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 [...]
Pumping of concrete is economical if the quantity of concrete required is more than about 1150 m3 or uninterrupted supply of concrete is needed over a long period as at the beginning of each period of pumping the pipes have to be lubricated by mortar (at the rate of about 0.25 in3 per 1000 m length of 150 mm diameter [...]
The following points highlight the twelve methods used for moving concrete from mixer to the form. The methods are: 1. Pan Method 2. Transportation by Wheel Barrows 3. Transportation Dumpers and Trucks 4. Transportation by Tipping Lorries 5. Transportation by Monorail and Jubilee Trucks 6. Transportation-by Belt Conveyer 7. Transport-by Hoist and a Few Others. Method # 1. Pan Method: [...]
In this article we will discuss about the methods of transportation and placement of concrete. Transportation of Concrete: After mixing, concrete should be transported and placed at site as quickly as possible without segregation, drying, etc. Hence transportation of fresh concrete is very important operation. Depending upon the type of work and equipment available various methods of transporting of concrete [...]
In this article we will discuss about:- 1. Introduction to Compaction of Concrete 2. Voids in Concrete 3. Methods 4. Types of Vibrators. Introduction to Compaction of Concrete: The process of compaction of concrete consists essentially of the elimination of entrapped air from the concrete. The oldest means of achieving this aim is by punning with a rod, or by [...]
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 [...]