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Encapsulation of dry superplasticizers in matrix-based encapsulation systems was investigated. As basic material, commercially available fly ash was granulated by high-shear agglomeration. Due to a high variability of factors affecting the encapsulation process and later release of admixtures, the design-of-experiments method was applied to reduce the quantity of experiments. Statistical evaluation indicates that the particle characteristics of the agglomerates were mostly influenced by the binder viscosity during the investigations. The delayed admixture release was enhanced by high binder viscosity and low energy input during the agglomeration process due to a coating of the bigger superplasticizer particles by the smaller fly ash. These results will help to develop encapsulated construction chemicals with controlled admixture delivery for the future application in a wide range of different building materials.

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Encapsulation and controlled release of active agents is a common practice to improve processing and properties of materials and final products in different industries. Today, a large variety of chemical admixtures are used in construction materials, the performance of which could be improved by a better dosage control. This work presents investigations on the controlled release of encapsulated construction chemicals for future applications in construction materials. The high shear mixing technology was used to produce matrix based encapsulations by agglomeration applied to commercially available construction materials. The agglomeration process was varied by the use of different agitator types, the variation of the agitator speed and the application of additional coating materials. The particle size distribution as well as the particle shape of the produced agglomerates was analyzed by automatic image evolution and scanning electron microscopy. The release behavior of the capsules in aqueous solutions was investigated by UV spectroscopy. The obtained results confirmed a theoretical model for the encapsulation and release of admixtures, which was derived from pharmaceutical drug release concepts and adapted to construction materials. The results indicate that the matrix based encapsulation is a promising technique for future applications in the field of construction materials.