Introduction
BackgroundLightweight aggregate concrete (LWAC) has potential to offer weight reduction without significantly having to compromise the structural properties. Still, however, this material has not realized its potential as a commonly accepted alternative to normal weight concrete (NWC) or other construction materials. Main reasons for this are somewhat higher material and production costs, a common skepticism related to production properties, design/structural performance and durability, and the lack of sufficient and generally valid guidelines, rules and standards. Furthermore, a dependency on local/national conditions as to materials resources has provided specialized guidelines and standards in a way as to limit an all-European and cross-boarder application and trading with the materials. Another motivation to promote LWAC is that the growing shortage on traditional aggregate resources in great parts of Europe, combined with increasing focus on pollution and waste handling, is forcing the building and construction industry to look for alternative solutions that can combine these issues.
Project InformationBased on this background an European consortium was established in 1995 with the aim to run a project within the framework of the Brite EuRam III program. The baseline is an international state-of-the-art and extensive national research in which the consortium partners have played a key role. The project draws on this present knowledge, co-ordinates, validates and utilizes the results in an extended development towards a more generally applicable, European concept for LWA concrete technology.
Concrete with different strengths was produced using four types of cements, one ordinary Portland cement (OPC) and three blended cements with 10% pulverized fuel ash (pfa), 25% pfa, and 15% slag respectively. The pfa was added to the cement clinker during the end of the grinding process. The the slag was preground. Carbonation was tested using the phenolphtalein method. The concretes were exposed to four different climates:(1) 50% RH, 20 C and normal CO 2 content (0.03%) of air; (2) 50% RH, 20 C and 0.1% C0 2 ; (3) outside in the natural environment unsheltered from rain; (4) outside in the natural environment sheltered from rain. Curing time before exposure was varied. The preliminary results showed that concrete with blended cements carbonated somewhat faster than concrete with OPC. The influence of curing time before exposure and exposure condition was found to be evident but independent of the blend.
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