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Superplasticizers (SPs), also known as high range water reducers, are additives used for making high-strength concrete or to place self-compacting concrete. Plasticizers are chemical compounds enabling the production of concrete with approximately 15% less water content. Superplasticizers allow reduction in water content by 30% or more.
Water reducers are special chemical products added to a concrete mixture before it is poured. They are from the same family of products as retarders . The first class of water reducers was the lignosulfonates which has been used since the 1930s.
These low range water reducing dispersants are commonly manufactured from lignosulfonates, a by-product from the paper industry. High range superplasticizers (dispersants) have generally been manufactured from sulfonated naphthalene condensate, although polycarboxylic ethers represent more modern alternatives. Both of these high range water ...
The performance of a concrete mix can be altered by use of admixtures. Admixtures can be used to reduce water requirements, entrain air into a mixture, to improve surface durability, or even superplasticise concrete to make it self-levelling, as self-consolidating concrete, [14] the use of admixtures requires precision in dosing and mix design ...
The reduction in cement content and increase in packing density of materials finer than 80 μm, like fly ash etc. can reduce the water-cement ratio, and the high-range water reducer (HRWR) demand. The reduction in free water can reduce the concentration of viscosity-enhancing admixture (VEA) necessary to ensure proper stability during casting ...
HPC is concrete that develops a strength greater than 50 megapascals (7,300 psi) at 28, 56, or 90 days. These strengths generally require well-graded hard rock aggregates, a fairly high proportion of cement plus fly ash, water-reducing admixtures, and the silica fume, with relatively low water content.
Raising the water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. Changes in gradation can also affect workability of the concrete, although a wide ...
In areas with high evaporation rates, this process often takes place overnight when temperatures are cooler. Once the pores are saturated as much as possible with water, the coating is applied. Hydrophobic chemicals are in a powder form and mixed with water at a ratio of five parts powder to two parts water for application by brush.