DE3729090A1 - Stabilisation of concrete against microbial attack in particular sulphur bacteria - Google Patents

Abstract

The destruction of domestic sewers by microbial activities, in particular sulphur bacteria, is known and has been thoroughly studied hitherto. Satisfactory solutions for preventing or repairing damage are not known. The process of the invention for stabilising concrete against microbial attack, in particular against sulphur bacteria, is characterised in that biocides are added in the presence of a hydrophobicizing agent to the cement mixture or to the hydraulic binder. A variant of the process of the invention is characterised in that concrete or other surfaces containing hydraulic binders are treated with mixtures of biocides and hydrophobicizing agents in the form of solutions, emulsions or hydraulically setting sealing slurries.

Description

Concrete and mortar are conditioned by the chemical properties of inorganic binder, such as cement, susceptible to aggressive Me and sulfur bacteria. Such aggressive media are z. B. at Underwater structures of seawater, in other buildings, water, the contain aggressive ions such as bicarbonate, hydrogen sulfate or Chloride.

Furthermore, in municipal sewers created by the activity of Sulfur bacteria is a particularly aggressive medium, which concrete zer disturbs.

This is mainly the Thiobacillus thioparus and Thiobacillus ferrooxidans and the sulfate-reducing bacteria Desulfovibrio desulfuricans.

Concrete building materials contained in their finished micelles, pores, capillaries and defects through which water diffuses. With optimal growth conditions of aerobic or anaerobic sulfur bacteria in pollutant containing wastewater occurs in this Kapillargefüge to chemical Changes in the hydraulic binder - especially by the as Metabolic product resulting sulfuric acid. This mainly affects the mechanical properties, in particular the resistance to about chemical influences of all kinds; or in other words, the bak terially formed sulfuric acid destroys the concrete.

There was therefore no lack of attempts. Concrete and mortar against the micro to protect biological infestation. So one has in the German disclosure DE 32 08 004 in a cumbersome; triple impregnation procedure proposed a conservation and restoration.

Similarly, the two-step impregnation process of U.S. Pat. Patent 42 58 090, wherein after a pretreatment of the concrete surface with fluorine silicates a post-treatment with biocides in organic solvents is made.

In German Patent Application 22 50 644 is a 4-stage Im impregnation process at certain time intervals with copper naphthenate suggested in 50% white spirit solution.

In EP-0 140 826, finally, a Portland cement mixture with high basic supplements presented which of the bacterial activity withdraws the acidic medium.

The invention relates to biocide and hydrophobic additives for concrete and mortars, hydraulically binding compositions, such as cement, as well as Surface treatment for such made with hydraulic binders Mortar or concrete and other building materials such as clinker, aerated concrete, concrete contains foamed plastics, and asbestos fleece, these additions to it serve, the hydraulic binders on the one hand hydrophobic and on the other stable against microbial attack, especially sulfur bacteria, close.

An advantage of the invention is that the hydrophobic additive attack prevented by aggressive water and the biocidic active ingredient either through loose chemical binding or wrapping in the capillary area prior to elution (Leaching) by water etc. protects. This leaves the biological activity the added biocides active ingredients over long periods of time.  

Concrete therefore becomes very effective according to the method of the invention Against microbial attack, especially against sulfur bacte- ria protected when the cement mixture or the hydraulic binding simultaneously adding a biocide and a hydrophobing agent. Finished concrete components can be used equally with a mixture of Biocid and water repellents in the form of solutions or emulsions become.

Suitable water repellents are, for example, emulsions of Si liqueurs, paraffins and linseed oil, and of various synthetic resins and Bitumen. Also, mixtures of oils or fatty acids, such as stearic acid or Montanwachssäuren and Paraffinsulfonaten, fatty acids and emulsions of Oil-form polyethylenes. Also alkali soaps of fatty acids; like sodium or ammonium stearate in dissolved or emulsified form. Especially advantageous proved paraffin emulsions, which according to the German Offenlegungs 23 43 457 are accessible.

Suitable biocides are, in particular, those active substances which are resistant to sulfate reducing or oxidizing bacteria are active such. As phenols which optionally substituted by halogens or alkyl groups. Organic mercury Compounds such as phenylmercuric acetate, or phenylmercury oleate, etc. Aldehydes and dialdehydes in pure or acetalized form, also quater ammonium compounds, copper naphthenate, trialkyltin oxide, chlorocresol, Triphenyltin hydroxide, o-phenylphenol, tributyltin maleate, 4-chloro-3,5-xylenol, m-chlorosalicylic acid, p-chloro-metaxylenol, 2- (4-thiazolyl) benzimidazole, tetra Chloro-4- (methylsulfonyl) pyridine, copper powder, thymol, naphthalene, colloidal Silver solutions, etc.

Particularly advantageous agents can be used, which after the EP-077 947 are accessible. These are amine sulfur dioxide Adducts.

After the German patent application DE-31 43 342 are also very effective same bactericides (sulfitobetaines) obtained according to our patent to use coveted favorably.

In general, the biocidally active ingredients become together with the hydrophobicity added to the concrete mixture. However, it can also be hydrophobic emulsions containing the biocides added to the mixing water become.

A preferred embodiment of the method according to the invention is adding the mixture of biocide and water repellent to the cement-sand mixture Add and then add the mixing water.

The biocidal agents are in a concentration of 0.00001 parts to 2 parts added to 100 parts of cement / sand.

The hydrophobizing emulsions, which may also contain the biocides, may the hydraulic binder when applying the mortar or concrete together with additional water, which is necessary anyway to prepare, are added. in the In general, one uses 0.1-10, preferably 0.2-3 wt .-% of Hy hydrophobing agent (calculated as solids - calculated without water) on the amount of hydraulic binder.

But you can also the surface of the hydraulic binders ange made building materials, eg. As the mortar or concrete, after their processing with treat the biocidal emulsions, z. B. by spraying or brushing.  

Finally, it is also possible, the biocides or water repellents to add to the hydraulic binders already during grinding. You can do that the water repellents, together with the biocidic agents, in the Add grinding drum, with additional water or glycol added can be added. The amount of glycol or water can be z. Eg 0.1- 10 wt .-%, based on the amount of cement or slaked lime, amount. In the milling process, other additives with basic We can also kung be added, such as. B. finely divided dolomite or limestone sand or in general carbonate rocks. Also oxides of calcium and mag Nesium are advantageous as supplements, because thereby the alkali reserve of the Concrete or the hydraulic binder is increased.

In addition to the biocidal hydrophobing agents, the hydraulic binders when mixing, if necessary, a mixture with these and on their usual additives z. B. aqueous dispersions of polymers on the Base ethylenically unsaturated carboxylic acid ester z. B. of vinyl esters, such as Vinyl acetate, vinyl acetate / versatate copolymer and vinyl propionate, or acrylic esters and / or methacrylic esters, such as Acrylsäureethyl- and tert. butyl ester, fer be added based on butadiene, styrene and / or vinylidene chloride. Even with the usual surface treatment methods for prefabricated Concrete parts made of hydraulic binders can be biocide hydrophobic Means advantageously used in admixture with plastic dispersions become.

Test procedure

As a test method with minor modifications, the API-RP 38 method (Recommended Practice for Biological Analysis of Water Flood Injection Waters, API-RP 38 American Petroleum Institute May 1959). The test specimens containing the biocidal active ingredients in changing compositions in addition to containing a water repellent, are after a several weeks used for the test. Suitable test bottles are 0.7 l bottles with vacuum cap.

The concrete test pieces are divided in half with a nutrient solution consisting of:

Yeast extract | 1.00 g / l L-ascorbic acid 0.10 g / l Sodium lactate (as aqueous solution v. 50%) 4.00 g / l MgSO₄ 0.20 g / l K₂HPO₄ 0.01 g / l Ammonium iron-II-sulphate 0.20 g / l NaCl 10.00 g / l

pH = 7.54 (adjusted with NaOH)

and a bacterial culture solution (Desulfovibrio desulfuricans, provenance: Assling, Landau) at 36 ° C incubated.

Due to the composition of the nutrient solution arises through the metabolism the bacteria black Fe II. sulfide, whose precipitation the presence of the Bacteria (Table, p. 8).  

Preliminary tests have shown that the pH of the test solutions through high alkalinity of the concrete test specimens to 11-12.5. The high alkalinity is obviously responsible for a very strong one Inhibition of bacterial growth.

To a gradual activity of the examined biocides in dependence to be able to recognize the pH value, the test was changed so that the pH is readjusted daily with HCl to a pH of 7.5. because it was found that blank samples (without biocide) of the concrete test specimens after spä 2 days were positive (black). The parts mentioned in examples are parts by weight.

Example 1

100 parts of cement PZ 35 F (DIN 1164) are 100 parts standard sand 0.200 parts Normsand II, 1 part of a montan wax-containing paraffin paste sion (German Offenlegungsschrift 23 43 457) and 45 parts of water mixed. Out the mass obtained, prisms of dimensions 4 × 4 × 16 cm are poured, formed after curing for one day, and then placed under water for 27 days to be cleaned.

Thereafter, the prisms of the bending tension and compression test according to DIN 1164 under worfen.

Water penetration depth | 1.5 cm flexural strength 8.0 N / mm² Compressive strength 49.0 N / mm²

example 2

From a mixture of 100 parts of cement PZ 35 F, 100 parts Normsand 0.200 parts Normsand II, 20 parts of a commercial 50%, aqueous dispersion of a copolymer of butyl acrylate / styrene, a part of paraffin emulsion according to the German Offenlegungsschrift 23 43 457 and 45 parts of water prisms are prepared as in Example 1.

The prisms are demolded after 24 hours of storage and then put under 27 days Stored water. After that is the

Water penetration depth | 2.0 cm flexural strength 8.1 N / mm² Compressive strength 43.0 N / mm²

example 2b

For a prism without plastic dispersion and paraffin emulsion is prepared and examined under the same conditions, penetrates Water until completely wet.

The bending tensile strength is 7.33 N / mm², the compressive strength 42.0 N / mm².

example 2c

In a prism, with the addition of a plastic dispersion and prepared without the addition of the paraffin emulsion, the water is Penetration depth 3 cm, the bending tensile strength 8.02 N / mm² and compressive strength 40.4 N / mm²

example 2d

In a prism, without plastic dispersion, but with a part of silicone oil is produced, shows a water penetration depth of 3 cm a bending tensile strength of 80.2 N / mm² and compressive strength of 42.0 N / mm².  

example 3

6,800 parts cement PZ 45 F
20,000 parts of sand 0-4 mm
8,800 pieces of gravel 4-8 mm
14,000 parts of gravel 8-16 mm
2,900 parts of water
0.100 parts montan wax-containing paraffin emulsion (DE OS 23 43 457)
0.075 parts of N-dimethyl-dodecylamine. SO₂ complex

are mixed in a compulsory mixer. From the obtained mass Cube of dimensions 10 × 10 × 10 cm poured out after 24 hours be formed. After 7 days of water storage and storage in the climatic room is tested according to DIN-1164.

example 4

A screed mortar off
11,500 parts of cement PZ 45 F
35,500 parts of sand 0-4 mm
4,500 parts of water
0.100 parts montan wax-containing paraffin emulsion (DE OS 23 43 457)
0.075 parts of N-dimethyl-dodecylamine. SO₂ complex

is mixed in a compulsory mixer. The resulting mass becomes prisms of dimensions 4 × 4 × 16 cm poured.

After 24 hours is formed. According to DIN-1164, the bending tension and pressure strength tested.

example 5

A sealing slurry out
35,000 parts cement PZ 45 F
15,000 parts of tress cement
15,000 parts of quartz powder W 3
32,000 pieces of quartz sand H 32
25,000 parts of water
0.100 parts of montan wax-containing paraffin emulsion (DE OS 23 43 457)
0.075 parts of N-dimethyl-dodecylamine. SO₂ complex

are mixed in a compulsory mixer. The resulting mass becomes prisms of dimensions 4 × 4 × 16 cm poured. Molded after 24 hours.  

According to DIN-1164, the bending and compression strength is tested.

The water impermeability is tested in accordance with DIN-1048. After 28 days of water pressure of 1.5 bar no water is penetrate into the concrete.  

table

Stabilization of concrete test specimens against Desulfovibrio desulfuricans (Prov. Assling)

Claims (2)

1. A process for the stabilization of concrete against microbial infestation, especially against sulfur bacteria by biocides, characterized in that biocides in the presence of ei Nes water repellents of the cement mixture or the hydrau lic binder added. 2. Method of stabilizing concrete against Microbial infestation, especially against sulfur bacteria by Biocides according to Claim 1, characterized in that concrete is used or other hydraulic binder containing surfaces with Mixtures of biocides and water repellents in the form of Treated solutions or emulsions.