New civil tech

MAIN BARS AND DISTRIBUTION BARS In any reinforcement detailing there are two sizes of bars used in the slab. That is main reinforcement bars and distribution bars. In this article, we will discuss the difference between main bars and distribution bars. To understand properly we need to know the bending moment on a slab. Let’s take an example. When a lo ad is applied to a slab the bottom of the slab will experience positive moment (Sagging) and the supports will experience negative moments (Hogging). The bottom part, as well as the top part of the slab, will experience high tension at the same time.     The deflection will be very high in shorter span and low in longer span. A high amount of tension will be acting in the support which is near than the other one. FUNCTION OF MAIN REINFORCEMENT BARS: Main reinforcement bar is provided at the shorter span direction in order to transfer the bending moment developed at the bottom of the slab. The purpos...

The  hydration of cement is an exothermic reaction that is carried out when cement comes in contact with water. The reaction will result in several by-products that will contribute to the strength of the concrete or mortar formed. Fig.1. Hydration Reaction - Changing Microstructure of Cement  Cement Hydration The chemical reaction that takes place between the cement and water is referred as hydration of the cement. The hydration reaction is an exothermic reaction. The cement hydration will liberate a considerable amount of heat. This is called as  Heat of liberation or Heat of Hydration.  The mixing of cement with water will result in rapid evolution of heat that will last for few minutes. This evolution of heat is probably due to the reaction of a solution of aluminates and the sulfates. This rapid heat and reaction are depressed by the  addition of gypsum.  The Early heat of hydration i...

Size and Weight Of Bricks For India Standard size of bricks is 19 cm × 9 cm × 9 cm Normal size (with mortar) is 20 cm × 10 × 10 cm. The commonly adopted nominal size of traditional bricks is 23 cm × 11.4 cm × 7.6 cm. It is found that the weight of 1 m 3 of bricks earth is about 1800 kg. Hence the average weight of a brick will be about 3 to 3.50 kg

Classification of Bricks The bricks can broadly be divided into two categories: 1. Unburnt Bricks:  The unburnt or sun dried bricks are dried with the help of heat received from sun after the process of moulding. These bricks can only be used in the construction of temporary and cheap structures. Such bricks should not be used at places exposed to heavy rains. 2. Burnt Bricks:  These are classified in four categories: First Class Bricks These bricks are table-moulded and of standard shape and they are burnt in kilns. The surfaces and edges of the bricks are sharp square smooth and straight. First class bricks have all qualities of good bricks. These bricks are used for superior work of permanent nature. Second Class Bricks These bricks are ground moulded and they are burnt in kilns. The surface of these bricks is somewhat rough and shape is also slightly irregular. These bricks are commonly used at places where bricks work is to be provided with a coat of p...

Brick Composition of Good Brick Earth Following are the constituents of brick earth: 1. Alumina It is the chief constituent of every kind of clay. A good brick earth should contain about 20 to 30 per cent of alumina. This constituent imparts plasticity to earth so that it can be moulded. 2. Silica A good brick earth should contain about 50 to 60 per cent of silica. Presence of this constituent prevents cracking, shrinking and warping of raw bricks. It thus imparts uniform shape to the bricks. Excess of silica destroys the cohesion between particles and bricks become brittle. 3. Lime It should be present in a finely powdered state and not in lump. Lime prevents shrinkage of raw bricks. Sand alone is infusible. But it slightly fuses at kiln temperature in presence of lime. Excess of lime causes the brick to melt and hence, its shape is lost. Lumps of lime are converted into quick lime after burning and this quicklime slakes and expands in presence of moisture. 4....

Timber, Lime and other Materials Timber Classification of trees Trees are classified according to their mode of growth. Following is the classification of trees: 1. Exogenous Trees Conifers are also known as evergreen trees and leaves of these do not fall till new ones are grown. As these bear cone-shaped fruits, they are given the name conifers. These trees yield soft woods. Deciduous trees are also known as broadleaf trees and leaves of these trees fall in autumn and new ones appear in spring season. Timber for engineering purposes is mostly derived from deciduous trees. These trees yield hard woods. Comparison of Soft Wood and Hard Wood 2. Endogenous Trees These trees grow inwards and fibrous mass is seen in their longitudinal sections. Timber from these trees has very limited engineering applications. Examples of endogenous trees are bamboo, cane, palm, etc. STRUCTURE OF A TREE From the visibility aspect, the structure of a tree can be divided into tw...