Project Abstract

Abstract
The utilization of granulated calcined clay in the production of high-strength concrete has been a topic of interest in the construction industry due to its potential to enhance the performance of concrete mixtures. This research project aims to explore the effectiveness of incorporating granulated calcined clay as a supplementary cementitious material to improve the strength properties of concrete. The study involves investigating the influence of varying proportions of calcined clay on the compressive strength, flexural strength, and durability of concrete mix designs. The experimental program includes the preparation of concrete specimens with different levels of granulated calcined clay replacement for cement. Concrete cubes, beams, and cylinders are cast and cured under standard laboratory conditions to evaluate their mechanical and durability properties. Compressive strength tests are conducted at different curing ages to assess the impact of calcined clay on the early-age and long-term strength development of concrete. Flexural strength tests are performed to determine the effect of calcined clay on the tensile behavior of concrete. In addition to strength properties, the durability aspects of concrete containing granulated calcined clay are also examined. Chloride ion permeability tests are conducted to evaluate the resistance of concrete to chloride ingress, which is crucial for structures in aggressive environments. The microstructure of concrete specimens is analyzed using scanning electron microscopy (SEM) to observe the hydration products and the interfacial transition zone between aggregates and cementitious matrix. The findings of this research provide valuable insights into the feasibility of enhancing concrete strength through the incorporation of granulated calcined clay. The results demonstrate the potential of calcined clay as a sustainable alternative material that can contribute to the development of high-performance concrete with reduced carbon footprint. By optimizing the mix design parameters and proportion of calcined clay, it is possible to achieve high-strength concrete with improved durability characteristics. Overall, this study contributes to the ongoing efforts in sustainable construction practices by exploring innovative ways to enhance concrete properties while reducing the reliance on traditional cement materials. The research outcomes offer practical implications for the construction industry to adopt environmentally friendly practices and improve the overall performance of concrete structures.

Project Overview

INTRODUCTION

1.1   BACKGROUND OF THE STUDY

  Cement is a significant source of anthropogenic release of carbon dioxide. The CO2 derives mainly from kiln fuel combustion, transport and distribution and decarbonating of limestone. The latter source is fairly constant. Thus one procedure to lower the release of carbon dioxide is reducing the clinker content of the cement by shifting the production from CEM I to CEM II or CEM III cements. Another approach is replacing cement partially in concrete mix design by Type II additions like fly ash, granulated blast furnace slag or silica fume. An alternative to these afore mentioned options provides the use of calcined clay either as reactive part of the cement [1] or as Type II addition in concrete [2]. Metakaolin is known as a very reactive calcined clay and has been in focus of many investigations [e.g. 3, 4, 5, 6, 11]. Its widespread use in concrete is prohibited mostly by its high price compared to other Type II additions. Suitable and less expensive clay qualities consist rather of a mixture of clay minerals, which range between the clays used in the ceramic industry and those required for the cement production than of single type clay minerals. Thus it is worth taking a closer look at mixed clays. The reactivity of any calcined clay depends on both its mineral composition and the calcination temperature [e.g. 1, 3 – 11]. In most cases these investigations used homogenous clay samples that were calcined at constant temperature and for a period of several hours. Furthermore these clays were ground prior to calcination ensuring a complete reaction to take place. If coarse crushed clay is fed into a rotary kiln it is exposed to varying temperatures on its journey through the kiln combined with temperature gradients due to the size of the chunks after crushing and in addition a varying degree of oxidation. This paper focuses on the impact of such calcined clay on various mortar and concrete properties and its inherent ecological potential.