7. The sharp corners are visible on the fracture surface which indicates the presence of stress concentration at that area. 8. Stress concentration are arise due to several reason such as poor radius of curvature, weld repair on the pull rod, slag inclusions, corrosion etc. 9.
This low permeability reduces the effects associated with the absorption of chemicals which include the corrosion of steel reinforcement and erosion of the concrete itself. This increases the repair cycle and lifespan of the concrete and the structure as a whole, while also creating the conditions that allow certain chemical reactions to occur that will help to heal or fill the cracks of the concrete
Over the last three decades, significant studies have been executed to examine the impact of steel fibres as reinforcing matrix on the mechanical properties and impact resistance. The previous findings revealed that steel fibres significantly improves the mechanical properties, impact resistance and crack resistance of the reinforced concrete. Steel fibres bridge gap between adjacent surfaces of existing micro-crack, delay crack formation and limit crack propagation by reducing the crack tip opening displacement. This mechanism is known as a bridging
The effects on both are defined below PLASTIC SHRINKAGE Plastic shrinkage takes place while the concrete is still in the plastic state due to loss of water by evaporation from the surface of the concrete, which leads to surface cracking. Adding polypropylene fibers to concrete has been reported to be very effective in reducing the plastic shrinkage cracking. It has been reported that there is unexpected reduction in plastic shrinkage and bleed water migration to the surface of the polypropylene fiber reinforced concrete specimens compared to that of the plain concrete specimens. HARDENED SHRINKAGE Dry shrinkage can be controlled to some extent by use of polypropylene fibers. But researchers couldn’t lead to credible agreeable result in this aspect.
1. structural factor which happen because of shape size or the choice of materials, or due to the geometry design, or manufacture error or the improper materials and this type of failure occurs usually in a weak point of errors like edges or corners. 2. Performance factor. Cause usually the factors lead to building collapse regardless the natural reasons are a human error so it might have found some weak points in any building. Reasons why building fall down 1.
The concrete cross-section is separated based on the confinement condition which is confined (inner or core part) and unconfined concrete (outer part). For simplicity, the area of concrete is not reduced by the area of the longitudinal reinforcement bars. The unconfined concrete was separated into the left, the right, the top and the bottom sides as presented in Figure 4.16. In defining this moment-curvature curve, Microsoft Excel application was employed. Although SAP2000 has been facilitated with default plastic hinge models, Inel and Ozmen  advises applying a user-defined plastic hinge model in order to obtain a reasonable PA output.
(Lintern, Roach, and Chen, 2002) 1.4.3. Laminar Calcrete This develops as indurate sheets of carbonate overlying hardpan Calcrete or other hand surfaces. (Wright and Tucker, 1991). The laminae can be as thinner than 1mm and the total thickness of this Calcrete is normally even lesser than 250mm. this may occur as a thick layer without any underlying hard surface.
It is one of the widely used methods of enhancing the flexural strength of the Reinforced Concrete (R.C.) slabs. The enormous usage of external prestressing systems to strengthen R.C. continuous slabs needs more researches to have a fully understanding of its
To produce the dense impermeable concrete allow water-cement ratio not more than 0 .45 shall be used. The minimum compressive strength of concrete at 28days shall be 21Mpa tested on standard cylinders. The 7 days crushing strength shall not be less than 2/3rd of the specified 28 days strength. COVER TO REIFORCEMENT In order the reinforcing steel from corrosion by the exposure to air, moisture and other harmful agents particularly in coastal environment and severe exposure conditions and develop necessary bond resistance between the steel and concrete, a minimum cover between the outer faces of steel and concrete shall be provided. For corrosion protection the minimum clear cover to reinforcing bars for ay reinforced concrete construction In the coastal areas shall be as : slabs-50mm, beams-63mm, Columns-63mm, and concrete cast against and permanently exposed to earth -75mm.