This CD contains the proceedings from the Twelfth International Conference on Recent Advances in Concrete Technology and Sustainability Issues held in Prague, Czech Republic, in October 2012. The 34 papers include Advances in Geological CO2 Sequestration and Co-Sequestration with O2; Self-Compacting High-Performance Concretes; Dynamic Performance of Eco-Friendly Prestressed Concrete Sleeper; Parameters Influencing the Performance of Shrinkage-Compensating Concrete, and much more. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-289

This paper investigates the properties of the foamed concrete containing Nano silica, as compared with the foamed concrete containing micro silica, as well as comparing the properties of these two concretes with the concrete witness concrete. To conduct this study, Nano silica with an average size of 12nm and 1 to 6% of the cement weight was used; in addition, micro silica with an average size of 230nm and 1 to 6% of the cement weight was utilized. In this study the size of the air-voids in the hardened concrete ranged from 0.1 to 1 mm. The air voids were due to the protein- based foaming agent. The Type 1 cement used in this project was based upon ASTM C 150 .The samples were produced in two forms, that is, with and without sand. The compressive strength test was conducted for the samples at the ages of 7 and 28 with an approximately dried density of 600 and 1600 kg/m3.The SEM images were obtained from the failure section. The results indicated that in initial days, samples containing Nano silica have greater compressive strength than those containing micro silica and also the no-sand samples containing Nano silica show a greater increase in the amount of compressive strength than those containing micro silica and witness samples. The micro structural examination of the foamed concrete by using the SEM images suggests the improvement in the concrete micro structure and mechanical properties containing Nano silica.

Marl was calcined at temperatures between 600 and 1000 ºC and compressive strength of mortars was tested after 28 days curing at 20 ºC, when 20% of OPC was replaced by calcined marl at equal w/c-ratios. The clays were hold for 45 min. at the respective temperatures and the optimum calcination temperature with respect to reactivity as pozzolan seemed to be 800 °C. Higher replacement levels were tested for the most reactive temperature and even with a replacement level of 50% OPC the same strength as without cement replacement could be achieved. The 1-day strength for mortar with 50% calcined marl replacing cement was sufficient for demoulding concrete in field practice. Pozzolanicity was tested on pastes of calcined marl and calcium hydroxide in different ratios with an alkaline solution by the use of thermal analysis, XRD and SEM. Ca(OH)2 consumption and formation of hydration products was analysed after curing for 28 days and 6 month at 20 & 38 ºC.

The construction industry has been effective in reducing its contribution to global warming particularly in the production of construction materials. Unfortunately this is not true to the same extent in the design of appropriately constructed facilities to cope with global warming. It was fortuitous that steps taken to stem the release of greenhouse gases in the production of sustainable construction materials also resulted in a significant and immediate reduction in the cost of production. However, this economic driver is not operative in the design of constructed facilities. Consequently, departing from a rigid adherence to linear elements to the more economical use of plate and surface components, as well as the use of advanced materials, deserve greater attention. Such changes are recommended, the most important one being the quest for economical housing for masses of people currently needing to relocate as a result of weather extremes created by global warming. Problems associated with rising sea levels, scarcity of potable water and loss of soil productivity are consequences of global warming. These are the driving forces behind the need of people to relocate which in turn is generating the impending need for infrastructure. Solutions exist for these problems, but worldwide economic conditions will influence their resolution unduly unless more energy efficient facilities can be constructed.

Ground bottom ash (GBA) from Municipal Solid Wastes Incinerators (MSWI) does not perform as well as other mineral additions -such as silica fume or fly ash produced by coal burning- due to the presence of aluminium metal particles which react with the lime formed by the hydration of portland cement and produce significant volume of hydrogen in form of gas bubbles which increase the porosity of concrete and reduce its strength. Due to this drawback, a new process was developed to separate the aluminium metal particles through a mechanical removal of metals and a wet grinding of bottom ashes. At the end of the process, GBA was used as aqueous slurry to replace portland cement. In the present work GBA with a maximum size of 1.7 mm (0.07 min) was used to replace about 10% of portland cement in self-compacting concretes (SCC). Mixtures with shrinkage-reducing admixture (SRA) and a CaO-based expansive agent were also manufactured to reduce the drying shrinkage and the related cracks. Moreover, an alternative way to reduce both number and length of cracks was adopted by using SRA combined with polyvinyl alcohol (PVA) macrosynthetic fibres. Corresponding mixtures with silica fume or fly ash were also manufactured. GBA performed as well as silica fume in terms of mechanical properties, durability and crack behavior, and much better than fly ash.