CS249039B1 - Aerating additive for concrete and mortar with cement bonding - Google Patents

Abstract

Air-entraining admixture for concretes and mortars with cement binder, composed by weight of 10 to 85 parts of sodium allylbenzene sulfonate, 10 to 85 parts of sodium salt of ethoxylated fatty alcohol and 5 to 80 parts of the condensation product of sodium linginsulfonate with monomethylolphenol, increases the workability of the concrete mixture and the frost resistance of hardened concrete. Aeration of concrete to a value of 4 to 2% by volume with this admixture causes a smaller decrease in the strength of hardened concrete compared to the use of existing admixtures.

Description

The subject of the invention is an air-entraining admixture for concretes and mortars with a cement binder.

The currently known additives for aerating concrete mixtures and mortars can be divided into two groups. The first group includes organic substances that create foams, such as soaps, fats, saponified resins, commercial detergents, etc. The second group includes mainly aluminum dust, which releases hydrogen when reacting with calcium hydroxide.

To increase the frost resistance of concrete and increase the heat resistance of mortars, only additives of the first group, surface-active additives, are considered. To increase the useful properties, mixtures of surface-active additives are chosen, for example a combination of sodium lignin sulfonate and sodium abietan, or a mixture of distillation residues of synthetic fatty acids, sulfite stills, borax and animal glue, as described in the USSR copyright certificate No. 694 468, or a mixture of distillation residues of synthetic fatty acids, sulfite stills, an inorganic salt such as sodium nitrate, calcium nitrate, calcium nitrite, as described in the USSR copyright certificate No. 694 469, or distillation pitches from benzene rectification, sulfite stills and potassium carbonate, which is described in the USSR copyright certificate No. 761 437.

The use of mixtures of sodium lignin sulfonate and sodium abietan is associated with problems arising from the instability of the additive solution, prone to precipitation of the abietan portion. The mixture is also very sensitive to calcium ions, which leads to the formation of inactive, water-insoluble calcium abietan. The use of distillation residues of fatty acids and distillation pitches is associated with the risk of uneven quality of the resulting additive, which must be precisely dosed into concrete mixtures and mortars to prevent excessive aeration and thus a decrease in the strength of hardened concrete and mortars.

249,039

It has been found that these disadvantages are significantly reduced in the additive according to the invention, the active ingredient of which is formed from 10 to 85 parts by weight of sodium alkylbenzene sulfonate containing 1 to 10 carbon atoms in the alkyl chain, 10 to 85 parts by weight of the sodium salt of a sulfonated ethoxylated fatty alcohol with 12 to 25 carbon atoms in the alkyl chain with a number of 5 to 25 ethoxyl units, 5 to 80 parts by weight of the condensation product of 50 to 99 parts by weight of sodium lignin sulfonate with 1 to 50 parts by weight of monomethylolphenol.

When using this additive, air is absorbed into the concrete mixture during the mixing process and foam is formed by the effect of the air-entraining additive. The walls of the foam bubbles are made of water with a monomolecular layer of additive molecules, firmly bound by their hydrophilic ends to water. The walls of the bubbles have sufficient cohesion so that they do not rupture during deformations of the bubbles due to sedimentation and compaction processes and to withstand the pressure of the enclosed air when heated by the heat of hydration.

In addition to aerating the concrete mix, which increases the frost resistance of hardened concrete, the additive has a positive effect on the workability of the mix. When used to aerate the concrete mix at 4 to 5% by volume, it does not affect the cement setting process. Compared to existing additives, it causes a smaller decrease in the strength of hardened concrete with the same aeration.

From the following example of the action of an aqueous solution of sodium abietane of 4% by weight dry matter and a 4% by weight aqueous solution of a mixture of 60 parts by weight of sodium alkylbenzenesulfonate with three carbon atoms in the alkyl and 30 parts by weight of the sodium salt of a fatty alcohol sulfonated and ethoxylated with twenty ethoxylate units with twelve carbons in the alkyl chain with 10 parts by weight of the condensation product of 95 parts by weight of sodium ligninsulfonate with 5 parts by weight of monomethylolphenol

- 3,249,039 shows a higher effect of the additive of the invention on the properties of concrete samples prepared from 900 kg of aggregates of fraction 0-4 mm, 360 kg of fine aggregates of fraction ^8 mm and 540 kg of aggregates of fraction $«£16 mm, 340 kg of slag Portland cement and 183 liters of water.

Type and dosage of the ingredient Liquefaction cm Aeration % Compressive strength after 28 days MPa Sodium abietane 8 4.5 20.9 0.22 liters Ingredient according to the invention 13 4.5 23.8

This effect has been verified on multiple mixtures of cement, water and aggregate.

The aerating additive of the invention can also be successfully used in the production of aerated expanded clay concrete precast products.

Claims (1)

Aerating agent for concrete and mortar with cement binder, characterized in that it consists of 10 to 85 parts by weight of sodium alkylbenzenesulfonate containing 1 to 10 carbon atoms in the alkyl chain 10 to 85 parts by weight of a sodium salt of a sulfonated ethoxylated fatty alcohol having from 12 to 25 carbon atoms in the alkyl chain of 5 to 25 ethoxy units, 5 to 80 parts by weight of the condensation product 50 to 99 parts by weight of sodium ligninsulfonate with 1 to 50 parts by weight of monomethylolphenol.