Modified aliphatic water reducing agent and preparation method

Abstract

The invention discloses a method for preparing a modified aliphatic water reducing agent. The water reducing agent is a high-performance water reducing agent synthesized by taking acetone, formaldehyde and sodium metabisulfite as main raw materials and assisting with a proper amount of active agent and accelerating agent under certain conditions. The method comprises the following steps that: weighed tap water, sodium metabisulfite, sodium hydroxide and acetone are added into a four-mouth boiling flask with a reflux condenser tube, a thermometer and a stirrer, and are mixed evenly, then an accelerating agent, namely azodiisobutyronitrile is added into the flask, the temperature is increased, and the thermal insulation is performed after a sulfonation reaction; and the formaldehyde is dripped after the sulfonation reaction is finished, and the dripping speed is controlled. An acrylic acid active agent is added into the obtained product to obtain the modified aliphatic water reducing agent. The method is simple, is easy for industrialized production, reduces production cost, improves working performance (comprising the water-reducing rate and the flowability, workability, water retention property, plasticity retention performance and compressive strength of prepared concrete), and has obvious economic benefit and social benefit.

Description

technical field [0001] The invention belongs to the field of concrete admixtures in building materials, and more specifically relates to a modified aliphatic water reducer, which is suitable for concrete construction where the minimum temperature is above 0°C, dense steel bars, complex cross-sections, narrow spaces, and difficult to vibrate; mainly The invention is applied to highways, bridges, railways and other construction aspects, and also relates to the preparation method of the modified aliphatic water reducer. Background technique [0002] With the rapid development of the construction industry and water conservancy projects, new requirements are constantly put forward for the performance of concrete in all aspects. Ordinary concrete is difficult to meet the new construction technology requirements. Admixtures have been widely used as the fifth component of concrete in many countries. Water reducer is the most used admixture in concrete, and it can be divided into o...

AI Technical Summary

Problems solved by technology

Its disadvantages are: poor compatibility and poor predictability to concrete. For example, when polycarboxylate water reducer is used together with other admixtures, the concrete slump loss is too fast and rapid hardening is easy to occur. Compatibility problems between cement and chemical admixtures; in concrete using high-performance water reducing agents, when the unit water volume decreases and the slump increases, the following problems often occur: the amount of water reducing agent is too large, the concrete viscosity is too large, Segregated bleeding phenomenon, difficult pumping

[0015] The aliphatic water reducer is based on carbonyl compounds, which condense with formaldehyde under certain conditions to form aliphatic polymer chains with a certain molecular weight, and open the carbonyl groups through sulfonation reactions to introduce hydrophilic sulfonic acid groups. Polymer surfactants containing hydrophilic groups such as sulfonic acid groups, hydroxyl groups, and carboxyl groups have a number average molecular weight between 3300 and 3500. The main raw materials are acetone, formaldehyde and sodium sulfite. The raw materials are cheap and easy to obtain, and the production cost is relatively low. Low, the use of aliphatic water reducing agent can significantly reduce the raw material production cost of concrete; the early strength develops rapidly, and the later strength also has a tendency to increase; excellent adaptability to cement, strong dispersion ability, can effectively reduce cement hydration heat, water retention It has good performance, does not contain chlorine salt, has no corrosion effect on steel bars, and has good compatibility. It can reduce the surface potential of cement particles in the cement-water-superplasticizer system, and has the effect of static electricity dissipation, and the surface of cement particles The negative potential changes very little within 1 hour, and it shows multiple adsorption characteristics on the surface of cement particles as a whole. The adsorption curve belongs to LS type, and the limit adsorption capacity is greater than that of naphthalene-based water-reducers, but aliphatic water-reducers also have some Disadvantages, such as: in the case of the same addition amount, the water reducing rate is lower than that of naphthalene and carboxylic acid, the slump loss is larger, and there is also the problem of cement color after use, so it needs to be modified

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