Views: 3 Author: https://www.concretedecor.net/departments/concrete-placing/the-magic-of-water-reducers/ Publish Time: 2021-09-27 Origin: https://www.concretedecor.net/departments/concrete-placing/the-magic-of-water-reducers/
Water reducers are divided into three general types: conventional, mid-range and high-range admixtures. While the properties of water reducers within the “conventional” category are typically very similar, the chemistries used by different manufacturers vary. Within the mid- and high-range products, not only does the chemistry vary, but the performance does, too. As Schlagbaum points out, you’re likely to see performance differences even within one supplier’s product line.
ASTM Specification C 494 Type A covers conventional water reducers. These water reducers reduce the water requirement a minimum of 5 percent. At the same time, without the addition of water, the slump is reduced 11⁄2 to 2 inches. Conventional water reducers are commonly used in everyday concrete for driveways, sidewalks, footers and basement walls.
Jumping to high-range water reducers — also called superplasticizers — this category falls under ASTCM Specification C494 Types A and F. Superplasticizers reduce the water requirement from 12 percent up to 40 percent.
“High-range or superplasticizers can be used to create a very low water-to-cement ratio for higher strength concrete, concrete with high slump, or in some cases both,” Thome says.
And, according to several experts, the technology is continuing to improve in this category.
Fallon observes, “In the old days (not so really long ago), general contractors needed to see the high-range water reducer going into the truck to make sure the slump was not achieved by water. Currently, high-range water reducers are added at the batch plant and arrive on the job site with the appropriate slump (based on specifications written for the job). If the slump is not high enough, a high-range water reducer can be added at the job site to get the right consistency for the job.”
Some of the newest formulas are based on polycarboxylate. As Sacco jests, when these superplasticizers are used in the mix you need to measure not in slump, but in spread — “it flows like pancake batter.”
Photograph courtesy of Euclid Chemical Company
Superplasticizers are so important to the industry these days, Fallon adds, “A concrete manufacturer that does not use a high-range water reducer these days is like a secretary not using a computer.”
Mid-range water reducers do not have an official ASTM designation, but the “unofficial” standard is for 5 percent to 15 percent water reduction.
According to Thome, “Mid-range water reducers generally will be used when there is a desire to reduce the mix design water and increase the slump moderately.”
Fallon reports an added benefit: “Contractors appreciate the added workability and the ‘creamy’ feel which helps in finishing. Truly, the mid-range water reducers had the contractor in mind.”
At this point, it should be clear that even contractors experienced with conventional water reducers can often benefit from the other two types if a specialized project comes up.
Rick Seymour, technical services manager at Lafarge N.A. in Glenwood Springs, Colo., points out, “Mid range and high range should be used where congested rebar is an issue, superior strength (low or high slump), flowability, extra durability or workability with other chemicals is required.”