All about civil construction knowledge- PARAM VISIONS

What is fly ash? - Where do we use fly ash in construction?

 1. What is fly ash?

Fly ash is produced as a by-product while burning pulverized coal in electric or steam generation plants. Typically, pulverized coal is blown into the combustion chamber with air where it ignites generating heat & mineral residue.




The residual by-product contains coarse as well as fine-sized ash particles. The coarse particles, known as bottom ash or slag settle into the bottom of the combustion chamber. 

The fine & lighter ash particles remain suspended in the flue gas. These suspended particles are separated from the exhaust gas by electrostatic emission control devices. Such collected fine ash particles from flue gas are known as fly ash.

The fly ash is generally spherical in shape with particle sizes ranging between 10 to 100 microns. They are light to dark grey in color depending upon the percentage of chemical & mineral contents.

Generally, they are cement grey in color as shown in the below image.

The color of the fly ash having 👇

A higher percentage of lime content 👉 light grey.

A higher percentage of carbon content 👉 dark grey.

A higher percentage of iron content 👉 brownish grey.



As the composition of an individual coal source differs from one another, the fly ash color changes as per the constituents present in the burned coal.


2. Where do we use fly ash in construction?

Fly ash is used 

1. In the manufacturing of portland cement.

2. In the production of construction materials such as fly ash bricks, concrete blocks, door frames, fencing poles, pavers, etc.

3. As a base material with sand while installing the pavers.

4. In embankment construction.

5. As a geopolymer component.

6. As a raw material in manufacturing lightweight building blocks.

7. As a catalyst along with silicon hydroxide.

8. As a soil stabilizer along with lime.

9. To fill the voids in the base layer of the asphalt roads.

10. In the production of low-grade concrete.

11. As a substitute material for a percentage of cement in the PCC pavements.

 

3. What are the advantages & disadvantages of using fly ash in concrete?


Advantages:

1. Enhances the workability of concrete.

2. Dense concrete with a higher level of compaction can be achieved.

3. Setting time of concrete can be varied by adding the specified percentage of fly ash to the mixture.

4. Reduces heat of hydration of cement in the concrete.

5. Enhances the permeability of concrete.

6. Saves money as fly ash is a cheaper substitute when compared to cement.

7. Reduces the shrinkage cracks in the concrete.

8. Controls bleeding of concrete to a certain level.

9. Fly ash helps to reduce the W/C ratio of concrete.

10. Helps to achieve uniform & smooth top surface finishings for the concrete.


Disadvantages:

1. Salt present in the fly ash has a tendency to create efflorescence.

2.  Fly ash extends the strength-gaining period of concrete. 

3. In wet climatic areas, fly ash-based products attract moss & fungal growth over the unplastered surface.




4. Not good at regulating freeze & thaw climatic variations.

5. Fly ash does not have uniform properties which makes it difficult to control the quality of concrete.

6. Due to the slower strength gain of concrete, we cannot dismantle the formwork quickly.


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Flakiness index test for coarse aggregates.

 Apparatus & items required:




 1. Weighing scale. 

 2. Tray.

 3. Aggregate sample.

 4. Metal thickness gauge.

 5. Set of sieves.

 6. Record sheet.


Criteria:

As per IS-2386, certain conditions to be followed while doing the flakiness index test are as below.

1. The flakiness index test is not applicable to the coarse aggregates retained over 63mm. sieve & passing through the 6.3mm. sieve.

2. The minimum weight of the sample to be taken for the particular size of aggregates are as below.


3. A number of aggregates retained over any sieve size should be at least 200 pieces for good results of the flakiness index test.


Go through the article 👇

👀. What is the flakiness index test of coarse aggregates?


Procedure:

1. Let us take approx. 6kg of 20mm. aggregate sample for the test procedure.

2. Set the sieves in increasing order so that the smaller one is placed at the bottom and the larger-sized sieve is placed at the top. The different sizes of sieves are shown below.




3. Now, we have to put the aggregate at the top sieve and shake them well. We can use a mechanical sieve shaker for good results, & if it is not available we can do the sieving manually. 

4. After the sieving action is complete, the fraction of aggregates of different sizes is retained over the particular sieves. The aggregates will pass through the 1st 5 sieves (63mm to 25mm.) & the fraction of the sample starts retaining from 20mm. sieve. 

5. We have to collect the sample of aggregates retained over the individual sieves separately. The collected samples should be kept on the floor in descending order one beside the another.

 That means the samples retained over 20mm, 16mm, 12.5mm.,10mm., & 6.3mm. sieve should be kept separately.

6. We have to take the total weight of samples retained over the individual sieve separately & record them before passing through the thickness gauge (As shown in the below table at 9.).

7. Now, we have to pass the aggregates of individual sieve samples through the corresponding slots of the thickness gauge.


As you can observe in the above image, all the aggregate samples retained over 16mm. sieve should be passed through slot J(20 to 16). The sample pieces passing through slot J & retained over the slot should be bifurcated separately.

The same procedure should be carried out for all the sieve samples by selecting the respective slots as per the aggregate sieve size.

8. The passed & retained stones for all the sieve samples are separated from each other.

9. Now, one by one the aggregates passed through the thickness gauge are weighed & the wt. is recorded in the sheet in descending order as shown below.




10. We have to add the total sample wt. & the weight of the fraction passed through the thickness gauge. Let the weight be W1 & W2 respectively.

11. Flakiness index 

= [total wt. of sample passing through various thickness gauges.÷ total wt. of an aggregate sample]х100

FI = [W2 ÷ W1] х 100

 The flakiness index should be within 35% for building concrete.

Here,

Flakiness index

 = [560gm.  ÷ 5980gm.] х 100

   FI = 9.36 ✔ OK

11. The same procedure is carried out for the aggregate of the same lot and the average of the two is considered the final flakiness index.


Recommendations:

For concrete<35%

For BTSD (bituminous surface dressing) < 25% 

For BTBM (bituminous bond macadam) < 15% 

For pavement construction < 15%

Combined FI + EI < 30%

FI 👉 Flakiness index.

EI 👉 Elongation index.


Thank you for going through this test procedure. Have a good day 😄.








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What is the flakiness index test of coarse aggregates?/ Importance of flakiness index test.

 1. What is the flakiness index of coarse aggregates?

The flakiness index of coarse aggregate is the percentage by weight of aggregate particles whose least dimension is less than 0.6 of their mean dimension. 

What does that mean?

Let us observe the metal thickness gauge as shown below.



The capsule-shaped openings for various sizes are provided over the thickness gauge.

The length of the given biggest opening is 100mm. This opening is made for passing the coarse aggregates having sizes between 50 to 63mm. (elongated size)

Therefore, the mean dimension of the aggregate

   = (50mm. + 63mm.) ÷ 2

   = 56.5mm.

The least dimension is the flattened or flaky size of the aggregate

= [0.6 🇽 mean dimension.]

= [0.6 🇽 56.5mm.]

= 33.9mm.

Therefore, the width side of the opening has a measurement of 33.9mm.

Similarly, all the capsule openings are made having the ratio of 1: 0.6, where 1 stands for the mean dimension of aggregate to be passed & 0.6 for the width or flaky side of the aggregate.

In other words, 

Flakiness index 

= [total wt. (W2) of aggregate sample passing through the various thickness gauge openings ÷ total wt.(W1) of an aggregate sample] х100

FI = [W2 ÷ W1] х 100


Note:

The flakiness index test is not applicable to the aggregates retained over 63mm. sieve & passing through the 6.3mm. sieve. 


2. Why do we need a flakiness index test? 

A flakiness index test is conducted to determine the shape of the aggregates. The presence of flaky or flattened coarse aggregates is undesirable in cement concrete, in making bituminous roads, & in the construction of pavements. 

Flaky-shaped aggregates are weak in creating a good bond & compaction in the concretes. They may break due to heavy traffic loads, which may result in failures or forming cracks over the road surfaces.

So, we conduct the flakiness index test to check whether the given aggregates have flaky particles within the specified limits.


3. What is the significance or importance of the flakiness index test?

The flakiness index test helps to maintain the quality of the construction works by minimizing the following defects arising due to the coarse aggregates.

1. The flaky or elongated aggregate particles have a high surface area-to-volume ratio. This reduces the workability of concrete.

2. Flaky aggregates affect the degree of packing or compaction of given mixtures.

3. Flaky particles create a weak bond that reduces the strength of the concrete.

4. Roads or pavements are subjected to regular loads & vibrations due to the moving traffic. Flaky aggregates are not good at taking the desired loads, which eventually break down causing the failure of the structure. 

5. Flakiness index test helps to find out the percentage of undesirable particles present in the sample & to choose the aggregates of the required quality for the particular type of work.



4. Which code is referred to for the flakiness index test?

1. Methods of test for aggregates of concrete.

Part-1, particle size & shape

 IS code 2386 (part 1): 1963


2. ASTM 4791-10 

Standard test method for flat particles, elongated particles, or flat elongated particles in coarse aggregates.

Go through the article 👇

👀. Flakiness index test for coarse aggregates.


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Test for silt content in sand./Procedure for finding the silt present in the sand.


 Materials required:




1. 250ml. measuring cylinder.

2. Sand to be tested.

3. Water.

4. Table salt.


Procedure:

1. Take 50 ml. of water in the measuring cylinder. Add a pinch of salt (approx. 2gm.) to the water present in the jar. Let the salt dissolve in the water.

2. Add 50ml. of sand sample into the jar so that the water level will touch the 100ml. mark over the jar.

3. Again add 50ml. of the water & salt so that the new water level reaches 150ml. mark over the jar.

4. Close the open end of the measuring jar with your palm & shake it vigorously so that sand particles get washed up by the water. The jar should be turned up & down several times. Do this action for 15 to 20 sec. & take care that no materials come out of the jar while shaking.

5. The mixture is then allowed to settle down by keeping the jar on the floor for about 3 to 4 hours. The silt present in the sand starts settling over the sand in the jar ( as shown in below fig.)



6. Now, we have to note down the volume of silt & sand separately from observing the markings given over the jar. 

Suppose, if the volume of silt = V1 ml. 

             & the volume of sand = V2 ml.

Then the percentage of silt content in sand 

  = [V1 V2] Χ100  %

V1 = [(top-level reading of silt) - (bottom-level reading of silt or reading of sand)]

V2 = Top-level reading of sand.

In any case, the silt content in the sand should not be above 8%. If the sand contains more than 8% of silt, then such sand should be rejected.

In my opinion, the silt content in the sand should not be more than 6%. Otherwise, there is a chance of microscopic cracks in plastering work.


Calculation eg:

The volume of the silt = V1 = 3ml.

The volume of sand = V2 = 52 ml.

Percentage of silt content in sand

=  [V1 V2] Χ100  %

 = [3 52] Χ100  %

 = 5.77% < 6%  ✔ OK


Note: 

1. Salt acts as a catalyst in enhancing the settlement process of silt over sand.

2. If you are using a measuring cylinder of a larger volume, keep in mind that the volume of water should be 2/3 of the total volume & sand should be 1/3 of the total volume for getting better results.

3. Repeat the test procedure with at least 3 samples, so that your test result will be nearer to accuracy.


What we should do, if the sand contains more than 8% of silt?

We should use a sand washing machine to remove the excess silt present in the sand.

Go through the article 👇

👀. Different types of sand washing machines.


Thank you for going through this test procedure. Have a good day 😄.


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What is contour interval?/ Uses of contour maps in surveying.

Let us go through some of the FAQs related to contour lines.

1. What is contour interval?

 A Contour interval is the elevation difference between the successive contour lines represented in a topographical map.




For eg: Suppose a contour map has a contour line of 80, 85, 90, 95, & so on, 

Then the contour interval  = [85 -80] 

                                          = 5 units.


2. What are the factors that affect the selection of contour intervals?

The contour interval depends upon the following factors.

1. Nature of ground surface:

Plain ground: The contour intervals are generally small & are parallel.

Steep slope: The contour intervals are generally big & are unequal 

2. Scale of the map:

The contour spacing will be large for a map having a small scale. For the larger scale map, the contour intervals are made of less spacing.

3. Purpose: 

For the precise & detailed survey work, the contour interval should be smaller. For the rough survey work such as location survey, finding catchment area, finding the capacity of water bodies, etc. we need larger contour intervals.


3. What are the uses of contour maps in surveying?

1. Contour map provides the topography of the ground.

2. Helps to select the location of infrastructures such as dams, bridges, pipelines, roads, etc.

3. We can determine the area & volume of the earth of a particular locality.

4. We can calculate the area & capacity of a reservoir or any water bodies.

5. The contour gradient can be drawn from the map.

6. We can find the difference in the height of any two points.

7. To find the economical route of communication between two places.

8. To ascertain the profile of the ground surface in any direction.


4. What are the different types of contour lines?

There are 3 types of contour lines on a map. They are




a. Index lines:

Index contour lines are shown as the dark & thick lines in the maps. These lines provide us the elevation data with respect to the sea level. Usually, one index line is shown after every five intermediate lines.

b. Intermediate lines:

These are the more common lines drawn in between the two index lines. They are thin lines when compared to the index lines.

c. Supplementary lines:

These are the dotted lines, indicating flatter terrain.


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Different types of concrete mixers./Classification of concrete mixers in construction.

 Concrete mixers are classified into the following  4 categories based on their,

A. Type of operation.

B. Power or fuel used.

C. Concrete mixer capacity.

D. Special purpose.

Now, let us go through the subcategories under each of these four types.


A. Type of operation:

1. Batch mixers:

This is the most common type of mixer used all over to obtain the required concrete. The concrete is prepared in batches as per the required grade. All the concrete raw materials are fed volumetrically or by weight into the drum or hopper. The concrete is prepared in part by part by following one batch after another.

These mixers are further classified as

✸. Drum mixers:  In this type of mixer, the main mixing unit is in the drum shape. 

a. Tilting drum mixer:



The raw material is fed at one side of the drum. After mixing the ingredients with water, the concrete is poured at the opposite end by tilting the drum with the help of a steering handle. 

The tilting mixer is available with or without a hopper as per the requirement.


b. Non-tilting drum mixer:



After preparing the concrete, the drum cannot be tilted to pour the mix. The mixer is lifted by the handle & inclined to pour the concrete. Usually, such mixers have a lesser capacity & are ideal for smaller construction works.


c. Reversing drum mixer:



The mixer drum contains chute-like partition blades to mix the ingredients. The material is poured in weigh batching hopper & the digital control panel shows the weight of the individual raw materials.

 The total ingredients are fed into the drum & the mixer drum is rotated in a clockwise direction. Once the concrete is ready, the drum is rotated in the anti-clockwise direction to pour out the mix at the other end. The control panel contains forward & reverse buttons to rotate the drum as desired.


✸. Pan mixer: The main mixing container is in a pan-like shape.



The mixing blades agitate the raw materials in the horizontal direction to prepare the concrete. Here, the pan is stationary & the four no. of blades do the mixing job. The ready material is poured out by opening the lock of the side door. 
The rotating blade throws out the concrete through the sweeping action. The door is closed & the process is repeated.   

2. Continuous concrete mixer:



A controlled volume of raw materials is fed into the shaft chamber through the hopper. The rotating shaft contains screw blades to prepare the mix.

 The screw pushes the mix forward & the prepared concrete is poured at the other end of the shaft. We get fresh concrete continuously without any breaks in between.



B. Power or fuel used:

a. Manual concrete mixer:



The mixer is run manually by rotating the handle. This type of mixer is used when the required volume of concrete is very low. Usually, while doing the PCC works in remote areas, such mixers are very useful.

b. Electrical concrete mixer:



The mixer is run by either single or 3-phased electrical motors. This type of mixer is used in industrial units where all the construction products like concrete blocks, RCC poles, RCC doors, etc. are manufactured.

In the electrical mixers, the drum may be either tilting or non-tilting type. The power of the electrical motor starts from 1/2 HP & it may go up to 10HP, depending upon the concrete manufacturing capability.


c. Diesel-operated concrete mixer:

This is the most common type of concrete mixer used all over construction sites. The diesel engine runs the rotation of the drum as well as the lifting operation of the hopper to feed the material.

While casting the slabs & beams we need a continuous supply of concrete. The electrical mixer stops working if there is a power outage. So, diesel mixers are the most convenient & preferred type at construction sites.   


C. Concrete mixer capacity:

a. Half-bag concrete mixer:



The capacity of the drum is between 3.5 - 5cu ft. Or in liters, the volumetric capacity ranges between 100 - 140 liters. 

The concrete volume of half bag is produced at a time or per batch of mixing. Convenient for smaller construction works where we cannot consume larger mix volumes within the initial setting time of concrete.


b. One bag concrete mixer:


This is the widely used type of mixer to produce one bag of concrete mix per batch. The capacity of the mixer is between 7 - 10 CFT. Or we can say, the capacity is between 200 - 280 liters. 


c. Two bags of concrete mixer:


The drum is heavier having a capacity of  400 to 650 liters. These mixers are utilized for bigger construction sites or for mass concrete works.


D. Special purpose mixer:

a. Twin shaft mixer:



These mixers are ideal for the ready mix industry where we need a rapid output of concrete. They have an output capability of 2cum. to 5cum. within a short period of time due to the twin rotation of shafts. 

They have hydraulically operated discharge doors & the input is inspected by the control panels.


b. Vertical shaft mixer:



In a vertical shaft mixer, the stirring spindle revolves & the stirring planet itself rotates in the reverse direction. This system creates a superior mix of concrete of the required property.

 These types of mixers are used in larger projects where concrete quality is the priority.


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What are laminate sheets?/ Price & specification of sunmica or laminate sheets.

 1. What are laminate sheets?




Laminate sheets are the protective top layer glued over all types of wooden furniture, plywood, particle boards, wall panels, etc. 

They have printed patterns of various color combinations to provide a beautiful & aesthetic look to the items.


2. How laminate sheets are manufactured?


The laminate sheets are composite products containing several thin layers pressed together. The core is made of HDF board or by the impregnation of craft or decor papers with phenolic resins.

It has a top wear layer to protect against abrasion, stain resistance, and wear resistance. The bottom or base layer is made of melamine resins to provide strength & dimensional stability. 

The second layer just beneath the wear layer is a decorative layer or a print film. The 2nd layer provides the needed designs in various colors or finishings for the aesthetic look.


3. What is the difference between Sunmica,  & laminate sheets?

Sunmica is a leading manufacturer brand that produces laminate sheets in India. Sunmica is the earliest & most popular brand in India that manufactures laminate sheets. 

Nowadays,  there are several laminate sheets producing companies in India. But in layman's terms, all types of laminates are still referred to as Sunmica by the general public.


4. What are the dimensions of laminate sheets?

Standard sizes of laminate sheets are

Length  👉 8'

Breadth 👉 4'

Thickness 👉 0.5mm. to 1.5mm.

                👉  0.5mm., 0.6mm., 0.8mm., 1.0mm., 1.2mm., 1.5mm.

                     

5. Where to use a particular type of laminate sheet?

The thickness of the laminate sheets is an important factor in deciding the price of that particular sheet. So while fixing the sheets, we have to select the particular thickness to save in our budget.

Less thickness means lower strength & durability & is also cheap in price.

Therefore,

 0.5mm.- 0.8mm. thickness 👉 should be used in the interior surface of wardrobes, Almera, kitchen cabinets, etc.

1.0mm. to 1.2mm. thickness 👉 should be used for furniture, the exterior of wardrobes, cabinets, shelves, etc.

1.5mm. thickness 👉 should be used for the exterior parts where there is a chance of impact loads such as doors, cupboard shutters, partitions, etc.

 

6. What is the cost of laminate sheets?

The cost of the laminate sheets depends upon the thickness, brand, color pattern, & type of material used in making the sheet.

However, the standard price of sheets depending on their thickness are,

0.5mm. & 0.6mm.   👉  500 to 650/sheet

0.8mm. & 1.0mm.   👉 750 to 1100/sheet.

1.2mm. & 1.5mm.   👉 1250 to 2400/sheet.


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Why do we use chicken mesh in construction?- Specification & installation of chicken mesh.

Let us go through some of the FAQs related to chicken mesh used in civil construction.

 1. What is chicken mesh used in construction?

Chicken mesh is a twisted flexible wire product having honeycomb-shaped openings. The name chicken mesh is due to its common & wide usage to fence the foul or chicken in the poultry industry. 

Due to their flexibility & specific properties, they became the ideal material to reinforce the plasterwork where & when necessary.

Go through the article 👇

👀.  Different types of chicken mesh for plastering.


2. Why do we use chicken mesh in construction?

The thermal expansion properties of various structural items are different depending upon their density, bond energy, and melting temp. etc. The coefficient of thermal expansion of brick, mortar, concrete, steel, & plastic, etc. differs from each other due to their specific characteristics.

When we build a structure, we encounter several joints or junction points between all these types of construction items at various locations. Due to their varying thermal coefficient, there is a huge chance of forming cracks or fissures at the junction or meeting points of these materials. 



If we install a strip of chicken mesh at the junctions, they act as a reinforcement material for the plastering work. Chicken mesh act as a cushion to nullify the effect of expansion & contraction over the plaster. 

Shortly, we can say that we use chicken mesh to prevent cracks in the plastering work at the junction points of different construction items. Chicken mesh is also used to reinforce the wall & plaster when there is a vibration or impact load acting over the wall.

By providing the chicken mesh, we can enhance the strength & durability of plastering.

Similarly, when we cut a groove at the masonry wall to install plumbing & electrical conduits, we fix the mesh over the groove to avoid cracks. 




Here, again by cutting the grooves, the bond between the masonry wall breaks at the groove cuttings. When we fill the groove with mortar & concrete, we create a junction point on either side of the cutting edge of the wall groove. 

Therefore, we need to fix the chicken mesh in all such areas to avoid the formation of cracks within the plaster.

 

3. What is the specification of chicken mesh used in plastering?




Material type 👉 Galvanized low carbon wire.

Wire gauge  👉  0.5mm to 2mm.

Hexagon or honeycomb openings 👉 12mm. to 50mm.

Roll width 👉 0.9m. to 2.5m.

Roll length 👉 50m. 100m. 200m.



4. What is the cost of chicken wire mesh?




The chicken wire mesh cost depends upon the type of material, wire gauge, honeycomb openings, brand, or quality of the product.

Considering all these factors, chicken wire mesh cost ranges between,

Per kg.   👉 INR 60/- to INR 90/- 

Per sqft. 👉   INR 4/- to INR 9/- 


5. How to install chicken wire mesh before plastering?



The chicken mesh should be fixed symmetrically on either side of the junction or joints. The minimum width of the mesh should be 100mm. & it should run throughout the joints.

Fiberglass or galvanized mesh is fixed by troweling or spraying a thin mortar slurry to hold them over the wall. Nails are used in fixing the metal meshes staggered at 100mm. on either side of the strip.

As you can observe in the above drawing, the width of the chicken mesh should be at least 4" (100mm.) in the case of column, beam & masonry joints. 

But when you fix the mesh over the RCC band, you should cover the band entirely by the extension of 2" (50mm.) on either side. As shown in the above drawing, the given thickness of the RCC band is 4". So, the total width of the mesh should be 8" ( 4" +2" +2").

 

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