Durability of Mortars Modified with Calcined Montmorillonite Clay

Safi Ur Rehman,Tariq Ali,Sajjad Wali Khan,Muhammad Noman,Khan Shahzada,Muhammad Yaqub

doi:10.28991/cej-2019-03091347

Abstract

This study aims to evaluate the performance of mortars containing locally available Pakistani montmorillonite (Mmt) clay mineral as partial replacement of cement in various curing environments. The local montmorillonite clay in “As is” (20°C) and “heated” (100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C & 1000°C) conditions was incorporated in mortar cubes as partial replacement of cement. Montmorillonite clay of all the temperatures was replaced by 15%, 20%, 25%, 30% and 35% of cement mass in mortar cubes. The Strength Activity Index (SAI) was calculated to determine the optimum activation temperature for the clay. Compressive strengths of the controlled mix and montmorillonite modified mortars were evaluated under the Sodium Sulfate (SS) (5% solution) and mixed (Sodium Sulfate + Sodium Chloride (SCS)) (5% +3.5% solution) curing environments to study its durability performance. Upon thermal treatment montmorillonite clay showed maximum activation at 800°C temperature. Mortar containing (800°C) calcined montmorillonite clay with 25% cement replacement exhibit competent compression results. Moreover, up on exposure to aggressive environments, montmorillonite clay mortars performed better than the control samples. The mortar cubes exposed to Sulfate environment (SS) were more damaged in compression than that exposed to mixed environment (SCS), for all replacement levels and time exposures.

Highlights

Concrete and mortar are the most-utilized man made construction materials around the world
This study investigates the activation of clay at different temperatures for local available montmorillonite clay in Pakistan
The Energy Dispersive X-Ray analyser (EDX) analysis both for “As is” and “800°C calcined” Mmt clay is shown in Figures 6 and 8, showing its elemental composition

Summary

Introduction

Concrete and mortar are the most-utilized man made construction materials around the world. These are made from naturally available materials, which made it a famous construction material since long. Beside many advantages durability of concrete and mortar in various corrosive environments are of a primary concern. Concrete structures exposed to corrosive environments for a long time deteriorate its performance chemically, physically as well as mechanically. Chemical deterioration is caused by the penetration of aggressive ions and its interaction with the resultant products of hydration This interaction of aggressive chemical ions with the hydrated cement phases cause expansion, cracking and spalling of concrete structures [6]. In the aggressive environment concrete deterioration is because of cement matrix dissolution, formation of non-binding phases and expansion [7]. Expansion of non-binding phases occur relative to substrate phases which initiate the fracture of concrete [7,8,9]

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