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 [...]
Till 1940, aggregates were considered as inert materials, but after 1940, it has been clearly established that aggregates are not fully inert. Some of the aggregates contain reactive silica which reacts with the alkalis (Sodium oxide Na2O and potassium oxide K2O) present in cement. For the first time in U.S.A. it was observed that many failures of concrete structures as [...]
Several mechanical properties of aggregate are of interest for the manufacture of concrete, specially high strength concrete subjected to high wear. Some of them are discussed here in brief: 1. Toughness 2. Hardness 3. Specific Gravity 4. Porosity of Aggregate 5. Bulking of Sand. Property # 1. Toughness: It is defined as the resistance of aggregate to failure by impact. [...]
In this article we will discuss about:- 1. Introduction to Practical Grading of Aggregates 2. Grading of Fine and Coarse Aggregates 3. Grading. Introduction to Practical Grading of Aggregates: The grading should be such that it could give a reasonable workability with minimum segregation. Segregation is very important in the production of good concrete. A workable mixture which could produce [...]
Usually the tests that can be adopted to determine the workability of concrete are: 1. Slump Test 2. K. Slump Test 3. Kelly Ball Test 4. Compacting Factor Test 5. Flow Test. 1. Slump Test: This test is used extensively at the site of Work all over the world. Actually this test does not measure the workability of concrete but [...]
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 [...]