Evaluation of Kahramanmaras (Sekeroba) barites for heavyweight concrete mixture design by packing model

Nowadays, the most widely used composite material in the world in construction industry is concrete. Concrete is used both as a load bearing material and as a decorative material. In some cases, different types of special concretes are developed for specific performance requirements. Heavyweight concrete is one of these types of concrete, and is known for its characteristic high unitweight. For heavyweight concrete production heavy aggregates are required for production. In this study, the barite aggregates obtained from an underground mine in the region of Şekeroba of Turkoglu district of Kahramanmaraş province were evaluated as heavyweight concrete aggregate by examining their physical, chemical, mechanical and mineralogical properties. Barite is used mostly in the oil industry. In oil and natural gas drilling, it is used as 'weighting material' in slurries and liquids. It is also used in the electronics, television screens, ceramics, glass and medical material production sectors. The production of special heavyweight concrete is also used in applications where it is necessary, for example in radiology departments of hospitals or for radiation shielding in nuclear power plants. After characterizing of physical properties of barite aggregate through laboratory testing, a packing model is used to calculate the packing density between cement and the aggregates with different sizes of crushed sand (0-5 mm F2), crushed stone-1 (5-12 mm C1), crushed stone-2 (12-19 mm C2) and 2 μm, 5 μ, 15 μ, 300 μ and 600 μ powder barite materials. Mineralogical-petrographic, XRD, chemical and physical experiments were carried out on these samples and the barite used in experiments was defined. Mineralogical-petrographic analyzes and XRD studies were carried out in parallel and the results were compared with each other. The result of the chemical analysis was interpreted by reviewing the previous research and the data was compared with the existing 1/100000 scale geological data and available literature. In order to be able to design a heavyweight concrete mixture, complying with the related standards and literature, experiments with mixtures in mortar phase were carried out and experimental works were concluded with the concrete phase after obtaining optimum mixture design properties. In the first part of the thesis work, the definition of heavyweight concrete and important issues when designing the mixture are mentioned. The purpose, scope and the method of work are explained. In the second part, introduction of Şekeroba barites zone, geographical location and its morphology, mining potential of the region and geology of the region, climate, and habitation and transportation information are given. In the third chapter, a literature study is given. Concrete constituents, classification of aggregates, alkali-aggregate reaction and its effects to the concrete, determination of mineralogical composition by XRD method and petrographic analysis, concrete plasticizer admixtures and their effect mechanism, material properties of barite and their area of application, heavyweight concrete mix-design and particle modeling theories, information about the particle packing model used for the mixtures are given. In the fourth chapter, chemical and physical properties of cement, admixture and barite aggregates and powder materials are defined and material characterization is made for production of mortar and concrete. The minerals of barite aggregates and their proportions are investigated by XRD and petrographic analysis. In the fifth chapter, a commercially available computer software program has been introduced for calculation of the packing model of barite aggregate and powder materials whose physical properties are determined so as to obtain the mixture of mortar and concrete. Within the scope of the thesis study, 21 mixes of mortar were produced by using different superplasticizer admixtures with barite powder material in micron size, followed by calculation of optimum filling ratio between the particles by using a packing model. For each mortar mixture, 9 samples were prepared and a total of 189 cube samples were obtained. Experimental results were observed by adding chemical admixture in 3 different ratios for each mixture. By choosing the mixture which gives the appropriate consistency in fresh state and compressive strength in hardened state, the heavyweight concrete mixture design is accomplished by using packing calculations. In the sixth chapter, Şekeroba barites were evaluated as heavyweight concrete aggregates for experimental study. The properties that allow the fresh concrete to be easily settled and poured into the mould, workability and uniformity of the concrete has to be provided prior to casting activity. In general, the concept of workability in heavyweight concrete can be evaluated and considered in a similar way to the traditional concrete theory. For the mortar samples mini-slump and flow properties were tested by experiments. Compressive strength test and density in hardened concrete are determined for the mortar cube and concrete samples. In the seventh chapter the results of the study and the general evaluation is accomplished. When all the results are evaluated, it is seen that the barites in Şekeroba region may be suitable according to standard specifications and for heavy concrete production. As a result of the thesis work, it is seen that Şekeroba barites are a natural resource for the production of heavyweight concrete in strategic construction projects that are planned in our country.