Abstract
Alkali Activated Concrete (AAC) is an alternative kind of concrete that uses fly ash as a total replacement of Portland cement. Fly ash combined with alkaline solution and cured at high temperature reacts to form a binder. Four point bending tests on two full scale beams made with AAC are described in this paper. Companion small material specimens were also casted with the aim of properly characterizing this new tailored material. The beam’s length was 5000 mm and the cross section was 200 mm × 300 mm. The AAC consisted of fly ash, water, sand 0–4 mm and coarse aggregate 6–10 mm; and the alkaline solution consisted of sodium hydroxide mixed with sodium silicate. No cement was utilized. The maximum aggregate size was 10 mm; fly ash was type F, containing a maximum calcium content of 2%. After a rest period of two days, the beam was cured at 60 °C for 24 h. Data collected and critically discussed included beam deflection, crack patterns, compressive and flexural strength and elastic modulus. Results show how AAC behavior is comparable with Ordinary Portland Cement (OPC) based materials. Nonlinear numerical analyses are finally reported, promoting a better understanding of the structural response.
Highlights
Concrete is an essential material in the building industry with a global consumption estimated around 25 billion tons every year [1]; it is considered one of the most widely used materials in the world
Beams and cylinders were tested at 28 days in flexure and in compression respectively; flexural tensile stress vs. Crack Mouth Opening Displacement (CMOD) curves were obtained according to EN 14651-5 [28], which requires that three point bending tests on notched specimens be performed under strain control
28th day was on (FRC) materials, it was considered useful for investigating the post-peak regime of Activated Concrete (AAC) materials
Summary
Concrete is an essential material in the building industry with a global consumption estimated around 25 billion tons every year [1]; it is considered one of the most widely used materials in the world. The production process of concrete, has a significant impact on global warming; this is especially due to the use of Ordinary Portland Cement (OPC), the main component of concrete. The need for environmentally friendly building materials for sustainable development is a major environmental issue in the construction industry; over the last decades, there has been a remarkable development of alkali activated materials as an alternative kind of concrete that uses an aluminosilicate powder as a total replacement of cement. Alkali activated cements are synthetized from powders rich in alumina and silica which are soluble in highly alkaline solutions. The combination of an aluminosilicate source and alkaline solution react to form a binder, playing a similar role of cement combined with water in the ordinary concrete. The aluminosilicate base that could be activated through the alkaline solution could be a metakaolin or industrial byproduct material such as fly ash Materials 2016, 9, 739; doi:10.3390/ma9090739 www.mdpi.com/journal/materials
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