US3577349A - Composition for destroying hardened cementitious mixtures - Google Patents

Abstract

A COMPOSITION FOR DESTROYING HARDENED CEMENTITIOUS MIXTURES COMPRISING METHYL ACETOACETATE AND WATER. A METHOD FOR DESTROYING HARDENED CEMENTITIOUS MIXTURES UTILIZING SAID COMPOSITION IS ALSO COVERED.

Description

United States Patent 3,577,349 COMPOSITION FOR DESTROYING HARDENED CEMENTITIOUS MIXTURES Robert Glenn Haines, South Charleston, W. Va., assignor to Union Carbide Corporation, New York, N.Y. No Drawing. Filed Jan. 31, 1969, Ser. No. 795,709

Int. Cl. C09d 9/00; Clld 7/05; 023g /02 US. Cl. 252-170 8 Claims ABSTRACT OF THE DISCLOSURE A composition for destroying hardened cementitious mixtures comprising methyl acetoacetate and water. A method for destroying hardened cementitious mixtures utilizingsaid composition is also covered.

This invention relates to a novel composition for destroying hardened concrete and/ or cement mortars, and to a process for the removal of hardened concrete and/0r cement mortars from various substrates. l

Concrete builds up on the bafiles and other inside surfaces of concrete ready-mix truck drums because of the inability or failure to remove all of the concrete from the ready-mix truck drums before the concrete begins to set-up. Since concrete adheres better to concrete than to smooth steel, concrete build-up in the ready-mix truck drums enhances more concrete build-up. Because of the angle of the baflles in conventional concrete ready-mix truck drums, rotation of the drum in one direction mixes the drum contents by continuously forcing the upper portion of the contents towards the back or larger closed end of the drum, whereas rotation of the drum in the opposite direction discharges the contents. Any good attempt at washing a ready-mix truck drum by rotating the drum in the mixing direction, if done before the concrete sets-up, will clean the backside of the baflles in essentially all of the back, larger closed end of the drum. However, the front side of the baffle, and front, smaller end of the drum can only be cleaned by diligent and timely use of a high pressure water spray. All ready-mix trucks have a high pressure water hose with a spray nozzle for this purpose, but when and how this water is used depends of course, on the individual operators of the truck. Depending on the slump of the concrete being hauled (low-slump concrete will form build-up in readymix truck drums faster than high-slump concrete), a poor truck operator will have one cubic yard of concrete build-up occur during a period of from 3 to 6 months. A good truck operator, i.e., one who regularly and thoroughly cleans the ready-mix drums, may not have this much build-up in more than 3 years. It must be realized, of course, that this more thorough drum cleaning does require operator time which may well result in an average of one less truck-load per day of concrete delivered. Once there is concrete build-up in the truck drum, there are various conventional ways in which ice it can be removed. Most ready-mix concrete firms use coarse aggregate and water with drum rotation and/or air hammers to remove the concrete build-up from their truck drums. Other firms, use shaped dynamite charges to destroy the concrete build-up. Either of these two latter methods, however, can cause considerable damage to the drums not to mention the danger involved with these methods. There are other problem areas in the art wherein concrete build-up presents problems. For example, concrete build-up is very detrimental to construction equipment, such as to precast forms, form clamps, mortar boxes, laboratory forms and other tools. The use of dy-namite charges and other physical means for removing this concrete build-up in construction equipment is obviously undesirable. More recently, the art has relied heavily on chemical compounds and/or compositions which can be employed as concrete dissolvers. Various organic and inorganic compounds have been found to be effective for this purpose. The inorganic compounds which are useful as concrete dissolvers generally include inorganic acids such as hydrochloric, phosphoric, hypochlorous and carbonic acid. Salts of these acids and alkalies such as sodium-hydroxide, sodium bicarbonate and ammoniumsulfate are also eifective. The organic chemicals which have been found to be effective as concrete dissolvers generally include organic acids such as oxalic, acetic, lactic, citric, tannic and humic acid as well as combinations of these acids and other organic compounds such as anhydrides or ethers of the above, the most widely used being hydrochloric or muriatic acid. Use of acids whether organic or inorganic for dissolving and/or destroying cementitious mixtures of course, present safety hazards whereas other known compounds although somewhat effective for destroying concrete, unfortunately, also destroy or reduce the desirable properties of cementitious mixtures even when present in minute, residual concentrations. It should be remembered that although a chemical compound may be effective for destroying concrete, inadvertent, residual concentrations of it should nevertheless be compatible with new batches of concrete or cementitious mixtures since there generally remain on the surface from which the concrete was removed, residual amounts of the chemical compound or dissolver. Thus there is still a need in the art for a concrete destroyer which is easy to apply, safe to use, and which possess properties which do not harmfully affect the properties of new cementitious mixtures such as compressive strength, setting time and durability.

It is therefore an object of the present invention to provide a novel composition for destroying hardened cementitious mixtures such as concrete and/or cement mortars.

Another object is to provide a process for the removal of hardened concrete and/or cement mortars from various substrates. Another object is to provide a novel composition for destroying hardened concrete inadvertently residual traces of which does not adversely alfect the properties of newly mixed concrete. These and other objects will be apparent from the following description of the invention.

As employed herein, the term cementitious mixtures is meant to include concrete, cement mortars, cinder blocks, masonary mortars, concrete lintels, concrete pipe, cementasbestos pipe, prestressed concrete and the like.

In an effort to provide a hardened cementitious destroyer such as a hardened concrete or mortar destroyer, which is easy to apply, safe to use, and residual traces of which does not affect the properties of new batches of freshly prepared cementitious mixtures I tried various compounds such as: ethylacetoacetate, alpha-chloroethylacetoacetate, ethyl levulinate, methyl levulinate, methyl pyruvate, methyl propionate and methyl chloroacetate. None of these compounds however, were found to be effective in destroying hardened cementitious mixtures with the exception of ethylacetoacetate which was found to possess a degree of effectiveness on very young concrete, i.e., 8 hour old concrete. However, ethylacetoacetate had little or no effect on older concrete, i.e., 24 hour concrete.

During the course of this experimentation, I tried methyl acetoacetate, a compound closely chemically related to the above compounds, and found surprisingly, and contrary to normal expectations that the methyl acetoacetate was extremely effective in destroying hardened concrete and this destructive ability was maintained in treating young as well as old concrete. Advantageously, it was found that in mixing new batches of concrete in equipment previously treated with methyl acetoacetate, that the new batches suffered little or no detrimental effects, and in fact there was actually an increase in the compressive strength of the new concrete which is attributed to the presence of the methyl acetoacetate or more correctly, to the reaction product of methyl acetoacetate and cement.

Broadly contemplated, the present invention provides a composition for destroying hardened cementitious mixtures which comprises methyl acetoacetate and water. More specifically, the composition for destroying hardened cementitious mixtures comprises from about 60% to 99% by Weight methyl acetoacetate, and from about 1 to 40% water. Optionally, though desirably, there can be included in the composition a penetrating aid which has been found to increase the aggressiveness of the methyl acetoacetate water solution to the hardened cementitious mixture.v

The methyl acetoacetate solution can be applied to the surface of the hardened cementitious mixture to be destroyed in any convenient manner known in the art. When the hardened cementitious mixture is present on exposed accessible surfaces such as on tools, mortar boxes, clamps, precast forms, and the like, the methyl acetoacetate water solution can be applied directly to the surface such as by pouring, spraying, dipping and the like. To reach inaccessible enclosed areas, such as the inner area of a drum of a ready-mix truck, the methyl acetoacetate solution is added to the enclosed area and the system agitated sufficiently to permit the solution to come in contact with any hardened cementitious mixture adhering to the drum including the bafiles of the drum.

The methyl acetoacetate-water solution apparently destroys the hardened cementitious mixture by reacting with the cement phase of the mixture. Application of the methyl acetoacetate to the hardened cementitious mixture produces a detectable heat of reaction and ultimately there results a low-density powder-like solid together with a yellow-orange liquid product. As a result of the reaction, the chemical composition of the cement phase is changed (a portion of the cement phase is actually solubilized) and the hardened cementitious mixture is destroyed.

The amount of methyl acetoacetate employed in the methyl acetoacetate-Water solution can be varied over a relatively wide range and depends in part, upon the age of the hardened cementitious mixture to be destroyed as well as the length of time available for destruction; Generally, in treating young hardened cementitious mixtures there can be employed as little as 25% methyl acetoacetate by weight, although higher concentrations such as 50% and 85% methyl acetoacetate by weight results in more destructive power in appreciably shorter periods of time. Merely as illustrative an 85 weight percent solution of methyl acetoacetate destroyed a 12 hour old concrete specimen (prepared with limestone coarse aggregate) in about 3 minutes, whereas 50 and 25 weight percent solution of methyl acetoacetate required 5 minutes and 40 minutes, respectively, to dissolve similar concrete specimens. Relatively similar results are achieved in treating older concrete, for example, in treating concrete which was about 17 hours old, with 85, 50 and 25 weight percent solutions of methyl acetoacetate, the time required to destroy the concrete was about 65, and 300 minutes respectively. Thus, although some water is necessary for achieving maximum effectiveness in destroying concrete, too much water i.e., substantially more than 15 weight percent water merely dilutes and so decreases the rate of concrete dissolution. Excellent results are obtained when the methyl acetoacetate in the methyl acetoacetate-water solution is in the range of about 80 to 90% preferably about by weight of the solution.

Optionally, and desirably, there can be included in the composition, a penetrating aid, which as its name indicates, serves to facilitate contact of the destroyer solution with the hardened cementitious mixture. A wide variety of penetrating aids can be employed for this purpose such as a detergent type penetrating aid of the anionic, non-ionic or cationic type.

Illustrative of the anionic type penetrating aids are the alkyl sulfates or ethoxy sulfates of secondary alcohols such as the sodium sulfate of tetradecanol; sodium sulfate of 2-methyl 7 ethyl undecanol-4 (Tergitol 4); sodium sulfate of 3,9 diethyl tridecan0l-6 (Tergitol 6) and the sodium ethoxysulfate of C to C linear, secondary alcohols (Tergitol 15-S-3S).

Illustrative of the non-ionic type penetrating aids are the ethoxylates of branched secondary alcohols such as the ethoxylate of 2,6,8-trimethyl 4 nonanol (Tergitol 15-S-3) and the 9 mol ethoxylate of C to C linear, secondary alcohols ,Tergitol 15-8-9).

Illustrative of a cationic type penetrating aid is l-hydroxyethyl-Z-heptadecenyl glyoxalidine.

The above penetrating aids may be obtained from Union Carbide Corporation under the trademark Tergitol.

The penetrating aid can be added to the composition in an amount of up to about 5 %E by weight preferably about 0.5% by weight based on the weight of the composition.

The methyl acetoacetate to hardened cementitious mixture weight ratio can also be varied over a relatively wide range as from about 0.01 to 2 parts by weight methyl acetoacetate to 1 part by weight hardened cementitious mixture preferably 0.1 to 1 part by weight methyl acetoacetate to 1 part by weight hardened cementitious mixture.

The following examples will illustrate the present invention.

EXAMPLES 1 THROUGH 30 In these examples, the effect of concrete age and methyl acetoacetate solution concentration on destruction time is illustrated. Static tests were performed on the specimen, i.e., weighed specimens were immersed in a vessel containing the methyl acetoacetate solution and the specimens were checked periodically for weight loss. In Examples 1 to 3, the concrete specimens 'were broken concrete test cylinders and in Examples 4 to 30, the concrete specimens were 2" x 2" x 2 blocks. The concrete age, concentrations, course aggregate used, and results are summarized for convenience in Table I below.

TABLE I.-STATIC" TESTS WITH METHYL ACETOACETATE/WATER SOLUTIONS THE EFFECTS OF CON- CRETE AGE AND METHYL ACETOACETATE SOLUTION CONCENTRATION ON DESTRUCTION TIME Methyl aceto- Methyl acetoacetate conc. acetate to Coarse aggregate in solution, concrete wt. used in Example Concrete age wt. percent ratio Time required to destroy concrete concrete 85 1. 1.0 hr Limestone. 85 l. 0 Do. 85 1. 0 Do. 85 1. 0 Do. 50 0. Do. 25 0.25 Do. 85 1. 0 Ohio river gravel. 50 0. 5 D0. 25 0.25 Do. 85 1. 0 Limestone. 50 l). 5 D0. 25 0. 25 Do. 85 1. 0 Ohio river gravel. 50 0. 5 D0. 25 0.25 Do. 85 1. 0 37% dissolved in 31 hrs., specimen so Do. 50 0. 5 17% dissolved in 31 hrs.; specimen s0ft Do. 25 0. 25 7% dissolved in 31 hrs.; specimen so1id Do. 85 1. 0 3 mins Limestone. 50 0. 5 5 mins Do. 25 0. 25 40 mins Do. 85 1. 0 85% dissolved in 9 hours Ohio river gravel. 50 0. 5 22% dissolved in 9 hours Do. 80 0. 25 6% dissolved in 9 hours. Do. 80 1. 0 mins Limestone. 50 0. 5 81% dissolved in 129 hours Do. 0. 25 14% dissolved in 129 hours Do. 80 1. 0 38 %dissolved in 71 hours. D0. 50 0. 5 18% dissolved in 71 hours Do. 25 0. 25 10% dissolved in 71 hours Do.

TABLE II. ROLLING TESTS WITH METHYL ACETO- EXAMPLES 31 THROUGH 48 In these examples, the effect of concrete age and methyl acetoacetate solution concentration on destruction time utilizing a rolling test procedure is illustrated. The hardened concrete was located in the interior of a baffied five gallon steel container into which was introduced the methyl acetoacetate solution. Three such baffles each measuring 2 /2 to 3 inches wide of /8 inch steel were welded at a slight angle from vertical to the side of the containers. The concrete formed on and around the baffles. In the rolling test, the chemical solution was charged to the bafiled container which contained the concrete specimen, the container lid was clamped in place (the lid had a 1-inch diameter hole in the center of it) and the container placed on a laboratory roller and rotated continuously at 20 rpm. Periodically, the rotation was stopped and the concrete specimen was examined for deterioration. These rolling tests were continued until the specimen was completely dissolved. The concrete age, concentration and results are indicated in Table II.

ACETATE/WATER SOLUTIONS IN BAFFLED, FIVE- GALLON CONTAINERS The effect of concrete age and methyl acetoacetate solution concentration on destruction time 1 Apparently not enough methyl acetoacetate present.

EXAMPLES 49 THROUGH 52 These examples demonstrate the effect of a penetrating aid for the methyl acetoacetate solution in destroying concrete. In Example 50 the penetrating aid employed was Tergitol 7, an anionic detergent (sodium heptadecyl sulfate) available from Union Carbide Corporation. In Ex ample 51, the penerating aid employed was Terg-itol TMN a non-ionic detergent (trimethyl nonanol polyethylene glycol ether) available from Union Carbide Corporation and in Example 52, the penetrating aid was Terigtol amine 220, a cationic detergent (hydroxyalkyl alkenyl glyoxalidine). For convenience the characteristics and results of.the tests are indicated in Table III.

TABLE III.STATIC TESTS: THE EFFECTS OF VARIOUS TYPES OF DETERGENTS AS PENETRATING AIDS FOR METHYL ACETOACETATE IN DESTROYING CONCRETE Concrete specimens: 2" x 2" x 2" concrete cubes. Ohio river gravel coarse aggregate Contact time Ex. Dissolver" solution 1 hour 23 hours 27 hours 49.-- Methyl acetoacetate Cube 81% of original weight. Cube 57% of original weight. Reac- Cube 54% of original weight.

tion product a heavy paste. 50"..- Methyl acetoacetate plus 0.5 wt. percent Cube 75% of original weight. Cube 17% of original weight Cube disintegrated.

TE R GITOL 7 (anionic). I 51 Methyl acetoacetate plus 0.5 wt. percent Cube 01 original weight. Cube 16% of original weight Cube 13% of original weight.

TERGITOL TMN (non-ionic). t 52 Methyl acetoacetate plus 0.5 wt. percent Cube 84% of original weight. Cube 42% of original welght Cube 41% of original weight.

TE R GITO L AMIN E 220 (cationic).

7 EXAMPLE 53 The example demonstrates the effectiveness of methyl acetoacetate and compares its effectiveness with inhibited hydrochloric acid (38 wt. percent). The hydrochloric acid was inhibited with alkyl pyridine HB. The test characteristics and results are indicated in Table IV.

85% by weight methyl acetoacetate, about 14.5% water by weight and about 0.5% penetrating aid.

3. A composition according to claim 2 wherein said hardened cementitious mixture is concrete.

4. A process for destroying hardened cementitious mixtures which comprises contacting said hardened cementitious mixture, with a composition consisting essentially of TABLE IV I Contact Weight ratio, pH of time, Chemical W aterChem1cal-Specimens mixtures hours Remarks 4. 0 Small pieces falling from specimen. 5. 0 golution ambyer colore .1 l 5. peeimen 90 of angina weig 1t. Methyl acetoacetate 25 148 148 6. 4 5 Specimen 76 72 or original weight. 7 Specimen 57% of original weight.

2(4). Notling left but paste and stones. Inhibited hydrochloric acid (36 wt. percent) 2. 210 790 300 {8 25251323 ZZZ; 33351333153;- (10% H01) 1. O 21 Specimen 81% of original weight.

As will be evident and from the above examples a methyl acetoacetate in an amount of about 60-99% by water solution of methyl acetoacetate is extremely effective as a concrete destroyer and the most effective concentration is an 85/15 weight percent methyl acetoacetate water solution. The elfectiveness is even more pronounced when a penetrating aid is added to the solution. Although, a water solution of methyl acetoacetate is somewhat corrosive, corrosion tests on mild steel indicated that metal lost due to corrosion from the use of methyl acetoacetate to dissolve the concrete build-up that occurs in ready-mix concrete truck drums is not a significant factor in the useful life of the drums. This is because the reaction product of methyl acetoacetate, water and concrete is less corrosive to mild steel than water solutions of methyl acetoacetate. Moreover, no permanent detrimental effects were obtained in 24 hour immersion (immersion in eighty-five weight percent methyl acetoacetate-water solutions) tests on neoprene, black rubber, black gum rubber, rubber latex, polyethylene or tygon tubing. Thus, the methyl acetoacetate solution can be employed with tools or equipment fabricated from these materials.

What is claimed is:

1. A composition for destroying hardened cementitious mixtures consisting of methyl acetoacetate in an amount of about 60-99% by weight, water in an amount of about 140% by weight and a penetrating aid selected from the group consisting of anionic, nonionic or cationic detergents in an amount of about 0.5-5% by Weight.

2. A composition according to claim 1 containing about weight and water in an amount of about 140% by weight for a time sufiicient to destroy said hardened cementitious mixture.

5. A process according to claim 4 wherein said composition is employed in an amount of about 0.1 to 1% by weight based on the weight of the hardened cementitious mixture.

6. A process according to claim 4 wherein said composition also includes a penetrating aid selected from the group consisting of anionic, nonionic or cationic detergents.

7. A process according to claim 6 wherein said methyl acetoacetate, said water and said penetrating aid are employed in an amount of about 14.5% and 0.5% by weight respectively.

8. A process according to claim 7 wherein said hardened cementitious mixture is concrete.

References Cited Rose: The Condensed Chem. Dict. 6th Ed., Reinhold Publ. cd, 1961, p. 729.

LEON D. ROSDOL, Primary. Examiner W. E. SCHULZ, Assistant Examiner US. Cl. X.R.

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