Band 3, Heft 5

Influences of the environment attack marble and ultimately destroy it. Especially the black yeast-like fungi which are often found on marbles especially in Mediterranean monuments strongly attack the marble. Colonization of the surface and interspaces inside the rock on experimental rock slabs lead to additional heat absorption and transfer. This imposes a higher dilatation of the marble causing losses of particles and ultimately the désintégration of the rock structure. For the first time the mechanical destruction of rock material by micro-organism is experimentally shown.

The energy consumption and the C02 emissions during the production of two different concrete mixes with identical concrete properties were compared. The two concrete samples were prepared with and without the addition of a superplasticizer. Less energy was consumed and less C02 was emitted for the case of concrete production including a superplasticizer as compared to the case of concrete production without a superplasticizer. This is due to the fact, that when a superplasticizer is used, less cement is needed to produce concrete with the same properties as those of concrete without superplasticizers. However, the relatively small dijferences in the energy consumption and in the C02 emissions become insignificant, if the entire life cycle of a building is considered. Effects like durability and the need for maintenance are expected to have a much higher influence on the life cycle assessment of concrete buildings.

The aims of this paper are to study and characterize the siliceous sandstone used in the construction of an important Barroque church placed in the down town of Barcelona. The degree of resistance to the urban polluted environment is evaluated and the decay forms and weathering mechanisms studied by means of mineralogical analytical techniques. A complete restoration campain was carried out including the cleaning of the whole facade and sculptural elements. We studied the rock previous to, during and after the cleaning processes. The main results achieved are as follows: i) two rock types have been identified as building stones which may be differenciated by the mineralogy of the cement leading to a different behaviour and durability; ii) several decay forms have been identified, namely the darkening of the surfaces by dirt accumulation, the weathering of the feldspars forming the rock and the transformation of formed pyrite nodules; iii) the mechanisms leading to the decay forms identified are studied and a model for the decay (aesthetical and physical) of this kind of stone is proposed for urban environment. On the basis of these results a cleaning process with water and neutral detergent using non metallic brushes as proposed was applied. The results of this cleaning on each lithotype are evaluated by means of microscopical analyses of fragments of stone after cleaning. The different behaviour of both types of stone are analyzed and documented on a microscopical scale.

For about 50 years now, the injection process has been used as an alternative to mechanical barriers against capillary rising damp in walls. There are still many, however, who are not convinced of the effectiveness of this process due to frequent improper use of the injection process to be applied or a wrong choice of injection agents. The following article describes how the injection agent works and the principles of the various injection procedures which are currently used today. Special emphasis is placed upon pressure injection, especially the multi-injection procedure as developed in recent years to enable us to treat severely damp cavity walls. The effectiveness of this extraordinary successful injection procedure is underlined by means of selected examples.

In practice concrete structures are often exposed to various environmental impacts which determine strongly durability of concrete and concrete structures. Costs of restoration of damaged concrete structures may be extremely high, in some cases higher than demolition and rebuilding. Not only real costs and financial investment for repair measures may be exorbitant, but limited use and negative impacts on the environment have to be taken into consideration too. In this paper a concept to reach sufficient durability is being developed in which technical, ecological and economical requirements are implied. For the realisation of this concept cement-based coatings with particular high resistance against chloride penetration and carbonation play a central role. It will be shown in this contribution that this type of coatings can protect the load bearing structure in an efficient way for a predetermined period. In this way long-term durability of concrete structures and reinforced elements exposed to aggressive environment can be achieved in both an economic and ecologic way.