Pozzolanic activity of argentine vitreous breccia containing mordenite

V L Bonavetti,F Locati,P Maiza,S Marfil,V F Rahhal,E F Irassar

doi:10.3989/mc.2020.04019

Abstract

A vitreous breccia with variable amount of mordenite was studied for its use as pozzolan. The raw material was characterized by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and the zeolite content was estimated by the methylene blue staining technique. After being ground, physical characteristics, cation exchange capacity (CEC), pozzolanicity, and the compressive strength activity index (SAI) were determined. The staining technique and the CEC measurement were used to evaluate the average content of zeolite. The vitreous breccia has pozzolanic activity after 7 days, the water demand increases slightly, and its addition stimulates the early hydration of portland cement. At later ages, the pozzolanic reaction around the grains, as revealed by SEM studies, improves the compressive strength of blended cements having a SAI > 0.85 at 28 days.

Highlights

RESUMEN: Actividad puzolánica de una brecha vitrea argentina que contiene mordenita
Petrographic studies show that zeolitized vitreous breccia (ZVB) is heterogeneous, with vitreous sectors slightly zeolitized in the upper part of the outcrop and other sectors strongly altered to zeolite, sometimes with good crystallinity (Figure 1a), which predominates in the lower sector of the outcrop
For ordinary portland cement (OPC), the points representing [CaO] and [OH−] are above the calcium solubility isotherm, indicating that the solution is saturated in portlandite, except at 90 days when the [CaO] decrease is attributed to the CO2 dissolved in the supernatant solution

Summary

Introduction

RESUMEN: Actividad puzolánica de una brecha vitrea argentina que contiene mordenita. Se estudió una brecha vítrea con cantidad variable de mordenita para su uso como puzolana. Volcanic zeolite-rich pozzolans are very heterogeneous, so the characteristics and properties of both the raw material (such as mineralogy, texture, chemistry, crystallinity, grain size, morphology, etc.) and the zeolite-bearing material (zeolite vs glass proportion, particle size distribution, bulk chemistry, CEC, specific surface area, etc.) should be correctly assessed by different techniques Knowing these heterogeneities is essential as they can affect the pozzolanic activity [10] and the water demand of the material, and the properties of fresh and hardened concrete [11,12,13,14,15,16,17,18]. They can accelerate the early hydration of portland cement [15] and contribute to the formation of additional hydrates [12, 19]

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Conclusion