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Stumm A.,Xella Technology und Forschungsgesellschaft mbH
Cement, Wapno, Beton

New laws are likely which will make putting autoclaved aerated concrete (AAC) into landfi lls more diffi cult in the future. Consequently, a project was launched at Xella to reduce the sulphate content in AAC to almost zero. Positive side effects are no risk of thaumasite, agglomeration residue of lime and grey stains. The biggest source of sulphate besides cement is the pure calcium sulphate, which is added either as gypsum or anhydrite to the mixture. Additional calcium sulphate has been used in AAC to improve its material properties for many years. The reduction of calcium sulphate in ordinary cementitious AAC recipes leads to high shrinkage and less compressive strength of the material. Sulphate free AAC with a low bulk density is not yet being made in mass production. Due to the retarding effect on of the hydraulic binder cement, completely sulphate free recipes could not be handled in technologies like Durox, Hebel or Ytong yet. Cement and sulphate free AAC cakes tend to collapse either in the demoulding or autoclaving process, and especially low densities are diffi cult to process. Technological solutions and recipes were found to produce cement and sulphate free AAC with low bulk densities in moulds with the size of 5.4 m3. The material meets the requirements for the German bulk density class PP2/0.35 with λ 0.09 W/(mK). The shrinkage tests show values under 0.20 mm/m according to DIN EN 680. Finally, it was shown that cement free recipes lead to fewer transportation damages due to less brittle surfaces. Further research is currently in progress. Source

Naumann K.,Xella Technology und Forschungsgesellschaft mbH
Cement, Wapno, Beton

Design and calculation of building sound performance is standardized in EN 12354. The calculation method of this relatively new standard requires a lot of precise input data. Besides the mass per area of a massive component, values like the vibration reduction index and the loss factor are required. As a consequence of the implementation of EN 12354, plenty of research was initiated about the acoustic properties of different construction materials. In collaboration with different research institutes and Universities numerous measurements on AAC structures were performed. The results have become the basis for the integration of the EN 12354 into the German standard DIN 4109. Based on the experience gained in applying the calculation method of EN 12354-1, this paper gives an overview about the acoustic performance of single leaf AAC structures in comparison with other building materials. The sound reduction indices of pure materials as AAC, lightweight concrete or calcium silicate bricks are compared. In a second step, the calculated sound reduction indices are compared with measurement results of real buildings. It could be confirmed, that the determined sound reduction indices in planning of a building are in sufficient agreement with the measured and quantified sound insulation in the real building. It is concluded that there is a good correlation between calculated performance on the basis of the material parameters, and the actual measured sound performance for AAC structures. This proves a high level of certainty in achieving the required sound insulation in design and construction of AAC buildings. Source

Agency: Cordis | Branch: FP7 | Program: CP-IP | Phase: EeB.NMP.2013-2 | Award Amount: 6.55M | Year: 2013

H-House is aiming at the development of a number of building components for modern society where awareness for environmental aspects and living comfort are not compromised but complementing each other. The concept of H-House aims at components for the building envelope and components for the interior applied to both new buildings and for renovation. The purpose of an adequate building envelope is protection against moisture ingress, heat loss in winter, excessive heating in summer and noise. Components for the interior should be able to buffer heat and humidity peaks and prevent pollutants and noise. Solutions for both components for building envelope and components for the interior have to be durable, energy-efficient and affordable. Therefore, H-House will propose innovative sustainable faade and partition walls based on earthen materials, optimised cementitious materials with modified surfaces and wooden/cellulose materials. An innovative modification of the listed materials with additions of energy-saving and air purifying aerogel granulates will create optimal conditions for living. The concept of H-House covers chemical and physical activity of the developed building materials, their embodied energy, suitability in different environments, durability, cost-efficiency and long-term improvement of energy efficiency of buildings. The complementary consortium has a strong industrial dominance (9 partners) and 3 research institutes.

Straube B.,Xella Technology und Forschungsgesellschaft mbH | Walther H.,Xella Technology und Forschungsgesellschaft mbH
Cement, Wapno, Beton

The structure of this optimized autoclaved aerated concrete (AAC) consisting essentially of calcium silicate hydrate phases, especially of 11 Å tobermorite does not contain inorganic filler like calcite. The absence of quartz and crystalline fillers ensures lower thermal conductivity values even though the crystal structure of the silicate hydrate phases (CSH) phases. According to the tests, the calcium silicate hydrate pore structure with the residual quartz grain contents below 10% by mass is producible by ensuring that the SiO2 component in the hydrothermal process reacts fully or nearly fully (< 10% by mass of residual quartz grains) with the CaO component to give CSH phases, especially crystalline CSH phases, preferably to give 11 Å tobermorite which crystallizes out particularly efficiently. In terms of production, this is achieved by a common autoclaving process and by the use of very fine quartz flour as the SiO2 component. The production is not possible using cryptocrystalline or amorphous silica, for example with fumed silica or precipitated silica or with microsilica (amorphous SiO2 which forms in the preparation of silicon metals from ferrosilicon). Source

Schoch T.,Xella Technology und Forschungsgesellschaft mbH | Straube B.,Xella Technology und Forschungsgesellschaft mbH | Stumm A.,Xella Technology und Forschungsgesellschaft mbH

Ordinary autoclaved aerated concrete (AAC) (P2-0,35) was stored under different humidity conditions and a constant CO2 atmosphere of 1 % by volume. Additionally, AAC samples with a good and poor phase formation were produced and included into the weathering procedure. In addition to the artificial CO2 weathering, ordinary AAC was stored under rain protection outdoor for a period of 3 years. After storing the samples under different conditions and periods, the material was measured for its raw density, compressive strength and mineral phase content. The outdoor stored AAC was tested after 3 years for its thermal conductivity. Boundary conditions such as material moisture and drying behaviour of the AAC as well as ambient moisture, influence the material properties within the weathering procedure. Artificial CO2 weathering leads to other effects than natural weathering. AAC with well crystalline tobermorite does not change its compressive strength or thermal conductivity under natural climate conditions. A negative long-term development of the material properties can be excluded. © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

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