Q Bank for Civil Engineer LDCE Exam - Write short notes (11)

Q.No.25. Write short notes on: 

1. Leaky roof treatment. 

2. Inspection of FOB and other steel structure. 

3. Design mix concrete. 

4. Various methods of chlorination in Railway colonies and station. 

 Ans. (i) LEAKY ROOF TREATMENT It is very important for good maintenance that all buildings are made with leak proof roof. Water proofing system on the roofs gets deteriorated due to weathering effect, development of cracks and such other reasons. Disintegration of water proofing material , provision of less no. of drainage pipes, improper detaining at junction of parapet and roof etc are other major contributions in making the roof leaky. Basic requirement arresting leakage of roofs. 

i. Provision of adequate slope 

ii. Provision of adequate openings 

iii. Proper detaining at junction of roof with parapet wall 

iv. Expansion joints. Prevalent water proofing system for roofs 

i. Lime concrete terracing ii. Mud-phuska treatment 

iii. Water proofing using polyethylene films 

iv. Water proofing using polymer cementations slurry coatings 

v. Water proofing using polymer modified bitumen membranes 

vi. Water proofing using bitumen felts. 

Ans (ii) INSPECTION OF FOB AND OTHER STEEL STRUCTURES Every structure on the section/sub division shall be inspected in details by the section engineer (works) and Assistant Engineer.

The SE(W) shall record result in ink in the structural steel inspection register, in the standard form and submit the same by the prescribed date to the Asstt. Engineer, who should scrutinized the entries, issue such orders as deemed necessary and return the register, prompt action shall be taken to carry out repairs required. The SE(W) shall accompany the Asstt. Engineer on the later inspection of structures

carried out during the prescribed period. The Asstt. Engineer shall record results of his inspection in ink in the structural steel register in the form given, maintained by SE(W) and ensure expeditious compliance of notes recorded. 

STRUCTURES- The condition of which warrant special attention should be inspected more frequently. 

ENTRIES IN COLUMN “Condition of structure at the time of inspection” should be in the nature of statements. A defect once mentioned should not be omitted in future years unless it has been eliminated

through repairs in which case a note should be made to that effect. 

DETAILS OF INSPECTION During inspection the following points should receive intention- 

i. The condition of paint 

ii. Whether any corrosion in steel is taken place 

iii. In case of steel work connected to masonry such as tie rods or arched building and roof trusses whether any corrosion is apparent near the masonry. The condition of welds, rivets, bolts and the rods particularly of water storage tanks, cast iron tanks plates should be examined for any cracks whether any deformation of structure has occurred, foundation and bearing with particular references to tightness of anchor bolts. The inspection official shall make a through examination of every part of a structure in all respects, using ladders and scaffolding for examining portions beyond reach from the ground. If so considered necessary, the assistance of the bridge staff may be requisite for the purpose. 

 Ans. (iii) DESIGN MIX CONCRETE

The aim of concrete mix design is to determine the proportion in which cement, fine aggregate, coarse and water should be mixed to produce concrete of required strength, workability and durability with minimum cost.

 The design of concrete mix can be done by following methods :- 

1. Nominal Mix 

2. Design Mix Design Mix can be defined as the process of selecting suitable ingredients of concrete and determining their relative properties. With the object of producing concrete of required strength and durability as economically as possible. The purpose of designing as can be seen from the above definition in two fold. The first object durability, the second is make to the concrete in visible proportioning. With the given materials, the four variable factors to be considered in connection with specifying a concrete mix are – 

i. Water cement ratio 

ii. Cement concrete or cement aggregate ratio 

iii. Gradation of concrete 

iv. Consistency 

Ans (iv) VARIOUS METHODS OF CHLORINATION IN RAILWAY COLONIES AND STATION Definition- 

It is the method of disinfection by which the micro organisms are killed in chlorine. Chlorination serves not only for disinfection, but as an oxidant for other substances (iron, manganese, cyanide, etc) and for taste and odor control in water and wastewater. Other chemical disinfectants include chlorine dioxide, ozone, bromine, iodine. The last two chemical are generally used for personal application & not for the public water supply. 

TYPES OF CHLORINATION 

1. Plain Chlorination Chlorination of water relatively free from suspended matter without any other

treatment. 

2. Pre chlorination The application of chlorine to raw water before any other treatment to improve the coagulation and to remove the taste, odor & colour. 

3. Post Chlorination Application of chlorine to treated water after all the other treatment. Dosage chlorine range from 0.25- 5.0mg/lit in order to obtain the combined residual chlorine in range of 0.1-0.2mg/lit.

4. Double chlorination Chlorine is added to raw water at more than one point. This is done when water is highly contaminated. 

 5. Break Point Chlorination It is the amount of chlorine that is, needed to destroy bacteria and to oxidise all the organic matter and ammonia cal substances present in the water. The point at which the chlorine demand of water sample is met is called the break point. If further chlorine is added beyond the break point, free chlorine in the form of HOCL (Hypochlorous acid) and OCI (Hypochlorite ion) begin to appear in the water. 

6. Super chlorination This is done when there is epidemic in the area. The dose varies from 0.5 to 2.00

ppm depending upon the impurities of water.