The rheological properties of concrete mixtures are mainly reflected in the workability of concrete. It is a series of operations of mixing, conveying, pouring, tamping, and smoothing of concrete mixtures, which can make the concrete stable and stable under certain energy consumption. A kind of compact performance. The workability (or workability) of concrete directly determines the difficulty of concrete construction and its mechanical properties and durability after hardening.
Additives (such as water reducing agents, vulcanizing agents, etc.) have a great influence on the workability of concrete. A small amount of admixture can make the concrete mixture obtain good workability without increasing the amount of cement.
Not only the fluidity is significantly increased, but also the cohesion and water retention of the mixture are effectively improved, and the strength and durability of the concrete can be improved. According to the physical and chemical properties of concrete admixtures, water reducing agents can play a role in the following aspects.
(1) Water reducer can disperse cement particles to varying degrees. It can crush the flocculent blocks formed by cement when it meets water. In addition, many types of water reducing agents have more or less air-entraining effect, which reduces the viscosity of the cement slurry and increases the fluidity. It can make the concrete completely different in all mixing ratios. Under the changed conditions, the fluidity of the mixture is greatly increased. This effect is conducive to operation and mechanized construction.
(2) Under the conditions of appropriately changing the water-cement ratio, fine-tuning the mixing ratio of aggregate and lower water-cement ratio, the concrete mixture can have fluidity similar to that without water-reducing agent. As the water-cement ratio decreases, the strength of hardened concrete will be significantly improved. When using superplasticizers to reduce water consumption, use a relatively low water-cement ratio
(Less than 0.3) high-strength concrete can be prepared. For example, using 625# cement mixed with superplasticizer can be configured with 1000# super high-strength concrete. While increasing the strength of concrete, other properties of concrete, such as compactness, impermeability, and durability, have also been improved to varying degrees.
It can greatly reduce water when liquidity is fixed. The mode of action of superplasticizer molecules in these systems (the slurry of mineral particles) firstly depends on the adsorption of some molecules on the surface of the particles, and the molecules of the superplasticizer also transfer charges to the surface of the particles, which is conducive to the particles passing static electricity.
The repulsive force achieves better dispersion (decoagulation), and the adsorbed superplasticizer also plays a physical shielding role to keep the particles separated (ie steric repulsion), and further promotes the dispersion and fluidity of the particles in the slurry.