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Reinforced Concrete

Reinforced Concrete. Dr S.Sreenath Phd, MSc Engg, MSC (ICM), MBA. Curing of Concrete. Hardening of concrete is dependent on the presence of water. During mixing normally more water for full hydration.

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Reinforced Concrete

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  1. Reinforced Concrete Dr S.Sreenath Phd, MSc Engg, MSC (ICM), MBA

  2. Curing of Concrete Hardening of concrete is dependent on the presence of water. During mixing normally more water for full hydration. It is always necessary to ensure that the water is either retained or replenished to enable the chemical action to continue. A significant loss of water due to evaporation may cause the hydration process to stop. This will reduce the strength development. Title of presentation

  3. Curing Evaporation can cause early and rapid drying shrinkage, resulting in tensile stresses which are likely to cause cracking unless the concrete has achieved sufficient strength to withstand these stress. Curing is the process of keeping freshly laid concrete moist during initial hardening of concrete. Proper curing increases concrete strength, durability and resistance to abrasion and water tightness. Title of presentation

  4. Methods of curing Ponding or spraying Covering of concrete Steam curing Title of presentation

  5. Curing Time To commence as soon as the initial setting commence which is 15 to 45 minutes after placing. Curing time is the minimum period during which the concrete is kept moist. Usually curing for three to four days. Title of presentation

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  7. Repairing of Concrete Structure Cast-in-situ concrete structures are hardly built under ideal conditions. Defects may occur as the concrete is being cast or very soon afterwards. Two mostly seen defects during construction are Cracks and Honeycombing. Title of presentation

  8. Cracks Structural cracks. Non-structural cracks. Title of presentation

  9. Structural Cracks Due to error in design. Loading the structure in excess of the design load, due to change in use. Error or shortcomings in the method of construction. Wrong material used. Unforeseen accident. Title of presentation

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  11. Non – Structural Cracks Too rapid evaporation of moisture from the surface of the concrete while the concrete is still plastic. Thermal contraction cracking in the early life of the concrete. Drying shrinkage cracking. Rusting of reinforcement. Title of presentation

  12. Cracks Title of presentation

  13. Cracks Title of presentation

  14. Honeycombing Due to loss of grout under compaction or congested reinforcement. Title of presentation

  15. Honeycombing Title of presentation

  16. Repairing Cracks Need to investigate to determine its cause. To decide on the type of repair. Due to corrosion of reinforcement need to hack away the damaged concrete and carry out a repair. Minor cracks can fill with non shrink grout. Major cracks, pressure grouting will be required. Title of presentation

  17. Formwork Formwork for in-situ concrete may be described as a mould or box into which wet concrete can be poured and compacted so that it will flow and finally set to the inner profile of the box or mould. Formwork to be inspected during the erection of the formwork; just prior to and during concreting and during striking. Title of presentation

  18. Formwork failure Title of presentation

  19. Formwork Inspections By competent and experienced supervior and Engineer. During erection of formwork. Just prior to and during concreting. During striking. To ensure all works are carried out in a safe manner. Title of presentation

  20. Formwork Materials - Timber Extensively used. Structurally useful because of its strength in relation to its density. Comparatively easy to work to a variety of sizes and shapes either by hand or machine. It is durable under appropriate condition. It gives a good finish appearance. Title of presentation

  21. Formwork Materials - Plywood Extensively used. It is strong and light. Supplied in sheets of 1.2m wide and length of 2.4m, 2.7m and 3m. Title of presentation

  22. Formwork Materials - Steel Not adaptable as timber. More uses. Reduces the number of through ties. Title of presentation

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  25. Form work – Tools and Machineries Require good quality tools. Tools used in formwork construction are: Hammering and percussion tools. Sawing and cutting tools. Levelling tools. Wrenches drills etc. Title of presentation

  26. Formwork Design: Characteristics of good formwork Strength Dead load of the fresh concrete and reinforcing bar is approximately 2400 kg/cum. Formwork and formwork component strong enough to support the concrete and all imposed loads. Title of presentation

  27. Characteristic of good formwork - Rigidity Formwork must be sufficiently rigid to prevent bulging, sagging and movement. Title of presentation

  28. Characteristic of good formwork - Economy The relative cost of the formwork can be very high. For economical use of formwork, the following should be observed: Panels should not drop from height. Shutters to kept clean. Remove nail and other fixing carefully. Always place and store the formwork material in designated storage areas when not in use. Title of presentation

  29. Formwork Requirements Ease of assembling and dismantling. Desirable surface finish. Tightness of joint. Ease of handling. Title of presentation

  30. System formwork Title of presentation

  31. Types of Formworks – System Formwork Modular design. Repetitive use. Title of presentation

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  33. Metal Formwork Title of presentation

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  40. Thank you Title of presentation

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