Mineral water to add and subtract in concrete mixing, not only to the properties of fresh concrete, such as slump, viscosity, water retention and constructability, but also impact on the performance of concrete condensation hardening stage, therefore, it is on the performance of the hardened concrete, such as strength, elastic modulus, shrinkage, creep, infiltration resistance, frost resistance, carbonization, etc all can have an impact on performance.
First, the effect of water reducing agent on the rheological properties of new concrete
From the perspective of rheology, in order to prepare the fresh mixed concrete with good fluidity, it is necessary to disassemble the viscous structure between the cement particles in the slurry, which hinders the flow, so that the cement particles are fully dispersed in the water medium.
When added to fresh concrete water reducing agent, water reducing agent and molecular dissociation after adsorption on the surface of cement particles, the result of the cement particles with the same charge same charges are repellent effect, cement particle surface will increase electric potential as well as the solvent of water film formation on the surface of cement particles, etc which will lead to yield shear stress of fresh concrete is reduced, the viscosity coefficient decreased.
In this way, the macroscopic result is that the stability of the whole concrete dispersion system is improved and the fluidity is improved.
Second, the influence of adding water and reducing agent on the fluidity of concrete
The fluidity of concrete is generally indicated by the slump value.
In the concrete water consumption and cement dosage under the circumstance of constant, adding water reducing agent can increase the slump of concrete.
And in a certain range, with the increase of the amount of water reducing agent, the increase value of slump is also increasing.
Three, the relationship between the amount of water reducing agent and concrete water reducing rate
When the concrete cement dosage and the water quantity army keep the same, admixture decreases the water agent will increase the concrete slump.
But if the dosage and slump of concrete cement are kept the same, adding water and reducing agent can achieve the purpose of reducing the water consumption of mixture.
Tell on general sense, below the circumstance that dosage of cement is changeless, when achieving same slump, the ratio of the unit cubic meter concrete water quantity used after adding and reducing water agent and the unit cubic meter concrete water quantity when not adding and reducing water agent is called reducing water rate.
The concept of water reduction rate described here is different from the concept in the concrete admixture standard.
The water-reducing rate of concrete with water-reducing agent in addition to the kind of water-reducing agent, breed, admixture, but also with concrete mix ratio, concrete initial slump, cement type, cement mineral composition, admixture variety and admixture.
Ambient temperature.
