阅读说明：本技术 一种透水砖用减水剂及其应用 (Water reducing agent for water permeable brick and application thereof ) 是由 古瑞杰 张晓鹏 贺博林 段旭朝 王磊 于 2021-10-13 设计创作，主要内容包括：公开了一种透水砖用减水剂,所述减水剂由甲基烯丙基聚氧乙烯醚、丙烯酸和具有中链脂肪烷基的阳离子丙烯酰胺单体在引发剂存在下反应得到。此外,还公开了包含前述减水剂且固含量为10-30wt％的减水剂乳液以及前述减水剂在制备透水砖中的用途。本发明不仅可以明显提高净浆的流动度,使水泥浆体获得更佳的工作性能；同时获得了更高的减水率。(Discloses a water reducing agent for water permeable bricks, which is prepared by reacting methyl allyl polyoxyethylene ether, acrylic acid and a cationic acrylamide monomer with medium-chain fatty alkyl in the presence of an initiator. In addition, the water reducing agent emulsion containing the water reducing agent and having the solid content of 10-30 wt% and the application of the water reducing agent in preparing water permeable bricks are also disclosed. The invention can not only obviously improve the fluidity of the clean slurry and ensure that the cement slurry obtains better working performance; while achieving a higher water reduction rate.)

1. The water reducing agent for the water permeable brick is characterized by being prepared by reacting methyl allyl polyoxyethylene ether, acrylic acid and a cationic acrylamide monomer with medium-chain fatty alkyl in the presence of an initiator.

2. The water reducer according to claim 1, wherein the methallyl polyoxyethylene ether has an average molecular weight Mn of 1200-3600 daltons.

3. The water reducer according to claim 1, wherein the cationic acrylamide monomer having the medium-chain aliphatic alkyl group is obtained by quaternizing dimethylaminoethyl methacrylate with a halogenated hydrocarbon having the medium-chain aliphatic alkyl group.

4. The water reducer according to claim 3, wherein the medium-chain fatty alkyl group is selected from a linear or branched alkyl group of 8-16 carbon atoms.

5. The water reducer of claim 1, wherein the molar ratio of methallyl polyoxyethylene ether, acrylic acid and cationic acrylamide monomer with medium chain fatty alkyl groups is 10: (24-28): (2-6).

6. The water reducer of claim 1 wherein the initiator is selected from ammonium persulfate.

7. The water reducer according to claim 1 or 6, wherein the initiator is added in an amount of 1.4-3.0 wt% of the total amount of all monomers.

8. The water reducer according to claim 1, wherein the reaction temperature is 75-95 ℃; the reaction time is 2-10 h.

9. A water-reducing agent emulsion characterized by comprising the water-reducing agent according to any one of claims 1 to 8 and having a solid content of 10 to 30% by weight.

10. Use of a water-reducing agent according to any one of claims 1-8 or according to claim 9 for the preparation of water permeable bricks.

Technical Field

The invention belongs to the technical field of building materials, and particularly relates to a water reducing agent for water permeable bricks and application thereof.

Background

With the rapid development of economy and the acceleration of urbanization process, urban ground surfaces are covered by more and more impervious materials such as cement pavements, asphalt pavements and the like, so that traffic is facilitated, and meanwhile, many negative effects are caused. The impervious material blocks heat and moisture exchange between air and soil, so that urban temperature and humidity imbalance is caused, and an urban 'heat island effect' and 'rain island effect' are generated.

On one hand, the impermeable road surface greatly reduces the infiltration amount of urban rainwater, so that underground water cannot be supplemented, the underground water level continuously drops, and even the problems of ground settlement, seawater invasion and the like are caused; on the other hand, rainwater on the road surface enters a river through the urban drainage system, the pressure of the urban drainage system is increased, rainwater which cannot be drained away generates a large amount of accumulated water on the road surface, and urban flood occurs frequently. In addition, a large amount of pollutants on the road surface enter a river channel along with runoff through urban drainage pipelines or overflow under the rain wash, typical urban rainfall runoff pollution is formed, the urban rainfall runoff pollution is a main non-point source pollution source in cities, and the urban ecological environment is seriously influenced.

A large number of researches show that compared with the impervious pavement, the pervious brick pavement has the effects of relieving surface runoff, replenishing underground, purifying rainwater on the pavement, improving urban thermal environment, absorbing urban noise, improving urban surface soil ecological environment and the like.

The most widely applied and researched concrete permeable bricks in the prior art. The concrete permeable brick is prepared by mixing a cementing material, aggregate, an additive and water according to a certain proportion, and has certain water permeability, air permeability and water retention. The concrete water permeable brick is a communicated porous structure pavement which is directly paved and compacted. The concrete permeable brick takes single-grain-grade coarse aggregate as a framework, and cement paste or a mortar thin layer added with a small amount of fine aggregate is coated on the surfaces of coarse aggregate particles to serve as a cementing layer among the aggregate particles. As an additive, the water reducing agent can reduce the water consumption of unit concrete, simultaneously obtain the same or better fluidity and greatly improve the mechanical property of the concrete.

Water reducing agents have been through three generations since the middle of the last century development to date. The first generation of water reducing agent is represented by lignosulfonate, which has wide molecular weight distribution, strong retarding effect of lignosulfonate with large relative molecular weight, is used more in summer and is not suitable for being used in winter, and concrete is not hardened due to the retarding effect. The second generation water reducing agent is represented by a naphthalene water reducing agent, naphthalene is firstly oxidized into beta-naphthalenesulfonic acid in the synthesis process, then the beta-naphthalenesulfonic acid is subjected to condensation reaction with a large amount of formaldehyde, and then alkali is added for neutralization, so that the second generation water reducing agent is obtained, the pollution in the synthesis process is large, and the storage time is short. Compared with the former two-generation water reducing agent, the polycarboxylate water reducing agent has the outstanding advantages of low mixing amount and high water reducing rate, and excellent fluidity and concrete strength improvement can be obtained as long as the mixing amount is 0.15-0.25% of a gel system; the molecular structure is adjustable and controllable, and a polycarboxylate superplasticizer which can meet various construction requirements can be designed, such as a polycarboxylate superplasticizer which can be retarded and a polycarboxylate superplasticizer which can resist shrinkage; formaldehyde is not used in the preparation process, so that the preparation method is safe and environment-friendly; the high-performance polycarboxylate superplasticizer can be applied to high-performance premixed concrete engineering with large mixing amount of fly ash and slag, and is beneficial to sustainable development of building materials.

Chinese patent application CN103588411A discloses a concrete high-efficiency water reducing agent, which comprises a naphthalene high-efficiency water reducing agent and a calcium lignosulfonate water reducing agent; the weight ratio of the naphthalene-based high-efficiency water reducing agent to the calcium lignosulfonate water reducing agent is 1: 1-2.5. The naphthalene-based high-efficiency water reducing agent and the calcium lignosulfonate water reducing agent are compounded, so that the production cost can be effectively reduced, and the water reducing rate is improved.

Chinese patent application CN110015857A discloses a preparation method and application of a straw-starch-based mixed modified compound polycarboxylate superplasticizer. The water reducing agent is prepared by carrying out esterification-etherification modification on a mixture of hydrolyzed crop straw powder and common starch, and then carrying out graft copolymerization on the modified mixture and small monomers such as unsaturated polyether macromonomer, unsaturated carboxylic acid and the like. The water reducer is a compound concrete water reducer with the performances of a biomass-based water reducer and a polycarboxylic acid water reducer, is further coupled and complemented with the performances of the biomass-based water reducer and the polycarboxylic acid water reducer, overcomes the advantages and disadvantages of low water reducing rate but poor retardation effect of the straw-starch biomass-based water reducer, high water reducing rate and ultra retardation effect of the conventional polycarboxylic acid water reducer, has the characteristics of high water reducing rate and moderate retardation effect, and has the advantages of continuous and compact process, easy implementation and operation, good straw-starch modification effect, low cost, precipitation prevention and easy industrialization.

However, in general, the polycarboxylic acid or modified polycarboxylic acid water reducing agent in the prior art still has adaptability problem, and the water reducing rate still needs to be improved, so that the cement paste is difficult to obtain better working performance. Meanwhile, most of the water reducing agents are still in the stage of mainly product research and development and industrial production, the research work on the comprehensive performance of the polycarboxylic acid high-performance water reducing agent is not deep and detailed, and the accumulated experience is relatively less; atmosphere of honest communication is lacked among the same lines, and the atmosphere is groped and summarized in the test and application process basically by oneself; which influences the popularization, application and development of the polycarboxylic acid high-performance water reducing agent to a certain extent.

On the basis of the prior art, the invention provides a water reducing agent for water permeable bricks and application thereof.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a water reducing agent for water permeable bricks and application thereof. The water reducing agent of the invention can not only obviously improve the fluidity of clean slurry, but also enable the cement slurry to obtain better working performance; while achieving a higher water reduction rate.

In order to achieve the purpose, on one hand, the invention adopts the following technical scheme: the water reducing agent for the water permeable brick is characterized by being prepared by reacting methyl allyl polyoxyethylene ether, acrylic acid and a cationic acrylamide monomer with medium-chain fatty alkyl in the presence of an initiator.

The water reducing agent provided by the invention is characterized in that the methallyl polyoxyethylene ether is selected from 3600 daltons with an average molecular weight Mn of 1200-3600.

Preferably, the methallyl polyoxyethylene ether is selected from the group consisting of those having an average molecular weight Mn of 1800 and 3000 daltons.

According to the water reducing agent, the cationic acrylamide monomer with the medium-chain fatty alkyl is obtained by carrying out quaternization reaction on dimethylaminoethyl methacrylate and halogenated hydrocarbon with the medium-chain fatty alkyl.

The water reducing agent provided by the invention is characterized in that the medium-chain fatty alkyl is selected from straight-chain or branched alkyl with 8-16 carbon atoms.

Preferably, the medium chain fatty alkyl group is selected from linear or branched alkyl groups of 10 to 14 carbon atoms.

The water reducing agent provided by the invention is characterized in that the molar ratio of the methallyl polyoxyethylene ether to the acrylic acid to the cationic acrylamide monomer with the medium-chain fatty alkyl group is 10: (24-28): (2-6).

Preferably, the molar ratio of methallyl polyoxyethylene ether, acrylic acid and cationic acrylamide monomer with medium chain fatty alkyl group is 10: (25-27): (3-5).

The water reducing agent is characterized in that the initiator is selected from ammonium persulfate.

The water reducing agent provided by the invention is characterized in that the addition amount of the initiator is 1.4-3.0 wt% of the total amount of all monomers.

Preferably, the initiator is added in an amount of 1.8 to 2.6 wt% of the total amount of all monomers.

The water reducing agent provided by the invention is characterized in that the reaction temperature is 75-95 ℃; the reaction time is 2-10 h.

Preferably, the reaction temperature is 80-90 ℃; the reaction time is 4-8 h.

In another aspect, the invention provides a water reducing agent emulsion, which comprises the water reducing agent according to the invention, and the solid content is 10-30 wt%.

Preferably, the solid content of the water reducing agent emulsion is 15-25 wt%.

In a further aspect, the invention provides the use of a water-reducing agent according to the invention or a water-reducing agent emulsion according to the invention for the preparation of a water permeable brick.

In the application, the water permeable brick is used as a mixture formula of the water permeable brick according to the unit volume dm³Calculating 380-480g of P.I 42.5 portland cement; 80-140g of fly ash; 1200 and 1430g of reinforced building aggregate; 18-30g of water reducing agent emulsion; mixing water 100-160 g.

As a method for producing the water permeable brick, it is carried out according to a conventional method of those skilled in the art.

Compared with the prior art, the water reducing agent (emulsion) disclosed by the invention can obviously improve the fluidity of the net slurry, so that the cement slurry obtains better working performance; while achieving a higher water reduction rate.

Detailed Description

Hereinafter, specific embodiments of the present invention will be described in detail, and those skilled in the art can clearly understand the present invention and can implement the present invention according to the detailed description. Features from different embodiments may be combined to yield new embodiments, or certain features may be substituted in certain embodiments to yield yet further preferred embodiments, without departing from the principles of the invention.

The following examples are merely illustrative of embodiments of the present invention and do not limit the scope of the invention.

Example 1

Weighing 100mmol of dimethylaminoethyl methacrylate (DMAM) and 100mmol of lauryl chloride (DDC), adding 80mL of acetone and 5mmol of hydroquinone, stirring and reacting at 50 ℃ for 24h, cooling, crystallizing, filtering, washing for 3 times by anhydrous ether, recrystallizing by anhydrous ethyl acetate, and vacuum-drying at room temperature for 24h to obtain white crystals of DMAMDDC, wherein the yield is 87.4%.

¹H NMR spectra showed multiple proton resonance peaks at δ -0.74-0.92, 1.22-1.38, 1.60-1.86, and 3.26-3.45, indicating that white crystals were quaternized with DMAM and DDC. IR spectrum at 718cm^-1、1382cm^-1、1462cm^-1、2850cm^-1And 2918cm^-1Characteristic absorption peaks appear, and the quaternization reaction result is also confirmed.

Example 2

10mmol of methallyl polyoxyethylene ether (HPEG-2400, average molecular weight Mn 2400 Dalton) and 60mL of distilled water were added to a 250mL four-necked flask, heated to 85 ℃ with nitrogen, and stirred to dissolve the macromer HPEG-2400 sufficiently.

Preparing a 40mL mixed monomer solution A from 27mmol of monomer Acrylic Acid (AA) and 3mmol of cationic monomer DMAMDDC and a 10mL solution B prepared from 600mg of Ammonium Persulfate (APS) into a flask, slowly dropwise adding the mixed monomer solution A and the 10mL solution B into the flask within 2h, carrying out heat preservation reaction for 6h, adjusting the pH value to 7.0 by using a saturated NaOH solution after the reaction is finished, and controlling the solid content of the emulsion to be 20% to obtain the water reducer emulsion.

Drying a small amount of water reducing agent emulsion into solid, placing the solid in an agate mortar, adding powdered potassium bromide dried by an infrared lamp, grinding and uniformly mixing, and tabletting a powdered sample by adopting KBr to prepare a sample. IR spectrum at 722cm^-1、1255cm^-1、1297cm^-1、1382cm^-1、1468cm^-1、1627cm^-1、2874cm^-1And 2915cm^-1、3468cm^-1A characteristic absorption peak appears.

Example 3

10mmol of methallyl polyoxyethylene ether (HPEG-2400) and 60mL of distilled water were added to a 250mL four-necked flask, and the flask was heated to 85 ℃ with nitrogen introduction and stirred to dissolve the macromonomer HPEG-2400 sufficiently.

And (2) slowly dropwise adding 40mL of mixed monomer solution A prepared from 25mmol of monomer Acrylic Acid (AA) and 5mmol of cationic monomer DMAMDDC and 10mL of solution B prepared from 600mg of Ammonium Persulfate (APS) into the flask within 2h, carrying out heat preservation reaction for 6h, adjusting the pH value to 7.0 by using a saturated NaOH solution after the reaction is finished, and controlling the solid content of the emulsion to be 20% to obtain the water reducer emulsion.

Comparative example 1

10mmol of methallyl polyoxyethylene ether (HPEG-2400) and 60mL of distilled water were added to a 250mL four-necked flask, and the flask was heated to 85 ℃ with nitrogen introduction and stirred to dissolve the macromonomer HPEG-2400 sufficiently.

And slowly dropwise adding 30mmol of monomer Acrylic Acid (AA) into the flask to prepare 40mL of mixed monomer solution A and 10mL of solution B prepared from 600mg of Ammonium Persulfate (APS) within 2h, carrying out heat preservation reaction for 6h, adjusting the pH value to 7.0 by using a saturated NaOH solution after the reaction is finished, and controlling the solid content of the emulsion to be 20% to obtain the water reducer emulsion.

Evaluation of Performance

The performance evaluation of the water reducing agent adopts the test of special reference cement-P.I 42.5 portland cement (Shandong Lucheng cement Co., Ltd.) for the concrete admixture, and meets the requirement control of GB/T8076-.

The net slurry fluidity test is carried out according to GB/T8077 and 2012, the homogeneity test method of the concrete admixture, and the error is controlled within the range of 5 mm. The specific test method comprises the following steps: weighing 300g of cement, pouring the cement into a cement paste stirring pot which is wiped by a wet cloth, adding water reducer emulsion with the solid content of 0.3% and mixing water with the specified amount, and immediately stirring (during stirring, firstly placing the pot on a pot seat of a stirrer, lifting the pot to a stirring position, starting the stirrer, stirring at a low speed for 120s, stopping stirring for 15s, scraping cement paste on blades and pot walls into the middle of the pot, and then stirring at a high speed for 120s and stopping the machine). And (3) quickly injecting the mixed slurry into a truncated cone in a glass plate at a horizontal position, strickling, quickly lifting the truncated cone vertically upwards, measuring the diameters in mutually vertical directions by using a steel ruler after 30s, and taking the average value as the fluidity (mm) of the cement paste.

The testing method of the water reducing rate of the cement paste is consistent with the testing of the fluidity of the cement paste, and the water consumption W of the cement paste with the same fluidity is respectively measured by a polycarboxylate water reducing agent with the bending and fixing amount of 0.3 percent and the cement paste without the water reducing agent₁And W₀The percentage of the water consumption difference between the water consumption of the cement paste and the water consumption of the water reducer without being blended is the cement paste water-reducing rate of the water reducer, and the calculation formula of the water-reducing rate is eta (W)₀-W₁)/W₀*100％。

See table 1 for results.

TABLE 1

	Net pulp fluidity (mm)	Net slurry Water reducing Rate (%)
			Example 2	262.5	41.6
Example 3	257.5	40.9
			Comparative example 1	235	36.4

Comparative example 1 represents the chemical structure of a conventional anionic polycarboxylate water reducer. Compared with comparative example 1, the water reducing agent provided by the embodiment of the invention can obviously improve the fluidity of the net slurry, so that the cement slurry has better working performance; while achieving a higher water reduction rate.

It should be understood that the detailed description of the invention is merely illustrative of the spirit and principles of the invention and is not intended to limit the scope of the invention. Furthermore, it should be understood that various changes, substitutions, deletions, modifications or adjustments may be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents are also within the scope of the invention as defined in the appended claims.