Nowadays, concrete admixtures are widely used in various industries, from the construction industry to high-speed rail to water conservancy projects, etc., which are inseparable from admixtures. However, how to choose? As a practitioner, you have to know!
Hydraulic engineering concrete has the characteristics of large volume, high durability requirements, and the need for a large amount of fly ash and artificial aggregates. Therefore, concrete admixtures are required to have the following functions and properties.
1. Improve the construction performance of concrete. The concrete is required to have good workability, small slump loss, improve concrete cohesion, reduce bleeding and aggregate segregation, and ensure concrete homogeneity.
2. Save cement, reduce unit water consumption, improve the thermal properties of concrete, and simplify temperature control facilities. In mass concrete, saving cement is not only a matter of economic benefits, but more importantly, it can improve the thermal performance of concrete. Due to the reduction in unit cement consumption, the heat of hydration is reduced accordingly, which is conducive to simplifying temperature control facilities and can reduce and avoid the occurrence of temperature cracks in concrete.
When purchasing raw materials, you should choose from qualified material suppliers who have been evaluated. Different control methods should be formulated based on the impact of the materials on the quality of concrete. For example, for sand and gravel materials, they can be released for use after passing visual inspection, and then inspected according to the prescribed inspection cycle or prescribed batches. ; For cement, it should be stipulated that its manufacturers must pass quality system certification. Those whose quality is confirmed to be stable after use shall be classified and managed according to their quality levels. When entering the site, sampling and testing shall be carried out according to the specified batches, and the quality of the additives shall be regularly inspected. Compatibility and other indicators to control; for the management of concrete water-reducing agents and other admixtures, the manufacturer of admixtures used for concrete above C60 should be certified by the quality system and appraised, and inspection items should be specified for each batch. Admixtures entering the site must be inspected and can only be used after passing the test to avoid hidden dangers to the quality of concrete.
What concrete admixtures are needed for water conservancy projects?
3. Retarding effect. During the construction of large-volume concrete in summer, due to high temperatures and rapid condensation, in order to avoid cold joints during construction, retarding measures must be taken. Admixtures are required to have a retarding effect, and reduce the maximum temperature peak of hydration heat and delay the occurrence of the peak. time.
4. Improve durability (including anti-freeze, anti-permeability, anti-corrosion). Enhance water tightness (denseness) and change the internal pore structure and pore distribution of concrete.
5. Enhance crack resistance. In particular, it is necessary to improve the early crack resistance of concrete, change the tension-compression ratio of hydraulic concrete, and improve the deformation ability.
6. Can be adapted to cement concrete mixed with fly ash.
7. It should be easy to use and easily accepted by the construction department.
8. On the premise of meeting performance requirements and ensuring quality, the cost should be as low as possible.
Therefore, in order to improve the durability of concrete for water conservancy projects, in addition to controlling the quality of materials and selecting qualified medium and low-heat cement to prevent alkaline slip reactions, high-quality air-entraining agents (bubbles) should be used. Small bubble diameter, small spacing coefficient) and used in combination with high-efficiency retardant water-reducing admixture to improve the durability of concrete
This is how concrete admixtures are selected and used in water conservancy projects. You have learned ?
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