ABSTRACT
The study explores the investigation of the chemical composition, microstructure and mechanical properties of steel and cement mortar used in reinforced concrete. The compositions and mechanical properties of the locally produced steel were analyzed to ascertain their potential for applications for construction.
Two samples of construction steels produced and used in Nigeria were studied along. The chemical compositions of these steels were determined using Solaris CCD techniques. The microstructure of the steels was characterized using an Optical microscopy.
Similarly, two of the cement samples that are produced and commonly used in the Nigerian market were studied. The chemical compositions of the cements were determined using X-ray Fluorescence and X-ray Diffraction techniques. The cements were mixed with standard river sand to produce mortar with well controlled mixed proportions .The setting time and soundness of the mortar were determined along with their compressive and flexural strengths. The implications of the results were discussed for the development of manufacturing of steel and cement and construction codes that could significantly improve the safety and reliability of African buildings.
CHAPTER ONE: BACKGROUND AND INTRODUCTION
1.1 INTRODUCTION
Engineering failure of buildings has been a general concern to civil, structural and materials engineers. Studies have shown that some of these causes are as the results of bad designs, Faulty construction, Foundation Failure, Over Loads, Fatigue, and Thermal environmental effects on concrete. However, most of the failures are frequently are also attributed to the misuse of materials. The major constituents of materials used in reinforced concrete are cement, steel and aggregates. These materials are essential components of enhancing better mechanical properties and the durability of said reinforced concrete.
In virtually every construction project the safety and durability of the finished structure are critical to its success. Essential to achieving this, is the implementation of effective quality control procedures of construction materials such as steel and cement. Steel and cement are the two very essential construction materials of this century. The construction industry is largely dependent on these materials for durable and quality structures.
Ever since steel began to be used in the construction of structures, it has made possible some of the grandest structures both in the past and also in the present day .
For instance, Considerable progress has been achieved through the use of steel-fiber reinforced concrete (SFR) to enhance structures.
The fundamental properties of SFRC using these new materials have been investigated and compare with those of standard/ imported .
The tensile strength is important for concrete structures as a basic mechanical property and factor of good durability. Since concrete is generally weak and brittle in tension compared to its capacity in compression, steel –fiber reinforcing is a practical means developed for a better control of the tensile performance of concrete.
According to studies, Steel- fiber reinforced concrete (SFRC) has various excellent properties as a composite material; for instance, flexural strength, tensile strength, shear strength, toughness, impact resistance etc are improved by the used of steel fiber.
In order for this properties to be achieved, the production of the steel serving as a fiber must highly be considered [1].
1.2 STEEL
The chemical composition of steel is not the only mechanistic means to control the properties of structural steel. The chemical composition is linked to processing and microstructure for the overall quality of the steel. Most properties depend on the microstructure for a specific steel composition. For example, Yield strength and hardness of the steel are microstructure dependent. Such properties are described as microstructure-sensitive.
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