The development history of concrete mud inhibitors and research progress at home and abroad

The so-called concrete mud inhibitor is to help reduce the adsorption of soil during the actual production process. Concrete admixture is the main means to achieve high strength, high working performance and high durability of concrete. In recent years, concrete admixture technology has continued to develop and progress, mainly reflected in the introduction of new macromonomers and the popularization of room-temperature synthesis technology of polycarboxylate water-reducing agents. The main problems that have arisen are that the technical threshold of the industry is getting lower and lower, the homogeneity of enterprises is serious, and there is almost no core technology. Market competition tends to drive down prices or gain market share with promised deposits. This makes the development of the industry slower and slower, and vicious competition becomes serious. The author believes that a healthy admixture industry should have certain technical thresholds, and companies with core technologies should occupy a leading position in market competition. Therefore, the R&D and industrialization of mud-blocking agent technology as a core technology have great economic and social benefits.

Due to its special interlayer structure, soil will absorb a large number of polycarboxylic acid molecules. Research has found that when the sand mud content (bentonite) reaches 5%, the loss of polycarboxylate water-reducing agent can reach 50% in 30 minutes. The slump and fluidity of concrete in 1 hour are the same as those of concrete without polycarboxylate water-reducing agent. Basically the same, it can be said that the polycarboxylate water-reducing agent is completely ineffective. The soil composition is complex, especially bentonite (montmorillonite), which has the strongest adsorption capacity for polycarboxylate superplasticizer, followed by kaolin. The failure of polycarboxylate superplasticizer due to mud content has frequently caused concrete quality accidents. At present, there are only two main measures for admixtures to deal with the problem of mud: one is to wash the sand with water, and the other is to overdope the polycarboxylate water-reducing agent. Although washed sand can control the mud content of the sand from the source, it adds a process and the cost is unaffordable for most concrete companies. The use of over-admixing may lead to a series of more serious quality accidents, because the amount of over-admixing cannot be accurately controlled. Once over-admixed, the concrete will take too long to set or even not set. It can be seen that neither of these two methods can effectively solve the adverse effects of mud content on polycarboxylate superplasticizer.

The current development status of mud-blocking agent technology

The research progress of foreign mud-blocking agent technology

The first country to discover the impact of soil on polycarboxylate water-reducing agents is In Japan, Adarashi et al. found through research that the interlayer structure of clay will greatly absorb the molecules of polycarboxylate water-reducing agents, but the adsorption of naphthalene-based water-reducing agent molecules is less. This explains for the first time the effect of mud content on polycarboxylic acid water-reducing agents. The influence mechanism of water reducing agent.

Data from the 10th International Conference on Concrete Admixtures show that polyethylene glycol (2000) can be used as a mud inhibitor to alleviate the adsorption of polycarboxylate water-reducing agents by clay. In addition, some studies have found that inorganic cations (such as K+ ions) can effectively adsorb clay.

It is understood that multinational companies such as Grace Company of the United States have applied mud inhibitors to their series of polycarboxylate superplasticizers. However, since they are the key technologies of these multinational companies, no mud inhibitors have been seen. Patents and literature reports on the composition and structure of pharmaceutical products.

Although there has been some progress in international research on mud inhibitors, it is relatively slow. Some industrialized mud inhibitor products are protected by intellectual property rights and are not disclosed.

Research progress in domestic mud-blocking agent technology

Through the efforts of various research units and enterprises in recent years, the research on mud-blocking agents in my country has made certain progress: the published patent “A Concrete Mud Resistant” (Patent No. CN201510198113.1) uses water-based polymers, gallic acid, and diethylene glycol to produce a mud inhibitor. This product “can reduce the adsorption of concrete water-reducing agents on mud particles and improve high efficiency. The fluidity of the mud-containing concrete system significantly improves the slump retention of the concrete water-reducing agent.”

The concrete mud inhibitor described in the patent under substantive examination “A concrete mud inhibitor based on the flocculation of clay minerals and its preparation method” (Patent No. CN201410695499.2) has a main component of The flocculant of multi-ion complex salts is supplemented by stabilizers, slow-release agents, and reinforcing agents to eliminate the acidic corrosion of the flocculants and the side effects that affect the early strength of concrete. “It can effectively reduce the amount of water-reducing agent and the cost of concrete preparation.”

The expired patent “Sludge Inhibitor for Concrete and Preparation Method” (Patent No. CN 102276181 A) points out that after the molecules of mud and mud inhibitor are adsorbed, the water absorption rate of the mud particles will be reduced, thus Reduce the water demand of concrete to an appropriate value. “The polymer monomer of the mud inhibitor is a molecule with a branched chain structure. This branched chain can effectively reduce the possibility of mud particles coming close to each other to form a gel, so that the mud-containing concrete system has good fluidity.” The patent The mud inhibitor ingredients are alkenyl amine ether, (meth)acrylate, DA, alkenyl sulfate, EA, and vinyl ester.

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