Abstract

The effect of elevated temperature during storage and curing of ultra-high performance concrete (UHPC) formulated aerogel-incorporated mortar (AIM) samples was investigated. It was found that an effective aerogel loading of 60 vol% of total bulk volume was possible for producing AIM samples with suitable thermal and mechanical properties under optimized storing and curing conditions. AIM samples with compressive strengths of up to ≈19 MPa was achieved and the corresponding thermal conductivity was ≈0.4 W/(mK). For more insulating concrete, 70 vol% aerogel was needed and AIM samples with thermal conductivity as low as ≈0.1 W/(mK) were cast. In general, AIM samples with strengths of up to 5 MPa can be achieved when thermal conductivities of between 0.1 and 0.2 W/(mK) is desired. The obtained results here estimates that there is potential in improving the AIM samples to produce structural and insulating concrete through modification of storing and curing conditions to achieve the desired requirements of a thermal conductivity value of <0.1 W/(mK) with a corresponding compressive strength of >20 MPa.

Abstract

A crucial property for double-glazed sealed insulating window panes is to maintain their thermal insulating properties and thus low U-values. However, degradation and thus subsequent reduction or loss of low-conductance gas concentration may occur in the sealed glazing units by their exposure to outdoor climate.

The choice of spacers is important to keep as low thermal transport through the window panes as possible, i.e. low U-value. In addition, the type of spacers may also influence their durability and resistance towards ageing, which hence may be characterized by the low-conductance noble gas concentration, e.g. argon, krypton or xenon. Ageing and degradation of window panes may lead to a decreased or total loss of noble gas concentration and hence subsequent increased heating energy demand in buildings.

Thus, several double-glazed sealed insulating window panes, with aluminium spacers and Super Spacers, have been subjected to accelerated ageing by climate ageing and elevated temperature ageing. The durability and ageing of the sealed window panes have been studied and characterized by their spacer type and gas concentration. Furthermore, the decrease of gas concentration in sealed insulating window panes and the impact on the energy performance and in particular heating demand of buildings have been investigated.

Abstract

The application perspective of aerogel glazings in energy efficient buildings has been discussed by evaluating their energy efficiency, process economics, and environmental impact. For such a purpose, prototype aerogel glazing units have been assembled by incorporating aerogel granules into the air cavity of corresponding double glazing units, which enables an experimental investigation on their physical properties and a subsequent numerical simulation on their energy performance. The results show that, compared to the double glazing counterparts, aerogel glazings can contribute to about 21% reduction in energy consumptions related to heating, cooling, and lighting; payback time calculations indicate that the return on investment of aerogel glazing is about 4.4 years in a cold climate (Oslo, Norway); moreover, the physical properties and energy performance of aerogel glazings can be controlled by modifying the employed aerogel granules, thus highlighting their potential over other glazing technologies for window retrofitting towards energy efficient buildings. The results also show that aerogel glazings may have a large environmental impact related to the use of silica aerogels with high embodied energies and potential health, safety and environment hazards, indicating the importance of developing guidelines to regulate the use of aerogel glazings.

Abstract

Calcined marl was identified as an insulating binder substituent mate-rial for aerogel based mortars. Further synthesis of insulating organo-nanoclays through the incorporation of polyethylene glycol (PEG) or in situ polymerisation of polystyrene (PS) in clays displayed greater promises for further reduction of thermal conductivity independent of the compressive strength, unlike more con-ventional aerogel-incorporated concrete. The organo-nanoclays were characterized by Hot Disk thermal analyzer measurements. The results so far indicated the for-mation of organoclay particles from both ideal systems of bentonite and calcined marl with lowered thermal conductivities. The calcined clay appeared to maintain its binding properties, suitable for gelling excess aerogel together in the concrete matrix. Ultimately, the final hydration mix of aerogel, calcined clay-polymer binder, organo nanoclays and cements is targeted to form novel concretes with re-duced thermal conductivity comparable to existing insulating materials, while maintaining strengths of 20 MPa after 28 days of curing.