DE2443894C2 - Hydraulic cement compounds containing sand and their uses - Google Patents

Description

The invention relates to hydraulic. Containing sand Cement masses suitable for application in layer form and a hydraulic cement, the lime is able to release on contact with water and optionally a pigment or Extending agent, an opacifying agent, a waterproofing agent and a hardening accelerator contains. For the sake of simplicity, the invention is mainly referred to below described on paint.

Cement-based paints, hereinafter referred to as cement paints or cement paints are known. They are used in particular on exterior surfaces of buildings in the form of decorative Materials with waterproof properties applied. Such a material exists, for example essentially of white portland cement, finely divided calcium carbonate as a pigment and one Extender of a small amount of titanium dioxide to improve opacity, a fatty acid for Improvement of the waterproofing properties and an accelerator, which the desired Gives curing properties. Such a mass is supplied in powder form. The powder will mixed with water immediately before use. Sand is often the first layer applied added in order to avoid shrinkage and a better interlocking effect with the second coating as well as a greater opacity.

The previously known cement compositions of the type described can still be improved in so far as their ability to apply in the middle of a brush leaves a lot to be desired and they still drip relatively heavily. In addition, their curing properties at relatively low relative humidity can still be improved.

The invention has therefore set itself the task. Zcmcntmassen to create that improved Have the ability to carry a brush and are relatively drip-free and also at low levels relative humidity compared to known compounds have improved curing properties.

This object is achieved by the invention by means of a hydraulic cement mass according to the patent claim 1 solved.

The invention is based on the knowledge that by using 2 to 5% by weight of aluminum sulfate, which is a thixotropic Ge! with lime in the presence of water is able to produce w , the properties described above are improved.

In DE-PS 6 64 724 it is indicated that a reversible aluminum hydroxide sol the water resistance improved by cement or cement mortar. The problems of paints are discussed in this References not included, nor is aluminum sulfate mentioned.

The AT-PS 3 03 597 describes the use of Aluminum sulfate as a hardening accelerator for cement, a> mortar and concrete. This teaching leads from that According to the invention, use of aluminum sulfate in a paint is gone, as it cures quickly is undesirable due to the reduction in the useful life and life of the paint. It is therefore surprising that the cement composition according to the invention has the properties indicated above owns.

According to the invention, the term "hydraulic Cement «is understood to be a mineral substance that can reach a stone-like consistency Adding water hardens. The preferred hydraulic cement of the present invention is Portland cement, however, cements other than Portland cement can be used along with the one si thixotropic gel-forming agents, such as aluminum sulfate, provided that they release lime when they come into contact with water. The lime reacts with the aluminum sulfate to produce an alumogel. A cement with a high • to alumina content is an example of a different, hydraulic cement.

The addition of aluminum sulfate to a cement paint of the type described above leads to a significant modification of the paint properties. The painting is in its earlier stage more strongly gelled and can act as a suspension aid for settled sand. When using a iron-free aluminum sulfate, the gel-like cement paint is slightly lighter than the previously known '<' Cement paints.

Cement paints that are produced with a normal water content are more thickened than before known cement paints when aluminum sulfate is incorporated, taking them during their early stages >) become stiff to a greater extent. Cement paints containing 5.0 weight percent based on aluminum sulfate the dry matter contained, result in a fully thickened coat that practically does not apply after a 10 Minutes of standing period drips. The extent m> of gel formation with the addition of changing Amounts of aluminum sulfate on a typical cement paint, measured during the first 15 Minutes of freshly made paint using a gel strength tester "'given in the following table. A gel strength reading of 450 is the limit of the instrument. The water to powder ratio is in all of them Fall 0.4.

3 24 103 43 894 7 min 4th 15 minutes % Aluminum sulfate
(17-18% AI ₂ O ₃ ) Gel strength, g - cm ',
1 min 3 min 153 after
5 min 143 10 min 152 0 81 283 130 223 145 346 1 85 297 223 328 290 450 2 103 350 300 400 450 450 3 180 350 374 402 450 450 4th 190 400 450 450 450 5 Ϊ91 418 450

The addition of certain amounts of sand to known cement paints results in a modification of their properties as well as an improvement in many of their properties, in particular an improvement in adhesion to smooth, dense surfaces, so that the risk of flaking is low.

The benefits of sanded cement paints are well known. Mention should be made of an increased coating thickness, the leads to greater weather resistance, better opacity, especially under humid conditions, thus achieving a longer lifespan before a reduced opacity requires further treatment makes an improved solidification and curing necessary, with the risk of dust formation below dry conditions is less pronounced, a reduced shrinkage on drying and a less moisture wicking, resulting in improved adhesion with less risk of flaking on smooth, dense surfaces or surfaces that contain traces of soft material, as well as the creation of improved interlocking options for subsequent treatments.

Sanded cement paints suffer from certain disadvantages, these disadvantages increasing with increasing Increased sand content come to light. If the paint is made too thin, or if one fails to do it occasional stirring, then there is a tendency for the sand to settle out. This leads to an uneven Coating thickness and an uneven distribution of sand in the coating. With increased sand content the cement paint is less easy to apply and is opposed to a suction effect more sensitive, which harbors the risk of agglomeration of sand, with strong brushstrokes, thick overlaps and an uneven appearance are to be accepted. The sent Paints have a reduced areal coverage and are prone to in industrial areas a pollution.

The cement mass containing hydraulic sand according to the invention can be applied better than before known sanded cement paints. In particular, no sedimentation of the sand is found.

The addition of certain amounts of sand to gel-like cement paints formulated according to the invention and containing 5.0% aluminum sulfate has the effect that the sand is kept completely in suspension in amounts of up to 50% by weight. The application properties with high additions of sand are better than in the case of cement paints containing sand previously known. Cement paints containing 2 to 3% by weight of aluminum sulfate also keep the sand completely in suspension, in amounts up to about 30% by weight, the application properties also being improved, but to a lesser extent. The addition of sand to gel-like cement paints can result in a slight reduction in the brightness of the paint film obtained and a reduction in the surface coverage. The 2 ~> reduction in brightness can be compensated for by increasing the titanium dioxide content, with raw material costs being saved to a considerable extent by adding the sand.

The preferred amount of aluminum sulfate is 2.5% by weight.

The preferred amount of sand in the cement paints sanded according to the invention is between 20 and 40 % By weight, based on the unsanded dry matter, and preferably at 25% by weight (this corresponds to 20 Ji% by weight of the finished mass).

A typical and preferred sanded cement paint according to the present invention is shown below indicated, the amounts being to be understood in percent by weight.

White portland cement 62.55 Titanium dioxide 2.80 lime 7.20 Calcium chloride dandruff 4.25 stearin 0.80 zinc oxide 0.14 Aiphanoi 0.26 Aluminum sulfate (iron-free, 17 - 18% aluminum oxide) 2.00 sand 20.00

100.00

It should be pointed out that the gel structure of the compositions according to the invention leads to water retention contributes so that full hydration is given during the hardening of the cement.

The following examples illustrate the invention.

Eight masses are prepared in such a way that thoroughly during two 45 minute stages the following ingredients are ground together in the specified amounts (percent by weight). That Aluminum sulfate is added during the first stage.

Example 1 represents a known white cement paint and is used for comparison purposes, while Examples 2, 3 and 4 illustrate gel paints:

White cement

Granular titanium dioxide

chalk

Calcium chloride dandruff

zinc oxide

stearin

Primary alcohols C ₇ to C ₉

Aluminum sulfate, iron-free,

17-18% Al ₂ O ₃

80.81 75.88 80.79 78.17 2.46 2.46 3.08 2.50 9.85 9.85 4.22 10.00 5.35 5.35 5.35 5.32 0.16 0.16 0.16 0.18 1.01 1.01 1.01 1.00 0.36 0.36 0.36 0.33 0.0 4.93 5.03 2.50

100.00 100.00

100.00

100.00

Example 5 illustrates a comparative composition, while Examples 6 to 8 represent examples according to the invention. All four examples are carried out in such a way that 25% by weight of sand corresponds to the respective products of the examples! to 4 are added when leaving the mill, whereupon mixing takes place for a period of 10 to 15 minutes in a trough mixer.
2 »The properties of the products of Examples 5 to R are compared in Table 1 below. To carry out the comparative tests: the following test methods are used:

Test methods

Paste time:

Time in seconds that elapses until 300 g of powder added completely from 120 ml of water are wetted to form a smooth paste in a 600 ml polyethylene beaker.

Temperature rise:

Increase from average initial temperatures to the maximum temperature that occurs during the paste formation is achieved.

Painting yield:

Calculated in liters per kg of dry powder from the weight of 100 ml of paint.

Usability:

determined by painting the rough side of a hardboard at regular intervals during the service life, whereby the end of the service life is then regarded as having come becomes when the paint can no longer spread and strong brushstrokes are noticeable.

Colour:

Color of the powder cure coating, applied with a brush and under standard conditions at 20 ° C as well as. '' jier relative humidity of 85% cured during a period of 24 hours between every three applications, measured using a spectral reflectometer.

Opacity:

two coats of paint are brushed on black and white edges and during one Time lapse of 24 hours between each application at 20 ° C and a relative one Humidity of 85% cured, the cards are cured before and after the application of the paint woven, with the amount of paint used referring to its rate of spread is calculated in nWkg.

The reflectivity of the painting film is measured over both black and white parts of the Map at 565 πιμ using a spectral reflectometer measured.

The paint coats are then immersed in water for a period of 10 minutes, whereupon the excess water was wiped off and the reflectance reappeared both over the black as well as measured over the white card.

The contrast ratio of opacity is expressed as follows:

Reflectivity on black
Reflectivity over white

x 100.

50

Evaluation of the chalking:

The dustiness of the cured paint coating is determined, namely by light Rub the painted surface with a piece of velvet. A chalking score of 10

means no powder is removed, while a rating of 0 indicates powder is completely removed. The base consists of a hardboard with a thickness of 6 mm. A primer coat (03 mm) is applied and at 20 ° C as well as at a relative Moisture of 70% cured for a period of 24 hours. A paint film with a Thickness of 0.25 mm is applied to the paint E and at 20 ° C as well as at a relative Moisture of 70% cured for a period of 24 hours.

Curing times:

British Standard Test Method B. p. 12, Appendix F.

Shrinkage while drying:

A.S.T.M. C596-70, with the following modifications be respected:

well-dried powder instead of mortar; Demolding time 4 hours; Demec measuring system.

Compressive strength:

British Standard Test Method B. S. 12. Anhane C.

Table I. 24 43 894 b 8th 7th 8th 7th 4.0 4.0 2.0 20.0 20.0 20.0 % Aluminum sulfate Hot example No. 8th 8th 8th Sand % 5 9.4 8.7 6.9 Paste time (seconds) 0 0.55 0.60 0.55 Temperature rise, ⁰ C 20.0 0.88 0.97 0.87 Water / powder ratio 8th Paint yield (l / kg) 3.7 Area coverage capacity, 0.50 2.7 2.5 2.4 2 coatings, no / kg dry powder, 0.87 0.8 0.8 1.0 rough side of the hardboard 2.2 2.2 2.1 new, raw cast 1: 3 smoothed out 2.6 155 160 165 Usage Time (Minutes) 1.0 80 70 125 20 ⁰ C, 50% relative humidity 2.1 32 ° C, 507o relative humidity Colour: 145 85 ,? 84.2 83.1 Dry powder 120 85.2 84.3 83.1 Color value .V 79.8 78.6 78.0 Color value Y Color value Z 83.7 76.1 76.4 75.5 Cured coating on asbestos: 83.8 76.2 76.9 75.8 Color value X 78.3 70.6 72.3 72.6 Color value Y Color value Z 75.9 78.3 78.6 76.5 Cured coating on asbestos: 76.0 78.5 78.8 76.8 Color value X 71.0 73.5 73.6 72.6 Color value K Color value Z 76.9 88.5 88.9 88.5 Opacity: 76.9 76.9 78.4 78.8 Dry contrast ratio% 71.5 6.3 4.8 6.0 Humidity contrast ratio% Speed of propagation
(m-Vkg) 88.4 10 10 10 Curing properties: 77.5 Chalking evaluation 6.0 60 80 75 B. p. 12 curing time 75 100 80 at the beginning (min) 10 at the end (min) 45 60

B. p. 12 Le Chatelier

Expansion (min) 1/2 1 1 1/2

Expansion when wet,% 0.05 0.03 - 0.03

Shrinkage on drying,% 0.44 0.48-0.47

Compressive strength:

3 days! 9.4 16.0 19.5 2!, 2

7 days 26.9 23.1 25.4 28.0

28 days 39.8 31.4 34.9 35.9

Special Aspekle, which when comparing the The above examples are discussed below.

Gel-like cement coatings according to the present invention have the formation of slightly thicker pastes when mixed than the known paint according to the example 1, where? · However: li? Texture creamier and glali .'..- is. Dilution with water with formation painting is possible without difficulty. With the usual water / powder ratio of 0.6, the gel-like paints stiffer and thickened than the known paint. The gel-like paints can Lightly brush onto all surfaces at a fully thickened consistency, usually with a Cement paint to be painted.

The gel-like paint of Example 2 mil 5.0% even stiffer and practically drips after mixing for the first 10 minutes since its manufacture not. The same painting according to the example ·! mis 2,594 » becomes very slightly stiff after mixing. No waiting period is required to ensure the consistency of the to get the finished coat of paint. It is less thickened than the gel-like paint of Example 2 at 5.0%.

The rise in temperature of gel-like cement paints according to Examples 2 to 4 during mixing is higher than in the case of Example I. The gel-like paint with 5.0% shows practically twice the increase compared to Example 1 during the gel-like coat with 2.5% lies between the two coats mentioned. The climbs to high However, temperatures do not lead to rapid curing and do not deteriorate the paint properties under working conditions. The temperature rise of the gel-like paints is partly due to the Heat of reaction between aluminum sulfate (a Lewis acid) and water.

The applicability of gel-like cement paints is better on all types of surfaces starting with smooth, dense concrete surfaces up to highly porous, roughly cast surfaces. When using the gel-like cement paints practically no splashing during painting, so that a clean painting is possible and there is less cleaning work to be done afterwards. The gel-like paint with 5.0% cuts in everyone Relationship best.

The paint yield of the gel-like cement paints and the known cement paint are similar. The area coverage of the gel-like paints on a surface of medium texture and The suction effect is somewhat lower than in the case of a known paint, due to the somewhat larger film thickness.

The opacity of the gel-like cement paints is slightly better than that of the known paint, as a result of the somewhat larger film thickness. The dry powder paint as well as the color of the cured one Coatings on glass of gel-like paints are better than in the case of the known painting. The V color value (=% lightness) in the case of the gel-like paint with 5.0% is 2.0% higher than the corresponding value of the known paint.

The service life as well as the B.S. 12 curing times under working conditions the gel-like cement paints are slightly longer than the corresponding values of the known paint, due to the slightly higher sulfate content. The lifespan of a increased temperature of 32 ° C of the gel-like coating however, it is shorter than that of the known paint and / was due to the rise in temperature.

The gel-like paint films are harder than the known paint film when hardening during a period of 24 hours at 45-50% relative humidity is carried out. From this it can be seen that the "gel" contains moisture in the film maintains during hydration. This property is very desirable and offsets the cement paint capable of being maintained under conditions which are currently unsuitable, e.g. arid climates.

The Lc Chatelier extension according to B. p. 12 as well as the expansion in the wet state according to VS.T.M. C.596-70 show that the extra sulfate in the gel-like cement paints do not lead to expansion. The shrinkage when drying the gel-like Paints is slightly larger than in the case of the known

The gelart'gen cement paints are at all times weaker than the known paint, and as a result of the thinning effect of the "gel" in the cement matrix.

The one during artificial weathering in a weatherometer using Method B.P. 3900, Part F. 3, achieved over a period of 900 hours Results using the gel types as well as the known paints are similar.

Natural weathering for a period of 1 year has shown that the gel-like paints and the known paints are of similar durability. The gel-like paint with 5.0% chalked up at this point in time a little easier than the well-known paintwork.

The sand made available with the grade T is practically colorless and of such a particle size, which is suitable for a satisfactory texture of a separate cement paint.

The addition of sand (cf. Examples 5 to 8) to gel-like paints and known cement paints has little effect on the time it takes for the powder to wet out and form a paste is required. However, sand has an auxiliary effect in that the thinning of the Paste is made easier with more water to adjust a paint consistency. A minimal one Sand content of 20% is required in this regard. With this amount of sand it is possible to use the separate gel-like cement paint and the separate known cement paint directly to achieve a To mix paint consistency without the need for an intermediate paste generation stage. at a single stage mixing will entrap a little more air, but the powder is completely wetted.

The addition of sand to gel-like cement paints as well as to previously known paints has one Reduction in the amount of water required to achieve a certain paint consistency so that the paint yield is decreased.

The addition of 25% sand (= 20% of the sand content in the product sent) to the gel-like Cement painting reduces the yield by approximately 8%.

The applicability of yellow Zemenian paints with sand decreases as in the case of known paints with sand as the amount of sand increases. A

Sand content of 40% is the maximum that can be tolerated in ["all of the paints. At least 20% is required to get a reasonable texture on slippery surfaces. Below 10% can the discrete coated grains of sand are observed, giving the impression of a poorly mixed or lumpy paint.

The gel-like coatings with sand can do better brushed on as well-known coats of sand, on all surfaces. In the case of surfaces with a high suction effect, the inclination of the Sand to agglomerate, while on smooth, dense surfaces the tendency of the sand, being distributed along the brushstrokes is also decreased. The gel-like paint at 5.0% is that; best of the gelatinous paints in this regard.

There is no sedimentation of the sand in the paint bucket in the case of gel-like paints that are up to Contain 20% sand, while a certain sedimentation can be observed in the case of the known sand paints. which contain 20% sand, provided the paint is not stirred frequently. Able to use higher sand contents the gel-like paint with 5.0% completely suspend the sand, while the gel-like paint with 2.5% something has to be stirred.

The area coverage measured on a surface with medium texture and porosity (rough side of a hardboard) decreases with increasing amount of sand. A 25% addition of sand too the gel-like paint reduces the area coverage by about 25% and that of the des known paint by about 20%.

The opacity increases as the amount of sand increases as a result of the increased thickness of the paint coating improved. Gel-like and known cement paints are similar in this respect.

The brightness of the paint coatings is reduced with increasing amount of sand. An encore before 25% sand to the gel-like paints as well as the known paints reduces the brightness by about 3%. Gel-like paints with sand are lighter than known paints with sand. The gel-like paint with 5.0% with 25% added sand is 2% lighter than the known paint with 25% added sand.

It is based on the addition of sand to the gel-like as well as known paints can. cor end be drawn, oass at least a 25% addition is necessary. to get the maximum benefits of the sand in an increased thickness of the paint coating, which increases the opacity and the permanent strength and also a pleasant texture is achieved. This sand is known to have the Adhesion of known cement paints is improved.

The gel-like cement paints are able to add 25% sand in a satisfactory manner To keep the suspension, the gel-like paint with 5% shows the best application properties.

The gel-like paint according to Example J differs differs from the gel-like paint according to Example 2 in its theological properties. The powder leaves simply with water to form a smooth paste as well as to produce a fully thickened one

Cn a nCitne.iCrcs

Becoming stiff during the first 10 minutes continues after these 10 minutes during application. The other properties are similar those of Example 2, with the exception of the color of the cured coating and the opacity, which are better as a result of the higher titanium dioxide content. Example 7, which is similar to Example 3. however, according to which sand is added shows that stiffening occurs to a considerable extent during the initial period after manufacture. It is is similar to Example 7 in other properties, except for the color of the cured coating as well as the opacity, which are better. However, the color of the cured coating is somewhat more matt than in the case of example 1.

The sand content of samples that were used in the implementation of Examples 6 to 7 were taken during packaging, / inherent that the distribution of the Sand within the batches is excellent. All values are between 19 and 20%.

Experiments in the open air have the advantages of the gelai-igen cement paints given in the preceding examples confirmed.

Claims (5)

Patent claims: 1. Hydraulic. Cement mass containing sand, suitable for application in layer form and contains a hydraulic cement that is capable of releasing lime when it comes into contact with water, and optionally a pigment or extending agent, an opacifying agent, a waterproofing agent and a curing accelerator contains, characterized in that it also contains 2 to 5 wt .-% aluminum sulfate contains 2. Cement mass according to claim 1, characterized characterized in that the hydraulic cement consists of Portland cement. 3. Cement mass according to claims 1 to 2, characterized in that it is 2 to 3 wt .-% Contains aluminum sulfate and up to 30% by weight of sand, the percentages being based on the weight of the Relate the mass without sand. 4. Use of dsv core remover according to Claims 1 to 3 as a paint in dispersion in water. 5. Use according to claim 4, characterized in that the weight ratio of Water to powder is 0.55 to 0.60.