How many concrete mix ratios are suitable?
The so-called "concrete mix ratio" - concrete, sand , stone and the proportion of water between them.
The various properties of concrete, such as strength, performance and various properties of concrete mixtures are directly affected by its ingredient mix; As the ratio changes, the various properties of the concrete also change; and the specific dosage of concrete will also affect the profit of the concrete. In order to meet the workability and fluidity stipulated in the applicable standards and ensure the concrete rebound, performance and other characteristics mentioned in the construction project, as well as save a large amount of concrete, control costs, and achieve the effective purpose of the tertiary industry , you must choose a suitable concrete mix ratio.
The concrete mix ratio must be calculated according to the net weight?
Concrete material composition (weighing The accuracy of weight) is a key criterion to ensure the quality of concrete projects and save raw materials. Generally, the weighing deviation for concrete, water, admixtures and other cementitious organic matter shall not exceed ±2% by weight. The stone weighing deviation shall not exceed ±3%.
Because sand, stone, concrete and other materials have different temperatures and hardnesses, the weight of materials with the same volume is often very large. Therefore, the concrete mix proportions are controlled based on weight calculation. This mix ratio calculation method is more accurate than the volumetric method.
Why does concrete crack after hardening?
Concrete hard bottom There are very few reasons for cracking after melting. It is usually caused by two reasons. Generally, concrete structures are overloaded and cause tensile and shear forces. If the compressive strength of the concrete does not resist the tensile and shear forces, cracking will occur. The reasons for the deformation of concrete include dry shrinkage, temperature changes, oxidation and structural factors. At this time, the amount of shrinkage should be reduced as much as possible in terms of material, preparation, maintenance, etc. On the other hand, the amount of shrinkage needs to be reduced from the aspects of decoration engineering and layout. Try to make up for the various situations where hereditary cracking is easy.
Why does the surface of concrete become white after hardening?
Concrete After the hardened base is dried, external precipitation, surface water, health care water, etc. penetrate into the hardened base body through the permeability coefficient, causing the cement suspension or saturated solution of carbonates to be discharged, and then mix with the CO2 in the air. It reacts into sulfur organic matter, which sticks to the surface of the solidified body after the water evaporates. This situation is called whitewash, also known as "wall cancer".
Baihua can be cleaned with soap solution at first. If it is carbonated, it can be cleaned with water and sulfuric acid and then washed away by hand. However, although Baihua has been scrubbed, it is still It will be discharged again to avoid blooming. Be sure to use evenly poured and high-density concrete to reduce the permeability coefficient. Then appropriately reduce the water-cement ratio and reduce the mud content in the aggregate. Use clean mixing water and high High-quality concrete, mixed with water-reducing admixture, proper maintenance, and making every effort to avoid precipitation intrusion on site can prevent it from happening before it happens.
What is the adaptability of concrete water-reducing agent to concrete?
1. Is concrete calcite Stability causes whether the mineral components are stable, which in turn affects the ability of the concrete water-reducing agent to adapt to concrete.
2. The cement production process, such as shaft kilns and rotary kilns, how well the chilling countermeasures in the refrigeration mechanism are controlled, the temperature during gypsum grinding, etc., lead to The mineral components, crystal phase state, and lime paste shape in the concrete change, thereby affecting the adaptability of the concrete water-reducing agent to the concrete.
3. The potential of water-absorbing adsorbent in concrete: C3A>C4AF>C3S>C2S. The hydration rate of concrete is directly related to the mineral components.
4. After the concrete is stored for a period of time, the temperature decreases, which improves the high temperature adaptability of the concrete water-reducing agent, and f-CaO absorbs water in the gas Then it is converted into Ca(OH)2, and the CO2 in the adsorbed gas is converted into CaCO3, thereby reducing the Mwo, improving the workability of the concrete, alleviating the damage to the slump of the fresh concrete, and shortening the initial setting time of the concrete. Increase.
5. Generally, the water demand of Portland cement is slightly more than that of fly ash concrete. It has good water retention and solubility, but it usually collapses and damages quickly.
6. C3A concrete with higher water content has rapid slump damage and good water solubility.
7. Hydrophilic admixtures in concrete have good water solubility; pozzolanic concrete has poor water solubility and is prone to bleeding.
8. Temperature and temperature will directly affect the ability of the concrete water-reducing agent to adapt to concrete.
9. The gradation of sand and stone in the mix ratio and the proportion of sand, stone, water and glue also affect the adaptability of concrete water-reducing agent to concrete. ability.
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