A kind of preparation method of starch-based concrete water reducer

Abstract

The invention discloses a preparation method of a starch-based concrete water reducing agent. The method comprises the following steps: (1) preparing starch pulp by using starch as a raw material, adding concentrated sulfuric acid to react, and drying to obtained acidolysed starch; (2) mixing the acidolysed starch, maleic anhydride, urea and sulfanilic acid to react so as to obtain grafted modified starch; (3) preparing the grafted modified starch into a solution, adding hydrogen peroxide and glyoxal to mix, regulating pH value of the mixed solution, and reacting to obtain the starch-based concrete water reducing agent. The method has the advantages that the water reducing efficiency of the starch-based concrete water reducing agent prepared by the invention is obviously improved in comparison with the naphthalene series or aliphatic series water reducing agent, and the cement adaptability, and the water retaining property and cohesion property of the concrete mixer are obviously improved in comparison with the polycarboxylic acid water reducing agent. The preparation process is simple, the synthesis device is simple, the pollution caused by organic reagents can be avoided, and the cost of recycling of organic solvents can be reduced.

Description

technical field [0001] The invention belongs to the field of concrete water reducers, in particular to a preparation method of starch-based concrete water reducers. Background technique [0002] The development of my country's water reducing agent industry is facing the demand of high performance, cost reduction and environmental friendliness. With the development of construction technology, the trend of high-performance concrete is becoming more and more obvious. Common water-reducing agents such as wood calcium and sugar calcium cannot meet the water-reducing requirements of high-performance concrete, and many water-reducing agents are made of petroleum. Derivatives are used as raw materials. For example, the naphthalene-based water-reducer in the second-generation water-reducer uses industrial naphthalene as the raw material. Industrial naphthalene is a widely used industrial raw material, and the performance weakness of the naphthalene-based high-efficiency water-reducer...

AI Technical Summary

Problems solved by technology

[0005] 1) The acid hydrolysis of hydrochloric acid will introduce chloride ions into the sulfonated starch, causing chloride ion erosion in reinforced concrete, reducing the durability of reinforced concrete structures, and affecting its service life. Therefore, the national standard specifies the concentration of chloride ions in concrete admixtures. strictly limited

[0006] 2) Select small molecular organic solvents to synthesize sulfonated starch by solution method, the reaction conditions are mild, but there is a problem of organic solvent recycling

If the solvent is not recovered, organic solvents with small molecular weight and high volatility will cause serious pollution to the environment, which does not meet the theme of national sustainable green development. However, the commonly used dichloromethane solvent in literature reports is not only highly volatile, but also highly toxic. It will seriously endanger the health of operators; the recovered solvent needs to introduce special recovery equipment and consume a lot of energy, resulting in a sharp increase in production costs, loss of cost-effective advantages, and difficulty in popularization and application

In fact, due to the similar polarity between the organic solvent used and the product of the starch superplasticizer, and the special helical tubular structure of the starch, it is very easy to cause the penetration and embedding of the organic solvent to form a sol-like substance, which makes it difficult to recover and separate the solvent.

[0007] 3) Sulfonated reagents mostly use very expensive reagents such as chlorosulfonic acid and sulfamic acid, and generally use a large amount, and it is difficult to recycle raw materials, resulting in increased production costs. Compared with other admixtures, they do not have an absolute advantage

[0008] 4) Since the starch structure contains a large number of hydroxyl groups, the preparation process mostly focuses on the introduction of sulfonated or esterified groups, and a large number of hydroxyl groups are not treated, resulting in good water retention and increased hydration layer thickness. Strong retarding effect, which seriously hinders its wide-scale use

[0009] The patent number is 200910164282.8, and the invention patent titled "a preparation method of oxidized-etherified starch used as a concrete water reducer" discloses an oxidized-etherified method, that is, using sodium hypochlorite and ethylene oxide to prepare starch-reduced starch. Water agent, but ethylene oxide is expensive, and there are safety hazards in the reaction process

[0010] The application number is CN104017093A, and the invention patent titled "A Preparation Method of Hydrophobic Starch Sulfate and Its Application in Cement Water-reducing Agent" discloses a method using reactants such as sulfamic acid, urea, and aliphatic tertiary alcohols. The method of preparing starch sulfate at a high temperature of 80-150°C introduces substances with more carbon atoms. Although it can improve its water retention and improve its fluidity, alcohols are the terminators for cement hydration , and a small amount of alcohol can have a great impact on the final setting of cement

[0011] In the article "Research on the Development of Sulfonated Starch Used as a New Cement Water-Reducer", Cheng Fa et al. used dichloromethane as the solvent and chlorosulfonic acid as the sulfonation reagent to prepare a starch water-reducer with water-reducing effect. It has been confirmed that sulfonated starch with a certain degree of substitution of sulfonic acid groups can achieve a high water-reducing rate and has a strong retarding effect. This retarding effect is mainly caused by two factors: on the one hand, the modified starch chain The hydroxyl group in the cement hydration product and the calcium ion complex in the cement hydration product reduce the calcium ion concentration in the solution, make the hydration product crystallize, prolong the crosslinking time, and slow down the strength development; on the other hand, the modified starch complexes with the calcium ion The substance is attracted by the electric charge to adsorb on the surface of cement clinker particles, forming a thick hydration layer, which plays a good role in dispersion and lubrication, but at the same time, the thick hydration layer also hinders the diffusion of hydration products into the solution. , leading to slower hydration reaction, longer induction period, and delayed setting time, but too strong retarding performance will lead to restrictions on the dosage of starch superplasticizer, especially in projects with tight schedules, long-term retarding It will bring huge losses, which will greatly hinder the large-scale use of starch superplasticizers

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