DD278090A1 - METHOD OF THE CHEMICAL DECOMPOSITION OF CEMENT-CONTAINING SUBSTANCES, IN PARTICULAR MOUNTED AND CONCRETE - Google Patents

Abstract

The invention relates to a method of chemical decomposition of cementitious substances, in particular moieties and concretes, which are to be removed and removed as deposits on other hard material bases, such as in mixers, in and on formwork elements, tools or vehicles. According to the invention, a cementitious substance having a soluble mixture consisting of 50 parts by weight in% of an acidurea, 2-20 parts by weight of a light soluble salt of a carboxylic acid, dicarboxylic acid, oxycarboxylic acid or oxydicarboxylic acid, 30-40 parts by weight in% water and / or 2-20 Mass fractions treated in% of a light sulphate. Due to the good diffusibility of the mixture in the pores interior spaces, the high aggressiveness towards the cement stone the short-term occurrence of driving phenomena, it very quickly leads to a loosening of the Gefueges and Abloesen from a base.

Description

field of use

Dio invention relates to an ancestor of chemical decomposition zemonthaltigor substances, before allom hardened mortar and Botonmischung, which are to be removed and removed as deposits on other hard material substrates, such as in mixers, in and on formwork elements, tools or vehicles.

Known state of the art

The Zortoilen and Entfornon of hardened Zomont ·, Boton- and mortar statements is bokannterwoise made by mechanical methods, but also chemischom ways. Generally speaking, a number of means of expansion based on burnt lime are known for grinding natural and artificial stones. By these means, a silent smashing of Betonmatorialien is possible. However, in the best case scenario, they guarantee crumbling and removal of more or less thin layers of deposits. There are also natural or artificial vorgesohono cracks, crevices or I Icher required \ r> dio the Expansivmittol must be brought in and can werdon effect due to increase in volume.

A chemical erosion of hardened cementhaltigor substances must therefore a decomposition of Zemontstoins, d. H.

Structural damage, underlying.

There are already known ancestor in which recognized harmful properties of chemicals have been exploited on the Zemontstein for gentle destruction and removal fostor zementhaltigor deposits in mixers, shuttering or other substrates.

DE-OS 2126051 discloses the use of Mothylacetoacotatlösung which in any way, for example, by pouring, spraying, dipping brought into contact with the momentarily entangled Krusto in contact. Under recognizable Reaktionswäro oin part of the Zementphaso is clearly solved and destroys the gohärteto cementitious material. This method is liable to the disadvantage that only oin schichtenwoisos destruction and ablation is possible. Destroying larger quantities thereby requires a great deal of time and effort.

In DE-PS 1133299 in water, concrete and / or alcohol-soluble esters of short-chain organic acids and short-chain alcohols are proposed. The main Nachtoil this Stoffgomische is i ⁿ the high volatility and flammability. There are additional expenses to ensure the necessary occupational health and fire protection required.

Other known cement-damaging agents are, in addition to the inorganic mineral acids, organic acids as well as certain carboxylic acid derivatives, such as acid amides and fats. In this case, the calcium compounds of Zomentsteins be converted into more or less soluble calcium salts, with dangerous reaction products, u. a. Hydrogen sulfide, can arise. Existing metal parts are more exposed to corrosion.

With the invention, a gentle, at the same time effective decomposition zemeoth 3ltiger substances, mainly of mortars and concretes is to be achieved, with only oor minor technical effort for additional mechanical work and health and occupational safety measure is sought.

Essence of the invention

The invention has for its object, a decomposition of cementitious substances to reach far into Gofügeinnere by a solvent with good diffusibility in don Poronraum and at the same time high aggressiveness gegonübor the cement stone.

According to the invention the object is achieved in that the cementhaltigo substance with a soluble mixture consisting

50% by mass in% of an acid amide

2-20 parts by weight in% of an easily soluble salt of a carboxylic acid, dicarboxylic acid, Oxycarbonsäuro or Oxydicarbonsöuro and / or

2-20% by weight of a readily soluble sulphate and 30-40% by weight of water in%.

Suitable acid amide is preferably formamide, as readily soluble organic salt sodium acetate, as sulfates (NH ₄ I ₂ SO ₄ , Na ₂ SO ₄ , K ₂ SO ₄ , MgSO ₄ or Al ₂ (SO ₄ I ₃ .

Depending on the amount of cementitious substance to be dissolved or depending on porosity, strength and hardness, treatment is generally carried out by spraying, dipping or storing in a soluble mixture, usually at normal temperatures Higher temperatures increase the effect of mochanism Reaction is the rate of ammonia release.

Boi of the hydrolysis of the acid amides as well as by reactions of the carboxylic acid salts with the hydration product of the cement paste obviously neoplasms, which lead after only a short time to driving phenomena. Although the destruction phenomena of the concrete by sulfate ions are known, they are effective for this purpose only in conjunction with an acid amide. With the good diffusibility of the acid amide in the concrete, the sulfate ions in the concrete matrix react with the constituents of the hydrated cement u: id lead to driver shocks. As a result, a loosening of the microstructure by decomposition quickly occurs, followed by cracking. The material becomes crumbly after a sufficient period of exposure. Also, the binding forces mr metal deck, chipping are the result reduced. The composition of the soluble mixture in terms of water and electrolyte content is to be adapted to the specific application. Fully cured concretes show greater resistance to the new mixture of those in the age of hardening of 3 to 16 hours.

embodiments

The invention has been successfully tested on a laboratory scale with test specimens based on different cement ranges.

Table 1 shows the test specimens and their most important passwords with which the method according to the invention was carried out. A specimen itself was prepared in such a way that in the fresh cementitious substance in the middle of a metal sheet (steel sheet) was embedded for later investigation of the release behavior. These specimens were treated by dipping with mixture compositions according to Tables 2 and 3.

In evaluation of the test results it is clear that a detachment of the zemet-containing substance from the metal sheet is successfully achieved by the inventive combination of the mixture components. The foal of Säuroamids in Mix 6 prolongs the mechanism of action by almost 50%.

Table 1 Composition and characteristics of the specimens (with steel insert 40 χ 70 χ 1.5 centered embedded for detachment test)

Test specimens dimensions cement Water / cement Cement / surcharge Porosity in V% 1d 3d after 7d 28 d Strengths in N / mm ² 1d 3d 7d after 28 d Zemont prisms 40 χ 40 x 70 PZ 4/45 0.4 - - - - 34.2 - - - 56.3 Standard mortar 40 χ 40 χ 70 ZZ4 / 25 0.5 1: 3 25.3 22.9 21.5 20.6 3.1 7.1 10.4 30.0 Concrete backs ZZ4 / 25 - 1: 5.2 - - - 34.1 - - - 41.1

Table 2: Ablösoversuche on 28-day-old Probokörporn (Zomoniprismon)

No. Composition of the solution 50% 50% Detachment from the Motal'bloch after days Crack formation in the specimen after days 1 HCONH ₂ H ₂ O 50% 20% 30% 15 18 2 HCONH ₂ CH ₃ COONa 14 18

HCONH ₂

_MgSO4

H ₂ O

50% 15% 35%

HCONH ₂

Na ₂ SO ₄

H ₂ O

50%

5%

45%

CJL HCONH ₂ Al ₂ (SO ₄ I ₃ H ₂ O 50% 10% 40% 18 50% 50% Detachment from the metal sheet after days 20 6 (NH ₄ I ₁ SO ₄ H ₂ O 20% 80% 30 50% 20% 30% 9 39 Table 3: Replacement test on 28 Tago alton test specimens (mortar prisms) 50% 15% 35% 11 No. Composition of the solution 50% 5% 45% 23 Crackbone in the test specimen after days 1 HCONH ₂ H ₂ O 50% 10% 40% 13 10 2 HCONH ₂ CH ₃ COONa HjO 20% 80% 14 10 3 HCONHj MgSO ₄ H ₂ O 25 27 4 HCONH ₂ Na ₂ SO ₄ H ₂ O 15 CJL HCONH ₂ AI ₂ (SO ₄ I ₃ HjO 15 6 (NH ₄ I ₂ SO ₄ H ₂ O 28

Table 4: Destruction attempt on Betonrückständün at the age of 28 days

Composition of the solution

Cracking after days

HCONH ₂ 50% 14 HaO 50% HCONHj 50% 12 CH ₃ COONa 20% H ₂ O 30%

Claims (4)

270 270 Claims: 1. A method of chemical decomposition of cementitious substances, in particular ν of mortars and concretes, characterized in that the cementitious substance with a Ic seek mixture consisting of 50 parts by mass in% of an acid amide 2-20 parts by weight in% of a readily soluble salt of a carboxylic acid, dicarboxylic acid, Oxycarboxylic acid or oxydicarboxylic acid and / or 2-20 parts by weight in% of a slightly soluble sulfate and 30-40 parts by weight in% water
is treated. 2. The method according to claim 1, characterized in that formamide is used as acid amide. 3. Process according to claims 1 and 2, characterized in that sodium acetate is used as easily soluble organic salt. 4. Process according to claims 1 to 3, characterized in that are used as sulfates alkali metal sulfates, ammonium sulfate, magnesium sulfate or aluminum sulfate.