Following are the 10 advantages of glass block masonry:
1. It is non-porous and impervious.
2. It does not absorb moisture from the atmosphere.
3. The light getting in through these block panels is diffused and may be given any desired tings of color, pleasing to eyes.
4. It has a high degree of thermal insulating property.
5. As the surface of the glass block masonry is even and smooth, it does not catch dirt. It can also be easily cleaned.
6. It does not allow condensation on the inside surface, in cold countries, which is a very great advantage in certain industries where high humidity has to be controlled within the building.
7. It has great noise-reducing properties. Though, the sound insulation property depends on the thickness and size of the glass and the air space between the glass.
8. It is considered more sanitary.
9. If used on the external wall, window openings are not required as sufficient light is admitted through the blocks themselves.
10. It provides good privacy condition by obstructing clear visibility from outside.
Water stops are provided to prevent water from entering the structure through the joints. At the time of construction, they are set in place and later become a part of the structure.
What are the Reasons to Provide Water Stops in concrete Structure?
➤ To prevent the passage of water or other fluid.
➤ To increase the stability of the concrete structure.
➤ To prevent the concrete structure from decaying due to water.
➤ To prevent the chemical reaction.
➤ They can prevent the structure from the adverse effect of the environment.
➤ To prevent the dampness of the structure.
➤ At least, they prevent the cracking due to any of the above reasons.
As they prevent the passage of water, they are suitable in case of water-retaining structure, basement and underground construction.
Types Of Water Stops
Water stops can be divided into three types:
Rubber water stop
Metallic water stop
Mastic type water stop
1. Rubber water stop
This water stop is made either from rubber or material having a lot of rubber. They should be accurately fixed in concrete to prevent them from being lifted by water pressure.
2. Metallic water stop
These types of water stops are made from steel, copper, zinc, etc. non-corrosive metal strips usually 14 to 16 gauge thick. On either side of the joint, the strip remains half embedded in concrete. The metal strip is bent in V or semi-circular shape at the joint.
3. Mastic Water stop
Mastic water stop is developed at the site of the joint by pouring mastic material into the joints. This form of water stop is ineffective in that case, where it is likely to be subjected to pressures and thrusts. So, it is not much more acceptable.
Points to be Considered During Construction of Stone Masonry
The construction of stone masonry is more costly than brick masonry, but stones are more durable, hard, and strong as compared to brick.
The weight of stones are heavy, they are not available in regular in size. So, the construction with such materials has some difficulties, but we can overcome such difficulties as well as we can get a better construction by taking some measures and care during the stonework.
Following are the 15 important points to be remembered or considered during the construction of stone masonry:
1. The stones which will be used in stone masonry must be enough strong, hard, durable, and well-seasoned.
2. It should ensure that the stones are well watered before using them. Otherwise, they will absorb water from the mortar, which leads to reduces the strength of the mortar joint.
3. All the stones should be laid on their natural bed.
4. The dressing of stones should be done properly as per the requirements of the work.
5. As possible as the unnecessary vertical joints should be avoided.
6. Remains gaps between stones should be well filled by stone chippings and set with mortar.
7. In stone masonry, chips, or small pieces of broken stones should not be used.
8. Double scaffolding should be adopted if the stonework is carried out at a higher elevation.
9. The stonework should be carried out slowly and properly by skilled labor.
10. Mortar may be used as mud, lime, or cement, but in the case of basements or sites subjected to water-logged conditions, cement mortar or hydraulic lime mortar should be used. However, for stone masonry, lime mortar is the most appropriate mortar.
11. It should be seen that no tensile stress is developed in masonry because they are very weak in tension.
12. As far as possible the stonework should be raised uniformly.
13. The mortar used for the work should be properly proportioned as specified.
14. The vertical faces of the stonework should be checked by means of a plumb bob.
15. Large flat stones should be laid under the ends of girders, roof trusses, etc.
Comparisons Between Stone Masonry and Brick Masonry
Both brick masonry and stone masonry have some advantages and disadvantages, Following are the 18 differences or comparison between stone masonry and brick masonry:
1. Brick masonry is more economical than stone masonry.
2. Stone is much stronger, more durable, and weather resistant than brick.
3. Because of more strength, durability, and weather-resisting characteristics, the stone is used in the construction subjected to more rigorous and severe conditions. Brick masonry under such conditions may not last long.
4. Stone masonry is less resistant to fire than brick masonry
5. Doors and windows frame can be fixed easily in the case of brickwork.
6. Bricks are available in regular sizes, and they can be used with a specific pattern which is known as ‘brick bonds’. But, in stone masonry, no definite pattern is possible due to their different shape and size.
7. A brick wall may be constructed as thin as 10 cm. But in the case of a stone wall, the thickness of the wall is usually not less than 38 cm.
8. Stones are not available everywhere so, the construction of stone masonry is possible only in some places where the stones are easily available. But brickwork can be done anywhere because bricks can be manufactured anywhere by establishing brick kilns.
9. Due to the large size of the stone, it is difficult to handle. But brick can be easily handled as they are small in size.
10. Less skilled labor is required in brick masonry as compared to stone masonry.
11. Brickwork is more progressive than stonework.
12. In brickwork no dressing is needed whereas in stone masonry proper dressing is required.
13. Bricks are easily affected by chemical reactions due to the presence of salts in urine or sewage, but stone masonry is not affected by such reactions.
14. Plaster on stonework is not required, whereas plaster on brickwork is required to protect the surface of the brick from environmental effects.
15. Brick is light in weight, but the stone is heavy in weight.
16. In stone masonry, different joints are required whereas in brick masonry different bonds are used.
17. Life of brick masonry is less than stone masonry.
18. Dead load of stone masonry is more than brick masonry.
Joints in stone masonry are provided to hold the stones tightly with each other. Following are the 10 types of joints in stone masonry.
Square or Butt Joint.
Lapped or Rebated Joint.
Tongued and Grooved Joint.
Table Joint.
Dowelled Joint.
Cramped Joint.
Plugged Joint.
Saddle Joint.
Slate Joint.
Rusticated Joint.
1. Square or Butt Joint
The butt joint is a very simple and easy and commonly used joint in ordinary stone masonry work. In this type of joint, two adjacent stones are placed in such a way that their square faces are abutted with each other.
2. Lapped or Rebated Joint
The lapped joint is provided where the movement of stone pieces is to be prevented. In this case, rebates are provided to prevent the movements of stones. This joint is also known as a rebated joint. The length of the rebate should not be less than 70 mm. This joint is mostly used in arch work, coping on gables etc.
3. Tongued and Grooved Joint
In the case of the tongued and grooved joint, a projection is kept on one stone and a corresponding sinking is provided in the other stone as shown in the figure. This joint prevents sliding of one stone over the other, but they are more expensive than the above two types of joints, so they are less preferable. This joint is also known as a joggle joint.
4. Table Joint
Table joint is suitable where the lateral pressure is high and need to prevent. In this case, to prevent the lateral pressure, a joggle is formed on the upper surface of the bed stone and a corresponding recess is formed on the bottom surface of the stone which laying above the bed stone, see figure. The recess of the upper stone is fastened on the joggle of the lower stone.
The depth of the projection should be about 4 cm, and the width of the projection should be one-third of the breadth of the stone. This joint is used where the lateral pressure is very high such as sea walls.
5. Dowelled Joint
In this joint, a hole is made into each stone. Then the dowels which are small pieces of hard stone, slate, gunmetal, bronze or brass are used for connecting these stones and secured with cement, see figure.
Usually, the thickness of the dowels are 2.5 cm, and they are around 10 cm to 15 cm long. This joint prevents unwanted displacement of stones. When the dowelled joint is provided for columns, is named as a bed plug.
6. Cramped Joint
In cramped joint, the holes are made on the adjacent stones which will be as dovetail shape(which are shown in the figure). In this case, to connect these stones cramps are used instead of dowels.
The cramps are the piece of non-corrosive metal like gunmetal, copper etc. and their ends are turned down about a depth of 4cm to 5cm. The length of the cramps may vary from 200 mm to 300 mm. The width and thickness may vary from 2.5 cm to 5 cm and 0.5 cm to 1.0 cm respectively.
After placing the cramp into the proper position, the rest of the spaces are grouted with lead or cement mortar. The cramped is provided to prevent the joint to open out due to slippage of one of the stones.
7. Plugged Joint
The plugged joint is same as a cramped joint. In this joint dovetail-shaped cuts are made in the sides of adjacent stones as shown in the figure. After arranging the stones in their proper position, molten lead is poured in the joint. This joint is mostly used for copings, cornices etc works.
8. Saddle Joint
This type of joint is provided to protect the joints of the cornices and such other sloped surfaces. With the help of this arrangement, any water moving on the slope is diverted from the joints. This is also known as water joint.
9. Slate Joint
In this type of joint, grooves are made on the sides surface of the adjacent stones. A piece of slate is placed in between the corresponding groove of the adjacent stones.
10. Rusticated Joint
This type of joint mostly used in plinths or masonry in lower storeys of buildings. This joint may be different types such as channelled joint, vee joint, mould joint etc.
5 Advantages of Automatic Signalling System in Railway
At present, automatic signalling system is very popular and secured signalling system in railway. 5 advantages of the automatic signalling system in railway are as follows:
1. Automatic signalling system helps to eliminate errors due to human, which leads to greater safety and efficiency.
2. To operate automatic signals, the number of workers required is less which reduces the operating costs.
3. In this system, any types of signal boxes, instruments and tools are not required which further reduces the costs.
4. Increased efficiency of operations will increase traffic density. This will also result in less number of locomotives and vehicles requirements.
5. Modernization in traction for high speed and heavy loads warrants requires the use of automatic signalling for efficient services.
