Abstract
This work deals with anomalous concentrations of natural mordenite in the southeast of Spain. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies evidenced that the samples contain mainly monomineral zeolitic phase of mordenite (70% to 74%), usually accompanied by smectite (montmorillonite), the principal component of bentonite. A study of the applicability of these zeolites is presented to establish the potential use as pozzolanic cements. For comparative purposes, synthetic commercial mordenite is also characterized and tested. The initial mixtures were prepared using cement and mordenite at a 75:25 ratio. Chemical analysis and a pozzolanicity test showed the high pozzolanic character. These mixtures were further added to sand and water, yielding the cement specimens to be used as concrete. Mechanical test results showed that the mechanical compression at 7 and 28 days fall into the range of 19.23 to 43.05 MegaPascals (MPa) for the cement specimens built with natural mordenites. The obtained results fall in the same range of cement specimens prepared with natural clinoptilolite, using mixtures within the European requirement for commercial concretes. Thus, these results and the low cost of natural mordenite of San José de los Escullos deposit supports the potential use of natural mordenite as pozzolanic cement.
Highlights
Cement is the major constituent material used in the production of concrete
The results presented above, obtained for the characterization of the natural mordenite samples through X-ray diffraction and scanning electron microscopy, indicate a mineralogical composition
The results of the chemical analysis of the mixture made of 75/25 cement/zeolite ratio of the mordenite samples both natural and synthetic allow us to conclude that they are suitable for use as additives in the production of pozzolanic concrete because their values are within the limits established by the regulations
Summary
Cement is the major constituent material used in the production of concrete. The main component of Portland cements is clinker, a mixture of calcium silicates and aluminates obtained after sintering calcium carbonate at 1400–1500 ◦ C, in a process that produces CO2 emissions to the atmosphere.The manufacturing of one ton of cement produces about one ton of CO2 , with the construction industry being responsible for about 7% of all CO2 generated in the world. The main component of Portland cements is clinker, a mixture of calcium silicates and aluminates obtained after sintering calcium carbonate at 1400–1500 ◦ C, in a process that produces CO2 emissions to the atmosphere. One way to reduce these emissions is to decrease the amount of clinker present in the cement by replacing part of it with pozzolanic materials with cementing characteristics such as natural zeolites. Zeolites can react with bases favoring the formation of silicates and aluminosilicates which are able to harden upon hydration. CSH and CAH represent hydrated calcium silicates and hydrated calcium aluminates that can be produced upon the reaction of zeolites with Ca(OH) yielding an amorphous aluminosilicate compounds called pozzolana
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