Abstract
This work presents the results of the study of the physical, chemical, mineralogical and pozzolanic properties of the altered volcanic tuffs (AVT) that lie in the Los Frailes caldera, south of the Iberian Peninsula, and demonstrates their qualities as pozzolans for the manufacturing of mortars and pozzolanic cements of high mechanical strength. The main objective of this research is to show to what extent the AVTs can replace portland cement (PC) in mortars, with standardised proportions of 75:25% and 70:30% (PC-AVT). To achieve these objectives, three AVT samples were studied by a petrographic analysis of thin section (PATS), DRX, FRX and MEB. The pozzolanic properties were determined by three methods: electrical conductivity (ECT), chemical pozzolanicity tests (CPT) at 8 and 15 days and mechanical strength tests (MS) of the specimens at 2, 7, 28 and 90 days. Studies of a PATS, DRX, FRX and MEB showed that the AVT samples’ constitutions are complex where smectite (montmorillonite), mordenite, quartz, halloysite, illite, kaolinite, volcanic glass and lithic fragments coexist. The results of the ECT and CPT tests confirmed the pozzolanic properties of the samples analysed and proved an increase in mechanical strength from 2 to 90 days of testing.
Highlights
Many natural materials are currently used as pozzolanic agents aimed at improving the quality of cements, mortars and concretes [1,2,3,4], with low production costs and with good CO2 emission mitigating properties, [5,6,7], the reduction of hydration heat [8] and the increase of resistance to attack by external agents on construction structures [9]
The process of zeolitization of the phenocrystals was possibly produced by the penetration of fluids from the hydrothermal alteration of the volcanic glass, which circulated through the planes of cruises of pyroxenes and amphiboles; this deduction seems to make sense when compared to the conclusions of References [43,44,45]
This research established that, despite the complex mineralogical, petrological and chemical constitutions of the samples, the pozzolanic properties seem to increase instead of decrease. The basis of this statement is evidenced by the presence of volcanic glass where its degree of devitrification and thermodynamic instability make it reactive [15]; does glass provide these properties to the samples studied but, to mordenite, smectite and halloysite, which have inherent properties, such as the cation exchange capacity (CEC), sorption and extensive surface area reinforce pozzolanic reactivity
Summary
Many natural materials are currently used as pozzolanic agents aimed at improving the quality of cements, mortars and concretes [1,2,3,4], with low production costs and with good CO2 emission mitigating properties, [5,6,7], the reduction of hydration heat [8] and the increase of resistance to attack by external agents on construction structures [9]. These natural materials are widely distributed in the Earth’s crust, and their exploitation is carried out according to sustainable geological and mining parameters [10]. Volcanic tuffs can match and outperform other minerals and industrial rocks, such as zeolites, bentonites, perlites, pumicites, trachytes, rhyolites and kaolinites [23,24,25,26,27,28], with regards to their cementing properties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
