Working Principle of Concrete Admixture Polycarboxylate Superplasticizer
The determining factor in the effectiveness of a concrete admixture polycarboxylate superplasticizer (PCE) is its adsorption properties. These properties depend primarily on the molecular structure of the polymer, the chemical conditions in the pore solution, and the physicochemical properties of the cement surface.
The high charge density, that is, a large number of carboxylate groups in the main chain, leads to rapid and complete adsorption of polymers. This is facilitated by the rapidly reacting surface of the cement grain, with the dominant role played by the C3A phases. The reactivity of the cement surface is affected by the content of sulfate ions in it. The content of sulfate ions in the pore solution is critical.
If clay is present as an admixture in the sand, then the PCE polymers can become irreversibly embedded in the clay layers, which reduces their action as concrete admixture polycarboxylate superplasticizer, i.e. their effectiveness is largely lost.
To maintain the effectiveness of the PCE concrete admixture polycarboxylate superplasticizer, it is important that its properties are optimally matched to the conditions of its use. To maintain its constant action in concrete over a long period of time, the constant quality of the cement used, as well as sand, concrete aggregates and other components, is of decisive importance.
It is recommended to check the effect of these changes on the performance of the PCE concrete admixture polycarboxylate superplasticizer in advance.
If necessary, it is necessary to adapt the concrete admixture polycarboxylate superplasticizer to new conditions or choose another, more suitable polymer. Application examples of PCE concrete admixture polycarboxylate superplasticizer
Closely related to the development and first use of PCE concrete admixture polycarboxylate superplasticizer was the development of self-compacting concrete (SCC). The production of self-compacting concrete is impossible without highly effective plasticizers. Especially in the production of precast concrete, self-compacting concrete (SCC) in Western Europe already has a large market share, in particular in the Netherlands, Denmark and Sweden.
The high content of fine particles and the generally low W/C ratio necessitate the use of a high performance PCE based plasticizer. In addition, the action of PCE concrete admixture polycarboxylate superplasticizer has a positive effect on the viscosity of self-compacting concrete.
In addition to the production of precast concrete, PCE concrete admixture polycarboxylate superplasticizer have recently years conquered the production of ready-mixed concrete. High efficiency and consistency retention are important technical arguments for the use of these concrete admixture polycarboxylate superplasticizer. In addition, the ability to produce softer concretes, up to self-compacting concrete (SCC), offers great economic potential.
Plasticizers based on polycarboxylate esters, thanks to their special mechanism of action and flexible chemical structure, allow manufacturers of concrete admixtures to use these special properties according to the application. In the production of precast concrete, the share of PCE additives used on the Western European market is already more than 50%.
With regard to ready-mixed concrete, these products are currently used mainly for the production of self-compacting concrete (SCC) and their potential is far from being exhausted. These examples show that concrete admixture polycarboxylate superplasticizer can also contribute to cost-effective and high-quality performance of specifications and make concrete an attractive, inexpensive and promising building material.