Cracking behavior and crack patterns of ferrocement are more or less similar to reinforced concrete with some differences. Cracks, in ferrocement, at service load are very fine so that is not visible from the naked eye, and cracks in ferrocement are very small but large in numbers. Crack propagation is not sudden as it is in reinforced concrete. Progressive cracking behavior is dependent on reinforcement type and the number of mesh layers. When chicken mesh is used, after the first crack, mesh deviates from linearity. With the increase in the number of mesh layers, the crack arresting mechanism is better, and crack width decreases with an increase in the number of mesh layers. The specific surface of reinforcement does not have strong relation with cracking behavior. Average crack width in bending has relation with tensile strain developed in extreme mesh layer and wire spacing of the mesh.
When ferrocement panels are tested under four-point flexure loading, cracks started appearing at mid of the panel i.e. pure flexural tension zone. At failure, in the zone of shear, very few cracks appear. It means panels failed predominately in flexure. Crack propagation is very low in ferrocement because the cracking load is immediately transferred into reinforcement. Crack width does not increase by increasing the load applied until stabilization stress is developed. Once the stabilization stress is developed, the width of cracks starts increasing.
Two types of inclined cracks are developed in ferrocement; flexure-shear cracks and web shear cracks. In ferrocement, crack spaces are much smaller than RCC this makes it a more ductile material. Nonstructural cracks may also develop due to movement of formwork, shrinkage, internal cracks due to internal heat of hydration or thermal stresses, etc. Structural cracks in ferrocement develop due to stress concentration, creep, foundation settlement, fire, earthquake, fatigue, vibration, overloading, etc.. Cracks may also appear due to corrosion of reinforcement. Repairing of cracking zone in cover coat due to temperature and drying shrinkage is not required but cracks appeared due to overloading i.e. structural cracks should be repaired.
The writer is the author of a research paper on Ferrocement which can be accessed here. This article is part of writer’s published work and should not be reproduced without the author’s permission.