ESTER-BASED CONCRETE SURFACE RETARDERS
Compositions and methods of the invention for retarding the surface of a concrete or other hydratable cementitious composition involve the use of at least one alkyl-ester-of-hydroxycarboxy compound contained in the form of particles or as a discontinuous phase distributed within a continuous non-aqueous carrier phase that is spray-applicable in liquid form. The set retarder helps to achieve lower pH and to avoid irritating fogs during spray application of the surface retarder when compared to prior art acid-containing surface retarders.
1 . A method for retarding the surface of a concrete or other hydratable cementitious material, comprising spray-applying a surface-retarder composition onto a surface of a concrete or mortar or other hydratable cementitious material so as to retard the curing thereof or otherwise onto a surface of a mold into which a concrete or mortar or other hydratable cementitious material is placed; and subsequently removing a portion of the surface of said cementitious material on which said surface-retarder composition has been applied by spraying a jet of water to remove the retarded portion of the surface material or otherwise removing said cementitious material from said mold surface; said surface-retarder composition comprising at least one oil/solvent-soluble or oil-dispersible alkyl-ester-of-hydroxycarboxy compound contained in the form of particles or as a discontinuous liquid phase distributed within a continuous non-aqueous carrier phase which is spray-applicable in liquid form.
2 . The method of claim 1 wherein said at least one oil/solvent-soluble or oil-dispersible alkyl-ester-of-hydroxycarboxy compound is selected from the group of alkyl-ester having an alpha-hydroxycarbonyl group and or alkyl-ester of a hydroxycarboxylic acid, or mixture thereof.
3 . The method of claim 1 wherein said at least one oil/solvent-soluble or oil-dispersible alkyl-ester-of-hydroxycarboxy compound comprises an alkyl ester of citric acid, an alkyl ester of tartaric acid, an alkyl ester of malic acid, an alkyl ester of gallic acid, an alkyl ester of glycolic acid, an alkyl ester of gluconic acid, an alkyl ester of lactic acid, an alkyl ester of mandelic acid, an alkyl ester of salicylic acid, or an alkyl ester of 4-hydroxybutanoic acid.
4 . The method of claim 1 wherein at least one oil/solvent-soluble or oil-dispersible alkyl-ester-of-hydroxycarboxy compound is an alkyl ester of citric acid.
5 . The method of claim 4 wherein said alkyl ester of citric acid is triethyl citrate.
6 . The method of claim 1 wherein said at least one oil/solvent-soluble or oil-dispersible alkyl-ester-of-hydroxycarboxy compound is an alkyl ester of tartaric acid.
7 . The method of claim 6 wherein said alkyl ester of tartaric acid is diethyl tartarate.
8 . The method of claim 1 wherein said at least one alkyl-ester-of-hydroxycarboxy compound is a mixture of triethyl citrate and diethyl tartarate.
9 . The method of claim 1 further comprising: (A) at least one filler selected comprising calcium carbonate, silicon dioxide, sand, mica, talc, clay, barium sulfate, sodium silico-aluminate, alumina, barium carbonate, dolomite, magnesium carbonate, magnesium oxide, kieselghur (diatomaceous earth), or a mixture thereof; (B) at least one additive selected from the group consisting of a pigment, a colorant, or a dye comprising titanium dioxide, iron oxide, chromium oxide, cobalt oxide, zinc oxide, carbon black, or mixture thereof.
10 . The method of claim 1 wherein said continuous non-aqueous carrier phase comprises a petroleum-based solvent, a vegetable oil, an animal oil, a mineral oil, or mixture or derivative of the foregoing.
11 . The method of claim 10 wherein said at least one alkyl-ester-of-hydroxycarboxy compound comprises diethyl tartarate, triethyl citrate, or a mixture thereof contained in a solid particle form that is dispersed in a vegetable oil.
12 . The method of claim 11 wherein said vegetable oil is rapeseed oil; and said composition further comprises titanium dioxide.
13 . The method of claim 1 further comprising a conventional set retarder.
14 . The method of claim 1 wherein said surface-retarder composition is spray-applied onto a surface of a concrete, mortar, or other hydratable cementitious composition and a portion of said surface is removed by spraying water.