Anti-mud dry-mixed mortar admixture and preparation method thereof

Abstract

This invention belongs to the technical field of building material admixtures, specifically relating to an anti-mud-type dry-mix mortar admixture and its preparation method. The anti-mud-type dry-mix mortar admixture is composed of the following percentages: sulfonated chitosan: 20%-40%, air-entraining agent: 5%-15%, powdered polycarboxylate superplasticizer: 20%-40%, and setting regulator: 10-25%. The preparation method of the sulfonated chitosan is as follows: first, dissolve 50 parts of chitosan with an average molecular weight of 10,000 to 30,000 in 1... In a 2wt% acetic acid solution, heat to 40°C and stir to dissolve. Add 0.45 parts of ammonium persulfate and stir until dissolved. Begin adding components A and B dropwise. Component A is a sodium p-styrene sulfonate solution, composed of 60 parts sodium p-styrene sulfonate and 45 parts water. Component B is a vitamin C aqueous solution, composed of 0.2 parts vitamin C and 40 parts water. The dropwise addition time for components A and B is 2 hours. This dry-mixed mortar admixture has good dispersibility and water retention, and can meet the working requirements of dry-mixed mortar.

Description

Technical Field

[0001] This invention relates to the field of building material admixture processing, and more particularly to an anti-mud-type dry-mixed mortar admixture and its preparation method. Background Technology

[0002] Dry-mixed mortar refers to a mixture of dried and screened sand, cementitious materials, and admixtures in a certain proportion. It can be transported to the construction site in bags or in bulk and used directly after being mixed with water (Building Materials Technology and Application, 2021, 4: 22-24). Sand accounts for the highest proportion (by mass or volume) in dry-mixed mortar; therefore, the quality of the sand directly affects the quality of the mortar. Currently, river sand and manufactured sand are the main types of sand used in dry-mixed mortar. However, in recent years, with the scarcity of natural sand resources and the requirements of national policies for environmental protection, and with the advantages of low cost and adjustable gradation of manufactured sand, more and more enterprises have begun to use manufactured sand as raw material for concrete or mortar (Engineering Technology Research, 2020, 5(6): 143-144.). However, the biggest problem with manufactured sand is that the raw materials for manufactured sand are widely available and the quality is relatively poor. In particular, the mud powder content of manufactured sand has a serious negative impact on the workability and mechanical properties of concrete or mortar (Fujian Building Materials, 2021, 7: 1-3, 21.).

[0003] The mud powder contained in manufactured sand is mainly composed of various clay mineral phases, mostly layered aluminosilicate minerals. As the mud content increases, the mortar becomes more susceptible to cracking, shrinkage and mass loss increase, and strength decreases. In addition, clay weakens the ability of water-reducing agents to disperse cement particles, mainly manifested in problems such as high water-reducing agent dosage and poor slump retention (Jiangxi Building Materials, 2015, 8:8,10).

[0004] To avoid the adverse effects of clay on the performance of water-reducing agents, researchers have conducted extensive studies on the structural design of water-reducing agents and clay sacrificial agents, thereby reducing the negative impact of clay on the dispersion performance of water-reducing agents.

[0005] Chitosan is a natural polymer with an amino group in its structure, which allows it to readily adsorb onto negatively charged clay particles, reducing the adsorption of polycarboxylate superplasticizers by the clay and mitigating the adverse effects of the clay. Furthermore, chitosan possesses antibacterial properties, effectively extending the shelf life of additives. Finally, chitosan also has a certain thickening and water-retention effect.

[0006] Clay powder exhibits a much higher adsorption rate and capacity for PCE than cement, and the intercalation adsorption of PCE by clay powder degrades PCE's dispersion ability on cement particles. To address these issues, many researchers have modified PCE to overcome the adverse effects of clay powder, leveraging the designability of its molecular structure. Silane-modified PCE is a significant approach. Compared to ordinary PCE, silane-modified PCE demonstrates stronger adsorption capacity and a greater adsorption capacity on cement particle surfaces, significantly improving its dispersion ability in clay-containing cement pastes. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an anti-mud-type dry-mixed mortar admixture and its preparation method, so as to solve or reduce the influence of high mud content of manufactured sand on the performance of dry-mixed mortar, thereby obtaining mortar with better performance.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0009] An anti-mud dry-mixed mortar admixture, comprising the following percentages of materials: sulfonated chitosan: 20%-40%, air-entraining agent: 5%-15%, powdered polycarboxylate superplasticizer: 20%-40%, and setting regulator: 10-25%.

[0010] Furthermore, the preparation method of the sulfonated chitosan is as follows:

[0011] a1: First, dissolve 50 parts of chitosan with an average molecular weight of 10,000 to 30,000 in 100 parts of 2 wt% acetic acid solution, heat to 40°C and stir to dissolve;

[0012] a2: Add 0.45 parts of ammonium persulfate and stir until dissolved;

[0013] a3: Start adding materials A and B. Material A is a sodium styrene sulfonate solution, consisting of 60 parts sodium styrene sulfonate and 45 parts water. Material B is a vitamin C aqueous solution, consisting of 0.2 parts vitamin C and 40 parts water. The dripping time for materials A and B is 2 hours.

[0014] a4: After the reaction was completed, the sulfonated chitosan was precipitated with 95% ethanol and washed three times. After drying, it was ground and passed through a 60-mesh sieve to obtain the sulfonated chitosan.

[0015] Furthermore, the preparation method of the powdered polycarboxylate superplasticizer is as follows:

[0016] b1: Add 420 parts of ethylene glycol monovinyl polyoxyethylene ether to a four-necked reaction flask, add 280 parts of water and stir until dissolved, and adjust the temperature to 15-20℃;

[0017] b2: Prepare components A and B. Component A is an aqueous solution of acrylic acid and vinyltriethoxysilane, with 35 parts acrylic acid, 14 parts vinyltriethoxysilane, and 40 parts water. Component B is a mixed aqueous solution of mercaptoethanol and reducing agent E51, with 0.8 parts mercaptoethanol and 0.65 parts reducing agent E51.

[0018] b3: Add 2.6 parts of hydrogen peroxide (27.5%). After stirring evenly, start adding A and B components dropwise. The addition time for component A is 60 minutes and the addition time for component B is 90 minutes. After the addition is completed, let it mature for 1 hour. Add liquid alkali to neutralize to pH 5-6, and the reaction is complete.

[0019] b4: Spray drying is performed to obtain powdered polycarboxylate superplasticizer.

[0020] Furthermore, the air-entraining agent is one or both of triterpenoid saponins and sodium dodecylbenzenesulfonate.

[0021] Furthermore, the coagulating agent is one or both of sodium gluconate and white sugar.

[0022] A method for preparing an anti-mud dry-mixed mortar admixture, wherein the anti-mud dry-mixed mortar admixture is obtained by mixing sulfonated chitosan, an air-entraining agent, powdered polycarboxylate superplasticizer, and a setting regulator.

[0023] The beneficial effects of this invention are:

[0024] 1. Chitosan is abundant in resources and has properties such as thickening and water retention, antibacterial and anti-mud properties. After grafting sulfonic acid groups, it has certain cement particle dispersion properties, thereby reducing the amount of water-reducing agent used.

[0025] 2. The silane modification of polycarboxylate superplasticizer can effectively improve its dispersion performance and enhance the bonding performance of mortar;

[0026] 3. The admixture described in this invention can effectively mitigate the adverse effects of using manufactured sand with high clay content on mortar performance. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to embodiments.

[0028] Example 1:

[0029] A mud-resistant dry-mix mortar is composed of the following raw materials and weight percentages: 79% sand, 15% cement, 5% fly ash, and 1% mud-resistant dry-mix mortar admixture. The sand is manufactured sand with a mud content of 3%.

[0030] The anti-mud dry-mixed mortar admixture comprises the following components by mass percentage: sulfonated chitosan: 30%, air-entraining agent: 15%, powdered polycarboxylate superplasticizer: 30%, and setting regulator: 25%.

[0031] The preparation method of sulfonated chitosan is as follows:

[0032] a1: First, dissolve 50 parts of chitosan with an average molecular weight of 10,000 to 30,000 in 100 parts of 2 wt% acetic acid solution, heat to 40°C and stir to dissolve;

[0033] a2: Add 0.45 parts of ammonium persulfate and stir until dissolved;

[0034] a3: Start adding materials A and B. Material A is a sodium styrene sulfonate solution, consisting of 60 parts sodium styrene sulfonate and 45 parts water. Material B is a vitamin C aqueous solution, consisting of 0.2 parts vitamin C and 40 parts water. The dripping time for materials A and B is 2 hours.

[0035] a4: After the reaction was completed, the sulfonated chitosan was precipitated with 95% ethanol and washed three times. After drying, it was ground and passed through a 60-mesh sieve to obtain the sulfonated chitosan.

[0036] The preparation method of powdered polycarboxylate superplasticizer is as follows:

[0037] b1: Add 420 parts of ethylene glycol monovinyl polyoxyethylene ether to a four-necked reaction flask, add 280 parts of water and stir until dissolved, and adjust the temperature to 15-20℃;

[0038] b2: Prepare components A and B. Component A is an aqueous solution of acrylic acid and vinyltriethoxysilane, with 35 parts acrylic acid, 14 parts vinyltriethoxysilane, and 40 parts water. Component B is a mixed aqueous solution of mercaptoethanol and reducing agent E51, with 0.8 parts mercaptoethanol and 0.65 parts reducing agent E51.

[0039] b3: Add 2.6 parts of hydrogen peroxide (27.5%). After stirring evenly, start adding A and B components dropwise. The addition time for component A is 60 minutes and the addition time for component B is 90 minutes. After the addition is completed, let it mature for 1 hour. Add liquid alkali to neutralize to pH 5-6, and the reaction is complete.

[0040] b4: Spray drying is performed to obtain powdered polycarboxylate superplasticizer.

[0041] The air-entraining agent is one or both of triterpenoid saponins and sodium dodecylbenzenesulfonate.

[0042] The coagulant is one or both of sodium gluconate and white sugar.

[0043] A method for preparing an anti-mud dry-mixed mortar admixture, wherein the anti-mud dry-mixed mortar admixture is obtained by mixing sulfonated chitosan, an air-entraining agent, powdered polycarboxylate superplasticizer, and a setting regulator.

[0044] Example 2:

[0045] A mud-resistant dry-mix mortar is composed of the following raw materials and weight percentages: 79% sand, 15% cement, 5% fly ash, and 1% mud-resistant dry-mix mortar admixture. The sand is manufactured sand with a mud content of 5%.

[0046] The anti-mud dry-mixed mortar admixture comprises the following components by mass percentage: sulfonated chitosan: 32%, air-entraining agent: 15%, powdered polycarboxylate superplasticizer: 31%, and setting regulator: 22%.

[0047] Example 3:

[0048] A mud-resistant dry-mix mortar is composed of the following raw materials and weight percentages: 79% sand, 15% cement, 5% fly ash, and 1% mud-resistant dry-mix mortar admixture. The sand is manufactured sand with a mud content of 7%.

[0049] The anti-mud dry-mixed mortar admixture comprises the following components by mass percentage: sulfonated chitosan: 34%, air-entraining agent: 14%, powdered polycarboxylate superplasticizer: 31%, and setting regulator: 21%.

[0050] Example 4:

[0051] A mud-resistant dry-mix mortar is composed of the following raw materials and weight percentages: 79% sand, 15% cement, 5% fly ash, and 1% mud-resistant dry-mix mortar admixture. The sand is manufactured sand with a mud content of 9%.

[0052] The anti-mud dry-mixed mortar admixture comprises the following components by weight percentage: sulfonated chitosan: 35%, air-entraining agent: 13%, powdered polycarboxylate superplasticizer: 32%, and setting regulator: 20%.

[0053] Example 5:

[0054] A mud-resistant dry-mix mortar is composed of the following raw materials and weight percentages: 79% sand, 15% cement, 5% fly ash, and 1% mud-resistant dry-mix mortar admixture. The sand is manufactured sand with a mud content of 12%.

[0055] The anti-mud dry-mixed mortar admixture comprises the following components by mass percentage: sulfonated chitosan: 36%, air-entraining agent: 14%, powdered polycarboxylate superplasticizer: 34%, and setting regulator: 16%.

[0056] Mortars for each embodiment were prepared according to the requirements of "Standard for Test Methods of Basic Performance of Building Mortar" JGJ / T70-2009 and "Premixed Mortar" GB / T25181-2019, and their corresponding properties were tested. The results are shown in Table 1.

[0057] Table 1. Relevant performance indicators for each embodiment

[0058]

[0059]

[0060] As can be seen from Table 1, the increase in mud content has varying degrees of impact on the various performance indicators of dry-mixed mortar, but the adverse effects of mud content can be weakened or overcome by adjusting the composition of admixtures.

[0061] Although the present invention has been disclosed above with reference to preferred embodiments, the embodiments are merely examples for illustrative purposes and are not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. The scope of protection claimed by the present invention should be determined by the claims.

Claims

1. An anti-mud dry-mix mortar admixture, characterized in that: It is composed of the following materials by weight percentage: sulfonated chitosan: 20%-40%, air-entraining agent: 5%-15%, powdered polycarboxylate superplasticizer: 20%-40%, setting regulator: 10-25%; The preparation method of the sulfonated chitosan is as follows: a1: First, dissolve 50 parts of chitosan with an average molecular weight of 10,000 to 30,000 in 100 parts of 2 wt% acetic acid solution, heat to 40°C and stir to dissolve; a2: Add 0.45 parts of ammonium persulfate and stir until dissolved; a3: Start adding materials A and B. Material A is a sodium styrene sulfonate solution, consisting of 60 parts sodium styrene sulfonate and 45 parts water. Material B is a vitamin C aqueous solution, consisting of 0.2 parts vitamin C and 40 parts water. The dripping time for materials A and B is 2 hours. a4: After the reaction was completed, the sulfonated chitosan was precipitated with 95% ethanol and washed three times. After drying, it was ground and passed through a 60-mesh sieve to obtain the sulfonated chitosan. The preparation method of the powdered polycarboxylate superplasticizer is as follows: b1: Add 420 parts of ethylene glycol monovinyl polyoxyethylene ether to a four-necked reaction flask, add 280 parts of water and stir until dissolved, and adjust the temperature to 15-20℃; b2: Prepare components A and B. Component A is an aqueous solution of acrylic acid and vinyltriethoxysilane, with 35 parts acrylic acid, 14 parts vinyltriethoxysilane, and 40 parts water. Component B is a mixed aqueous solution of mercaptoethanol and reducing agent E51, with 0.8 parts mercaptoethanol and 0.65 parts reducing agent E51. b3: Add 2.6 parts of 27.5% hydrogen peroxide. After stirring evenly, start adding A and B components dropwise. The addition time for component A is 60 minutes, and the addition time for component B is 90 minutes. After the addition is completed, let it mature for 1 hour. Add liquid alkali to neutralize to pH 5-6, and the reaction is complete. b4: Spray drying is performed to obtain powdered polycarboxylate superplasticizer; The air-entraining agent is one or both of triterpenoid saponins and sodium dodecylbenzenesulfonate; The coagulating agent is one or both of sodium gluconate and white sugar; This anti-mud dry-mix mortar admixture is obtained by mixing sulfonated chitosan, air-entraining agent, powdered polycarboxylate superplasticizer, and setting regulator.

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