In recent years, with the country's implementation of the natural sand and gravel mining restriction policy and the increasing engineering volume, the demand for artificial sand is increasing. Qualified artificial sand resources are becoming more and more scarce, and artificial sand with rough surface and prominent edges and corners abounds. Its fineness modulus is large, the gradation is unsuitable, and the sand and gravel content is high in mud and powder, which makes concrete practical in production and application. Problems such as high water consumption, poor workability, easy segregation and bleeding, and inability to guarantee strength emerge in an endless stream. Based on the diversity of materials and the demand for high water reducing rate, the large-scale application of polycarboxylate superplasticizers has become a trend.

Numerous studies have shown that the main factors affecting the adaptability of polycarboxylic acid-based superplasticizers include: macromonomer type, main chain polymerization degree, branched functional groups, etc. Li Xiaoyan used the (2+2) monomer combination method, combining polyester monomer and acrylic monomer, to prepare a highly adaptable water reducing agent in the laboratory. It has been verified that it has high water reducing rate, high adaptability and high slump retention.

The combined use of water reducer and retarder can further prolong the setting time of concrete, reduce the loss of concrete slump over time, and effectively improve work efficiency. Tests show that when the content of citric acid is 0.05% to 0.15%, the fluidity is in the range of continuous growth, but when the content of citric acid is higher than 0.15%, the fluidity of sulfoaluminate cement decreases, which may be It is because the ratio between the retarder and the superplasticizer is inappropriate, so the phenomenon of competitive adsorption occurs, which inhibits each other and reduces the fluidity. Wu Yonghua et al. used sodium gluconate in combination with a polycarboxylate superplasticizer and found that there was a synergistic retardation effect between the retarder and the superplasticizer, which improved the fluidity of the cement slurry and improved the early stage of the cement mortar. and later strength.

Incorporating appropriate air-entraining agents into concrete can improve durability and rheology. Air-entraining agent is a kind of surfactant, which can be divided into rosin resins, fatty alcohol sulfonates, dodecylbenzene sulfonates, saponins, etc. At the same time, the air-entraining agent can improve the toughness, crack resistance, workability and freeze-thaw resistance of concrete, and make concrete develop towards high performance. And because the added amount of air-entraining agent is small, it only accounts for a few thousandths or even a few ten thousandths of the added amount of concrete admixtures, so it is usually mixed and dissolved with admixtures before use.

The addition of the thickener is to solve the problem that the yield stress and plastic viscosity of the concrete are too low, which will lead to the deterioration of the stability of the concrete slurry, and then cause a series of phenomena such as bleeding and segregation. Bleeding and segregation often occur in the use of large-volume concrete. Appropriate addition of thickeners during the preparation of concrete can improve the bleeding rate of concrete and better meet the needs of actual use. However, the main problem is that the water-retaining thickener and the polycarboxylate water-reducing agent are prone to incompatibility, resulting in uneven layering of the concrete admixture. Especially for mass concrete, the thickener can also improve the compressive strength of concrete within a certain range, and the cracks in mass concrete can also be solved by adding an appropriate amount of thickener. Based on the use of different types of thickeners, the ability to improve the strength of concrete is also different. Blindly increasing the amount of thickeners may also cause the concrete system to become viscous and have no fluidity, which is counterproductive.

1 Experimental part

1.1 Raw materials

Cement: P·O42.5 ordinary Portland cement; superplasticizer: solid content (active ingredient) accounts for 8% of the total mass, the synthetic monomer is C5, the water-reducing rate of the paste is 18%, and the amount of the admixture is glue 2.0% of the dosage of the coagulating material; retarder: sodium gluconate A, sodium gluconate B, sodium gluconate C, the dosage of the retarder is 3% of the dosage of the admixture; air-entraining agent: the dosage is 1% of the dosage of the admixture ‰～2‰; Thickener: Replace with thickener A, thickener B, and thickener C.

1.2 Experimental instruments

Cement mortar mixer; cement consistency setting time tester; concrete 60L vertical mixer; concrete air content tester; concrete compressive strength tester.

1.3 Testing and Characterization

1.3.1 Experiment on t