CN108483967B

CN108483967B - Cement additive and application thereof

Info

Publication number: CN108483967B
Application number: CN201810466105.4A
Authority: CN
Inventors: 孔祥明; 苏彤; 庞晓凡
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2018-05-16
Filing date: 2018-05-16
Publication date: 2021-03-16
Anticipated expiration: 2038-05-16
Also published as: CN108483967A

Abstract

The invention provides a cement additive and application thereof. The cement additive comprises a water-soluble polymer containing a structural unit A derived from an unsaturated carboxylic acid or derivative monomer thereof and a structural unit B derived from an unsaturated sulfonic acid or derivative monomer thereof. The cement additive of the invention can be used as an additive of cement, in particular sulphoaluminate cement, and has excellent retardation effect.

Description

Cement additive and application thereof

Technical Field

The invention relates to a cement additive and application thereof.

Background

Concrete is one of the materials widely used worldwide, of which cement is an important component. Portland cement is currently the most widely used, but in some special projects many disadvantages are exposed, such as marine projects, repair projects, anti-seepage projects, shotcrete and anchor rods, GRC products and construction in cold environments, which puts higher demands on the performance of the concrete. The concrete projects have high construction difficulty, high requirement on durability, severe use environment and relatively difficult maintenance, so that the concrete with more excellent performance and environmental protection is needed.

Compared with Portland cement, the sulphoaluminate cement has the basic characteristics of early strength, high impermeability, high frost resistance and corrosion resistance, and meets the basic requirements of the special engineering. Energy-saving and emission-reducing target for industrial production of CO₂The emission of (C) is a strict requirement, and the cement industry is CO₂The main part of the dischargeOne of the sources. In contrast to the production of portland cement clinker, CO is produced during the production of sulphoaluminate cement clinker₂The discharge amount is low. Therefore, the sulphoaluminate cement with energy conservation, environmental protection and excellent performance gradually draws attention of the society.

Unlike silicate cement, the sulphoaluminate cement is produced with alumina, gypsum and limestone in relatively low grade as material and through burning to produce clinker with anhydrous calcium sulphoaluminate and dicalcium silicate as main minerals and grinding with proper amount of dihydrate gypsum. Due to the composition, the sulphoaluminate cement has the characteristics of fast hydration, fast setting and hardening. The sulphoaluminate cement mainly comprises an aluminum phase (anhydrous calcium sulphoaluminate and tetracalcium aluminoferrite), and can quickly generate ettringite after being mixed with water, so that the ettringite is coagulated and hardened. Therefore, the control of setting time, dispersibility and fluidity and the retention of fluidity over time in sulphoaluminate cement systems are always technical difficulties and keys. When the sulphoaluminate cement is used for mixing mortar or concrete, special retarders and dispersants are usually needed to regulate and control the setting time and the workability of the concrete or the mortar.

The commonly used retarder comprises borax, boric acid, and carboxyl compounds such as sodium citrate, sodium tartrate, sodium gluconate, etc. These retarders are generally effective in extending the setting time of the sulphoaluminate cement from tens of minutes to tens of minutes or even 1-2 hours. However, longer setting times (3-4 hours) are not achievable with such retarders. Meanwhile, in a high-temperature construction environment, the setting time of the mortar concrete is greatly shortened, and the retarder cannot meet the engineering requirements. Another disadvantage of the traditional retarder is that the later strength of the mortar or concrete is adversely affected along with the increase of the mixing amount. Therefore, a retarder special for sulpho-alumina cement, which has an ultra-long retardation time, high-temperature adaptability and a function of not reducing the later strength, is urgently needed.

From another perspective, the control of the workability of mortar or concrete has been the key to the strength and durability of cement products and concrete molding. The water reducing agent can obviously improve the fluidity of concrete when the water consumption of the concrete is kept constant; or chemical additives that can greatly reduce the amount of water used while maintaining fluidity have become essential components in modern concrete (or mortar) formulations. However, when the traditional water reducing agent for silicate system is used in sulphoaluminate cement alone, the slump and fluidity retention performance is poor, and when the traditional water reducing agent is used in combination with a retarder, the compatibility problem of the water reducing agent and the retarder also exists, which is mainly caused by the reason that the water reducing agent reduces the dispersing ability and even loses the dispersing ability due to the competitive adsorption of the small molecular retarder. Therefore, the water reducing agent with the function of retarding is urgently needed in the field.

Disclosure of Invention

In a first aspect, the present invention provides a cement additive comprising a water-soluble polymer having a molecular structure in which a repeating unit comprises or only comprises a structural unit a derived from an unsaturated carboxylic acid or a derivative monomer thereof and a structural unit B derived from an unsaturated sulfonic acid or a derivative monomer thereof.

According to one embodiment, the cement additive comprises only the water-soluble polymer according to the invention.

In some embodiments of the invention, the molar ratio of the structural unit a to the structural unit B is 20:1 to 1:1, preferably the molar ratio of the structural unit a to the structural unit B is 10:1 to 1:1, such as 2:1, 4:1, 6:1 or 8: 1.

In some embodiments of the invention, the water-soluble polymer is in a linear molecular structure.

In some embodiments of the invention, the water-soluble polymer is obtained by a random copolymerization reaction.

In some embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer thereof is at least one of Acrylic Acid (AA), methacrylic acid, itaconic acid, fumaric acid, maleic acid, and maleic anhydride.

In some embodiments of the invention, the unsaturated sulfonic acid or derivative monomer thereof is at least one of 2-acrylamido-2-methylpropanesulfonic Acid (AMPS), sodium p-styrenesulfonate (SSS), sodium vinylsulfonate, and Sodium Allylsulfonate (SAS).

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer is acrylic acid, and the unsaturated sulfonic acid or derivative monomer is 2-acrylamido-2-methylpropanesulfonic acid.

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer is acrylic acid, and the unsaturated sulfonic acid or derivative monomer is sodium p-styrenesulfonate.

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer is acrylic acid, and the unsaturated sulfonic acid or derivative monomer is sodium allylsulfonate.

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer is methacrylic acid, and the unsaturated sulfonic acid or derivative monomer is 2-acrylamido-2-methylpropanesulfonic acid.

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer thereof is itaconic acid, and the unsaturated sulfonic acid or derivative monomer thereof is 2-acrylamido-2-methylpropanesulfonic acid.

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer thereof is fumaric acid, and the unsaturated sulfonic acid or derivative monomer thereof is 2-acrylamido-2-methylpropanesulfonic acid.

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer thereof is maleic acid, and the unsaturated sulfonic acid or derivative monomer thereof is 2-acrylamido-2-methylpropanesulfonic acid.

In some preferred embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer is maleic anhydride, and the unsaturated sulfonic acid or derivative monomer is 2-acrylamido-2-methylpropanesulfonic acid.

In some preferred embodiments of the present invention the water soluble polymer is formed by random copolymerization of monomers in the presence of an initiator, a reducing agent and a chain transfer agent, wherein the monomers include an unsaturated carboxylic acid or derivative monomer thereof and an unsaturated sulfonic acid or derivative monomer thereof.

In some embodiments of the invention, the monomers consist of unsaturated carboxylic acid or derivative monomers and unsaturated sulfonic acid or derivative monomers.

In some embodiments of the invention, the specific steps of preparing the water-soluble polymer include:

step S1: mixing the monomer and water to form a first mixture;

step S2: mixing the reducing agent, the chain transfer agent, and water to form a second mixture;

step S3: the first mixture and the second mixture were added dropwise to a flask, respectively, while adding an initiator.

According to the present invention, the step S1 and the step S2 may be performed simultaneously, or sequentially.

In some embodiments of the present invention, the unsaturated carboxylic acid or derivative monomer thereof is at least one of Acrylic Acid (AA), methacrylic acid (MAA), Itaconic Acid (IA), Fumaric Acid (FA), maleic acid, and Maleic Anhydride (MA).

In some embodiments of the invention, the initiator is at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, benzoyl peroxide.

In some embodiments of the invention, the reducing agent is at least one of vitamin C, sodium sulfite, sodium bisulfite, potassium sulfite, potassium bisulfite, ferrous sulfate, and sodium formaldehyde sulfoxylate.

In some embodiments of the invention, the chain transfer agent is at least one of thioglycolic acid, mercaptopropionic acid, mercaptoethanol, and mercaptopropanol.

In some embodiments of the present invention, the molar ratio of the unsaturated carboxylic acid or derivative monomer thereof to the unsaturated sulfonic acid or derivative monomer thereof is 20:1 to 1:1, more preferably 10:1 to 1:1, and still more preferably 2:1, 4:1, 6:1, or 8: 1.

In some embodiments of the invention, the molar ratio of the reducing agent to the chain transfer agent is from 0.01:1 to 1:1, preferably from 0.05:1 to 0.5:1, more preferably from 0.1:1 to 0.25:1, and most preferably from 0.15:1 to 0.20: 1.

In some embodiments of the invention, the molar ratio of the chain transfer agent to the unsaturated sulfonic acid or derivative monomer thereof is 0.01:1 to 5:1, preferably 0.05:1 to 1:1, more preferably 0.1:1 to 0.8:1, such as 0.1155:1 to 0.6919: 1.

In some embodiments of the invention, the molar ratio of the initiator to the unsaturated sulfonic acid or derivative monomer thereof is 0.01:1 to 5:1, preferably 0.05:1 to 1:1, and more preferably 0.1:1 to 0.6: 1.

In some embodiments of the present invention, the molar ratio of the chain transfer agent to the unsaturated carboxylic acid or derivative monomer thereof to the unsaturated sulfonic acid or derivative monomer thereof is from 0.005:1 to 0.025: 1.

In some embodiments of the invention, the molar ratio of the initiator and the unsaturated carboxylic acid or derivative monomer to the unsaturated sulfonic acid or derivative monomer is from 0.005:1 to 0.025: 1.

In some embodiments of the invention, the molar ratio of the reducing agent and the unsaturated carboxylic acid or derivative monomer thereof to the unsaturated sulfonic acid or derivative monomer thereof is from 0.002:1 to 0.006: 1.

In some embodiments of the invention, the temperature of the aqueous solution of the initiator is from 55 to 65 ℃, preferably 60 ℃.

In some embodiments of the present invention, in the step S3, the first mixture and the second mixture are respectively added slowly and dropwise into a flask, and the initiator is added instantaneously at the beginning of the dropwise addition.

In some embodiments of the invention, the dropping time of the first mixture is 2 to 4 hours, preferably 3 hours.

In some embodiments of the invention, the second mixture is added dropwise over a period of 3 to 4 hours, preferably 3.5 hours.

In some embodiments of the present invention, the reaction system is incubated for 0.5 to 3 hours, preferably 0.8 to 1.5 hours, more preferably 1 hour after step S3.

The invention also provides a cement composition comprising a sulphoaluminate cement and the cement additive of the invention. In some embodiments of the invention, the cement composition does not include other water reducers and/or set retarders.

In some embodiments of the invention, the cement additive is incorporated in an amount of 0.1 wt% to 5 wt%, preferably 0.5 wt% to 2 wt%, more preferably 1 wt% to 1.5 wt%, based on the weight of the sulphoaluminate cement.

The invention also provides the use of the cement additive in cement, preferably sulphoaluminate cement.

In some embodiments of the invention, the water-soluble polymer is used in cement to extend the setting time of the cement or to enhance the fluidity early in the setting of the cement and/or to enhance the strength after setting of the cement.

When the cement additive is used in a sulphoaluminate cement system, the cement additive has the combination of various excellent performances of retarding coagulation, dispersing and reducing water, improving later strength and the like. Compared with the traditional comb-type polycarboxylic acid water reducing agent, the comb-type polycarboxylic acid water reducing agent does not contain polyester or polyether macromonomer, can greatly prolong and effectively control the retention of slump and fluidity under the condition of not doping retarder, does not bleed, and meets the engineering requirements; compared with the traditional retarder, the setting time of the sulphoaluminate cement can be greatly prolonged, the sulphoaluminate cement does not lose efficacy in a high-temperature environment, and the later strength of the concrete is not adversely affected along with the increase of the mixing amount.

The invention has the following beneficial technical effects: by designing the molecular structure of the sulphoaluminate cement admixture, the slump and the fluidity can be greatly prolonged and effectively controlled without mixing a retarder, bleeding is avoided, the setting time of the sulphoaluminate cement is greatly prolonged, the sulphoaluminate cement does not lose efficacy in a high-temperature environment, the later strength of the concrete is not adversely affected along with the increase of the mixing amount, and the engineering requirements are met.

Drawings

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the initial fluidity of different polymers in SAC systems as a function of the loading.

FIG. 2 shows the effect of varying molar ratios of AA (acrylic acid) and AMPS (2-acrylamido-2-methylpropanesulfonic acid) copolymers at 1 wt% loading on the fluidity retention of a sulphoaluminate cement slurry in a SAC system.

FIG. 3 shows the effect of copolymers of AA with AMPS (2-acrylamido-2-methylpropanesulfonic acid), SSS (sodium p-styrenesulfonate), and SAS (sodium allylsulfonate) respectively, at 1 wt% loading in SAC systems on the fluidity retention of sulphoaluminate cement slurries.

FIG. 4 shows the effect of AMPS copolymer with AA, MAA (methacrylic acid), MA (maleic anhydride), IA (itaconic acid), FA (fumaric acid) copolymers at 1 wt% loading on the fluidity retention of sulphoaluminate cement slurries in SAC systems, respectively.

FIG. 5 shows the effect of varying molar ratios of AA (acrylic acid) and AMPS (2-acrylamido-2-methylpropanesulfonic acid) copolymer on the fluidity retention of a sulphoaluminate cement slurry at a 1.5 wt% loading in a SAC system.

FIG. 6 shows the effect of AA copolymer with AMPS (2-acrylamido-2-methylpropanesulfonic acid), SSS (sodium p-styrenesulfonate), and SAS (sodium allylsulfonate) at 1.5 wt% loading on flow retention of a sulphoaluminate cement slurry in a SAC system.

FIG. 7 shows the effect of AMPS copolymer with AA, MAA (methacrylic acid), MA (maleic anhydride), IA (itaconic acid), FA (fumaric acid) copolymers at 1.5 wt% loading on the fluidity retention of sulphoaluminate cement slurries in SAC systems, respectively.

FIG. 8 shows the effect of different molar ratios of AA (acrylic acid) and AMPS (2-acrylamido-2-methylpropanesulfonic acid) copolymers on setting time of sulphoaluminate cement slurries at different loadings (SC is sodium citrate in the figure) in SAC systems at 20 ℃.

FIG. 9 shows the effect of copolymers of AA with AMPS (2-acrylamido-2-methylpropanesulfonic acid), SSS (sodium p-styrenesulfonate), and SAS (sodium allylsulfonate), respectively, on setting time of a sulphoaluminate cement slurry in a SAC system at 20 ℃.

FIG. 10 shows the effect of AMPS (2-acrylamido-2-methylpropanesulfonic acid) copolymers with AA, MAA (methacrylic acid), MA (maleic anhydride), IA (itaconic acid), FA (fumaric acid), respectively, on the setting time of a sulphoaluminate cement slurry in a SAC system at 20 ℃.

FIG. 11 shows the effect of different molar ratios of AA (acrylic acid) and AMPS (2-acrylamido-2-methylpropanesulfonic acid) copolymers at 1 wt% loading on compressive strength at various ages of sulphoaluminate cement mortar in SAC systems. (a) effect on sulphoaluminate cement slurry strength.

FIG. 12 shows the effect of AA at 1 wt% of copolymer with AMPS (2-acrylamido-2-methylpropanesulfonic acid), SSS (sodium p-styrenesulfonate), and SAS (sodium allylsulfonate) in SAC systems on compressive strength at each age of sulphoaluminate cement mortar.

FIG. 13 shows the effect of AMPS copolymer with AA, MAA (methacrylic acid), MA (maleic anhydride), IA (itaconic acid), FA (fumaric acid) at 1 wt% loading on sulfoaluminate cement slurry strength in SAC systems, respectively.

Detailed Description

In order that the invention may be readily understood, a detailed description of the invention is provided below. However, before the invention is described in detail, it is to be understood that this invention is not limited to particular embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

The invention adopts an aqueous solution free radical copolymerization method to synthesize the water-soluble polymer, and all materials in the examples are analytically pure unless otherwise specified.

Example 1

Synthesis of PAS 2: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 27.8g of acrylic acid 27.8gAA, 40g of AMPS (2-acrylamido-2-methylpropanesulfonic acid) and 100g of water were uniformly mixed to prepare dropping liquid A, and 1.23g of 3-MPA, 0.23g of 0.23gVc (vitamin C) and 55g of water were uniformly mixed to prepare dropping liquid B. Dropping liquid A and BDropping the solution B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the solution A is 3H, the dropping time of the solution B is 3.5H, and 1.31g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured and found to be 27.4%.

Example 2

Synthesis of PAS 4: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 41.7g of 41.7gAA, 30g of AMPS and 100g of water are mixed uniformly to prepare dropping liquid A, and 1.54g of 3-MPA, 0.66gVc and 60g of water are mixed uniformly to prepare dropping liquid B. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 1.64g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 26.9%.

Example 3

Synthesis of PAS 6: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 45.87g 45.87gAA, 22g AMPS and 100g water are mixed uniformly to prepare dropping liquid A, and 1.58g3-MPA, 0.67gVc and 60g water are mixed uniformly to prepare dropping liquid B. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 1.68g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 26.8%.

Example 4

Synthesis of PAS 8: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 50.04gAA, 18g AMPS and 100g water are mixed uniformly to prepare dropping liquid A, and 1.66g3-MPA, 0.71gVc and 60g water are mixed uniformly to prepare dropping liquid B. Dropping liquidDropping the A and the B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the A is 3H, the dropping time of the B is 3.5H, and 1.77g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 27.3%.

Example 5

Synthesis of PASSS 4: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 41.94g of 41.94gAA, 30g of SSS and 100g of water are mixed uniformly to prepare a dropping liquid A, and 1.54g of 3-MPA, 0.66gVc and 60g of water are mixed uniformly to prepare a dropping liquid B. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 1.65g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 27.2%.

Example 6

Synthesizing PASAS 4: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 48.74gAA, 22g of SAS and 100g of water are mixed uniformly to prepare dropping liquid A, and 1.66g of 3-MPA, 0.71gVc and 60g of water are mixed uniformly to prepare dropping liquid B. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 1.78g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 26.9%.

Example 7

Synthesis of PMAAS 4: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 49.81g of MAA, 30g of AMPS and 100g of water are uniformly mixed to prepare dropping liquid A, and 1.78g of 3-MPA, 0.76gVc and 60g of water are uniformly mixed to prepare dropping liquid AB. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 1.9g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 29.3%.

Example 8

Synthesis of PMAS 4: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 56.76gMA g of AMPS and 30g of water are mixed uniformly to prepare dropping liquid A, and 1.98g of 3-MPA, 0.85gVc g of water and 80g of water are mixed uniformly to prepare dropping liquid B. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 2.11g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 29.0%.

Example 9

Synthesizing PIAS 4: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 75.29gIA g, 30g AMPS and 120g water are mixed uniformly to prepare dropping liquid A, and 1.54g3-MPA, 0.66gVc and 100g water are mixed uniformly to prepare dropping liquid B. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 1.64g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 29.6%.

Example 10

Synthesis of PFAS 4: 35g of water is weighed and poured into a three-neck flask in a constant-temperature water bath kettle, and a stirring paddle is used for uniformly stirring at the rotating speed of 200rpm and heating to 60 ℃. 67.18gFA, 30g AMPS and 120g water are mixed evenly to prepare dropping liquid A, 1.54g3-MPA, 0.66gVc and 100g water are mixed evenly to prepareTo prepare dropping liquid B. Dropping the dropping liquid A and the dropping liquid B into a three-neck flask at a constant speed by a peristaltic pump, wherein the dropping time of the dropping liquid A is 3H, the dropping time of the dropping liquid B is 3.5H, and 1.64g of H with the mass concentration of 30% is weighed when the dropping is started₂O₂The aqueous solution was added to a three-necked flask. After the dropwise addition, the temperature was maintained for 1 hour. After the reaction, the actual solid content was measured, and the measurement result was 29.6%.

Performance testing

Blank is sulphoaluminate cement slurry without any admixture; the PCE is a common polycarboxylic acid water reducer in the market, and is prepared by mixing AA and HPEG according to a molar ratio of 4:1, the molecular formula is as follows; SC is sodium citrate;

PAS 2, PAS 4, PAS 6 and PAS 8 represent AA (acrylic acid) and AMPS (2-acrylamido-2-methylpropanesulfonic acid) water-soluble polymers with monomer molar ratios of 2, 4, 6 and 8, respectively;

PASSS 4 and PASAS 4 respectively represent AA (acrylic acid) and SSS (sodium p-styrene sulfonate), SAS (sodium vinyl sulfonate) monomer mole ratio is 4 water-soluble polymer;

PMAAS 4, PMAS 4, PIAS 4, PFAS 4 represent water-soluble polymers with a molar ratio of MAA (methacrylic acid), MA (maleic anhydride), IA (itaconic acid) and AMPS (2-acrylamido-2-methylpropanesulfonic acid) monomers of 4, respectively.

The molecular structure of PCE is simple, and m/n is 4

The sulfoaluminate cement doped with the water-soluble polymer prepared in examples 1 to 10 was used as experimental examples 1 to 10, and data of some indexes were measured, using sulfoaluminate cement doped with a commercially available polycarboxylic acid water reducing agent or sodium citrate without any additive as a comparative example.

The initial fluidity and the retentivity of the net slurry of the comparative example and the experimental examples 1 to 10 are determined under the condition of 0.35 water-cement ratio by referring to GB/T8077-2012 test method for homogeneity of concrete admixture; the setting time of the cement in comparative examples and experimental examples 1-10 is determined by referring to GB/T1346-2011 method for testing water consumption, setting time and stability of standard consistency of cement; referring to GB/T17671-1999 Cement mortar Strength test method (ISO method), the mortar compressive strengths of comparative examples and Experimental examples 1-10 were measured, and a sulphoaluminate cement, designated by SAC, was experimentally tested. The results are shown in the table and the figure.

Test 1

The initial fluidity of the different polymers in comparative and experimental examples 1 to 10 was measured as a function of the amount of incorporation. See table 1 and figure 1 for results.

TABLE 1 initial fluidity of different polymers in SAC systems as a function of the amount of incorporation

Note: at the water cement ratio of 0.35, no additive is added, and the initial fluidity of the blank cement paste is 105

Table 1 and fig. 1 show that for a SAC cement system, initial dispersion effects of synthesized water-soluble polymers at different mixing amounts are smaller than those of common water reducing agents PCE in the market, and no HPEG monomer is contained in the molecule, i.e., no PEO long side chain is contained, so that a flocculation structure of cement is not thoroughly broken, and although the water reducing rate is not high, a bleeding phenomenon does not occur, and the applicability is possibly better in practical application.

Test 2

As can be seen from FIG. 1, the initial fluidity stabilized after the addition of 0.01, and therefore, the fluidity retention of the sulfoaluminate cement slurry was measured for each of the comparative example and the experimental examples 1 to 10 in which the addition of 1 wt% was 1.5 wt%. See table 2, table 3 and fig. 2-7 for results.

TABLE 2SAC systems fluidity retention of sulfoaluminate cement slurries at 1 wt% loading for different polymers

TABLE 3 fluidity Retention of Sulfoaluminate cement slurries of different polymers at 1.5 wt% loading in SAC systems

As can be seen from tables 2 and 3 and FIGS. 2 to 7, the fluidity retentivity of the water-soluble polymer synthesized by the method for synthesizing the SAC water reducing agent is obviously superior to that of the common water reducing agent PCE (the water reducing agent PCE is added, and the sulphoaluminate cement slurry has no fluidity retentivity), and the fluidity is relatively slowly reduced. The difference between the 1.5 wt% and the 1 wt% is larger. The polymer of the invention can slow the hydration of sulphoaluminate cement under the condition of not adding other small molecular retarders, so that sulphoaluminate cement slurry has good fluidity retainability, the workability of the sulphoaluminate cement can be improved and adjusted by adding the polymer, and the application of the sulphoaluminate cement in engineering is guaranteed.

Test 3

The effect of different polymers at 20 ℃ on setting time of sulphoaluminate cement slurries (SC sodium citrate) at different loadings in SAC systems was determined for the different polymers in the comparative and experimental examples 1-10. See table 4 and fig. 8-10 for results.

Table 4 shows the effect of different polymers in SAC system at 20 ℃ on setting time (min) of sulphoaluminate cement slurry (SC is sodium citrate) at different mixing amounts

Under the water cement ratio of 0.35, the initial setting time of blank cement slurry without any additive is 12min, and the final setting time is 18 min.

TABLE 41 initial setting time/min

TABLE 4.2 Final setting time/min

It is demonstrated by table 4 and figures 8-10 that for the synthesized water-soluble polymer, the initial setting time and final setting time of the cement at different loadings were significantly longer than SC, and the setting time had a good linear dependence on the loading of the water-soluble polymer for the SAC cement systems. The polymer can effectively prolong the setting time of the sulphoaluminate cement, delay the hydration of the sulphoaluminate cement, simultaneously has good linear correlation between the setting time of the sulphoaluminate cement and the mixing amount of the water-soluble polymer, and has larger saturated mixing amount, so the setting time of the sulphoaluminate cement can be accurately improved and adjusted through the mixing amount of the polymer, and the engineering requirement can be met. In addition, the synthesized water-soluble polymer retarder has the water reducing function, and can adjust the fluidity of the sulphoaluminate cement while retarding the coagulation.

Test 4

FIGS. 11-13 are graphs showing the compressive strength of different polymers at 1 wt% loading to sulphoaluminate cement mortar at various ages in SAC systems, comparative and experimental examples 1-4. See table 5 and fig. 11-13 for results.

TABLE 5 compression Strength of different polymers in SAC systems at 1 wt% blend to sulphoaluminate cement mortar at various ages (MPa)

Table 5 and FIGS. 11-13 show that the synthetic water-soluble polymers have no adverse effect on the post-strength of SAC cement mortar. For the cement which is stabilized to obtain 28 days, the compressive strength of the cement doped with SC is equivalent to that of the blank cement, the compressive strength of the cement doped with PCE is lower than that of the blank cement, while the compressive strength of the cement doped with the four polymers is obviously higher than that of the blank cement, on the other hand, the compressive strength of the cement doped with the four polymers is obviously lower than that of the blank cement doped with the four polymers after 4 hours, which shows that the cement doped with the polymers of the invention has slow setting time, but the compressive strength is high after the cement is set stably, and has the effects of retarding and enhancing the compressive strength.

And (3) knotting: the water-soluble polymer of the invention can be used as a special additive for sulpho-aluminium cement, can be used as a water reducing agent with retarding effect in function, and can also be used as a retarder with water reducing effect. At first, no one researches the functional additive at present, and the conventional polycarboxylic acid water reducing agent alone cannot delay the hydration of the sulpho-aluminum cement, so that the cement paste can lose fluidity rapidly and cannot meet the engineering requirement. At present, the hydration of the sulphoaluminate cement is delayed mainly by adding the small-molecule retarder, and then the fluidity of cement paste is adjusted by adding the water reducing agent, but the requirement cannot be met generally, and the strength of the sulphoaluminate cement is reduced by adding the small-molecule retarder generally; the addition of the polymer has a retarding effect on early sulphoaluminate cement, a large amount of ettringite is generated when the sulphoaluminate cement is hydrated, so that the cement paste loses fluidity, and the polymer can delay the generation of the ettringite, so that the fluidity of the cement paste can be ensured for a long time. But the strength of the low-aluminate cement after stable hardening cannot be reduced, because the polymer does not have a PEO side chain of a common water reducing agent, the water reducing rate is slightly low, but the bleeding phenomenon cannot occur, the cement is uniformly hydrated, meanwhile, a common small-molecule retarder is added to delay the hydration, insoluble precipitates are generated to influence the strength, the polymer synthesized by the invention can be adsorbed on the surface of the ettringite, on one hand, the loss of the fluidity of cement slurry caused by the mutual lapping of crystals due to the growth of the ettringite is inhibited, on the other hand, the accumulation of the ettringite crystals can be improved, so that the pore structure of the hardened cement is improved, the strength cannot be lost, and the strength of the cement is increased instead.

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.

Claims

1. The application of a cement additive in sulphoaluminate cement comprises a water-soluble polymer, wherein a repeating unit in a molecular structure of the water-soluble polymer comprises or only comprises a structural unit A from an unsaturated carboxylic acid or a derivative monomer thereof and a structural unit B from an unsaturated sulfonic acid or a derivative monomer thereof, and the molar ratio of the structural unit A to the structural unit B is 4: 1-8: 1; the unsaturated carboxylic acid or derivative monomer is at least one of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and maleic anhydride, and the unsaturated sulfonic acid or derivative monomer is at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, sodium vinylsulfonate and sodium allylsulfonate.

2. Use according to claim 1, characterized in that the molar ratio of the structural unit a to the structural unit B is from 4:1 to 6:1 or from 6:1 to 8: 1.

3. Use according to claim 1, characterized in that the molar ratio of the structural unit a to the structural unit B is 4:1, 6:1 or 8: 1.

4. Use according to any one of claims 1 to 3, wherein the water-soluble polymer is formed by random copolymerisation of monomers comprising or only comprising an unsaturated carboxylic acid or derivative monomer thereof and an unsaturated sulphonic acid or derivative monomer thereof in the presence of an initiator, a reducing agent and a chain transfer agent.

5. The use according to claim 4, wherein the unsaturated carboxylic acid or derivative monomer is at least one of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, and maleic anhydride;

and/or the unsaturated sulfonic acid or the derivative monomer thereof is at least one of 2-acrylamide-2-methyl propane sulfonic acid, sodium p-styrene sulfonate and sodium allyl sulfonate;

and/or the initiator is at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate and benzoyl peroxide;

and/or the reducing agent is at least one of vitamin C, sodium sulfite, sodium bisulfite, potassium sulfite, potassium bisulfite, ferrous sulfate and sodium formaldehyde sulfoxylate;

and/or the chain transfer agent is at least one of thioglycolic acid, mercaptopropionic acid, mercaptoethanol, and mercaptopropanol.

6. Use according to claim 1, wherein the cement additive is used in cement for extending the setting time of cement or for increasing the fluidity of cement at the initial stage of setting and/or for increasing the strength of cement after setting and hardening.

7. A cement composition comprising a sulphoaluminate cement and a cement additive as defined in the use according to any one of claims 1 to 6.

8. The cement composition according to claim 7, wherein the cement additive is incorporated in an amount of 0.1 to 5 wt% based on the weight of the sulphoaluminate cement.

9. The cement composition according to claim 8, wherein the cement additive is incorporated in an amount of 0.5 to 2 wt% based on the weight of the sulphoaluminate cement.

10. The cement composition of claim 8, wherein the cement additive is present in an amount of 1 wt% to 1.5 wt% based on the weight of the sulphoaluminate cement.