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The study presents the results from the development of a grouting material based on hydrated lime with addition of pozzolana, which is referred to as hydraulic lime, suitable for the repair of cracks in a variety of earthen building techniques. The goal was to develop a material also compatible with earthen structures exposed to dynamic loads. The grouting mortar was designed to be adaptable in strength properties and at the same time to have sufficient robustness for preparation and use on the construction site.
Results showed a satisfactory performance of the grout concerning fresh and hardened mortar properties as well as injectability.
Beton ist als Massenbaustoff vielseitig einsetzbar. Eine der neuesten Entwicklungen ist Ultrahochleistungsbeton (UHPC). Seine besonderen Eigenschaften ermöglichen eine zusätzliche Funktionalisierung der Oberflächen, da annähernd beliebige Mikrostrukturen exakt abgeformt werden können. So lassen sich beispielsweise Fassadenelemente aus UHPC bereits bei ihrer Herstellung im Betonfertigteilwerk mit selbstreinigenden Oberflächen ausrüsten. Eine andere Möglichkeit ist eine Anwendung als Datenspeicher. Wie das Beispiel der Schallplatte aus UHPC zeigt, lassen sich Muster, die hier die Schallinformationen enthalten, exakt von einer Matrize kopieren.
Thermal treatment improves the excellent properties of UHPC. Recent studies have shown that an increase in compressive strength of more than 30 % is possible. However, the accurate conditions of thermal treatment for a maximal strength are considered as yet undetermined. A multitude of parameters can be varied: temperature, pressure, water saturation, and duration of the process steps. These parameters influence the phase development and in consequence the macroscopic properties of UHPC. The primary objective of the presented study was the optimisation of the conditions for thermal treatment, concerning compressive strength. It focuses on pre-storage time and duration of the treatment at defined temperatures and pressures (90 °C and 185 °C/1.1MPa).
As expected, experimental results showed a fundamental change of phase composition in hydrothermally treated UHPC in comparison to standard cured UHPC: Ettringite decomposes at higher temperatures and is absent after thermal treatment; the amount of portlandite and clinker phases decreases. The change of phase composition is accompanied by increased compressive strength.
Experimental studies of calcium-silicate-systems at hydrothermal conditions predict the formation of the crystalline C-S-H phase tobermorite. In fact, this is a typical phase occurring in other hydrothermally treated calcium-silicate-systems like Autoclaved Aerated Concrete (AAC). Commonly, high strength is attributed to the presence of tobermorite; however, in the presented study tobermorite was not detected in the hydrothermally treated UHPC. Therefore, tobermorite cannot be responsible for the increased strength of hydrothermally treated UHPC.
In conclusion the development of phases and strength of UHPC at hydrothermal conditions differs fundamentally from AAC and the experimental studies with water saturation. Results of these systems cannot be transferred to UHPC. In thermally treated UHPC, the hydration of clinker is enhanced and the puzzolanic reaction is intensified. Hence, more C-S-H is formed that fills pores and cracks, leading to a denser structure and finally to higher strength.
In the past few years, the share of earthen building materials used in constructions in Central Europe has increased. That is due to growing acknowledgement of its qualities regarding balancing of humidity, absorption of odours and acoustical insulation.
To regulate these (mostly indoor) uses, the German Institute for Standardization (DIN) has published norms for adobe, earth mortar for masonry and earth plaster. In addition to these traditional building materials, earthen panels have been developed. As an ecological alternative to gypsum plaster boards, they combine climatic advantages of traditional materials with economic advantages of industrial processing, i.e. prefabrication and drywall techniques. Earthen panels are a composite layered material, comparable to Textile Reinforced Concrete (TRC). Most products contain an inner layer of reed tubes which improve the tensile strength and reduce the weight. Often, one or both surfaces are reinforced with a fibrous net to prevent cracks in the plastering that is usually applied on top. Additives range from straw to expanded clay. Special panels contain waxes that improve their heat storage capacity or water pipes to allow the usage as flat heating and cooling systems.
This paper presents an innovative way to combine an external ultra-high performance concrete (UHPC) supporting layer with an insulation layer of autoclaved aerated concrete (AAC) or cellular lightweight concrete (CLC) to create light-weight façade elements, which are improved in functionality and in energy efficiency. The durability of the façade elements is improved by developing UHPC with self-cleaning properties. One approach is based on the photocatalytic activation of the external UHPC shell by incorporation of TiO2 particles. The second approach consists of the modification of the UHPC surface by micro structuring in combination with the application of water-repellent agents to create durable super hydrophobicity. The current results obtained from laboratory testing are promising and demonstrate the feasibility of the approaches.