In normal circumstances (generally where temperature are above 200C), and where ordinary cement is use, forms may be struck after expiry of following periods: Walls, columns and vertical sides of beams 24 to 48 hours as may be decided by the engineer in charge Slabs (props left under) 3 days Beam soffits (props left under) … Read more
Advantages of Precast Concrete Following are the advantages of precast concrete: The concrete of superior quality is produced as it is possible to have better technical control on the production of concrete in factory. It is not necessary to provide joints in the precast construction. The labour required in the manufacturing process of the precast … Read more
Effects of Improper Curing Following are the major disadvantages of improper curing of concrete: The chances of ingress of chlorides and atmospheric chemicals are very high The compressive strength and flexural strengths are lowered. The cracks are formed due to plastic shrinkage, drying shrinkage and thermal effects. The durability decreases due to higher permeability. The … Read more
Properties of Cement Concrete The cement concrete possesses the following important properties: It possesses a high compressive strength. It is a corrosion resistance material and atmospheric agent has no appreciable effect on it. It hardens with age the process of hardening continues for a long time after the concrete has attained sufficient strength. It is … Read more
The following light weight aggregates are generally used to produce lightweight concrete: Breeze or Clinker These aggregates are obtained from coal and are very light. Some types of coal produce clinker which expands on coming in contact with water and is injurious to concrete causing it to crack. The more the combustible matter remaining in … Read more
Fibre Reinforced Concrete Fibre reinforced concrete is a composite material consisting of cement paste, mortar or concrete with closely spaced and uniformly dispersed fibres of polypropylene, nylon, asbestos, coir, glass and carbon (circular or flat). Properties Fibres introduced in concrete impart the following properties: Increased static and dynamic tensile strength Improved impact strength Limited crack … Read more
Introduction Specific gravity is defined as the ratio of the mass of a given volume of the bituminous material to the mass of an equal volume of water, the temperature of both being specified as 270C. Apparatus Specific gravity bottle of 50 ml capacity, ordinary capillary type with 6 mm diameter neck or wide mouthed … Read more
Polymer Concrete Polymer concrete is conventional concrete made with ordinary Portland cement wet cured, and impregnated with a liquid/gaseous monomer (methyl methacrylate) and polymerized by gamma radiation or chemically initiated means i.e. by using thermal catalytic method (adding 3% by weight benzoyl peroxide) to the monomer as a catalyst. The impregnation is aided by drying … Read more
Vacuum Concrete The concrete from which water is extracted by a vacuum process before the hardening takes place is known as vacuum concrete. The type of concrete having relatively high slump in order to achieve consolidation is usually useful in case of thin slabs and walls. This is achieved by withdrawing considerable amount of water … Read more
Lightweight Concrete It may be defined as the concrete of substantially lower unit weight than that made from gravel or crushed stone. Ordinary concrete is quite heavy and its density is 2300 kg/m3. It is not suitable for use in floor filling as filler in general. If used, it adds considerably to the dead weight … Read more