A tree structure basically consists of three parts, namely, trunk, crown and roots. The functions of the trunk is to support the crown and to supply water and nutrients from the roots to the leaves through branches and from the leaves back to the roots. The roots are means to implant the trees in the soil, to absorb moisture and the mineral substances it contains and to supply them to the trunk.

From the visibility aspect, the structure of a tree can be divide into two categories :

• Macro structure ( Visible to naked eyes )
• Micro structure ( Apparent only at great magnifications )

Pith

The innermost central portion or core of the tree is refer as the pith or medulla. It varies in size and shape for different types of trees. It consists entirely of cellular tissues and it nourishes the plant in its young age. When the plant becomes old, the pith dies up and decays and the sap is then transmit by the woody fibers deposit round the pith. The pith of branches is nothing but merely a prolongation of the pith of stem.

Heart wood

The inner annual rings surrounding the pith constitute the heart wood. It is usually dark in color. As a matter of fact, it indicates dead portion of tree and as such, it does not take active part in the growth of tree. But it imparts rigidity to the tree and hence it provides strong and durable timber for various engineering purposes.

Sap wood

The outer annual rings between heart wood and cambium layer is refer as the sap wood. It is usually light in color and weight. It indicate recent growth and it contains sap. The annual rings of sap wood are less sharply define than those of heart wood. It takes active part in the growth of tree and the sap moves in an upward direction through it. The sap wood is also refer as the alburnum.

Cambium layer

The thin layer of sap between sap wood and inner bark is refer as the cambium layer. It indicates sap which has yet not be convert into sap wood. If the bark is remove for any reason, the cambium layer gets expose and the cells cease to be active resulting in the death of tree.

Inner bark

The inner skin or layer covering the cambium layer is refer as the inner bark. It gives protection to the cambium layer from any injury.

Outer bark

The outer skin or cover of the tree is refer as the outer bark. It is the outermost protective layer and it sometimes contains cracks and fissures. Outer bark consists of cells of wood fiber and is also refer as the cortex.

Medullary rays

The thin radial fibers extending from pith to cambium layer are refer as the medullary rays. The function of these rays is to hold together the annual rings of heart wood and sap wood. These rays are sometimes broken and in some varieties of trees, they are not very prominent.

The entire manufacture of portland cement process in a modern plant is now control through a microprocessor base programmable logic control system to maintain a consistently uniform quality of cement and a high rate of production. The entire operation of the plant is control centrally in a single control room and the plant employs minimum of manpower as compare to previous plants construct prior to 1980.

Following three distinct operations are involve in the manufacture of normal setting or ordinary or Portland cement :

• Mixing of raw materials
• Burning
• Grinding

Mixing of raw materials

The raw materials such as limestone or chalk and shale or clay may be mix either in dry condition or in wet condition. The process is accordingly refer as the dry process or the wet process of mixing.

Dry process ( modern technology )

In this process, the raw materials are first reduce in size of about 25 mm in crushers. A current of dry air is then pass over these dry materials. These dry materials are then pulverise into fine powder ball mills and tube mills. All these operations are do separately for each raw material and they are store in hoppers. They are then mix in correct proportions and make ready for the feed of rotary kiln. This finely ground powder of raw materials is refer as the raw mix and it is store in storage tank. The flow diagram of mixing of raw materials by dry process.

Wet process ( old technology )

In the earlier part of the century i.e., from 1913 to 1960, the wet process was used for the manufacture of cement. From 1913 onwards, the cement industry underwent a number of changes mainly to suit the requirements of the manufactures and the govt. policies till early 1982.

All the cement plants set up after 1980 use the dry process for the manufactures of cement. But the method of preparing the wet process and flow diagram of mixing of raw materials are given below :

Burning

The burning is carry out in a rotary kiln. A rotary kiln is form of steel tubes. Its diameter varies from 2.50 m to 3 m. Its length varies from 90 m to 120 m. It is lay at a gradient of about 1 in 25 to 1 in 30. The kiln is support at intervals by columns of masonry or concrete. The refractory lining is provide on the inside surface of rotary kiln. It is so arrange that the kiln rotates at about one to three revolutions per minute about its longitudinal axis.

Grinding

The clinkers as obtain from the rotary kiln are finely ground in ball mills and tube mills. During grinding, a small quantity, about 3 to 4 per cent, of gypsum is add.

The gypsum controls the initial setting time of cement. If gypsum is not add, the cement would set as soon as water is add. The gypsum acts as a retarder and it delays the setting action of cement. It thus permits cement to be mix with the aggregates and to be place in position.

The grinding of clinkers in modern plants is carry out in the cement mill which contains chromium steel balls of various sizes. These balls roll within the mill and grind the mixture which is collect in a hopper and taken in the bucket elevator for storage in silos.

The cement from silos is fed to the packer machines. Most of the modern plants have electric packing plant having provision to account for the weights of empty bags of different types and to ensure a 50 kg net weight of cement bag within +- 200 g limit. Each bag contains 50 kg or 500 N or about 0.035 m3 of cement.

These bags are automatically discharge from the packer to the conveyor belts to different loading area. They are carefully store in a dry place. The flow diagram of burning and grinding operations.

Ball Mills and Tube Mills

These mills are use to carry out grinding of raw materials or mixture of raw materials or clinkers. The ball mills are use to have preliminary grinding and the tube mills are use to carry out final grinding.

Ball Mills

The vertical section of a typical ball mill. It is in the form of steel cylinder of diameter about 2 m to 2.50 m and of length about 1.80 m to 2 m.

The cylinder is place in a horizontal position and it rotates around a steel shaft. On the inside of cylinder, the perforate curve plates are fix. The ends of these plates overlap each other. The cylinder is fill partly with steel balls of size varying from 50 mm to 120 mm.

The action of ball mill is very simple. The material to be ground is fed from the top. When the mill is rotate about its horizontal axis, the steel balls strike against the perforate curve plates and in doing so, they crush the materials. This crush material passes through an inner sieve plate and then through an outer sieve plate. It is collect from an outlet at the bottom of outer casing of mill.

Tube Mill

It is in the form of a long horizontal steel cylinder of diameter about 1.50 m and of length about 7 m to 10 m. The cylinder is fill partly with steel balls of size varying from 20 mm to 25 mm.

The action of tube mill is similar to that of ball mill. But fine grinding is achieve due to steel balls of smaller size. A worm is provide to feed the material to the mill. The pulverised material is collect at the outlet funnel. In case of large scale production, the air separators may be employ to separate finely ground particles. In this arrangements, the current of air is use to carry away the finely pulverise particles.

To combine preliminary and final grinding, the compartment mill or multiple chamber mill may be adopt. Such a mill has different chambers or sections in which steel balls of different sizes are place. The material to be ground is allow to pass through chambers in succession. The chambers with steel balls of bigger size are place first and they are follow by chambers having steel balls of smaller size.

It is thus seen that a compartment mill combines the actions of ball mill and tube mill. It results in saving of floor space and it simplifies the grinding process. The cost of grinding also works out to be less by the installation of such a mill.

Common Names

ZE Building – Zero Energy Building

ZNE Building – Zero Net Energy Building

ZEB – Zero Energy Building

NZEB – Net Zero Energy Building

Definition

The buildings which produce energy by renewable sources at the site and consumes the same amount energy is termed as Zero Energy Buildings.

Methodology

Zero Energy Building get half or more of its energy from the power grid and return the equal amount after sometime.

According to daily and seasonal position of sun, window and door type and placement, overhang depth, insulation type and values of the building elements, air tightness, the efficiency of heating, cooling, lighting and other equipment, as well as local climate are take care of.

Zero energy buildings are built with significant energy saving features. The heating and cooling loads are lower by using high efficiency equipment, insulation, high efficiency windows, natural ventilation, and other techniques.

Zero energy buildings are often design to make dual use of energy including white goods, for example, using refrigerator exhaust to heat domestic water, ventilation air and shower drain heat exchangers, office machines and computer servers and body heat to the heat of the building. These buildings make use of heat energy that conventional buildings may exhaust outside.

Advantages of Zero Energy Buildings

• Detachment of building owners in future from increased prices of energy.
• Increase in comfort level due to uniformity in temperature.
• Requirement reduces for energy penance.
• Overall cost of new construction is less as compared to afterthought retrofit.
• However higher resale value of ZEB.

Disadvantages of Zero Energy Buildings

• Initial cost is higher however ZEB execution is expensive
• Limited manpower is skilled for its construction, therefore it is difficult to find skilled labour or manpower.
• While peak demand of grid occurs, other houses may use less energy but the energy demand for ZEB does not reduces.

Conclusion

To conclude we may say that ZEB results in reduce in carbon emission, independency of fossil fuels increases. Also prevents seasonal energy storage, requirement of energy austerity reduces and energy efficiency improves.

India’s first Net Zero Building is Indira Paryavaran Bhawan, located in New Delhi.

Rollers of different types are use for compaction of soils. The compaction depends upon the following factors : Contact pressure, Number of passes, Layer thickness, Speed of roller etc. Various types of roller which is use in construction sites are shown in below :

Smooth Wheel Rollers

A smooth wheel roller generally consists of three wheels; two large wheels in the rear and one small wheel in the front. A tandem type smooth wheel roller consists of only two drums; one in the rear and one in the front. The mass of a smooth wheel roller generally varies between 2 to 15 Mg. These rollers are operate by internal combustion engines.

Note : Some authors express 1000 kg mass as one tonne (1t). As tonne is not a standard SI unit, it is better to express 1000 kg as 1 Mg.

Smooth wheel rollers are useful for finishing operations after compaction of fills and for compacting granular base courses of highways. These are not effective for compaction of deep layers of soils, as the resulting compaction pressures include are low. Futher, these rollers also cause stratification in deep layers due to non uniform compaction. These rollers are generally use to ” seal ” the surface of the fill at the end of day’s work to provide a smooth surface to quickly drain off any rain water.

Pneumatic tyre rollers

Pneumatic tyre rollers use compress air to develop the require inflation pressure. The contact pressure depends upon the area of contact and the inflation pressure. The roller generally consists of 9 to 11 wheels fix on two axles, with the pneumatic tyres so space that a complete coverage is obtain with each pass of the roller. The rollers are available in a wide range of load sizes. The gross mass of the roller varies between 5 to 200 Mg. However, the rollers with mass more than 50 Mg are rarely use. The inflation pressure varies between 200 to 1000 kN/m2. The rollers are available as a self propel unit as well as towed unit.

The roller compacts the soil primarily by kneading action. These rollers are effective for compacting cohesive as well as cohesionless soils. These rollers are the best type of equipment for general use. Light rollers ( mass up to 20 Mg ) are effective for compacting soil layers of small thickness up to 15 cm, whereas heavy rollers are useful for layers of thickness up to 30 cm.

Sometimes, the rollers are design to produce a wobble effect, due to which a slightly weaving path is track. This improves the compaction of the soil. Pneumatic tyre rollers are generally provide with a weight box or ballast box. The box can be fill with ballast to increase the weight of the roller.

Sheep foot rollers

In ancient time before the advent of the rollers, it was usual practice to pass a flock of sheep on the newly form soil fill to cause its compaction. The same principle is use in the design of sheep foot rollers.

The sheep foot rollers consists of a hollow drum with a large number of small projections ( known as feet ) on its surface. These projections penetrate the soil layers during the rolling operations and cause compaction. The drums are mount on a steel frame. The drum can be fill with water or ballast to increase the mass. Sheep foot rollers are available both as a self propel unit and a towed unit. As rolling is done, most of the weight of the roller is impose through the projection on the soil. The contact pressure is generally between 700 to 4200 kN/m2. The roller may sink into the soil if the contact pressure is more than the bearing capacity of the soil.

The sheep foot rollers are ideally suit for compaction of cohesive soils. The rollers compact the soil by a combination of tamping and kneading action. When the roller is pass for the first time, the projections penetrate the soil layer and lower portion of the layer is compact. In successive passes, compaction is obtain in the middle and the top portion of the layer. This continually rising effect of the compaction is refer as walking out of the roller.

The depth of layer that can be compact depends upon the length of the projections and the weight of the roller. Small rollers can compact layers of 15 cm thickness, whereas heavy rollers can compact layers of 30 cm thickness. In general, the thickness of the layer compact is keep not more than 5 cm greater than the length of the projection.

Vibratory compactors

In vibratory compactors, vibrations are include in the soil during compaction. The compactors are available in a variety of forms. When the vibrator is mount on a drum, it is refer as vibratory roller. These rollers are available both as pneumatic type and the smooth wheel type. In a smooth wheel type, a separate motor drives an arrangement of eccentric weights to create high frequency, low amplitude, up and down oscillations of the drum. These rollers are suitable for compacting granular soils, with no fines, in layers up tp 1 m thickness. However, if there is appreciable percentage of fines, the thickness has to be reduce. In a pneumatic tyre vibratory compactor, a separate vibrating unit is attach to the wheel axle. The ballast box is suspend separately from the axle so that it does not vibrate. These compactors are suitable for compacting granular soils with thickness of layer of about 30 cm.

Another form of a vibratory compactor is a vibrating plate compactor. In this system, there are a number of small plates, each plate is operate by a separate, vibrating plates is limit to small depths. Their main use is to compact granular base courses for highways and runways where the thickness of layers is small.

Vibratory compactors can compact the granular soils to a very high maximum dry density.

The PVC or polyvinyl chloride is the most versatile plastic and the use of PVC pipes in buildings is becoming popular day by day. It is possible to substantially change or modify the properties of PVC resin by the technique of compounding i.e., addition of other additives to PVC.

It is thus possible to prepare a PVC rigid pipe. The other applications to which PVC can be put up include footwear, bottles, gramophone records, waterstops, cables, making toys, bags, tubes, floor coverings, etc.

Precautions taken while design and installation of PVC

• The design of PVC pipes should accommodate adequate provisions in respect of appropriate air vents, etc.
• Fittings such as tees, elbows, caps, etc. use in PVC piping system should be fit well with the pipes. If such fittings are too tight, they will develop stress in the system and if they are loose, they will cause leakage of water through pipe system.
• The PVC pipe system should be suitably test after installation and before putting the system in service.
• Trenches for laying PVC pipes should be as narrow as possible and at the same time, they should be wide enough to allow convenient installations of the pipes.
• Turbulent flow of water through PVC pipes should be avoid.
• They are available in different colours. But it is advisable to avoid red and black colours on external expose walls.
• Provide with sufficient supports and additional supports in the form of hangers, anchor, etc. should be freely use to eliminate external stresses.
• Not be use at places likely to be subject to heavy loading.
• They should not be bent too much to avoid any stresses in them.

Advantages of PVC pipes

• Good insulating properties and hence the temperature of water passing through such pipes is not affect by the outside temperatures.
• Permit high, smooth and undiminished flow of water.
• No problem of incrustation.
• Possess high Hazen Williams Constant and it results into adoption of smaller size of PVC pipes as compare to the sizes of pipes of other conventional materials under similar conditions.
• Prove to be economical as compare to other pipes of conventional materials such as asbestos cement, cast-iron and galvanize iron.
• Provide resistance to a variety of chemicals.

Disadvantages of PVC pipes

• Liable for creep phenomena requiring closer spacing when install above ground level.
• Cannot be use at high temperatures as they are basically thermo-plastic. The recommend range of temperature for pressure applications is -1 degree celsius to + 49 degree celsius and for non-pressure applications, the higher temperature up to 80 degree celsius can be use.
• Do not have the same strength as cast-iron or galvanize iron pipes.
• Possess higher coefficient of expansion as compare to the cast iron or galvanize iron pipes.

It may however be note that the above drawbacks of PVC pipes are not very serious and they are now wide use as pressure pipes for rural water supply, electrical conduits, telephone ducts, tube well castings, etc.