Influence of PCE-superplasticizer on the nucleation and growth of products obtained during the hydration of portland cement and the intercalation of polymers in C-S-H phases.

• Applicant: Professor Dr.-Ing. Horst-Michael Ludwig
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: from 2006 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 20497792

In concrete and mortar production the use of polycarboxylate based polymers (superplasticizer) leads to improved workability and increased strenght due to reduced water/cement ratios. As a drawback the strength development is retarded caused by the interaction of these superplasticizer with cement compounds. The application is aimed to investigate the causes of this retardation of the cement hydration and the possibility for a certain polymer architecture combining the liquefaction with no retardation. Based on the results obtained from the dissolution of the pure clinker phase C3S and from the pure crystallization of cementitious hydrous phases influenced by superplasticizer different in their structure, the cement hydration should be accelerated by modification of the system. Thus a polymer induced acceleration is obtainable. Besides kinetic studies dedicated to the hydration of cements influenced by polymers the intercalation of polymers in C-S-H phases is main topic in the 3rd part of the project. It is to investigate if such intercalation will improve both mechanic (mainly tensile strength) and strain (mainly creeping) properties of the cement stone.The application will continue the one year fonded project (LU 1652/1-2) which is aimed to separate the hydration parts into dissolution and crystallization both influenced by superplasticizers. Special attention is paid on the reaction kinetics. During the first fonding the suitability of used methods was proved and these methods can be used for the dissolution and crystallization experiments.The dissolution process will be extended by the influence of different organic additives. Homogeneous crystallization experiments will be performed on calcium-silicate-hydrate (C-S-H) phases, portlandite as well as ettringite as main hydration products. In these investigations the influence of the superplasticizer structure (side chain length, amount of functional groups, etc.) on the crystallization rate is investigated. The third point is the intercalation of organic polymers into the crystal planes of C-S-H phases as origin phase causing the strength in cement is investigated. By adaption of principles of biomineralization an increased performance of the material is expected. This topic is a new field for the research on cements and will lead to a significant effort in the field. Furthermore detailed knowledge of basic principles of the hydration mechanisms and new materials properties are aimed for interdisciplinary discussion on materials sciences (geology, bionic).

• DFG Programme: Research Grants
• International Connection: Israel
• Participating Person: Professor Steve Weiner, Ph.D.