Category: PRECAST CONCRETE

Different kinds of defects are found in timber. Generally, they are caused by the nature of the soil on which the tree is grown, the fertility it gained during growth and changes occurred in the environment during its growth. The defects to be generally looked into while selecting timber for woodwork are discussed below. Knots…

Characteristics of good timber are given below in the order of decreasing significance: Strength The timber should be strong enough to effectively act as structural members, such as joists, beams, rafters, etc. Further, it should be in a position to sustain loads applied gradually or suddenly to it. Preferably, the strength should be adequate in…

As per Indian Standards (IS: 4021–1967), it is preferred that timber used for building construction purposes is of one of the following four types: Classification of Teak Teakwood is classified into three grades, viz., superior, first and second depending on the defects. The classification of teak based on the permissible defects, viz., cross grain, knots, pith, pockets or streaks, sapwood,…

Basic Structure of a Tree A tree consists of a trunk, a crown and roots. The functions of the roots are to implant the tree in the soil, absorb moisture and mineral substances it contains and in turn supply them to the trunk. The trunk supports the crown and serves to provide water and nutrients…

Timber is a product of wood from felled trees suitable for construction purposes. Timber is one of the oldest and natural civil engineering construction materials. Three terms pertinent to timber one of interest. They are: Wood, as a building material, has a number of valuable properties, viz., relatively high strength, low bulk density, low heat…

Different types of precast concrete units are discussed below. 9.6.1 Hollow Concrete Blocks Hollow concrete blocks are manufactured in various shapes and sizes. Blocks of concrete are moulded in a machine. Details of standard size blocks, which are used for different works, are given below: The face thickness of blocks is maintained as 5 cm…

Modular Co-ordination For prefab construction and for the precast elements, modular co-ordination has to be followed. In this case, some basic module has to be adopted for general application to buildings and their components. The value of the basic module chosen is 100 mm for maximum flexibility and convenience. The symbol used for the basic…

 Advantages Precast concrete has several advantages over cast-in-situ concrete: Disadvantages There are certain aspects that discourage the use of precast concrete units under the following conditions:

Prefabrication is most suitable for large-scale housing programmes. Prefabrication technique is used as a cost-effective measure. As the components of any structure can be manufactured under controlled conditions, there is vast improvement in quality. It helps to use the locally available materials with required characteristics. The speed of construction is generally fast compared to cast-in-situ…

The term cast-in-situ concrete is applied to concrete members which are cast or poured in forms that are set up at the final position of the structure. In contrast, the term precast concrete is applied to individual concrete members of various shapes, which are designed to fit in a part of a whole structure, which…