US2008034A - Water and weatherproofing magnesia cement - Google Patents

Description

Patented July 16, 1935 WATER. AND WEATHERPRooFING MAGNESIACEMENT- l l l recl ottnian, Jersey City, N.

N0 Drawing;a'Application March 26, 1934, v

Serial No. 717,425

' sciai s. (01. 106- 4217) The object of this invention is, primarily, to

impart-watch, and weatherproofness to" magnesi'a cement, thus eliminating the disadvantages associated with waterabsorbent building material, and tomake this valuable material available for outdoor application. 'I'he; dreaded porosity of plastic building mate'rialis the result of the'evaporation of the excess water used for plasticizing the dry aggregate cannot and should not be'eliminated.

1 The propositions to fill in these pores are based ona misconception; and none provides for the elimination of eiilorescences and erosion on not strictly insoluble material. 7 l

" Closing the surface pores of the finished productfwith [an impervious coat of oil, paint or varnishis expensive and of only temporary effect. Such dressings neverenter into the material to anyappreciable depth, wear away withthesur-- face, and soon the oils and resins used loseftheir protective qualities under theeifect of light and airand require frequent renewals. j

Only integral waterproofing through the entire massof concrete with a substance of a permanent naturef and effectiveness promises satisfactory and lasting fresults, but a certain degree of porosity has to be maintained in the product to absorb 'the'pres'sureofthe drying and shrinking outer'shell' upon'thestill wet and expanded core duringjthe setting. e e 1 Th use of water-repellent admixtures in the concrete makes this possible; the, degree of porosity can be controlled by regulating the concentration of the binder. Water-repellent cement, which activelythrows oif the moisture and easesjthe internal strain'during the drying pee riodgpermits of the use "of more concentrate.

binders. which favors faster setting, while the correspondinglyhigher magnesite contents assure a gharder and stronger product. Insoluble metallic soaps are by far the most powerful, reliable and permanent aids in waterproofing plastic materials. Usually oils have beenjconsidered the active waterproofing principle, and the cements were loaded with an excess of this less effective and permanent material, while the soaps rnerelyserved as useful accesseries and in utterly insuflicient quantities or were used solely as emulsifying agents for the oils and plasticizers. The poor andoften short-lived re sults so obtained discredited the wholewater proofing scheme and discouragedfurther atirregular, and the, many fallacious and often a friction within the structure, that mustinvariably lead to destruction. Such erratic distribution of the soaps, due to the inherent stickiness, takes place during the mixing operation even when the soap has been produceddirectly in the cement mixture by the reciprocal action of solutions of an alkalisoap and a metallic salt. v

I have found, however, that this stickiness can be completely obliterated withoutdissolving the soap in an inopportunely large excessof oil. .If

the dry powder is just pepticized cold in a small quantity of a fatty oil, about 3 parts of oil to'rl part of dry soap, it losesits stickiness and changes within a few minutes to. aperfectly transparent, elastic ands'lippery gelatinous mass of low cohesion, that spreads readily in the dry aggregate. At the same-time it loses, while in this condition, its antagonism against water and emulsifies with it or with an aqueous solution of asalt. The dry aggregate takes to this emulsifiedbinder even more eagerly than to the plain aqueous solution.

I have alsofo'undthat it is not at all necessary to. emulsify the soap first with the-binder. If it has been properly pepticized,iitcan be incor porated in the dry aggregate directly and simultaneoeusly with the aqueousbinderandv plasti cizer. In this event it is advisable-not toladd all of the binder at once, but onlyenough to dampen the 7 dry aggregate without impeding the dis tribution 0f thesoap.' Afterwards the damp mass will take in "any additional amount of water. or aqueous solution without disturbing the dis-' tributed soap. No intricate rules have tobefdllowed in this case. careful mixing of the pepticized soap with the, dry aggregates"Peptizationis complete as .soon as the soap "powder has become transparent. In this 'conditon it keeps indefinitely, but shows a disposition to turn gummy on-long standing. and in coldweather may become rather'stiif. and will benefit by the addition or a small amount of a lighter oil. Any metallic soap will answer; the amounts required depend on molecular weight and the valence of the base. Using, as anex- All that is necessary is a ample, aluminum palmitate, a magnesium chloride solution of 25 B., with 56.40% MgCl2.6 aq., which is perfectly safe for water-repellent magnesia cement, 35% calcined magnesite in the dry aggregate, and a quantity of chloride solution that carries MgClzfi aq. to the amount of 85%- 88% of the weight of magnesite used, I take 1 oz. to 1 /2 oz. of aluminum palmitate for every 25 fl. oz. of binder required, or about -7 oz. per gal. and pepticize this powder in 34 fi. oz. of parafiin oil, to which I eventually, if too stiff, may add 1-2 fl. oz. of kerosene.

While basing these calculations on the use of the best known binder for magnesia cement, its chloride, I do not mean to limit myself to the exclusive use of this particular salt and its acid. Any soluble metallic salt, which forms with MgO and water an insoluble basic or oxysalt, that crystallizes into a hard and compact mass, can be utilized, such as sulphates (epsom salt), phosphates a. 0., and it need not be a salt of magnesia. Only alkalis and lime are unsuited as bases, the former, because they do not form insoluble double salts with heavy metals from mere aqueous solutions, the latter because magnesia and lime are incompatible in close contact. The use of free acid in the binder, instead of its salt, while permissible for plain cement, is also prohibited in our case, because it would decompose the metallic soap, set free the fatty acid to recombine with some oxide present, and annul the effect of peptization.

Where it appears preferable to first combine the protective substance with the aqueous binder and introduce it into the dry aggregate in the form of an emulsion, the preliminary treatment of the soaps and the relative proportions needed remain the same, but the proceedings are somewhat more complicated. Metallic salts flocculate oil-in-water emulsions, and if present in the water from the start, prevent their formation altogether. Water-soluble emulsifying agents, such as are employed in Waterproofing hydraulic cement, are here useless.

A true and stable emulsion with a solution of a metallic salt must be of the water-in-oil type and have a water-insoluble but oil-soluble emulsifying agent, that forms a protective film around the oppositely charged droplets of binder and keeps the same suspended by mutual repulsion.

Any water-insoluble but oil-soluble natural or artificial gum or resin can .be. employed. As a concrete example I may mention a 5% to solution of common pine rosin in a light oil, added to the mixture of pepticized soap and binder at the rate of 1 fluid oz. to every 25 fl. oz. of binder used and immediately shaken up with it in order to break up and disperse the binder in the soap.

Violent agitation during the emulsifying operation, or in transit, and the Brownian movement of the floating droplets cause collisions, whereby the protective films burst and the released droplets unite to larger drops, which follow the law of gravitation and sink downward, flocculating the emusion.

By increasing the viscosity of the emulsion and reducing the size of the dispersed droplets I have found it possible to minimize the danger from such collisions and greatly prolong the life of the emulsion. I obtain this result by the use of minute quantities of a caustic alkali added to the emulsion at the conclusion of emulsification". Added at an earlier stage, before all the binder has been dispersed in the soap, the alkali is liable to combine with the metallic salt, and

its effect is lost. Extreme care in the use of the alkali is necessary under all circumstances, for the successful emulsification is governed by a definite acidity (or H-ion concentration) within very narrow limits, and the slightest transgression may reverse and flocculate the emulsion. Just one drop of a concentrate solution of ammonia added to the emulsion of 25 cc. of binder in 1 gram of pepticized aluminum palmitate, or 1 fl. oz. of ammonia in about 4 gal. of binder, followed by 20-30 seconds of mild agitation, transforms the slushy emulsion into a stiff and finecreamy salvelike mass, in which not the faintest traces of droplets are discernible. The oils for peptization must be used sparingly, for the emulsion tends to throw off any excess of oil present, and drying oils should be avoided, since they impair the effectiveness of the otherwise permanent soaps by their incrustations, after they have lost their own usefulness through oxidation.

If these precautions are observed, the soaps properly conditioned for thorough and uniform distribution as prescribed and incorporated in the dry aggregate in sufficient quantities, either method of introduction will produce equally good and gratifying results of a permanent character. Essential is that metallic soaps constitute the basic principle of the waterproofing device, that oils be used only to the extent, that is absolutely indispensable for proper peptization of the soap, and that the use of drying oils be avoided. The thorough and uniform distribution of the pepticized soap in the dry aggregate will offer no difficulty. The abnormal tendency of the pepticized metallic soap to associate with water is only transitory and completely disappears after the magnesite has claimed the salt of the binder, the fillers have absorbed the small amount of oil, and the cement has dried out, leaving a permanently water-repellent metallic soap intermingled with the concrete framework.

Water never enters deeper into a cement so protected than below surface, even after an immersion lasting fully 3 days, nor does it creep up on a partly submerged body more than above water level. Absorbent material of otherwise like composition, partly submerged, will be found completely saturated with water to the core and up to its very top alreadyafter one hour. For not waterproofed cement, which completely saturates itself by capillary force far beyond its actual contact with water, the water absorption is a direct function of its volume; the water absorption of a water-repellent concrete body is a function of its surface area, and only as far as it is actually in contact with water. A waterproofed floor or outdoor stucco will, therefore, actually absorb less than one-half of the amount of water which the immersion test indicates, for in the latter the test piece is completely surrounded by water, while only one side, not its back and edges, are exposed under ac-, tual working conditions. If the tests, a 24-hour immersion in water, arerepeated after the sample has been allowed to dry out again indoors to constant weight, the water absorption will invariably be found lower at every new test and has sometimes gone as low as 27% and 19% after 10-12 tests. Absorb: ent samples, just as invariably, show an ever increasing absorption up to and 18% and finally disintegrate.

Similar results have been observed in weather exposures: none of the waterproofed samples showed any signs of deteriorationafter an exfor exposed structures is remote.

posure of 3 monthsin the rainy season, not even a sample that had been only 6 hours old when the first downpour occurred, and the water absorption was as low as for not exposed samples after the third or fourth immersion test. The plain, absorbent samples, simultaneously exposed, had turned spongy and friable.

There are still other differences in their mutual conduct. "While plain samples eagerly absorb water and waterproofed cement refuses it, oils are refused by plain cement, while waterrepellent material greedily absorbs any amount of fatty oil applied to its surface.

Cement mixtures carrying pepticized metallic soaps also possess a much higher cohesion (are more fatty") than plain cement and come clear off the mixing trough and tools used without waste. I

The yield in concrete is from 10% (20 16% higher than from the same amount of dryaggregate without soaps.

A water-repellent cement actively and speedily throws off what little water succeeds in entering its surface; a mopped up floor is dry and comfortable again within an hour, danger from frost Plain cement tenaciously retains its copiously absorbed moisture. V

Oils used in the quantities required for a satisfactory protection againstv moisture interfere with the setting reaction, retard it, and impair the strength of the product. Due to their mobility they are also liable to migrate in the finished product, rise to the surface under capillary pressure, and are lost in the cleaning. Drying oils not only lose their own usefulness through oxidation, but may even render otherwise permanent additions ineffective by their incrustations. Samples waterproofed exclusively with the aid of boiled linseed oil have been found entirely unprotected already after 6 months. Samples waterproofed with metallic soaps have proved even more water-repellent after 6 years,

than when they were new.

Metallic salts are powerful protectors and give satisfactory results already with surprisingly small quantities; at the rate of 1 of the total weight of the finished and dry product they offer full protection against moisture, and permanently so, regardless of wear, and even improve under continued attacks of moisture. Being solids they do not migrate in the concrete body like the oils; every particle remains at the exact spot assigned to it during the mixing. Their little bodies neither flood nor incrustate the magnesite, but merely attach themselves to the particles of dry aggregate and protect the same without interfering with the speedy setting or affecting the strength of the product. To the contrary, by allowing the use ofstronger binders they promote and accelerate setting. Sample slabs can be taken out of the moulds and set on edge without danger of sagging or warping already 2 hours after mixing the cement.

rial is to have traced and pointed out the rear causes of the failures of most waterproofing devices, which comprise shortcomings in the nature of the materials used as well as particularly in the method of their application, and to have found ways for the elimination of the main obstacles to their successful utilization. I have also aimed at reducing the operating expenses and confining the working methods to the fewest and simplest steps necessary, which can safely be entrusted to laborers of ordinary intelligence and skill.

I claim:

1. A method of preparing an emulsion to be used in making magnesia cement consisting in first pepticizing water-irisoluble metallic soap cold in a small quantity of a fatty oil, intermingling therewith a solution of a metallic salt intended to act as binder for the cement, and a suitable emulsifying agent while agitating, and finally adding to the emulsion so obtained a small amount of a caustic alkali with resumed agitation, to act as a stabilizer for the emulsion.

2. A water-, and weatherproof magnesia cement containing a metallic salt combined with magnesium oxide as an insoluble basic or oxysalt to act as the binder for the cement, an insoluble metallic soap as the protector against moisture, a small amount of a fatty oil used for pepticizing the soap preparatory to incorporating it in the cement, a water-insoluble but oil-soluble natural or artificial gum or resin as emulsifying agent for the mixing of the aqueous binder with the pepticized soap, and a trace of an alkali used to improve and stabilize this emulsion.

3. An integrally and permanently water-, and weatherproofed magnesia cement produced by the action of a strong metallic salt solution upon calcined magnesite and containing a water-insoluble but oil-soluble natural or artificial gum or resin used as emulsifying agent for uniting ordinarily immiscible components, and an alkali added to stabilize the emulsion so obtained, prior to its incorporation in the dry aggregate.

4. In the manufacture of magnesia cement waterproofed with theaid ofan insoluble metallic soap: the steps necessary for the unobstructed incorporation in the cement mixture of both, a water-repellent metallic soap and. a strong aqueous solution of a metallic salt serving as binder for the magnesite, which consists in first pepticizing the soap in a small quantity of a fatty oil in order to temporarily inhibit the water repellent effect of. the soap, and then simultaneously distributing by a simple mixing o-r kneading operation the pepticized soap and part of the binder in the dry aggregate, finally adding the balance of the binder to the damp mass.

5. In the manufacture of magnesia cement waterproofed with the aid of a water-repellent metallic soap, the alternate steps of first emulsie fying the pepticized soap with the metallic salt solution serving as binder for the magnesite, stabilizing the emulsion with a trace of a caustic alkali for shipping and storing, and incorporating the emulsion as a whole in the dry aggregate including calcined magnesite, in a single mixing 7