Band 5, Heft 1

Ion concentration profiles in sandwich-brick specimens have been determined experimentally at different degrees of water saturation. Based on the experimental data, ion diffusion coefficients were determined by inverse analysis. The diffusion equation served as a basis for an optimization technique. It has been shown that the ion diffusivity in bricks decreases markedly as the moisture content decreases. The interface between two adjacent bricks slows down the ion migration at low water content in particular. It is planed to investigate the interface between mortar and bricks in further experimental and numerical studies.

Gypstop, a new product based on silica colloid, has been developed by Eka Chemicals Company in Sweden. It is used in the restoration and conservation of cultural heritagestone monuments. These deteriorate due to the combined effect of gases and salts which may have a synergystic effect. This paper describes the principle of desalination and subsequent consolidation of porous stone and the procedure of using Gypstop. Some of the deteriorated limestone blocks have been treated with the Gypstop in Egypt. It has shown that the Gypstop protects the stone from further weathering. Restoration and conservation of different stone monuments have been carried out. The periodical evaluation of the field treatment has confirmed that the Gypstop has unique characterstic of desalination and subsequent consolidation of the stone monuments. It thus strengthens them and significantly improves their durability.

Variable obsen>ations concerning frost resistance of high performance concrete have been made. The question arises which are the decisive factors influencing durability under the action of frost and de-icing salt. The proposed experiments are to be carried out in cooperation with F.A.- Finger - Institute of Bauhaus University Weimar. The aim of this study is to determine possible change of durability of high strength concrete, and to investigate the origin thereof. Measures to reduce the risk of reduced durability have to be found.

In practice, hydrophobing impregnation has been established as an effective surface protection system against water and de-icing salt attack. Cracks in concrete, whether impregnated by a hydrophobing treatment or not, are unavoidable and can therefore lead to damage. In absorption tests on laboratory samples, the significant influences of cracks on the penetration behaviour of capillary water have been determined and quantified. The experimental results show that the water uptake depends on the craclc width and the penetration depth of the hydrophobing agent. There exists a 'critical' crack width depending on the penetration depth of the hydrophobing agent which can maintain the hydrophobing behaviour. Finally practical conclusions of the present work are drawn.

Sealing materials against pressuring water and leaking diesel have been developed as shaped gaskets, pastes and liquid injection materials based on acrylic polymers. Not only do these have optimized application properties, they are also greatly improved in ecotoxicology and working safety. Abstract Sealing materials against pressuring water and leaking diesel have been developed as shaped gaskets, pastes and liquid injection materials based on acrylic polymers. Not only do these have optimized application properties, they are also greatly improved in ecotoxicology and working safety. To check the ecotoxicologicctl properties, application-near testing devices, with which the ecological conditions can he simulated, have been developed for both hardened sealing materials and liquid material injections.

Recent developments in injection grouts used for consolidation are proposed. Special compositious have been developed, made out of lime, cement and pozzolan. The stability, the viscosity and the mechanical properties are illustrated. Comparison is made with polymer grouts and with double injections using mineral and polymer grouts consequently. The influence of injections on the load-bearing capacity of the masonry is calculated. Some elements for the judgment of the safety and reliability of masonry structures are pointed out.