Abstract
The requirements for concrete restoration are not only aspects of retrofitting or restoration of bearing capacity but also aspects of preservation of historic structures, such as industrial monuments or civil engineering structures and buildings of the 1960s [1]. Thereby the facsimile replication of the concrete surface is a particular challenge. For the manufacture of delicate and complex structures with restricted accessibility self-compacting concrete (SCC) is well suited [2]. A modification with polymers normally ensures the durability of repair mortars or concretes (PCC) [3]. The combination of PCC and SCC to the Polymer-modified Self-Compacting Concrete (PSCC) for the restoration of historic concrete constructions is the logical consequence, to combine the advantages of both materials and is therefore an interesting alternative to well established materials and methods. Historic concrete constructions are often manufactured of concretes with very stiff consistencies, the so called tamped concretes. So there is a need to develop materials and methods for the rehabilitation of structures made of tamped concrete. For this reason, first investigations have been performed to the recipe development and optimization of its composition, but also properties, furthermore to the design possibilities and how polymers influence the concrete properties. In Germany between 1920 and 1970 industrial buildings and hydraulic structures have been built with concretes, where the content of Portland cement clinker was nearly complete substituted by latent hydraulic materials. The binders of those concretes contain large quantities of blast furnace slag and calcium sulphate and are called super-sulphated cement (SSC). Because of the high sulphate content, the compatibility of concrete structure with SSC is not given to concretes or mortars with other cements. If there is an adequate range of moisture, harmful new formations of phases will occur in the contact zone between SSC-concrete and the other concrete. In the field of rehabilitation PCC are well established. These are polymer-modified mortars or concretes with Portland cement, which are not suitable for the rehabilitation of structures of SSC-concrete. An alternative is the polymer-modification of SSC-concretes with polymers.
Highlights
Within the scope of the research project nuBau-Transfer “Methods for the development and application of innovative, functional materials for the restoration of buildings” different materials for repair and restoration of buildings have been developed and optimized
At first the studies focused in the development and application of a filler type Polymer-modified Self-Compacting Concrete (PSCC) with a polymer content of 10 % of the cement weight
The measured values for bonding strength were always higher than 2 N/mm2 and the failure occurred in all cases in the substrate
Summary
Within the scope of the research project nuBau-Transfer “Methods for the development and application of innovative, functional materials for the restoration of buildings” different materials for repair and restoration of buildings have been developed and optimized. The polymers in the structure of the hardened concrete reduced the elastic modulus and the compressive strength. The reference concrete is not resistant to freeze-thaw and de-icing salt It can be stated, that a polymer modification is necessary to guarantee the durability of this concrete. The methodological approach was based on successive investigations on paste, mortar and concrete. The rheological properties of the pastes, the base mortars and concretes have been determined using selected methods und compared to the results of the already established concrete compositions. The stabilizing effect of the polymers is well illustrated in figure 6 Another aspect of the investigations was the influences of the design concept or rather type of SCC (filler-type, viscosity agent-type and combined-type) on the rheological behavior of the fresh concrete, the hardened concrete properties and the appearance of the concrete surface.
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