INVESTIGATION INTO THE CAUSES, EFFECT AND PREVENTION OF CRACKS IN BUILDING: A STUDY OF AKANU IBIAM FEDERAL POLYTECHNIC TABLE WATER FACTORY

ABSTRACT Civil Engineering constructions all over the world are faced with cracking defects which can cause collapse leading to human, economic and financial loss. Often these cracks are seen in walls, columns and beams. This study was carried out by employing several observatory and analytical techniques to observe and understand the types and nature of cracks associated with the water factory building situated in Akanu Ibiam federal polytechnic, Unwana. Field and laboratory testslike the particle size analysis, Atterberg limit test, triaxial test and rebound hammer test investigations was done using two(2) trial pits which show that the site is characterized by clayey sand, poorly-graded sand with gravel and classified as A-2-7 using the AASHTO classification system.Soil sample indicated a moderate degree of expansiveness with a free swell index of 30%. Angle of soil friction for the two trial pits (1and 2) is 250 and 270 respectively; while soil cohesive values are 39kN/m2, and 30kN/m2 respectively and the unit weight of the soil is 17kN/m3 and 15kN/m3respectively. The net safe bearing capacity estimated for the sites are 413.9kN/m2, and 404.6kN/m2. Structural evaluation of the building imposes a load of 52.8KN for a 1.2m by 1.5m shallow footing; hence the net footing pressure is 27.5kN/m2. This value is less than the net allowable bearing capacity on the site. The rebound hammer test also shows that the characteristics strength of concrete (column) is 21N/mm2which is within tolerable limit. This was evident as there was no crack on beams and columns as well as the crack width of the base. However due to the fact that the cracks, were developed from the walls which were as a result of vibratory effects of the table water machineries, imposed load from water tanks and excessive weight of the machines. A concrete wall instead of sandcrete from the trench level to a height of at least 600mm and constructing a reinforced floor with a thickness of about 250mm to 300mm to be able to receive the vibratory effects from machines and resisting the imposed loads from the water tanks through the reinforced floor slab is recommended.