Sound absorbing materials for Office and Home

 

The materials used for reducing the reflection of sound waves in buildings are called Sound absorbing materials.

There are many materials which may be used for reducing the sounds effects and also  in buildings  to reduce noise pollution.

Examples of these materials are following

1) Perforated card boards

2) Porous materials

3) Heavy curtains

4) Maps

5) Pictures put upon the walls

6) Carpets on the floors

7) Wood-wool Acoustic Panel

8) Moss Panels

9) Fabric Acoustic Panels

10) Cloth papers

11) Ceiling Baffle

12) Printed Acoustic Panels

13) Fiber boards

14) Porous plaster

15) Oil Cloth

16) Glass Silk

17) Porous Plastics

18) Sound Absorbing Foam (Pro Studio Acoustics Tiles)

19) Acoustic Panels (ATS Acoustics)

20) Acoustic Curtains (Utopia Thermal Blackout Curtains)

21) Moving Blankets (Sure Max Heavy Duty).

22) Door Sealing Gasket & Sweep Kit.

 

These materials suitably applied to walls ,ceiling and floor of a room or Hall to reduce reflection of sound waves from their surfaces. Sound absorbing materials should be porous ,inelastic ally flexible, compressible or they may be having combination of two or more of these properties.

The absorbent co-efficient of commercial sound absorbing materials can be increased by various means such as perforating ,slotting or by providing small apertures into the body of materials , by doing so energy centre of sound dispersed sideways.

Architectural Soundproofing . This  includes everything used in the structure of a building, such as soundproof windows, soundproof walls, doors, and decoupling products used to install them.

Auralex Acoustics Studio foam Wedgies Acoustic Absorption Foam, 2" x 12" x 12", 24-Panels, Charcoal

 

Pro Studio Acoustics - Blue/Charcoal - 12"x12"x2" Acoustic Wedge Foam Absorption Soundproofing Tiles - 12 Pack

 

       Acoustic Panels (ATS Acoustics)

            Acoustic Curtains

               Perforated card boards

          Wood-wool Acoustic Panel

     ceiling baffles sound absorption

              Printed acoustic panels

        Fiber boards for sound proofing

Standard staircase dimensions

 

There are some principles to be observed while designing a staircase for homes as listed below.

A- Step Proportioning.

The riser and tread of every step should be of regular dimensions throughout the length of the stair. The proportion between going and rise of stop should be carefully worked out so as to provide comfort and ease to the users.

The following rules should be followed for finding a suitable relation between going and rise of steps in stair.

1) Rise + Going = 400 to 450 mm.

2)  (2x Rise) + (Going) in mm = 550 to 600 mm

3) Going x Rise, both in mm = 40000 to 41000  Sq.mm

while designing steps ,take 300 mm going and 140 mm rise as a standard value. For every 20 mm deduction from tread ,add 10 mm to the rise.

The following dimensions of tread and rise are generally used for different buildings

1) Residential buildings 250x160 mm.

2) Public buildings such as theatres ,colleges, banks etc.

3) Industrial Buildings ,The tread should not less than 250mm and rise not more than 190 mm.

It should be noted that the rules given above only act as guide but the actual dimensions of tread and rise depend upon the space available height of building and layout of stair.

B- Pitch of stair

The pitch or slope of the stair should neither be more than 40 degree nor less than 25 degree for at ease ascend and descend by the users.

C- Width of the stair

The width of the stair should be such that a person going up can pass a person coming down without any difficulty. The minimum width of stair in a residential building should be 1 Meter whereas in case of public building a minimum width of 1.5 Meter is desirable.

D- Length of flight

The number of steps in a flight should not be more than 12 otherwise it becomes difficult to move up and down the flight and the minimum number in a flight should be 3.

E-Head Room

An sufficient head room must be provided .It should not be less than 2.14 m vertically or 1.5 m at right angles to the line of nosing.

F- Winders

They should be avoided as for as possible because they are liable to be dangerous and involve extra expenditure in construction. Winders are difficult to be carpeted and are especially unsuitable for public buildings. However,  they are to be provided when the area of the staircase is limited, In such cases , winders should be placed at the lower end of the flight.

In a quarter space ,i.e. 90 degree turn ,only three winders should be provided.

G- Hand rails and balustrades.

A staircase should be provided with a hand rail along with balustrade to provide assistance ,comfort and safety to the users. The height of hand rail should neither be more than 0.85 meter and nor less than 0.75 meter.

H-Materials of stair

The stair should be constructed of sound materials of  fire resisting quality. It should preferably be constructed of R.C.C according to building bye-laws being followed in locality.

I- Location of stair

The staircase should be located in such a position that it can be easily and speedily approachable. It should be provided in center of the building where enough light and ventilation is ensured specially at turning points in a staircase.

In residential building stair should be located near the main entrance and screened from outside for privacy. In public building it should preferably be located obvious from the main entrance.   

How to calculate circular slab reinforcement

 

Suppose we have a circular slab having internal diameter of 11'-0" and external diameter as 12'-6" (including both walls) and RCC slab having 1/2" dia bars @ 6" c/c both ways.

So solving this example we will use following formula

Spacing of  bars will be started from point "A" and will be gradually increased adding each bar from point "A" towards Points "C" .This process will provide us half reinforcement of single layer and 1/4th of two layers of reinforcement.

 

L =  2 (( 2R-S)S))^1/2

L =  Length of  each bar with respect of positioning of bar from points ''A" and "B"

S = Spacing of each bar from point "A" towards point  "C" OR Spacing of each bar from point "B" towards point  "C".

R =Effective radius slab (Clear span of slab + two bearings for MS bars.

L =  2 (( 2R-S)S))^1/2

Before putting values in above listed formula let me check the correctness of  formula by checking the length of central bar adding 2 bearings of 4.5"as it will be 11'-0" + 2(4.5") = 11'-9"

Trial for central bar will be done as follows

L =  2 (( 2R-S)S))^1/2

L= 2x ((2x5.875-5.875)5.875))^1/2

=2x ((34.5156))^1/2

=2x (5.875)  = 11.75'

So the formula is correct to calculate the length of all bars

 

Bar-1 at 6"  = L= 2x ((2x5.875-0.5) 0.5))^1/2 =4.743'

Bar-2 at 1'= L= 2x ((2x5.875-1) 1))^1/2 =6.557'

Bar-3 at 1.5'= L= 2x ((2x5.875-1.5) 1.5))^1/2 =7.842'

Bar-4 at 2'= L= 2x ((2x5.875-2.0) 2.0))^1/2 =8.831'

Bar-5 at 2.5'= L= 2x ((2x5.875-02.5) 02.5))^1/2 =9.617'

Bar-6 at 3'= L= 2x ((2x5.875-3.0) 3.0))^1/2 =10.25'

Bar-7 at 3.5'= L= 2x ((2x5.875-3.5) 3.5))^1/2 =10.75'

Bar-8 at 4'= L= 2x ((2x5.875-4.0) 4.0))^1/2 =11.135'

Bar-9 at 4.5'= L= 2x ((2x5.875-4.5) 4.5))^1/2 =11.423'

Bar-10 at 5'= L= 2x ((2x5.875-5.0) 5.0))^1/2 =11.618'

Bar-11 at 5.5'= L= 2x ((2x5.875-5.5) 5.5))^1/2 =11.726'

Common Bar-12 at 5.875'= L= 2x ((2x5.875-5.875) 5.875))^1/2 =11.75

Length of one side bars from Point "C" (Excluding central bar) = 104.50 Ft

Length of one mesh  (Including central bar) = 2x104.50 Ft+11.75 =220.75 Ft

Length of 2- Meshes (Main and Distribution bars) = 2x220.75=441.50 Ft

Weight of bars = Total Length of Bars x Unit Weight in Unit length

Weight of 1/2" dia bar in One Ft length = 0.302 Kg/Ft

Weight of bars = Total Length of Bars x Unit Weight in Unit length

                          = 441.50 x 0.302 = 133.33 Kgs

Add 3% for wastage margin =133.33x1.03 = 137.33 say 138 KGS

 

What is slump in concrete

 

Slump is vertical settlement of the concrete after the mould has been withdrawn and the vertical difference between height of mould and the highest point of subsided concrete.

Following slump test apparatus is used to do slump test.

The apparatus for determining the slump includes following items 

1- Slump Cone ( Steel mould in form of a truncated cone).

2- Tamping Rod (Is used to tamp the slump cone and for Roding of concrete

3-Measuring Tape (measure vertical displacement of concrete after removal of cone)

4-Smooth Surface Sheet (Provides smooth surface to keep slump cone vertical).

5-Trowel. (Used to Fill the concrete in cone).

6-Hand Level (after removal of cone Hand level is placed horizontally over the Slump cone to measure vertical displacement of concrete.)

Testing Procedure

Place the slump cone on leveled sheet and fill the cone with concrete in 3" consecutive layers with Roding to compact concrete until it fills up to the top of cone. During filling of concrete cone should be in hold with placing of feet on lower pedestals and may be lifted above holding the hooks fixed in the middle of the cone. Now after removal of cone place the cone near settled concrete and place the hand level on the top of cone extending up to the top of concrete and then measure vertical displacement with measuring tape.

What should be the slump of concrete.

Although the slump test is not entirely satisfactory since it gives widely varying results and also does not give a true measure of workability but it is of value in the field as a control test and is useful in comparing the consistence of successive batches of concrete made with the same ingredients ,and is one of the simplest tests to carry out at site. Provided no change is made in the aggregate or it's grading ,slump tests will indicate whether correct water and cement contents are being maintained. For a given slump  and aggregate grading, water required for the unit volume of concrete is constant irrespective of the change of the cement content.

The amount of the slump depends not only on the amount of water in the mix but also on the nature of aggregates ; rounded stones give a greater slump than angular stones for the same mixture.  

Recommended values for slump in Millimeters.
S No	Types of Work	With Vibrations	Without Vibrations
1	Mass Concrete, Large sections, roads	10 to 25	50 to 75
2	Foundations ,Footings ,Sub-Structures, Walls and other heavy sections.	26 to 50	40 to 115
3	Thin Sections such as slabs ,columns, beams with congested reinforcements	40 to 80	100 to 175

 

How slump is recommended ?

This is very important to understand about the practical recommendations of slump and here is the details which includes Selections of materials and proceeding with job mix formula with number of hit and trial tests to obtained required strength of concrete. During each test of job mix slump test has been conducted and recorded in laboratory and when that slump is recommended on which designed strength of concrete has been obtained.  

Types of Slump

There are three types of Slumps .

True slump refers to common drop of the concrete mass evenly all around without collapse.

Shear slump indicates that the concrete lacks cohesion. It may undergo segregation and bleeding and thus is undesirable for the durability of concrete.

Collapse slump indicates that concrete mix is too wet and the mix is regarded as harsh and lean.

This Blog contains supporting images which are property of Google only.

Effect of water-cement ratio on strength of concrete

 

The workability of concrete increases as water content of mix increased, water lubricates the mixture of concrete. But increase in water content causes the decrease in strength of concrete .Excessive use water weakens the concrete ,produces shrinkage cracks and decreases density of concrete.

 Water occupies the space in concrete and as it evaporates it leaves voids and cracks which decrease the strength of concrete. The volume of water voids may be as much as 10 percent of the total volume of concrete. An excess of 10 percent of water may reduce the strength by about 15 percent and an excess of 30 percent of water may reduce the strength up to 50 %. Lower the water content the stronger the concrete but quantity of water must be sufficient to produce a workable mix required for particular method of compaction to be adopted for concreting.

Concrete made with low water cement ratio is unworkable. If stiff or dry concrete is used then honey-combing will result decrease in density and strength. An unworkable concrete results in incomplete compaction giving rise to air voids. If 5% Air voids exists in concrete may cause 30 % strength loss and 10 % air voids may cause as much as 50 percent strength loss.

Water Cement Ratios Adopted for different mix of Concretes.
S No	CONCRETE MIX	WATER CEMENT RATIO	QUANTITY OF WATER IN LITERS	REMARKS
1	(1:1:2)	0.42 TO .54	21 TO 27	For vibrated concrete ,the quantity of water may be reduced by about 20 %
2	(1:1.5:3)	0.52 TO 0.60	26 TO 30
3	(1:2:4)	0.58 TO 0.64	29 TO 32
4	(1:3:6)	0.68 TO 0.72	34 TO 36
5	(1:4:8)	0.90 TO 0.94	45 TO 47

Therefore there is an optimum value of water cement ratio for every mix which should only be decided after properly adopting of job mix formula, and water content has to be restricted within certain minimum limits. Concrete should be plastic to be worked around the reinforcement rods.

Sometime strength has to be sacrificed by adding more water to obtain higher degree of workability where concrete has to be placed in narrow and thin RCC sections.
The best mix is the one which gives the maximum workability with minimum amount of water .An increase in water content must be accompanied by proportionate increase of cement if strength is to be maintained.

Hydration of cement is incomplete without an adequate quantity of water, Less water impedes complete setting of cement and decreases the strength of concrete. The amount of water required to complete the hydration of cement is about 25 % of the weight of the cement.
Generally the water cement ratio for Concrete (1:2:4) mix is 0.60 ,Concrete (1:1.5:3) mix is 0.50 and for concrete mix (1:1:2) mix is 0.45.  

Water Cement Ratio Formula

 

The Ratio between weight of water and weight of cement is called water cement ratio.

Formula of water cement ratio is given below

WCR =  W/C

Water Cement Ratio = Weight of Water / Weight of cement

Water cement ratio is mathematical expression having no units but it can be expressed in percentage for example if we find WCR =.6 using job mix formula ,the amount of water may be calculated from formula as below.

 WCR =  W/C

Water Cement Ratio = Weight of Water / Weight of cement---------Eq.no.1

Putting Values in Eq.no.1 considering Weight of One bag of cement.

 0.6= (Weight of water /50 Kgs)

Weight of water = 0.6 x 50 Kgs = 30-Kgs

Here we knows that 1Kg = 1 Liter

So we can say according to designed WCR 30-Liters or 30-Kgs of water will be added to concrete mix.

WCR is designed formula for use of water in concrete mix with respect of weight of cement and it is very important for workability and strength of concrete. More water in concrete improves workability (Ease in concreting) of concrete but on other hand it decreases the strength of concrete.  

Roughly Water Cement Ratio for Concrete (1:2:4)  = 0.60

                                                  Concrete (1:1.5:3)  = 0.50

                                                     Concrete (1:1:2)  = 0.45

This Blog contains supporting images which are property of Google only.