High efficiency water reducing agent on concrete performance
The properties of fresh concrete
Water reducing effect: high efficiency water reducing agent is polymeric surfactant, has the very strong solid liquid interfacial activity. The fluidity of concrete is improved greatly, but the gas liquid interfacial activity of small, sparkling little, basically no air entrainment. As the volume increases, the water reducing rate is also improved.
The slump and loss: adding superplasticizer, concrete slump from 6 ~ 8cm, increased to 18 ~ 22cm, but losses quickly.
Setting: usually superplasticizer on setting time little effect. But different superplasticizer varieties, the use of cement and admixture is different, the result is different.
Bleeding: because of superplasticizer on cement concrete with strong dispersion, improved mixture homogeneity and stability, so it can reduce the bleeding.
The properties of hardened concrete
The effect of inorganic salt on concrete performance
Effects of inorganic salt on cement performance
Retarder on concrete performance
Effects of organic retarder is mainly made of C3A hydration slows, lignin sulfonate makes C4AF hydration delay. Lignin sulfonate composition is different, with different properties, sometimes makes false setting of cement.
Effects of organic retarder, particularly the various hydroxy carboxylic acid and its salts, such as tartaric acid, citric acid, malic acid, salicylic acid, gluconic acid and their salts are commonly used in the retarder. Effect of different varieties, different also, shall be determined through test.
Effects of inorganic retarder include borax, zinc, iron, copper, and cadmium sulfate, phosphate and phosphate. Retarding effect of unstable, phosphate and phosphate application more. The high C3A content in cement, when mixed with sodium phosphate will appear when the accelerated phenomenon.
The good performance of the retarder is volume low, retarding time can be adjusted and strong, do not produce abnormal coagulation. Some retarders on initial setting time effect, and little influence on the final setting time; another some of retarder instead. There are a number of Retarder on initial, final setting time have great influence.
Effects of the retarder on setting time of different effects, can be used to control slump loss, cement heat of hydration. The commonly used retarder admixture: molasses categories: 0.1 ~ 0.3%; lignin : 0.2 ~ 0.3%; hydroxy carboxylic acid and its salts : 0.01 ~ 0.1%; inorganic : 0.05 ~ 0.2%.
In a reasonable range of dosage, the late strength of concrete will generally improve. Retarder overdose after too much not only severely retarded, later strength will get bigger impact.
The effect of cement retarder by variety and quantity, admixture, mixing amount, mixture ratio, temperature and other factors, before use should be based on specific materials, temperature test, confirmed to meet the requirements before use, to avoid excessive retarding etc..
Air entraining agent on concrete performance
The workability of concrete: with air-entraining agent, the introduction of a large number of small bubbles in concrete, the concrete workability and stability are greatly improved.
The bleeding settlement contraction: gas, plasma surface area increases, the viscosity increase, significantly reduced bleeding settlement.
Effects of water reducing effect : a general reduction of water 5 ~ 10%.
The concrete strength: water-cement ratio constant, gas content increased by 1%, reduced intensity 5%; slump constant, strength reduction or increase.
The concrete shrinkage: no obvious effect.
The impermeability, erosion : improving.
The freezing thawing resistance: increase.