The compounding of early-strength water-reducing admixtures can adjust the relative density of the side chains of the product’s molecular structure and make use of strengths to offset weaknesses. The diversification of designed products is the basis for a good compounding. It is also possible to introduce products with unique characteristics to improve quality. For example, introduce a slump retaining agent with excellent slump retention or a slow-release slump retaining agent. When costs must be controlled, mid- to high-grade early-strength superplasticizers can be selected. Some of the compound combinations are weighted averages of characteristics, and some can obtain the cumulative effect of 1+1>2. The effect that cannot be achieved alone may be achieved by a variety of combinations.
The slump damage of concrete is the most important problem faced by early-strength superplasticizers. The compounding (including slump-preserving agent) is the best way to consider the slump-preserving properties and can be well integrated into the concrete. The quality or fluctuation of raw materials (especially sand), etc. While adjusting the slump retention, the slump of the concrete should generally be slightly reduced within 1 to 2 hours. High slump retention should be avoided to prevent the slump from returning to high after short-term transportation and causing delayed bleeding.
The prerequisite for compounding is that different types or types with different characteristics must be generated, which can only be established by manufacturers with product research and development capabilities. Pure admixture manufacturers need to go through their own experiments to select and purchase different storage materials for on-demand matching and use.
It is taboo to mix early strength with admixtures such as naphthalene series and hydroxysulfonate series. It has been introduced in the past that it can be interoperable with the above types of products, but no major applications and marketing have been seen. , this kind of compounding cannot be controlled in proportion, so we should be cautious. However, compounding of compoundable additives such as aliphatic additives is not ruled out. Before compounding, it is still necessary to determine the synergistic effects and impact on effectiveness through experiments.
Weak, causing the usual early strength to be unable to be solved, so the dosage is increased or the concentration and cost need to be increased, so that sometimes the saturation point of the early strength superplasticizer is so high that the admixture supplier cannot bear it. The cost of fees. Excessive reliance on admixtures in concrete should be corrected as much as possible.
The functional ingredients of early-strength superplasticizer products
In order to effectively improve the fresh-mixed properties of concrete and obtain early-strength superplasticizer products suitable for on-site concrete use, in addition to the selected In addition to the production process, it is also necessary to improve the retardation, air content, adhesion, appearance and other construction properties of concrete through simple physical compounding of multi-components with certain functions.
The physical compounding of retarder is essential. The incorporation of retarder components is an important component to adjust the setting time of admixtures at different temperatures. Under permitted conditions, one or more retarders can be used in combination (common ones include sodium gluconate and sodium citrate). , phosphate, glycogen, lignosulfonate, etc.), especially sodium gluconate and glycogen have good adaptability. The amount of retarder is adjusted with the temperature. Adding sodium gluconate has a better effect. Sometimes adding some retarder is helpful to reduce slump damage, but it cannot be used as a more effective way to prevent slump. When compounding a retarder, at least the retarder multi-component must have a certain water-reducing effect, which should be considered when calculating the total number and cost.
Adding air-entraining agents is a reasonable way to increase the air content of concrete and improve the water solubility and viscosity of concrete. It must have the synergistic effect of air-entraining agents and defoaming agents, so the two need to go hand in hand. . At present, there are many types of defoaming agents and air-entraining agents. It is best to conduct compatibility tests with early-strength admixtures. The first step is to solve the storage stability of early-strength superplasticizer products. Common air-entraining agents include fatty alcohol sulfonates, alkyl sulfonates, sodium alkenyl sulfonates, rosin resins, etc. The air content of concrete must be moderate. Although concrete with too much air content is soft and easy to handle, it will easily cause a reduction in strength.
Concrete bleeding is a common minor problem. Bleeding often causes the concrete to separate and block the pump. There is floating slurry on the surface of the concrete, and there are quicksand ripple defects. In particular, bleeding occurs about 2 hours after the concrete is poured. Water is more serious. Ways to control concrete bleeding include adding high-quality air-entraining agents and usage amounts. More powerful methods include adjusting the sand rate and increasing fine powder. Admixture methods also include adding emulsifiers. Common ones include dextrin, various Such as methyl cellulose (hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose), microbial glue, etc., and pay special attention to confirm the appropriate content and usage based on experiments to avoid incorrect operation or excessive use And cause negative effects.
Due to the long side chain molecular formula of early-strength superplasticizer, it is more sensitive to the incorporation of mud moisture content in concrete than other naphthalene-based, aliphatic and other admixtures. With the rapid development of infrastructure projects, many high-quality natural sand and gravel materials have been almost exhausted. In fact, high-grade mud-containing river sand, weathered river sand, and high-powder-containing artificial service sand will be widely used in concrete, because early The strong adsorption of mud powder in sand and gravel by strong admixtures has created new technical problems in ensuring the quality of concrete. Products such as anti-sludge agents that have been developed on the market to improve adhesion and adsorption have been frequently reported, but anti-mud products that reasonably meet the requirements�Products are still lacking, and research on this topic still requires diligent efforts by our country’s technical staff. It should be noted that the selection of sand for concrete should also be an important factor taken into consideration by the concrete shop when implementing technical rationality.
There are at least a variety of ingredients on the market used to compound early-strength superplasticizer products. Some of these products are new functional materials that are scientifically discovered to meet the needs of compounding, and some are common retarders. Careful comparative experiments must be conducted when using air-entraining multi-component applications
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