The additives in concrete areas following:
Early strength agent, water reducing agent, retarder, quick setting agent, antifreeze, anti-seepage agent.
The proportion of admixture in concrete is generally: 0.5 ~ 1%,Related extensions:
Concrete admixtures are referred to as admixtures for short, which refers to substances added to improve the performance of concrete during the mixing of concrete. The admixture of concrete admixture is generally not more than 5% of the cement quality. The quality of concrete admixture products must meet the requirements of the national standard “Concrete Admixture” (GB8076-2008).
Divided into four categories according to main functions:
(1) Admixtures for improving concrete mixes and easy performance, including various water reducing agents, air entertaining agents and pumping agents, etc .;
(2) Additives to adjust the setting time and hardening performance of concrete, including retarders, early strength agents and quick setting agents;
(3) Additives to improve the durability of concrete, including air-entertaining agents, waterproofing agents and rust inhibitors;
(4) Admixtures to improve other properties of concrete, including air-entraining agents, expansion agents, antifreeze agents, colorants, waterproofing agents and pumping agents.
If a high-performance polycarboxylic acid water-reducing agent is used, the dosage is generally between 1.0% and 2.5% of the cement quality. Its chemical structure contains carboxyl anion repulsion, and the three-dimensional effect of the hydrophilic three-dimensional protective film formed by the strong hydrogen bonds formed by the reaction of multiple ether side chains with water molecules, making it extremely strong cement dispersion and stable dispersion Sex. Its water reduction rate is as high as 30% -40%, saving cement by 25% while keeping the strength unchanged, and can increase the concrete strength by more than 30% while keeping the cement dosage unchanged.
There are some other indicators that need attention
1. The amount of admixture
Almost all admixtures have a better dosage range, and high-performance grouting admixtures are no exception. The mixing amount of the grouting admixture is in a better range, and the required excellent grouting performance can be obtained. It is also more economical in terms of cost performance. If the admixture is low, the application effect cannot be achieved; if the admixture is high, it is not only uneconomical, but also has an adverse effect on the performance of the grout.
Second, the more common is
1. Increasing the gas content of the grout, introducing many large bubbles into the grout, resulting in a reduction in the strength and durability of the grout;
2. Increasing the bleeding of the grout, resulting in the segregation of the grout, the construction performance is reduced, and the unevenness and sex are increased;
3. When the amount of retarding admixture is too much, the grouting material will not solidify for a long time. When the amount of air-entraining agent is excessive, it will cause the strength of the grouting material to decrease greatly.
3. The 8 factors that should be paid attention to when choosing additives
1. Prepare high-durability grouting material. It is recommended that Zhengzhou prestressed grouting material should be compounded with polycarboxylic acid admixture and air-entraining agent with search ability. If the construction performance meets the requirements, the modified naphthalene water reducer and air-entraining agent can also be selected.Danjiangkou self-leveling grouting material;
2. Preparation of grouting material with high shrinkage-reducing performance, you can choose shrinkage-reducing agent and polycarboxylic acid admixture with reducing ability or modified naphthalene water-reducing compound.
3. When preparing clear water grouting material, polycarboxylic acid admixture should be selected.Handan grouting material
4. When using high-performance grouting additive, the user can choose one or more concrete admixtures according to the specific situation. The admixture should be tested carefully before use, with particular attention to the adaptability of the admixture to cement and the compatibility of several admixtures when used in combination.
5. Despite the excellent performance, the performance grout admixture has some defects. The selection of additives should be based on the actual conditions of the project to meet the requirements of the project, and select the appropriate additives.
6. When preparing high-strength grouting materials, it is advisable to choose the polycarboxylic acid concrete admixture with a water-reducing rate.
7. Prepare the pumping grouting slurry. If you only choose to control the slump loss of the grouting slurry and the pump type is good, you can choose the sulfamic acid concrete admixture. Polycarboxylic acid admixtures and modified water-reducing agents are also suitable for the preparation of pumping grouting slurry.
8. For the preparation of large-volume grouting materials, it is advisable to choose polycarboxylic acid admixtures with shrinking performance and optimizing who can hydrate the heat release curve, and change to a naphthalene-based superplasticizer.