The concrete surfaces are kept wet for a certain period after placing of concrete so as to promote the hardening of cement. It consists of a control of temperature and of the moisture movement from and into the concrete. The term curing of concrete is used to indicate all such procedures and processes. Purposes of Curing: Following are the objects [...]
For repairing concrete works following methods may be adopted: 1. By the Use of Expanding Cement Method 2. By Dry Pack Method 3. By Replacement of Concrete Method 4. By Mortar Replacement Method or Pneumatically Placed Mortar 5. Pre-Packed Concrete. 1. By the Use of Expanding Cement Method: This method is specially useful for hydraulic structures. If small holes or [...]
In this article we will discuss about:- 1. Special Features of Under Water Repair 2. Steps Involved in Under Water Repair of Concrete 3. Modification in Mix Design 4. Placement Methods. Special Features of Under Water Repair: The special features of underwater repairs are as follows: 1. The underwater repairs are more complex and highly costly. Hence the repair operations [...]
Following factors affect the value of pulse velocity: 1. Smoothness of Contact Surface under Test 2. Length of Path of Pulse Velocity 3. Temperature of Concrete 4. Moisture Conditions of Concrete 5. Presence of Reinforcing Steel 6. Material and Mix Proportion of the Concrete. Factor # 1. Smoothness of Contact Surface under Test: There should be good acoustical contact between [...]
The factors have been found to influence the test results to a great extent are: 1. Effect of Size and Shape of Specimen 2. Effect of Conditions of Casting 3. Effect of Moisture Content of Specimen 4. Effect of Temperature of Specimen at Test 5. Effect of Bearing Conditions 6. Effect of Rate of Loading. Factor # 1. Effect of [...]
Generally the factors that affect the strength of concrete are: 1. Age of Concrete 2. Coarse Aggregate 3. Richness of the Mix 4. Curing of Concrete 5. Temperature of Concrete. Factor # 1. Age of Concrete: The relation between the water/cement ratio and strength of concrete applies to one type of cement at one age only. Different types of cements [...]
Sometimes it is essential to determine the proportions of various constituents of concrete. This can be done easily in the field if the concrete is fresh and analysis is done within five minutes of discharge of the concrete mix from the mixer or agitator. If it is not possible to start the test within five minutes after discharge of concrete [...]
Generally concrete is classified as Normal strength concrete (NSC), High strength concrete (HSC) and ultra-high strength concrete (UHSC). However there is no clear cut boundary for the classification. Indian Standard for mix design has suggested the boundary at 35 MPa (350 kg/cm2) between Normal and High strength concretes. However no boundary has been fixed between High strength concrete and ultra-high [...]
High performance terminology is a new coined term. A concrete mix which possesses the high workability, high strength, high modulus of elasticity, high density, low permeability and low resistance to chemical attack and high dimensional stability is called high performance concrete. In normal concrete, relatively low strength and elastic modulus are due to the high heterogeneous nature of the structure [...]
In this article we will discuss about the behaviour of concrete when compressive stress varies. When the compressive stress alternates between zero and a certain fraction of short term static strength the behaviour of concrete is very significant. As the stress increases from zero to a certain value of about 20 MPa, the strain also increases. On decreasing the load [...]