Self compacting concrete (SCC) is a new kind of concrete that combines a high flowability and a high segregation resistance obtained by a large amount of fine particles or the presence of a viscosity modifying agent and the use of superplasticizers. As self compacting concrete does not need external compaction, the pore structure, and more specifically the amount of capillary pores, is not influenced by the compaction method. These capillary pores play a very important role in the transport of water and gases in concrete and are of major importance for the understanding of degradation mechanisms. In order to verify the correlation between the transport properties and the capillary pores, tests were carried out. Water and gas permeability, capillary absorption, carbonation and chloride penetration tests were performed on 11 self compacting concrete mixtures and 1 traditional concrete mixture. The selection of the mixtures is made in order to consider some important parameters like the cement/powder and water/cement ratio, the amount of water, the amount of powder and the type of filler(limestone filler with two different grading curves). The amount of capillary pores was calculated by the method of Powers. The calculated values were compared with the test results and gave very good correlations.

It is well known that, in comparison with normal (usual) concrete, self compacting concrete (SCC) shows higher shrinkage because of the higher volume of binder, inevitable for achieving high fluidity and a good cohesiveness of the fresh concrete. It is necessary to avoid crack formation caused by drying or autogenous shrinkage as cracks could serve as flow paths and ingression zones for gases and salts or favour leaching. In order to diminish this negative effect of SCC’s, mixture concepts for the formulation of a shrinkage reduced SCC were developed. Different factors influencing the shrinkage behaviour are discussed. The effect of replacing cement by high volume of pozzolanic or inert additives as well as the effect of different shrinkage reducing admixtures (shrinkage reducing agents - SRA) was examined. Furthermore an optimization of the grain size distribution was evaluated. The measuring setup consisted of different methods, most important the measurement of free and restrained shrinkage (ring test) on mortar and concrete specimens. It could be shown, that through a significant reduction of the cement amount, accompanied by an effective shrinkage reducing admixture a massive shrinkage reduction of SCC’s in the range of 50% to 60% can be achieved.

The growing use of fluid concrete increases the need for understanding the conditions under which these materials can undergo bleeding and segregation. However, the interfacial and colloidal phenomena, which control water and solids migration in cementitious systems, are inherently complicated by the hydration of the cement components. Hence, to unravel the specific role of chemical admixtures on the stability of cement-based systems, the mode of action of these admixtures should also be investigated in dense colloidal slurries of ‘un-reactive’ minerals. Several highly insoluble minerals, having specific surface areas comparable to that of a Portland cement, were thus evaluated for this purpose. The state of flocculation of these materials in dilute and concentrated slurries was examined through sedimentation and rheological measurements under various conditions, and the results compared to observations on similar slurries containing cements. The comparison showed that calcium carbonate (CaCO3) exhibits surface and colloidal properties very similar to “un-hydrating” cement particles. In fact, CaCO3 pastes can be made to accurately reproduce most of the kinetic properties of a cement paste, including bleeding, sedimentation and all dynamic viscosity parameters. It is therefore proposed that CaCO3 pastes can be used to adequately model ‘physical-type’ effects occurring in cementitious systems at very early stage of hydration, i.e., in the first hour.

Polycarboxylate type Superplasticizers have become the most widely used in SCC since they show outstanding performance regarding water reduction and flow retention. In some cases, depending on polymer structure and binder used, incompatibility problems like rapid slump loss may be observed. In order to overcome such problems, the mode of action of different polycarboxylates was studied by measuring the adsorption of the polymer on cement, the flow in cement paste, the flow and strength development in mortar as well as in standard concrete and self compacting concrete. The structure of the polycarboxylate (molecular weight, length of side chains, grafting degree) strongly influences its adsorption on cement and thus the performance as Superplasticizer. The increase of flow of the cement paste and polymer adsorption follows a quasi linear relationship. However the polycarboxylate with the highest adsorption is not necessarily the best performing in SCC applications. The outstanding performance of polycarboxylates in SCC and the importance of using a knowledge based approach for reaching the optimal properties of this materials is demonstrated in case studies.

Among the harmful substances carried into reinforced concrete by water, none is potentially more damaging than chloride ions, which destroy the passivity layer on steel in alkaline environment leading to corrosion processes of reinforcement and loss of durability. In this work we present direct potetiometric measurements of chloride ions in the pore water of mortar samples by using Ag/AgCl indicator electrodes. The long-term stability of electrodes in highly alkaline environment of cementitious materials and selectivity to chloride ions were improved with the deposition of polymer membrane consisting of polyvinyl chloride matrix and chloride ionophore. The chloride ingress experiments were performed on cylindrical mortar samples with over 50 sensors embedded into the solid body of the sample. The ingress of dissolved chloride ions into the mortar sample was monitored for more than six months. The concentration profiles of chlorides at different places in the sample were determined and used for the evaluation of diffusion processes of chlorides through the pores of the microporous matrix.