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The type and function of concrete additive

The type and function of concrete additive

NO

Species

Application

Adjust the setting time of concrete admixture, hardening of the performance

1

Retarder

1) refers to the retarder can delay the setting time of concrete, and without any adverse effect on the later strength development of concrete admixture. 2) the effect of retarder. A. to delay the condensation, keep the workability of concrete, prolong exothermic, eliminate or reduce cracks and enhanced. B. join retarder of concrete construction and pumping concrete is suitable for high temperature season, the sliding mode of concrete and mass concrete construction concrete or long-distance transport of goods. 3) commonly used retarder. A. many hydroxyl carbohydrates; B. lignin sulfonic acid salts; C. hydroxy carboxylic acid salts; D. inorganic salt

2

Early strength agent

1) refers to the early strength agent can improve the early strength of concrete, and the later strength had no significant effect of admixture. 2) the effect of early strength agent. A. the hydration of tricalcium silicate and dicalcium silicate has catalytic effect, can be used for winter construction or repair projects. B. early strength agent soluble in water, with certain plasticizing effect of concrete, the general content is 0.5% ~ 2% of cement dosage, can make the compressive strength of concrete in the first 3 d increased by 50% ~ 100%, 7 d compressive strength increased by 20% ~ 40%. E. can lower the freezing point of water through the concrete and prevent concrete early seas. 3) commonly used early strength agent. A. chlorine salt early strength agent; Sulfate early strength agent. B. c. triethanolamine or triethanolamine and sodium chloride, sodium nitrite, sodium dihydrate gypsum or composite effect, such as compound early strength agent

Improve the rheological properties of concrete admixtures

1

Water reducing agent

1) water reducing agent is to point to in keeping the concrete mixture, liquidity conditions to reduce the amount of admixture mixing water. 2) the effect of water reducing agent. 8. Increased liquidity (increase liquidity mechanism is shown in figure 1). In the original mixture ratio remains the same, that is, water, under the constant water-cement ratio, strength, increase the liquidity of concrete mixture. B. to improve strength. Under the condition of the liquidity and the dosage of cement unchanged, can reduce water consumption, mixture decreased water-cement ratio, thus improve the strength of the concrete. E. saving cement. If keep the original design requirements of strength, in the concrete mixed with proper amount of water reducing agent is in reducing water use at the same time reduce the dosage of cement. D. improve other properties. Mixing and subtract superplasticizer can improve the concrete mixture adhesiveness and water retention; Improve the compactness of the hardened concrete, improved durability; To reduce and delay the hydration heat of concrete. 3) the common water reducing agent. A. lignin of water reducing agent; B. naphthalene series water reducing agent. C - resin water reducing agent

2

Air-entraining agent

1) air-entraining agent means for generating microscopic bubbles into concrete admixtures. 2) the role of air-entraining agent. A. air-entraining agent can reduce the interfacial tension of a liquid - gas phase of solid, improve air bubble film strength, and make the bubbles displaces moisture and sorption to solid phase (cement particles on the surface of the ability, can make the air inside the concrete in the process of mixing formation pore size of 0.01 mm ~ 2 n 'llTl micro bubble, stable uniform distribution in the concrete, improve the liquidity of mixture. B. due to the moisture content of fresh concrete evenly distributed on the surface of a large number of tiny air bubbles, so as to improve the water retention of mixture and adhesiveness, improve pore structure characteristics (small, closed, uniform), and significantly improve the permeability resistance and frost resistance of concrete. E. the strength of concrete is often drop with the increase of air content of 3) commonly used air-entraining agent. A. rosin resin class

To improve the durability of concrete admixtures

1

Rust and corrosion inhibitor

1) steel rust inhibitor and dispersant is a join concrete can prevent or reduce steel corrosion, and the other properties of the concrete admixture had no adverse effect. The role of corrosion inhibitors for 2). 8. Have a passivating effect on reinforcement (anodic rust inhibitor and dispersant) or inhibit the generation and development of corrosion (cathode or hybrid); B. don't change the basic performance of concrete (such as strength, density, etc.) or can improve and improve the performance of concrete. C. in alkaline or neutral conditions, can maintain a long-term effective. Classification of corrosion inhibitors for 3). Steel rust inhibitors have a variety of classification. According to the action mode and application objects are divided into: a. mixed type rust inhibitors: adding to the concrete, direct effects on reinforcement rust and corrosion inhibitor. Mainly used for new construction, can also be used to repair project. B. infiltration type rust inhibitors: infiltration type rust and corrosion inhibitor is a kind of low viscosity liquid, can be coated (or spray) on the concrete surface, by the surface tension of the capillary suction inside the concrete, reach the surface of the steel, form a protection film, also can be reinforced surface existing chlorine ion, make steel passivation again. The rust and corrosion inhibitor as well as the surface coating, and can be used as an additive mixing into concrete. 4) common rust inhibitors: a. inorganic reinforcement rust and corrosion inhibitor; B. organic rust inhibitor and dispersant; C. compound rust and corrosion inhibitor

2

Waterproofing agent

1) waterproofing agent refers to a kind of can fill capillary channel, reduce the water absorption and water under hydrostatic pressure of admixture. 2) the role of the waterproofing agent. Concrete waterproofing agent can significantly improve the permeability resistance of concrete, the enhanced coagulation and waterproof hydrophobic, which makes the water seepage of concrete, water quantity is reduced, the durability of the concrete. 3) common waterproofing agent. A. organic matter waterproofing agent. B. inorganic quality department waterproofing agent; C. mixed waterproofing agent