PSI - Issue 11

Bárbara Belén Raggiotti et al. / Procedia Structural Integrity 11 (2018) 36–43 Raggiotti et al./ Structural Integrity Procedia 00 (2018) 000 – 000

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reduced and this also constitutes a reservoir of many other industrial waste materials. And technological because they contribute to improving some of the properties of concrete (Rahhal & Eperjeci, 2012). The use of mineral admixtures in construction came before the use of cement, dating back to the 15th century BC in Greece, according to Malhotra and Mehta (1996). Nowadays normally used mineral admixtures are waste from other industries which would normally be disposed of in large quantities in inappropriate places, creating the risk of contamination of soil and water sources (Dal Molin, 2005). In recent years, care for the environment and the reduction of manufacturing costs have been a topic of discussion in most industries. The Portland cement industry has undergone a series of changes, one of which promotes the use of supplementary, natural, residual materials, or industrial by products whose production requires less energy. The term pozzolan was originally associated with natural volcanic ashes and scorched lands. The term has been currently expanded to all the siliceous and aluminous materials which, eventually ground, in the presence of water, may react chemically to the calcium hydroxide (CH) to form compounds possessing cementing properties, for which they are classified as natural and artificial pozzolans. This work proposes the use of natural zeolite as an active admixture containing reactive SiO 2 and Al 2 O 3 in its composition, contributing to the resistance of the concrete through the pozzolanic reaction to the Ca(OH) 2 whereby this material's pozzolanic reactivity is extremely interesting in the study of sustainable concretes. Natural zeolites were discovered by Axel A. F. Cronstedt in 1756. He recognized zeolites as a new class of mineral consisting of hydrated aluminosilicates containing alkali or alkaline earth species. Clinoptilolite is the most widely studied type of natural zeolite and is considered to be the most useful on account of its pozzolanic activity in cement mixes worldwide. In Argentina, however, despite the existence of deposits of this mineral, no research had been conducted into it. Natural zeolites are found distributed in deposits around the world. Natural zeolites have generally been considered low quality material because they are a mineral with a heterogeneous composition with different physical and chemical properties. They were used in the ancient world, especially as an admixture in building material, but it was later used mainly in environmental control processes, thus losing protagonism in the building industry. According to Agosto (2012), the potential disadvantages of applying natural zeolites may be put down to the fact that they are generally mineral mixtures in which the zeolite phase is often a variable constituent. However, in deposits with a higher degree of purity, it has been possible to detect the presence of the zeolite phase in a ratio of 80% or more. In Latin America, zeolites have been found in: Antilles, Argentina, Bolivia, Brazil, Chile, etc. In some cases these manifestations are recognized as deposits with reserves estimated and approved for industrial exploitation (Giannetto Pace et al., 2000). The most abundant zeolites in sedimentary rocks are: analcime, clinoptilolite, heulandite, laumontite and phillipsite. Today more than 50 natural zeolite minerals and 150 synthetic ones are known and used in different industries. In the cement industry, natural zeolite is a natural pozzolan popular in some regions of the world. It is used in large quantities as a kind of natural pozzolanic material in China (Najimi et al, 2012), Iran (Ahmadi & Shekarchi, 2010), Cuba (Rosell et al., 2006), among others. In China it is widely used as a mixing material for cement. The total amount consumed for this purpose is approximately 30 million tons a year. (Poon et al., 1999). According to a survey conducted by Najimi et al. (2012), zeolite tuff has been used as a pozzolanic material in some cement plants in Russia, Germany, Slovenia, Cuba, Serbia and Spain. It has been researched mostly in countries with natural zeolite deposits for concrete and mortar containing different amounts of it in properties of resistance, alkali-silica reaction, and the transportation of substances. Not many studies have been found related to aspects of durability, particularly in carbonation, freezing, thawing and functions like attacking sulfates and acids, chloride induced corrosion in reinforced concrete and contraction from drying. 1.1. Zeolites

2. Methodology

The experimental work has been divided into two parts, one in which the physico-chemical characterization of zeolite is presented, and another which assesses its potential as a pozzolan in structural concrete.