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Knowledge of Superplasticizers

Source: | Updated: Jan 28, 2016

Most superplasticizers do contain formaldehyde. They are either sulfonated melamine-formaldehyde condensates or sulfonated naphthalene-formaldehyde condensates. That may explain the allergic reaction you're having. The smell is probably not formaldehyde. In concrete heavily dosed with naphthalene-based supers, however, you may be able to smell naphthalene. It smells like moth balls. There are other options for producing flowable concrete. One way is to add both a conventional water reducer and a retarding admixture to the concrete. If you take this approach, watch out for setting problems, especially when slabs are poured. The concrete may set very slowly and delay finishing operations. On hot, dry days the surface may crust over while the underlying concrete is still plastic. The top surface appears to be ready to finish but is spongy and will deform under the finisher's weight or the weight of a power trowel. This can cause a wavy slab surface. Flowable concrete also can be produced by using a large dose of a conventional water reducer and adding enough accelerator to counteract the retardation effects. All water-reducers retard set to some extent and large doses can cause exceptionally long setting times unless an accelerator is added, too. Be aware that some accelerators contain calcium chloride and are prohibited on jobs where chlorides aren't permitted in the mix.

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