CS232092B1 - Additive to accelerate setting and hardening of cementitious mixtures - Google Patents

Abstract

The invention deals with an additive for accelerating the solidification and hardening of a mixture of cements based on Portland cement. Its essence is that it consists, stated in parts by weight, of 20 to 100 parts of alumina cement, 10 to 50 parts of ground lime and/or lime hydrate, and 10 to 100 parts of normal and/or alkaline bicarbonate. The addition of the stage of the invention enables the dosage of aluminate cement and alkaline carbonate to be reduced, which has a beneficial effect on improving the stability of the result of the physicomechanical properties of both hardened and cement mixtures. The additive according to the invention can be used wherever it is required to accelerate the hardening and hardening of cement mixtures, for example, applied by dry shotcrete technology, as well as in the production of dry prefabricated plaster mixtures, in the repair and restoration of damaged parts of concrete structures and the like.

Description

The present invention relates to an additive for accelerating the setting and hardening of cementitious compositions.

A cement mixture is known from English Patent 1237373 containing 60% -80% by weight of Portland cement 20% 40% clay cement and 0.2% 1.2% alkali carbonate having accelerated solidification and strength increase. However, the doses of clay cement required to achieve a sufficiently rapid increase in strength are too high, which is uneconomical due to the higher cost of clay cement compared to Portland cement. In addition, increasing the ratio of clay cement to Portland creates a risk of metastatic calcium aluminate hydrates, which may be manifested by undesirable deterioration of the long-term physico-mechanical properties of hardened cementitious slurries, mortars and concretes, in particular by decreasing strength and modulus of elasticity. 1 253 773 are suitable only for spit repair of surfaces of natural or artificial karaoke or concrete, minor repairs etc., but not for concrete elements or constructions where gradual deterioration of physico-mechanical properties is unacceptable.

Some reduction in the dosage of the alumina cement allows the alkali carbonate to alumina cement ratio to be increased to higher levels than those disclosed in the cited English patent, e.g. However, increasing the alkali carbonate dosage also results in a decrease in 28 day and long term strengths.

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These disadvantages are overcome by an additive for accelerating the setting and hardening of the cementitious mixtures according to the invention. Its essence in

is that it contains, by weight, 20100 parts of aluminous cement, 10 50 parts of ground lime and / or lime hydrate, and 10 to 100 parts of normal and / or acidic alkaline carbonate.

The additive according to the invention can be used in cement-containing cement mixtures based on clinker of Portland cement, e.g. Portland, troscortland or pozzolan Portland cement, and optionally filler and / or water

The additive according to the invention makes it possible to reduce the dosage of aluminous cement and alkali carbonates at the same or higher efficiency to shorten the setting times and increase the initial strengths of the cementitious mixtures.

The advantages of the additive according to the invention are illustrated by the following examples:

Implementation example no. 1

From Portland cement class PC 400 and with the additions of aluminous cement, lime hydrate and calcined sodium carbonate NagCO 2, cement slurries were made with a water coefficient = 0.3, from which test specimens of a 2 cm feline cat were made. After 3 pm Curing at 20 ° C was tested for their compressive strength. The composition and dosages of the ingredients as well as the strengths achieved are shown in the following Table. First

Move. No. 1,232,092

additive Compressive strength (MPa) after 4 hours at 20 ° C 1% Na2 CO3 4% aluminous cement 1.3 2% Na ₂ CO ₃ 3% aluminous cement 0.8 Additive according to the invention: 2% Na 2 O 4 3% aluminous cement 2% lime hydrate 1.7

From the comparison of the strengths shown in Tab. 1, it can be seen that the highest initial strengths were achieved with the additive slurry according to the invention.

Implementation example no. 2

Cement slurries with v / c = 0.3 were made from class 325 troscortland cement, aluminous cement, kaleinized sodium carbonate and lime hydrate.

The cementitious slurry was tested for start and setting time using a vicatile needle. Test specimens were also made of cement mashes - 2 cm feline cats, which cured in humid air (about 20 ° C, above 90% relative humidity).

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Strength in MPa after hours M- OJ OJ VO H 15.5 • t R-1 15.8 16.0 19.5 OJ * ABOUT OJ • m- 1 1 H Φ • p TO > ra 3 ra Φ 'Φ «A M- VO * ABOUT Λ i-1 Φ • P TO > TO '3 Λ! TO φ 'Φ fl PS A φ -P TO > 01 3 TO PS 'í ti PS ir \ c- about  * • φ VO · » ABOUT 1 Setting in minutes TO about about OJ • 3 · VO OJ ABOUT • 4 · OJ what about OJ cn vo · CM VO CM about • p TO • H > About TO N c- tn OJ and OJ and irs ΓΛ tn tn M · Additives and their doses N Φ -O a) > ra á TO • H CD -with th <th £ 05 O TO A M O ft Ρ » about Xi ΠΛ 'Φ o> o § / TO £ 5 • P • H <—1 TO rt φ • Φ 6 Φ m o With 2% aluminate cement and 2% lime hydrate With 3% aluminate cement and 1.5% lime hydrate * ' t pt P -P O 'TO ABOUT í§ j? o o § * © • P _ ΟΛ PJ H 3 O Pl pS-p o φ • H Pi OJ Λ r- <Φ TO 'TO Λ 6 i> OJ OJ OJ pt 4 »i PJ Φ B P < P -P O OJ o á <s & i> 8 á TO 'Φ • p m fi • HO S PiO Φ • H OJ ft H TO 'TO Xj {25 t> ^ tn * CM About CM P Pl Φ B Pt P -P O 'TO O 0 xs £ »Φ xs R S 2 PS (* \ XL TO O 'Φ • AFTER FRI pJ ο ^ φ • H ft iH OJ xm s * m O m nzeipuÁA. ejpod nopasjjd g

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From the results shown in Table 2, it can be seen that by combining aluminous cement, sodium carbonate and lime hydrate, higher calculated strengths can be achieved than by combining aluminous cement with sodium carbonate alone, or by combining aluminous cement with lime hydrate. In this case, it is possible to substantially reduce the doses of aluminous cement and sodium carbonate, while maintaining the requirement to accelerate the setting and hardening of the cement.

The additive according to the invention is suitable wherever it is desired to accelerate the setting and hardening of cement mixtures, e.g. in dry spray application of cementitious mixtures, in the manufacture of dry prefabricated mixtures which require rapid solidification and hardening, in the repair of defects and damage to concrete parts and structures, and the like.

Claims (1)

OBJECT OF THE INVENTION An additive for accelerating the setting and hardening of Portland cement clinker cement mixtures, characterized in that it contains, by weight, 20 * 100 parts of aluminous cement, 10% 50 parts of ground lime and / or lime hydrate, and 10 to 50 parts. 100 parts of normal and / or alkaline acid carbonate.