 106 99, C04B 702

Patent

active

048082295

DESCRIPTION:

BRIEF SUMMARY
The invention relates to building material plates made of an asbestos-free material mixture and to an economical method guaranteeing constancy in quality for making the same.
It is known to use EFA-binder additives for concrete building. In case of EFA-binder additives the electrofilter-draw-off (called EFA in the following) of combustion residues in the exhaust systems of high temperature coal dust firings are concerned. Up to now, such EFA-fillers have already been employed in concrete building so as to e.g. reduce hydration heat during the setting of concrete, to prevent the formation of microcracks in the cement stone or to increase the final strength and water-tightness of the cement stone and its acid resistance. Dependent on the dosage of the EFA-filler, the Ca(OH).sub.2 crystals occurring in the cement stone and having low strength are transformed into calcium silicate hydrates substantially determining the strength of the cement stone. Less strong tetracalciumaluminate hydrates interspersed by Fe.sub.2 O.sub.3 incorporations and monosulfates may be formed, as well.
The lifetime of fibers sensitive to lye is substantially increased by the far-reaching neutralization of Ca(OH).sub.2 in i.a. cement-combined building material plates compounded with EFA-binder.
It is the object of present invention to make building material plates from an asbestos-free material mixture, which as regards their longterm and lifetime properties, such as resistivity to fire and stress receptivity, are as far as possible equal to asbestos-reinforced plates.
In the mixing and shaping phase, the mixture of material for instance comprises cement clinker particles (Z) of specialized grinding fineness; the mixing water (W.sub.Z) required for their hydration crystal formation; fiber reinforcing substances of specific size distribution characteristic, which, in addition to fillers that do not impede cement hydration, contain cellulose fibers (C fibers); and so-called EFA minimum-sized glass bead additives (E). These additives maintain long term quality; wwith the admixture of additional (W.sub.E), they react in Pozzuolana-like fashion with the Ca(OH).sub.2 crystals that among others are produced in the cement stone. If sufficient EFA and W are added, the EFA additives largely convert these crystals into the calcium silicate hydrates that actually effect the strength and density of the cement, and in so doing they dissolve completely or in part, or become coated with these calcium silicate hydrate crystals.
In the manufacture of cement plates asbestos has been used up to now as a reinforcing basis, as one knows. Asbestos-reinforced cement plates have manifold excellent properties and can be produced economically. But experience has shown that the men occupied with the manufacture and processing of such asbestos-reinforced cement plates are subjected to a high health risk. To avoid said health risk for men working with fiber-reinforced cement plates a satisfactory substitute for asbestos is being searched for.
In terms of usable bending strengths of the molded building material elements according to the invention, if a limitation to useful bending capacities that are approximately 75% of those of high-strength asbestos cement molded elements is made substantially for the sake of avoiding microscopic fissures in the binder stone, which do not substantially threaten the strength of the stone but negate its watertightness, then the other physical properties (low thermal conductivity, high insulation capacity, a high degree of fire-proofness, very low water absorption capacity, very slight changes in shape from expansion and contraction due to changes in temperature and moisture) attainable with the molded building material elements according to the invention are at least as good as those attainable with asbestos cement molded elements.
In case of fire it is of additional advantage that with e.g. building material plates according to the invention which are employed as wall and ceiling coverings in fire zone limitations, no explosion-ty

REFERENCES:
patent: 4132555 (1979-01-01), Barrable
patent: 4306911 (1981-12-01), Gordon et al.
patent: 4406703 (1983-09-01), Guthrie et al.

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