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.