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The BCE-system, prestressed hybrids of AAC and HPC

By Bo Göran Hellers

Abstract

The BCE technology opens up a new method to reinforce Autoclaved Aerated Concrete (AAC) by separating the production into two stages, primarily a block production from a traditional plant and secondarily the combining of blocks with affusion of High Performing Concrete (HPC) into prestressed hybrid panels, vertical or horizontal. The first stage means a continuous output of a limited number of standardized format blocks, up to 300 mm height, the second stage a non-standard production of individual panels following a CAD/CAM managed procedure, giving full freedom to architectural variation. The second stage can be added to existing block producing facilities, even in cases when a genuine PFA recipe is applied. The BCE horizontal panels have a higher capacity of up to 9 m span, carrying a live load of up to 6 kN/ than those with unstressed reinforcement from a traditional AAC plant. Industrial wall panels as well as roof panels may be 12 m, the latter under limited snow loads as is the case on most locations. Vertical wall panels can be designed with reduced depth but with retained capacity. In comparison with existing concrete alternatives the BCE panels are carrying a lower embodied energy, generating lower emissions in production of carbon dioxide. The BCE technology is based on experience with a complete building system of AAC (Autoclaved Aerated Concrete), the Siporex alternative, with which I was involved in the 1970s. The Swedish market for this material was declining at the time due to a rather formal attitude from the national authorities on heat losses through walls and structures towards sky and ground. It was only later that a full understanding of sources of loss, such as through ventilation and windows, was recognized. So, the value of AAC was underestimated at the time which is now compensated for by growing imports of the material from the continent. But there was something objectionable also about the reinforced products – they were rather complicated to produce, limited to 3M-standard, and stored awaiting customer’s order. Only from Japan did we learn that no such storage was allowed, due to the cost of land. This seemed futuristic but was in fact a proof of sound economy. Was there a way to approach this attitude by reforming the production layout? The BCE technology was first tried in the 1980s, then published at the 3rd Int. Conference on AAC (Zürich, 1992) and again at the 5th Conference (Bydgoszcz, 2011). Throughout this long period I have received a most stimulating support from my colleague and dear friend Bo R Schmidt, once marketing manager at Siporex. A helping hand over the last period belongs to Hamid Bagheri, whose licentiate thesis on BCE from 2006, available on Internet (Prestressed hybrids of AAC and HPC – The BCE building system), is attracting growing interest.QC 20180117</p

Topics: BCE system, AAC, Autoclavated Aerated Concrete, Building construction, Building Technologies, Husbyggnad
Year: 2018
OAI identifier: oai:DiVA.org:kth-220883
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