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 [...]
Beams, slabs and columns are the most important components of the concrete structures. Due to the large number of cracks or damages observed in these components of the structures, the repair and rehabilitation of such members assumes greater importance. Techniques of repairs for beams, slabs and columns are discussed below: Repair of Concrete Floor and Slab System: For the change [...]
In this article we will discuss about the tests performed on concrete. Compression Tests: Compression test can be performed on the three types of test specimens, namely cubes, cylinders and prisms. Cubes of standard size of 150 mm are used in India U.K., Germany and many other countries of Europe. Cylinders are the standard specimens in U.S.A. France, Canada, Australia [...]
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 [...]
Based upon the different properties of concrete the non-destructive methods have been developed. The methods are: 1. Surface Hardness Test 2. Penetration Resistance Test 3. Pull Out Test 4. Dynamic or Vibration Methods. Method # 1. Surface Hardness Test: The hardness of the concrete surface usually is determined by the rebound hammer test. The rebound hammer test was developed in [...]
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 at site concrete is produced in batches with the locally available materials of variable characteristics. Thus concrete of one batch is likely to be different from the other. The magnitude of this variation depends upon many factors as follows: (a) Variation in the quality of the constituent materials. (b) Variation in the mix proportions due to batching. (c) The [...]
In this article we will discuss about:- 1. Introduction to Workability of Fresh Concrete 2. Factors Affecting the Workability of Fresh Concrete 3. Measuring the Workability 4. Effect 5. Segregation 6. Bleeding. Introduction to Workability of Fresh Concrete: The strength of concrete of a given proportion is affected very much by the degree of its compaction. Therefore it is desirable [...]
In addition to the petro-logical (rock structure etc.) character of aggregate, its external characteristics also are of importance which have marked influence on the properties of concrete. Following characteristics are of importance: 1. Shape and texture of particle. 2. Crushing strength of aggregate. 1. Shape of Particles: The shape of the particles depends upon the source of aggregate. The different [...]