Full Project – Crack control in buildings
CHAPTER ONE
1.1 BACKGROUND OF THE STUDY
Cracks are defect in buildings that renders such building unsafe to the occupants or any other purposes for which it is been constructed for. Cracks in buildings are of common occurrence. A building component develops cracks whenever stress in the component exceeds its strength (Allen et al., 2003).
Generally cracks occur in buildings as a result of several factors which include material characteristics, construction methods employed in the building, nature of insitu soil carrying the building foundation, structural overloading, momentary loading, chemical reactions (hydration of cement, repeated wetting and drying, sulphate attack, corrosion of reinforcement steel, carbonation when shrinkage occurs, etc.), movement in soils, restraint of internal movements and other physical changes. Of principal interest of this project is the control of crack in buildings caused by restraint of internal movements, which include temperature changes, moisture content changes, and drying alternating with wetting (American Concrete Institute Journal, 2007).
Bakeries are known to generate a considerable amount of heat and vibrations, thereby subjecting the structure to elevated temperatures. This results in a temperature gradient being set up across the structural materials (Simon, 2006).
All kinds of cracks that may develop in structures can be accounted for as a failure in the particular structural materials to resist the induced stresses, which have been imposed at any giving time. Furthermore, the extent of failure caused by cracking will depend on the extent of the cracking, which has taken place. Hence, slight cracks are not normally regarded as serious as they do not necessarily result in significant loss of stability. However, it is imperative that the severities of cracks are considered relative to the imposed stresses. The loss of efficiency of the building must also be considered when determining the seriousness of cracks (Gilbert, 2004).
A crack formed as a result of Thermal stress produced by rapid cooling from a high temperature. The stress is physical quantity that expresses the internal forces that neighbouring particles of continues material exert on each other.
Structural cracks are caused by a variety of issues, like poor soil bearing, overloading, swollen soil, and poor construction sites. Generally, structural cracks are accompanied by interior problems, like sloping floors and doors and windows that stick when closed. Structural cracks usually have some tell-tale signs. Depending upon the crack width cracks are classified as:
(a) Thin Crack: less than 1 mm in width.
(b) Medium Crack: 1 to 2 mm in width.
(c) Wide Crack: More than 2 mm in width.
(d) Crazing: Occurrence of closely spaced fine cracks at the surface of a material is called crazing.
In the repair of the cracked fabric of a structure, the type of fabric (concrete, brick wall, reinforced concrete, etc.) determines the approach of the repair. Cracks may be of uniform width throughout or may be narrow at one end, gradually widening at the other. The study of cracks whether vertical, horizontal or diagonal may be straight, toothed, stepped, map pattern or random and other relevant characteristics will give an insight into the manner of approach required to carry out repairs. It is also pertinent to determine whether a further movement of approach and kind of material (cement grout, polymer sealing, polymer injection, vacuum impregnation, etc.) required for the repairs (Gilbert, 2004).
As a principle, it is always good practice to make every possible attempt to reduce cracking to the absolute minimum particularly as cracks, however small or apparently insignificant, are often likely to provide capillary paths for water penetration, which will ultimately lead to the failure of the structure.
Bakery is a building structure housing the manufacture of the process of the bread production. It serves as a major source of employment in Katsina metropolis because of the high consumption rate of bread. The structure is constructed in such a way that it contains basically three various types of sections. These sections include the following: the mixing and milling section, the baking section and the storage section.
1.2 STATEMENT OF THE PROBLEM
It was the nature of many construction materials to crack as they age and as they expand and contract, particularly with exposure to moisture and the get wet and dry out alternately, there were cracks in common areas such exterior walls, interior walls and to corners of doors and window and ceilings causal, in the middle, (Nadin, 2013).
According to Rodger (2001) crack was an evidence of graded deterioration and damage to the structure of buildings. Cracks was of little consequence and it was established as static, simple repair by filing or re-pointing as all that is required. However, regarding the major causes of cracks in building focus in floor and walls has not been studied well. Hence, it seems important to conduct research to fill the gap. Therefore, this study attempted to identify the major causes of cracks in some selected bakeries in Katsina metropolis and their remedy.
1.3 AIM
The aim of this project is to assess the causes of cracks in some selected bakeries and to analyse the best ways to control those cracks that affect most of our bakeries in Katsina metropolis.
1.4 OBJECTIVES
The objectives of this study are to:
- To study the effect of temperature in building element.
- Study the effect of poor construction practices and construction materials.
iii. To analyse the causes of cracks in some selected bakeries.
- To find a permanent solution to some building cracks.
1.5 JUSTIFICATION
Cracks are a common occurrence in buildings at all temperatures. These cracks may be slight (affecting only the wall/ floor finishing) and usually only unsightly and, as important, unacceptable to the owners. However, excessive cracking may have deleterious results leading to serious structural weakening. Furthermore structures subjected to elevated temperatures are often susceptible to severe cracking of the structural members.
The preponderance of Small and Medium Scale Enterprises (SME) in Katsina metropolis, chiefly amongst which are bakeries and confectioneries is the principal reason of carrying out is study. This is because most of all the bread producing factories inspected in the course of this study were seen with cracks, some of which were severe and threatening the existence of the structure.
The knowledge gained from this study will be useful not only in the control of cracks in bread producing factories, but also to other concrete masonry structures. The exorbitant cost carrying out rescue works on cracked structures will be eliminated if adequate preventive measures as investigated by this study are implemented. Thus, this study will in the long term reduce wastages by individuals, companies and governments on renovation/ repair works if crack prevention is incorporated in the design and construction of structures.
1.6 SCOPE AND LIMITATION OF WORK
The subject will carry out an overview of three selected bakeries in Katsina metropolis with a view to identifying crack related problems and suggest useful methods for crack control in bakery. The recommendations of this study will be expected to serve as a future reference in the design and construction of bakeries and other concrete masonry structures.
1.7 LIMITATION OF WORK
The scope of this study is limited to structures with existent cracks. This is because the monitoring of cracks requires a much longer time then available for this study. It is pertinent to state here that the initiation and propagation of cracks is a process that takes years to occur. The study is principally interested in cracks caused by movements in the building structure itself, rather than movements in the soil carrying the building. This is because all the buildings considered in this study are “light weight” concrete masonry units not exceeding 3.5m high, and not expected to settle considerably albeit, it differentially occur but in rare cases compared to structures exceeding 3.5m high.
Full Project – Crack control in buildings