117. Softeners (plasticizers), added to the concrete mix

Superplasticizers are construction and chemical additives, with which plasticization is achieved a very strong and significant improvement in the consistency of mortar or concrete. To distinguish from other less efficient they are called plasticizers superplasticizers (Engl. "Superplasticizer"). Their effectiveness in relation to water saving in the manufacture of concrete generally higher than with conventional plasticizers lignosulfonate (see. Table 2.3). In Germany, the use of plasticizers in concrete regulated originally published in 1974, the "Directives for the production and processing of liquid concrete." The chemical composition distinguish two different groups of plasticizers, namely poly condensates and polycarboxylates. The latter are mostly more efficient than polycondensates, and generally, they are more expensive products. In the manufacture of concrete superplasticizers (diluents) that usually used raw materials without chlorine; in some countries it is forbidden to use it for reasons of protection against corrosion.

 

Table 2.3 -Dostigaemaya water savings for a variety of plasticizers

Пластификатор	Классификация	Экономия воды в бетоне, %
средняя	максимальная
Лигносульфонат	пластификатор	5 - 15
NSF	суперпластификатор	10 - 25
MFS	суперпластификатор	10 - 25
Поликарбоксилаты	суперпластификатор	20 - 30
Амфотерные поликарбоксилаты	суперпластификатор	30 - 45

polycondensates

Polycondensates - are polymers in which the water outlet (= condensation) form a chain molecule with repeating units (structural units). Since most high polycondensates or structuring degree of condensation are obtained as insoluble, resinous compounds, and they are also called condensate resins. In the construction chemicals in these polycondensates are used as superplasticizers:

· Naphthalene-formaldehyde condensate resin (ASN it. NSF, Eng. PNS = "polynaphthaline sulfonate")

 melamine-formaldehyde-sulphite condensate resin (IFS it. MFS, Eng. PMS = "polymelamine sulfonate")

The quantitatively dominating ASN resin with an annual rate of about 350 000 tons, compared with MFS-resins with the general manufacturing 100,000 tons (in both cases as a 40% aqueous solution). Conducted various experiments with phenol, urea, dicyandiamide and sulfanilic acid resins. Successful experiments were only a sulfanilokislota-melamine-cobalt-condensate resins. Compared with pure melamine resins, they show improved reception time of the flushing impact of the concrete. The resulting low cost urea-formaldehyde-sulphite resin insufficient stability during storage (further condensation into insoluble resins) proved to be a big disadvantage.