WO2015027192A2

WO2015027192A2 - Shrinkage reducing admixture for concrete

Info

Publication number: WO2015027192A2
Application number: PCT/US2014/052358
Authority: WO
Inventors: Joseph J. Biernacki; Donald P. VISCO; Hamed M. KAYELLO
Original assignee: University of Akron; Tennessee Technological University
Current assignee: University of Akron; Tennessee Technological University
Priority date: 2013-08-22
Filing date: 2014-08-22
Publication date: 2015-02-26
Anticipated expiration: 2016-02-22
Also published as: WO2015027192A3

Abstract

A cement admixture with a low molecular weight alkylamine compound or oxyalkylamine compound for which either autogenous shrinkage or drying shrinking reducing activity is demonstrated. The admixture includes one or more of (A) 2-Butylaminoethanol, (B) Butylmethylamine, (C) Diethylmethylamine, (D) 3-Ethoxypropylamine, or (E) 3-Propoxypropylamine. The admixture may be dissolved in water prior to mixing with cement.

Description

SHRINKAGE REDUCING ADMIXTURE FOR CONCRETE

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. Provisional Application No. 61 /868,918, filed August 22, 2013, and is entitled to that filing date for priority. The specification, figures and complete disclosure of U.S. Provisional Application No. 61/868,918 are incorporated herein by specific reference for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

This invention was made with the support of the United States government under IMSF Grant No. CMMI-0928539. The Government has certain rights in this invention.

FIELD OF THE INVENTION

This invention relates to a cement admixture for reducing shrinkage. More particularly, this invention relates to a cement admixture capable of reducing autogenous or drying shrinkage comprising an alkylamine or oxyalkylamine compound.

BACKGROUND OF THE INVENTION

The use of certain additives to reduce shrinkage of cement is known in the art. Shrinkage of concrete involves multiple related mechanisms. For example, as cement phases hydrate, the products occupy less space than the reactants. Shrinkage can also be induced by capillary stresses with the partially dehydrated pore structure of the hardened concrete. This condition can develop as the result of either drying (i.e., the evaporation of free water), or the consumption of water within the pores under sealed conditions (i.e., autogenous dehydration). Capillary stresses induced under these conditions decrease with decreasing surface tension of the pore solution, as does the water evaporation rate. Similarly, select chemical compounds that reduce the surface tension of the pore solution have been used to reduce both autogenous and drying shrinkage.

For example, U.S. Patent No. 4,547,223 discloses linear oxyalkylenes proven to reduce shrinkage of cement. The general formula for such is RO(AO)nH, where R is a C1 -7 alkyl or C5-6 cycloalkyl radical, A represents one or more C2-3 alkylene radicals, and n has a value of 1 - 10. A typical structure would be CH30(H2C-CH20)3H, but may include more repeating units and a cyclic end group.

Similarly, U.S. Patent No. 5,326,397 discloses amides of the form shown in Figure 1 , where R is a C3-C8 alkyl group or C5-C6 cycloalkyl group when n is 1 or a C2-C 10 alkylene or an oxyalkylene group when n is 22. U.S. Patent No. 5,622,558 discloses diols shown in Figure 2 as shrinking reducing admixtures in combination with fumed silica, where R groups are hydrogen or C1-C2 alkyl groups, and n is a 1 or 2 integer. U.S. Patent No. 5,679, 150 discloses that betaine structures are suggested as an addition to oxyalkylene scaffolds, see Figure 3, where R are alkyl groups, x is 1 to 5, and M is a metal cation or ammonium. U.S. Patent Nos. 5,556,460 and 5,603,760 disclose the use of some glycol ethers (low molecular weight oxyalkylene compounds) as shrinking reducing admixture molecules. These patents give more specific structures, elaborating on the above mentioned RO(AO)nH backbone, including triols, C5-C6 sugar alcohols, amines, oxyalkylene glycols, and a structure for preferred polyols, refer to Figure 4, where R' groups are C1 -C 14 alkyl groups, A is a C2-C4 alkylene group, and x, y, z are integers 0- 10. This patent includes a large variety of structures that contribute to reducing drying shrinkage, but the overall claim is for what structures are needed in a mixture in order to reduce shrinkage.

U.S. Patent Nos. 4,547,223; 5.326,397; 5,556,460; 5,603,760; 5,622,558; and 5,679, 150 are incorporated herein in their entireties by specific reference for all purposes.

Amines and long chain fatty acids, separately or in combination, however, have not been proposed as shrinking reducing admixture active compounds on their own. Some amines, however, are known to accelerate and even enhance strength development, as disclosed in Ramachandran, V. S. Concrete admixtures handbook: Properties, science, and technology, 2nd edition, Noyes Publications, 1995; Myers, D. and Gartner, E. Influence of tertiary alkanolamines on portland cement hydration, J. Am. Ceram. Soc, 76 (6), 1993, 1521-1530; Dodson, V. H., Strength enhancing admixture for concrete compositions, U.S. Patent No. 4,318,744, March 9, 1982; and Jenknavorian, A., et al., Nitrogenous strength enhancers for Portland cement, U.S. Patent No. 5,641 ,352, Jun 24, 1997, whereas glycol ethers typically retard set and, hence, strength development (all of which are incorporated here in their entireties by specific reference for all purposes). SUMMARY OF INVENTION

In various exemplary embodiments, the present invention comprises compounds of the alkylamine and oxyalkylamine family for which either autogenous (closed system) or drying (open system) shrinkage reducing activity is demonstrated in portland cement concrete.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 depicts the formula structure for an amide compound where R is a C3-C8 alkyl group or C5-C6 cycloalkyl group when n is 1 or a C2-C10 alkylene or an oxyalkylene group when n is 22.

Figure 2 depicts the formula structure of a diol compound where R groups are hydrogen or C1 -C2 alkyl groups, and n is a 1 or 2 integer.

Figure 3 depicts the formula structure of a betaine compound where R are alkyl groups, x is 1 to 5, and M is a metal cation or ammonium.

Figure 4 depicts the formula structure of polyols where R' groups are C1 -C14 alkyl groups, A is a C2-C4 alkylene group, and x, y, z are integers 0- 10.

Figure 5 illustrates data results characterizing autogenous drying shrinkage of the compounds.

Figure 6 illustrates the data results characterizing evaporative drying shrinkage of the compounds of Fig. 5.

Figure 7 illustrates the hydration calorimetric behavior for the compounds of Figures 5 and 6.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In several embodiments, the present inventions comprises one or more organic chemicals, typically from the family of non-ionic surfactants, more specifically the alkylamine and oxyalkylamine family, that when added to portland cement concrete unexpectedly reduce the surface tension of the pore solution (i.e., water remaining in the porosity of hydrating or hydrated cement), and thus inhibit shrinkage under autogenous (sealed) or evaporative drying conditions. Such chemicals function by disrupting the hydrogen bonding network at the surface of water, thereby reducing the surface tension.

The admixture disclosed herein comprises one or more of the following compounds, which have stronger surface tension reducing activity, along with better drying shrinkage reducing activity:

(A) 2-Butylaminoethanol

(B) Butylmethylamine

(C) Diethylmethylamine

(D) 3-Ethoxypropylamine

(E) 3-Propoxypropylamine

The chemical formula of the alkanolamine structure is

wherein R represents a hydrogen atom, C_1-10 alkyl group (linear or branched), an alkanol group such as methanol, ethanol, propanol, or butanol, etc., or a hydroxyl group (OH); n represents an integer from 1 to 4. Preferably, n is 3. The preferred compound of this structural formula is 2- butylaminoethanol.

The chemical formula of the disclosed amine structure is

wherein each R represents hydrogen atom or C_1-10 alkyl group (linear or branched); R' represents a hydrogen atom or a C_1-10 alkyl group (linear or branched); R and R' independently represent a hydrogen atom or alkyl chains that consist of 1 or more carbon atoms (e.g., methyl, ethyl, propyl, butyl, pentyl, etc.); and n represents an integer from 1 to 4. This formula suggests either a secondary or tertiary amine. For example, two preferred compounds of this structure are N- butylmethylamine and N,N-diethylmethylamine.

The chemical formula of the disclosed ether amine structure is

wherein each R represents hydrogen atom or C _1-10 alkyl group (linear or branched); R' represents a hydrogen atom or a C_1-10 alkyl group (linear or branched, e.g., methyl, ethyl, propyl, butyl, pentyl, etc.); and n represents an integer from 1 to 7. For example, two preferred compounds of this structural formula are 3-ethoxypropylamine (R is an ethyl group and n is 3) and 3- propoxypropylamine (R is a propyl group and n is 3).

The above compounds, individually or in combination, serve as a chemical admixture to cement. In several exemplary embodiments, the admixture is used with ordinary Portland Type I/II cements. Table 1 below provides details of the composition and physical properties of a typical cement of this type, although the compounds can be used with other cement compositions and types.

The above compounds can be used as an admixture with cement in place of commercial admixture compounds currently in use. One exemplary method of use is preparing cement paste by adding 0.35 parts water for one part of cement by weight, and then mixing. Mixing can be accomplished by normal means known in the art, such as mixing on the appropriate speed of a commercial stand mixer (typically equipped with a mixing hoop) for an appropriate period of time (e.g., 4 minutes). The chemical compound admixture is dissolved in the water prior to being mixed with the cement.

The shrinkage reducing admixture activity of these compounds has been experimentally demonstrated. The shrinkage of cement paste samples using these compounds were observed compared to control samples (i.e., with and without commercial additives) in both autogenous (closed) and open (controlled relative humidity drying) environments. Protocols for these experiments follows can be found in ASTM C I 698-09 Standard test method for autogenous strain of cement paste and mortar, Book of Standards Vol. 04.02, and ASTM C596-09 Standard test method for drying shrinkage of mortar containing hydraulic cement, Book of Standard Vol. 04.01 . Additional information about the identification and testing of the admixtures also is disclosed in the following documents, which are contained in the Appendix hereto, and are incorporated herein in their entireties by specific reference for all purposes:

Kayello, et al., "An Application of Computer- Aided Molecular Design (CAMD) Using the Signature Molecular Descriptor— Part 1. Identification of Surface Tension Reducing Agents and the Search for Shrinkage Reducing Admixtures," J. Am. Ceram. Soc. 97(2): 365-77 (2014).

Shlonimskaya, et al., "An Application of Computer-Aided Molecular Design (CAMD) Using the Signature Molecular Descriptor— Part 2. Evaluating Newly Identified Surface Tension- Reducing Substances for Potential Use as Shrinkage-Reducing Admixtures," J. Am. Ceram. Soc. 97(2): 378-85 (2014).

Referring now to Figure 5, autogenous shrinkage data is illustrated for the five compounds listed above, one commercial shrinkage reducing admixture, and a control that contained no admixture. Lines are averages of at least two experiments. Notably, all five compounds perform as well as the best commercial shrinkage reducing admixture tested.

Compound (D), 3-ethoxypropylamine, is a low molecular weight alkylamine that exhibits autogenous shrinkage reducing activity virtually identical to the higher molecular weight commercial polyoxyalkylene alkyl ether. Shrinkage reducing activity for 3-ethoxypropylamine or similar compounds has not been previously reported. Compound (D), 3-ethoxypropylamine, and Compound (E), 3 -propoxy propylamine, are compounds that combine functional groups found only in individual training set compounds, and thus are "hybrids." They are low molecular weight substances for which autogenous shrinkage reducing activity has not before been reported, and which have similar behavior to that of 2-propoxyethanol (a training set compound), including minimal expansion and good autogenous shrinkage reducing activity.

Characterization of evaporative drying shrinkage is illustrated in Figure 6 for the five compounds, the control, and another commercial shrinking reducing admixture. All five compounds perform well, with Compound (A), 2-Butylaminoethanol, and Compound (E). 3- Propoxypropylamine, performing as well or better than the best commercial compound tested.

Figure 7 illustrates the hydration calorimetric behavior for the same set of compounds. All of the shrinkage reducing admixture compounds retard hydration slightly pre-set. And, whereas the commercial shrinkage reducing admixtures retard hydration by as much as 90% post-set, four of the five developed compounds do not appear to retard, inclusive of diethylmethylamine.

Additional information may be found in the following references, both incorporated in their entirety by reference:

(1) KAYELLO, et al. "An application of Computer-Aided Molecular Design (CAMD) Using the Signature Molecular Descriptor-Part 1 . Identification of Surface Tension Reducing Agents and the Search for Shrinkage Reducing Admixtures" , J. Am. Ceram. Soc, 97 (2), pp. 365-377 (2014); and

(2) SHLONIMSKAYA, et al. " An Application of Computer-Aided Molecular Design (CAMD) Using the Signature Molecular Descriptor —Part 2. Evaluating Newly Identified Surface Tension-Reducing Substances for Potential Use and Shrinkage- Reducing Admixtures" J. Am. Ceram. Soc. 97(2) pp 378-385 (2014).

Thus, it should be understood that the embodiments and examples described herein have been chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited for particular uses contemplated. Even though specific embodiments of this invention have been described, they are not to be taken as exhaustive. There are several variations that will be apparent to those skilled in the art.

Claims

CLAIMS What is claimed is:

1. A cement admixture capable of reducing autogenous and/or drying shrinkage, comprising at least one alkylamine compound.

2. The cement admixture of claim 1 , wherein the alkyl group is butylmethyl.

3. The cement admixture of claim 1 , wherein the alkyl group is diethylmethyl.

4. The cement admixture of claim 1 wherein the compound is of the formula

wherein each R represents hydrogen atom or C_1-10 alkyl group (linear or branched); R' represents a hydrogen atom or a C_1-10 alkyl group (linear or branched); R and R' independently represent a hydrogen atom or alkyl chains that consist of 1 or more carbon atoms (e.g., methyl, ethyl, propyl, butyl, pentyl); and n represents an integer from 1 to 4.

5. A cement admixture capable of reducing autogenous and/or drying shrinkage, comprising at least one oxyalkylamine or alkanolamine compound.

6. The cement admixture of claim 5, wherein the compound is 2-butylaminoethanol.

7. The cement admixture of claim 5, wherein the compound is 3-ethoxypropylamine.

8. The cement admixture of claim 5. wherein the compound is 3-propoxypropylamine.

9. The cement admixture of claim 5, wherein the compound is of the formula

wherein each R represents a hydrogen atom or C_1-10 alkyl group (linear or branched); R' represents a hydrogen atom or a C_1-10 alkyl group (linear or branched, e.g., methyl, ethyl, propyl, butyl, pentyl); and n represents an integer from 1 to 7.

10. The cement admixture of claim 5, wherein the compound is of the formula

wherein R represents a hydrogen atom, C_1-10 alkyl group (linear or branched), an alkanol group such as methanol, ethanol, propanol, or butanol, or a hydroxyl group (OH); and n represents an integer from 1 to 4.