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 [...]
In this article we will discuss about:- 1. Introduction to Strength of Hardened Concrete 2. Type of Porosity for Strengthening Hardened Concrete 3. Influence of Gel/Space Ratio 4. Accelerated Curing Test to Prevent Drying of Concrete 5. Maturity Concept 6. Effect of Different Water/Cement Ratios 7. Conditions for Application of Water Cement Law. Introduction to Strength of Hardened Concrete: The [...]
Rise in the curing temperature speeds up the chemical reactions of hydration and affects the early strength of concrete without any ill effect on the later strength. However a higher temperature during placing and setting, although increases the early strength, but affects adversely strength beyond about 7 days onwards. The explanation for this may be that a rapid initial hydration [...]
In this article we will discuss about:- 1. Process of Hydration for Concrete 2. Objects of Concrete Curing 3. Necessity 4. Methods 5. Period of Concrete Curing 6. Maturity of Cured Concrete. Process of Hydration for Concrete: Concrete derives its strength by the hydration of cement particles. The process of hydration is not a momentary action, it continues for long. [...]
In this article we will discuss about the relation between compressive and tensile strength of concrete. The theoretical compressive strength of concrete is eight times larger than its tensile strength. This implies a fixed relation between the compressive and tensile strength of concrete. In fact there is a close relation but not a direct proportionality. The ratio of tensile to [...]
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 [...]