Microstructural, Mechanical and Radiological Characterization of Mortars Made with Granite Sand.

Francisca Puertas,Alicia Pachón,María Del Mar Alonso,Ana María Moreno De Los Reyes,Alfredo Gil-Maroto,Catalina Gascó,José Antonio Suárez-Navarro

doi:10.3390/ma14195656

Abstract

The study reported the effect of granite sand on strength and microstructural developments in mortars prepare from OPC with a high coal fly ash (FA) content or from hybrid alkaline cements. The radiological behaviour of the resulting mortars was compared to materials prepared with siliceous sand (with particles sizes of <2 mm) and the relationship between such radiological findings and mortar microstructure and strength was explored. A new method for determining natural radionuclides and their activity concentration Index (ACI) on cement mortars (specifically to solid 5-cm cubic specimens) was applied and validated. The microstructural changes associated in mortars have no effect on mortar radiological content measurements. The mortars with granite sand exhibited very high ACI > 0.96, which would ultimately limit their use. A conclusion of interest is that where information is at hand on the starting materials (OPC, FA, sand, admixtures), their proportions in the mortar and the mixing liquid content (water or alkaline activators) their radiological content is accurately predicted. The inference is that a mortar’s radiological content and ACI can be known prior to mixing, providing a criterion for determining its viability. That in turn lowers environmental risks and the health hazards for people in contact with such materials.

Highlights

Granite stone has been used as a construction material since antiquity, primarily for ornamental purposes in aqueducts, buildings and other civil works [1]
The findings for mechanical strength and microstructure of the mortars prepared with eco-efficient, high fly ash (FA) content or hybrid alkaline cements and granite or siliceous sand are discussed below
The item on the results of the radiological analyses addresses the effect of the use of granite sand on mortars in terms of their naturally occurring radionuclide content, along with the relationship observed between radiological content and mortar microstructure

Summary

Introduction

Granite stone has been used as a construction material since antiquity, primarily for ornamental purposes in aqueducts, buildings and other civil works [1]. It is still used today in countertops, walkways, staircases and footbridges, where it is appreciated for its high wearing resistance and low absorption and permeability [2]. Transporting the sludge to and depositing it in a spoil heap carry no small cost. One solution to those environmental and economic problems is to recycle this waste in other industrial processes, which would afford new business opportunities. The use of steel or other abrasive material blades to cut the granite generates sludge with a high iron oxide content, suitable for manufacturing stained ceramics [8]

Methods

Results

Conclusion