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Cement admixture for improved slump life

Inactive Publication Date: 2002-01-17
SIKA SCHWEIZ AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The improvement of workability can also be attained by use of more water but this influences negatively the properties of the cementitious composition in the hardened state e.g. the tensile and compressive strengths, resistance to frost, resistance to deicing salts, waterproofness, resistance to abrasion and chemical durability.
These polymers suffer from the problem of drastic loss of fluidity of the cementitious composition, with time.
This loss of workability is a big problem for applications where the cementitious composition like concrete, has to be transported over longer distances.
But maleic acid copolymers are known to suffer from the problem of strong retardation of the hardening of the cementitious composition.
But if this water reduction of more than 20% is realised, the composition suffers from slump-loss e.g. loss of fluidity with time.
Furthermore side chains which are connected to the backbone by amide or imide linkages are not considered as cleavable in the idea of this patent.

Method used

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  • Cement admixture for improved slump life
  • Cement admixture for improved slump life
  • Cement admixture for improved slump life

Examples

Experimental program
Comparison scheme
Effect test

example 1--

for Producing Polymer E1

[0080] A one liter reactor, equipped with a mechanical stirrer, a dropping funnel, a reflux condenser, a thermometer and two inlet tubes was charged with 308 g deionized water.

[0081] A monomer solution was prepared of 32.4 g acrylic acid, 57 g of a methoxy polyethyleneglycol acrylate with 11 units of ethyleneglycol, 160 g of a polyethyleneglycol methacrylate with 23 units of ethyleneglycol and 110 ml deionized water and filled in the dropping funnel.

[0082] A solution A was prepared of 10.8 g sodium persulfate in 40 g deionized water. A solution B was prepared of 8.0 g sodium disulfit in 40 g deionized water.

[0083] The reactor was heated and at a temperature of the water of 80.degree. C. the monomer solution was added from the dropping funnel and the solutions A and B were added separately with a tube-pump within 4 hours at 80.degree. C.

[0084] After the addtions the mixture was stirred at 80.degree. C. until the peroxide test was negative. After cooling to roo...

example 2-5--

for Producing Polymer E2-E5

[0085] The polymers are produced in the same manner as described in example 1. The monomers used and their dosages in grams are listed in table 1.

example 6--

for Producing Polymer E6

[0094] 160 g of a 50% aqueous solution of a 4000 molecular weight poly(acrylic acid) and 7.5 g 50 wt. % sulfuric acid were placed in a glass reactor fitted with a thermometer, a stirrer, a gas inlet tube and a distillation assembly. The solution was heated to 70.degree. C. and 140 g of a 350 number average molecular weight polyethyleneglycol-monomethyle-ther and 200 g of a 2000 number average molecular weight .alpha.-amino-polyethylene -glycol-.omega.-methylether were added.

[0095] The mixture was heated up under a steady stream of nitrogen and kept at 165.degree. C. After 6 h stirring at 165.degree. C. the mixture was cooled down. At 90.degree. C. 630 g water were added.

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Abstract

Described are polymers and cement admixtures which reduce drop in fluidity with time. Said admixture comprises at least one polymer of the present invention and at least one polymer A. The polymer of the present invention comprises side chains of which at least 10 weight-% can be cleaved in alkaline medium. The polymer of the present invention is an acrylic polymer which comprises side chains connected to the backbone by ester linkages. These side chains may be alkyl, hydroxy alkyl, cycloalkyl or polyoxyalkylene groups. Polymer A is a cement dispersing agent. The combination of polymer A with the polymer of the present invention in a weight ratio of 0.1:10-10:1, and preferably 1:10-10:1 reduces the drop in fluidity with time of cementitious compositions.

Description

[0001] This application claims the priority of European patent application 00 105 910.4, filed Mar. 22, 2000, the disclosure of which is incorporated herein by reference in its entirety.BACKGROUND OR THE INVENTION[0002] The present invention relates to an admixture for cementitious compositions which reduces the drop in fluidity with time.[0003] High range water reducing admixtures, also known as superplasticisers, for cementitous compositions such as cement pastes, mortars or concretes, are quite well known and used already since the late 1960's. They improve the workability of the composition and allow a reduction of the water to cement ratio. The improvement of workability can also be attained by use of more water but this influences negatively the properties of the cementitious composition in the hardened state e.g. the tensile and compressive strengths, resistance to frost, resistance to deicing salts, waterproofness, resistance to abrasion and chemical durability. Examples for...

Claims

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Application Information

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IPC IPC(8): C04B24/22C04B24/26C04B24/30C04B24/32C04B28/02C08F220/04C08F220/12
CPCC04B24/2641C04B24/2647C04B24/2652C04B24/2658C04B24/2688C04B24/2694C04B24/32C04B28/02C04B2103/308C08F220/04C08F220/12C08L33/06C08L35/00C08L71/02C04B2103/408C04B24/18C04B40/0028C04B24/223C04B24/226C08L2666/22
Inventor SCHOBER, IRENEBURGE, THEODOR A.VELTEN, ULFWIDMER, JURGBURGE, CHRISTIAN M.MADER, URS
Owner SIKA SCHWEIZ AG