CS251512B1 - Plasticizing admixture for cement compositions production with quick strengths growth - Google Patents

Description

The invention relates to a plasticizing additive for the production of cementitious composites with a rapid increase in strength.

Until now, plasticizing additives for cementitious mortars and concretes have been produced on the basis of ligninsulfone salts and, to a lesser extent, on the basis of other surfactants which, at suitable dosages in fresh cementitious mixtures, exhibit good plasticizing properties. All of these plasticizers add to the formation of a rigid structure of cement composites and reduce their strength. They reduce most of the strength of cementitious composites at an early stage of their hardening, and their negative impact on strength, depending on the type of cement used, often manifests itself even after 28 or more days of hardening. At higher doses, these additives cause a permanent decrease in the long-term strength of the cementitious composites. The main cause of the negative impact of conventional plasticizers on the development of strength of cementitious composites is their relatively long-term plasticization effect, caused by the significant stability of aqueous coatings formed by adsorption of water molecules on the solid phase surface in the composite mixture. Slow removal of these aqueous coatings slows the process of firmly joining the individual composite particles into a solid structure. The second reason for the reduction in strength is the marked aeration capability of conventional plasticizers, as a result of which a plurality of air cavities are formed in the composite composition which reduce the bulk density and strength of the composite. In view of this, conventional plasticizers cannot be effectively used in the manufacture of cement composites that require rapid strength enhancement, e.g. in prefabrication of concrete and reinforced concrete components, in various progressive concreting procedures of monolithic constructions, in winter concreting and in general in the production of concrete and other cement composites with very high strength. Therefore, with and in the production of cementitious composites with the required rapid strength increase, the plasticizers have completely replaced the superplasticizers. Unlike plasticizers, superplasticizers exhibit only a relatively short-term plasticizing effect and practically do not increase the air content of the composite composition. They increase the strength of cementitious composites at suitable doses. Most of the prior art superplasticizers are produced on the basis of sulfonated melamine-formaldehyde resins, or naphthalene sulfonate-251512 maldehyde resins. Due to the lack of a raw material base, superplasticizers of this kind are not produced in the Czech Republic and must be imported from abroad.

The above-mentioned drawbacks are overcome by the plasticizing additive for the production of rapid strength cement composites according to the invention, which consists of a solution comprising 100 parts by weight of anhydrous lignosulfone salt plasticizer, 5 to 100 parts by weight of ammonium rhodanide accelerator and 0.5 to 20 parts by weight of a silicone defoamer additive, wherein the concentration of the resulting additive is adjusted with water to a stable solution. The plasticizing additive may contain from 5 to 100 parts by weight of ammonium rhodanide accelerator additive from 5 to 100 parts by weight of sodium, potassium, calcium or sodium, potassium and formate rhodanide and 0.5 to 20 parts by weight of silicone antifoam additive from 0.5 to 20 parts by weight of amyl alcohol. , octyl alcohol or other medium-carbon alcohol or derivatives thereof with an emulsifier and instead of 100 parts by weight of a plasticizing additive based on lignosulfone salts of 100 parts of the anhydrous plasticizing additive based on synthetic polyphenolic tannins with plasticizing properties.

The invention of the plasticizing additive for the production of cementitious composites with a rapid increase in strength positively affects the strength of the cementitious composites and the modified additives exhibit the properties and effects that are characteristic of superplasticizers. The plasticizing effect in the fresh composite mixture caused by the additives lasts, depending on the treatment carried out and the dose of additive used, as a rule 40 to 150 minutes, depending on the preparation of the mixture. At doses of 1 to 1.5% by weight of the cement, these additives do not have an aerating effect.

As a rule, the fresh composite compositions produced with these additives exhibit less air content and higher bulk density than the corresponding composite compositions without additive. The plasticizing additives do not affect the development of the initial strengths and increase the long-term strengths of the hardened composite, even if the plasticizing effect is not utilized to reduce the mixing water dose in the composite. They increase the compressive strength of the cementitious composites by 0 to 10 ° / o, depending on the treatment of the additive and its dose in the composite. A more pronounced increase in the initial and long-term strengths of the cementitious composites produced with the additives is achieved by utilizing the plasticizing effect to reduce the dose of mixing water in the composite, respectively. reduction of the water coefficient value.

Plasticizing additives for the production of cementitious composites with a rapid increase in strength can be applied according to the particular purpose of their use with partially different efficiencies in the following composition.

Example 1

Plasticizing additive for the production of rapid strength cement composites, formed from a solution comprising 100 parts by weight of sodium lignosulfonate, 20 parts by weight of sodium formate and 2.5 parts by weight of silicone defoamer.

Example 2

A plasticizing additive formed from a solution containing 100 parts by weight of sodium lignosulfonates, 50 parts by weight of ammonium rhodanide and 2.5 parts by weight of a silicone defoamer.

EXAMPLE 1 a d 3

A plasticizing additive formed from a solution comprising 100 parts by weight of sodium lignosulfonates, 30 parts by weight of sodium rhodanide and 4 parts by weight of amyl alcohol with an emulsifier.

Example 1 4

A plasticizing additive formed from a solution comprising 100 parts by weight of synthetic polyphenolic tannins, 50 parts by weight of potassium formate and 4 parts by weight of octyl alcohol with an emulsifier.

The differences in the efficacies of the additives according to the results of the comparative tests are shown in the table. Comparison tests were performed with a cement mortar made of Portland cement PC 400 and standard sand with a mixing ratio of 1: 3 and a constant water ratio of 0.5. Additives made up 0.25% by weight of cement. The results of the tests of the mortar without plasticizer, the mortar with a plasticizer additive, the plasticizer and the mortar with additives according to Examples 1 to 4 are shown in the table.

Plasticizing additives for the production of cementitious composites with a rapid increase in strength can be used in the construction industry, in particular in the production of concrete and other cement-based composite building materials. Their special consideration should be assumed in the production of high-strength concrete, especially in the application of progressive concreting procedures of monolithic concrete structures, in the production of concretes for demanding traffic and other engineering constructions, in the winter concreting, in the industrial production of concrete components.

table

Properties of cementitious mortars with plasticizers

Malta bez Malta s Malta ingredients additive with ultra- set plastifi- In accordance with one Katori at- clade

Aqueous factor v / c Additive additive in% of cement weight

Mortar consistency:

R-casting rate in cm Required vibration compaction time

Air content in fresh compacted mortar in% volume Bulk density in kg. m ^-3 after 1 day after 28 days after 360 days Compressive strength in MPa after * 1 day after 28 days after 360 days

0.50 0.50 0.50 - 0.25 0.25 11.4 14.9 14.4 13.2 6.0 6.3 3.9 4.9 3.9 2 217 2 197 2 212 2 246 2 223 2 239 2 256 2 242 2 256 15.08 13,00 15.86 42.55 42.32 45.17 49.02 51,56 52.75

Mortar with additive according to example 2 Mortar with additive according to example 3 Mortar with additive according to example 4 0.50 0.50 0.50 0.25 0.25 0.2 5 13.9 14.6 14.8 7.0 6.2 6.2 3.8 3.9 4.0

2 219 2.16 2 211 2 249 2 243 2 242 2 262 2 255 2 257 16.63 16.0-2 15.97 46.57 46.06 44,76 53.50 52,14 51,76

SUBJECT

Claims (4)

SUBJECT A plasticizing additive for the production of rapid strength cement composites comprising a solution comprising 100 parts by weight of an anhydrous lignosulfone salt plasticizing additive, 5 to 100 parts by weight of an ammonium rhodanide accelerator additive and 0.5 to 20 parts by weight of an additive. a silicone defoamer, wherein the concentration of the resulting additive is adjusted with water to a stable solution. 2. A plasticizing additive according to claim 1, characterized in that, instead of 5 to 100 parts by weight of the ammonium rhodanide accelerator, it comprises 5 to 100 parts by weight of sodium, potassium, calcium, or sodium or potassium formate. We claim: 3. A plasticizing additive according to Claims 1 to 2, characterized in that, instead of 0.5 to 20 parts by weight of the silicone defoamer additive, it contains from 0.5 to 20 parts by weight of amyl alcohol or octyl alcohol or another alcohol having a medium carbon number of the molecule or derivatives thereof. with emulsifier bead. 4. The plasticizer according to claims 1 to 3, wherein, instead of 100 parts by weight of the lignosulfone salt plasticizer, it comprises 100 parts by weight of an anhydrous plasticizer based on synthetic polyphenolic tannins with plasticizing properties.