SUITABILITY OF ATAQA DOLOMITIC ROCKS AS CONCRETE AGGREGATES

Abstract

As a result of the huge investments in construction sector in Egypt, the demand of rocks to be used as concrete aggregate is increased. Dolomite is one of the mostly used concrete aggregate in Egypt. Ataqa area is considered as one of the biggest sources of suitable aggregate for concrete industry in Egypt. Dolomite is found in different place in Egypt such as Suez region, Nile Valley, Western Desert, Sinai, Red Sea district. This study aims to evaluate the quality of Ataqa dolomite as safe, inert, and sound source of concrete aggregate. Gebel Ataqa is located in the northern part of Eastern Desert, about 20 km south of Suez, between Latitudes of 30o 00’ and 29o 47’ N and Longitudes of 32o 16 and 32o 28’ E. with elevation 871 m. The geology of G. Ataqa has been outlined and discussed by several authors. The exposed sedimentary sequence at G. Ataqa has been subdivided into six formations ranging in ages from Cenomanian to Recent. The Eocene dolomite has lower hardness, more ability to weathering, higher porosity and pale color. It is used as building stones, filler powder. The Cretaceous dolomite has higher hardness, lower porosity and yellowish gray color. The quarries and crushers are located on eastern and northern sides of G.Ataqa, these areas are consider as a basin of accumulation of weathered rocks of G.Ataqa. Dolomite description, genesis, textures and problems relating to the alkali- aggregate reactions (AAR), alkali-silica reactions (ASR), alkali-silicate reactions, alkali-carbonate reactions (ACR) and historical reviews of AAR in world and Egypt are reviewed. The aim of the study is achieved by studying the different properties of rock and aggregate samples. These properties include mineralogy and petrography, physical, mechanical and chemical. The experimental work and field work have been conducted to achieve the aim of this study. Concrete trial mixes were done to check the performance of aggregate in concrete making. The field work was achieved in two levels, first level was achieved by collecting 200 single samples from quarries, the second level was achieved by collecting 9 technological samples, each one including 2 different grading sizes from 9 quarries which will be referred as Q1- Q9.