Crack In Concrete Research Paper

Assignment 2

CVE80006 Infrastructure Deterioration Modelling

Concrete Crack Diagnosis Assignment The phenomenon of cracking in concrete may depend on several factors such as the amount of loading, rate of bleeding, amount of stress and strain generated in concrete, the composition of concrete and method of fabrication. The cracking of concrete has become severe due to advance construction process which demands high strength structure requiring an increase in stress, strain, and deflection resistance. The cracks in concrete are mainly classified as structural crack and non-structural crack.

Structural Crack - Shear Crack and Extra Compression Loading Crack

Figure 1. Shear Crack

Figure 1[1] is an example of shear crack found at Swinburne

The plastic settlement cracks occur due to the settlement of heavy aggregates at bottom and water at top surface or due to concrete’s tendency to reduce its volume and a restraint in the reduction by either reinforcement or duct will cause adjacent concrete to settle and form crack over the restraining area. In exposed situations, this may increase the risk of corrosion of the reinforcement and pose a threat to durability of the structure. Cracks may develop further due to subsequent drying shrinkage, leading to possible cracking through the full depth of the concrete

Shrinkage crack is caused by contraction of the total body due to loss of water content or moisture. Plastic shrinkage cracks are also formed by loss of water content in the concrete structure by evaporation. When the pace at which the water is evaporating exceeds the rate at which moisture is being supplied to it (via bleeding from the concrete), plastic shrinkage cracks are formed. It generally occurs in the plastic state (partially hardened state). Plastic shrinkage crack may not affect the strength of structure but will ruin the appearance of the structure and the crack to full depth may allow water to penetrate it.

Figure 9. Plastic Shrinkage Crack

Figure 9[10] is a representation of plastic shrinkage crack where crack propagation is highly evident. There are several ways to minimize this crack such as in hot weather, lower the temperature of the fresh concrete by using chilled mixing water or replacing some of this water with crushed ice. Covering the concreted area to avoid excess evaporation or proper curing can help reduce this crack formation. The surface at which the concrete is supposed to be placed should be properly damped so that excess water is removed. Use of fibers or silica fumes can also help to reduce the crack formation.

5. Plastic Shrinkage in Shape of