Job Getting Tricks 99% Success

Job Getting Tricks 99% Success

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Hello Readers, I’m Ranadip, I’m going through some trouble at this moment, as a result being unable to post since a few days, I’ll be back shortly with a new post on next week, which will focus on the final year students who just passed out and struggling for getting a job in examination and interview (Technical), 99% chances are there that you will get a job if you follow those secret art of preparing for interviews, I’M PREPARING IT FOR YOU……Soooooo Please wait and keep your eyes on Techno Genome and My Civil . . . .It will be a collection of truly blaster information promising to bring something about what you will thank yourself that you will read that.


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Civil Engineering Interview Questions Definitely Asked

Concrete Cube TestThe Top 10 Civil Engineering Interview Questions You are definitely going to face in an interview for sure are as follows :-
 
1) What is Water-Cement Ratio and How it is related to the strength of concrete
 
2) What is Curing and Why it is necessary, What is the minimum curing period
 
3) What Do You Understand by M25 Concrete
 
4) What are the weights of 16mm, 12mm, 20mm, 25mm, 8mm Dia. Bars.
 
5) What are the minimum Propping Period of Beams and Slabs of various Spans.
 
6) How and Why Cube Test and Slump Test are done.
 
7) What are the advantages of Prestressed Concrete over R.C.C.
 
8) Quantity of materials required for different works
 
9) What is the Minimum Water required for Hydration of Cement
 
10) Why RCC Structures are Reinforced and with steel

For Answers Please view the following videos which have been prepared in two parts in which Answers to the above 10 questions in five plus five mode is given with detailed explanation.

 
If someone can answer all of these then He/She can crack the Technical Part of almost 70% of Interview cases. Do not share this with any one these Questions are simple yet secret, typically everyone ignores these Basic Questions.

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Concrete Mix Design Easy Guide As Per IS 10262-2009 With Example

Concrete Mix Design or Mix Design of Concrete is a procedure of determining the relative quantities and proportions of different ingredients of the concrete i.e. Cement, Water, Fine Aggregate, Coarse Aggregate, with the object of producing homogeneous fully compactable concrete having required Strength and Properties with economy.
It is manufactured in Concrete Batching Plant, or sometimes in Mobile Concrete Batching Plant. The Concrete Batching Plant automatically calculates the predefined  quantity of materials needed to produces concrete accurately measured by their weight and thoroughly mixed, in the Concrete Batching Plant the concrete produced is of homogenous quality and controlled concrete.
Now a Days with the advancement of concrete technology, the mix design of concrete is in a boom due to the requirements of High Grades of Concretes having required amount of workability, durability and other properties but the main factor is that these all things are achieved by mix design also with economy, that is there is nothing more in quantities of any ingredients of concrete than that required for producing particular type of concrete grade. Nominal Mixes can be adopted only upto the grade of M20, but above m20 grade, a concrete must be mix designed as per code provisions. Though most of us uses Nominal mix of 1:1:2 for M25 Grade, but it shouldn’t be done. There are various methods of concrete mix design, some of them are as follows :-
 
  • Indian Standard I.S: 10262-2009 method. 
  • Arbitrary Proportioning or Trial and Error method 
  • American Concrete Institute, ACI Committee 211 method 
  • Indian Road Congress, IRC 44 method 
  • Road Note 4 method 
  • Maximum Density and  Minimum Voids method 
  • High Strength Concrete Mix Design  method 
  • Mix Design of Pumpable Concrete 
  • British DoE method etc.
Today in this Article I will illustrate the method of Mix Design of Concrete with Example and providing a very easy and engaging Step By Step Approach as you have found in my other Articles. I will use The Latest Revision of The Indian Standard Code of Practice for Concrete Mix Design that is I.S.: 10262-2009 for the below illustration.
 

STEP 1 – Understand the Requirements of the Problem or Situation :-

 
First of collect the data and write down the following things
a) Grade of Concrete to be designed
b) Amount of Slump Required.
c) Exposure Type it will have in its service life
d) Any other special requirements like delayed setting etc.
e) Air Content
f) Will it be Reinforced or Plain Concrete
For our example let us consider M30 Grade of Concrete with 75-100mm Slump which will be exposed to mild exposure conditions and there is delayed setting is required by using Superplasticizer and with 2% Air Content and will be used in Reinforced Concrete Structure.
 

STEP 2 – Collect Data About the Available Materials for the Production of Concrete :-

Perform Tests where ever required and collect the following data for concrete producing materials which will be used
a) Type and Grade of Cement
b) Specific Gravity of the Cement
c) Nominal Maximum size of the coarse aggregate
d) Grading Zone of fine aggregate
e) Specific Gravity of the coarse and fine aggregate
f) Moisture Content in coarse and fine aggregate
g) Specific Gravity of the Admixture to be used
h) Shape of the Aggregate
 
In our example let us consider the following data : we are using 43 Grade OPC of Specific Gravity 3.15, the Nominal Maximum size of the coarse aggregate is 20mm, Sand is of Zone-II , the specific gravity of coarse and fine aggregates are 2.67 and 2.62 respectively. Moisture content in the coarse and fine aggregate are 1% (Including 0.5% Absorbed) and 4% (Including 1% Absorbed)  respectively. The specific gravity of the admixture is 1.145 and Aggregates are Angular.
 

STEP 3 – Computation of Target Mean Strength of Concrete :

All concretes are composed of various materials like cement, sand, stone chips and water mainly, which vary from time to time and batch to batch, and also after concrete is placed it undergoes different atmosphere in different cases, and concrete will also have different types of workmanship, compactions and other conditions at different cases, thus In production and casting of concrete nothing is constant, almost everything is variable, so we have to provide a suitable allowance for this variation, thus we need to design the concrete for some higher strength than the grade which is required so that it can compensate all those variables. For this reason we have to design the concrete for Target Mean Strength fck’ or ft. The Target Mean Strength is computed as follows :
fck’= fck + (k x s)
Where, fck’ = Target Mean Strength N/mm2
fck = Characteristics Compressive Strength of Concrete in N/mm2
k = A Statistical Co-efficient
s = Standar Deviation N/mm2
Now in our example fck = 30 N/mm2 for M30 Grade of concrete, k = 1.65 as per I.S. 456-2000 for 5% Tolerance, as adopted in the definition of Characteristics Compressive Strength, The value of ‘s’ first time design of M30 grade Concrete is 5 N/mm2 [I.S.: 456-2000 Page 23 Table-8 or I.S.: 10262-2009 Page-2 Table-1]
Therefore, fck’ = fck + (k x s) = 30 + (1.65×5) = 38.25 N/mm2
Therefore we have to design the concrete for 38.25 N/mm2  strength.
 

STEP 4 – Determination of the Free Water-Cement Ratio :

Now from the curve of Compressive Strength vs Water-Cement Ratio we have to find out the required Free Water-Cement Ratio for the strength 38.25 N/mm2 from the particular curve of the grade of cement to be used, or it can also be found out from the generalized curve of BIS, and also consider the value of Maximum Free Water-Cement Ratio from the I.S.: 456-2000 [Page 20 Table-5] and take lower of those two values.
 
 
 

 

Water-Cement Ration
COMPRESSIVE STRENGTH vs WATER-CEMENT RATION CURVE
 
From the above curve it is found out that the Water-Cement Ratio corresponding to the 38.25MPa and 43 Grade OPC is or from the Generalized curve of BIS is found out as 0.40 and as per I.S. 456-2000 is 0.45, Hence we must take the Free Water-Cement Ratio as 0.40
 

STEP 5 – Determination of the quantity of Water required per cu.m. of Concrete :

Now the quantity of water required for the production of concrete is to be determined as per I.S.: 10262-2009 Page-3 Table-2 and adjustments are to be made if required as per the code provisions. The basic selection of water is based on the Nominal Maximum size of the aggregate which is in our case is 20 mm so from the table we get Water content corresponding to the 20 mm Maximum Nominal size aggregate is 186 ltr. or 186 kg. But these values are for 25-50mm slump, but we need 75mm-100mm slump. Therefore we have to do the adjustments. Here the slump difference between the standardize and required value is (100mm – 50mm) = 50mm and as per I.S.: 10262-2009 we have to increase the water content given in the table by 3% for each increase of 25mm slump above 50mm (standardize value). Therefore in our case the required increase I water content will be ((Slump Difference/25)*3)%  = ((50/25)*3)% = 6%. Thus we need to increase the water content by 6%. Therefore the adjusted water content is (186 + 6% of 186) = (186+((6/100)*186)) = 197.16 kg [See I.S.: 10262-2009 Page- 2 Clause – 4.2]. In our case the aggregates are angular hence no adjustments are needed for water content. But we are using superplastisizer, hence the water content can be reduced by 20% minimum or as per manufacturers specification. Thus reducing the water content by 20% we get the final water content as (197.16 – ((20/100)*197.16)) = 157.73 kg.
 

STEP 6 – Determination of Cement Content :

Now as we know that Water-Cement Ratio = (Weight of Water/Weight of Cement) , therefore we get
Weight of Cement = (Weight of Water/Water-Cement Ratio)
In our case it will be Weight of Cement = (157.73/0.40) = 394.33 kg per cu.m. of concrete
As per I.S.: 456-2000 Page-20 Table-5 we get for Reinforced Concrete of M30 Grade the Minimum Cement Content is 320kg per cu.m. of concrete, and Maximum cement content for any grade of concrete is 450kg per cu.m. of concrete. Hence our calculated value of cement content satisfies both the minimum and maximum cement content criteria hence okay. If our value would have fall below the minimum vale then we had to take the grater of the calculated and the minimum value of cement content

STEP 7 – Calculation of Quantities of Coarse and Fine Aggregates :

The percentage of coarse aggregate of the total volume of aggregate have to be determined as per I.S.: 10262-2009 Page-3 Table-3 corresponding to the Nominal Maximum size of coarse aggregate ad Zoning of fine aggregate. In our case we have considered Nominal Maximum size as 20mm and Fine Aggregate as Zone-II, therefore the percentage of coarse aggregate by volume of total aggregate is 0.62 or 62%. This values of table are for Water-Cement Ratio of 0.50, and for other Water-Cement Ratios adjustments are to be made as Percentage of Coarse Aggregate is increased by 0.01 or 1% for every 0.05 decrease in Water-Cement Ratio from 0.50, and Percentage of Coarse Aggregate is decreased by 0.01 or 1% for every 0.05 Increase in Water-Cement Ratio from 0.50. In our case the Water-Cement Ratio is decreased by (0.50-0.40) = 0.10 hence the volume of Coarse Aggregate have to be increased by 2% or 0.02. Therefore the adjusted percentage of coarse aggregate is (0.62+0.02) = 0.64 or 64% of the Total Volume of Aggregate.
Now we have to compute the Total Volume of Aggregate by the following
Va = 1.0 – [v + {C/(Scx1000)} + (W/1000) + {S/(Ssx1000)}]
Where, Va = Total Volume of Aggregates in cu.m.
v = Air Content expressed in Decimal [ e.g. 2%=0.02]
C = Mass of Cement in kg
Sc = Specific Gravity of the Cement
W = Mass of Water in g
S = Mass of Admixture in kg
Ss = Specific Gravity of the Admixture
Considering Admixture content as 2% by weight of Cement In our example we get,
Va = 1.0 – [0.02 + {394.33/(3.15×1000)} + (157.73/1000) + {7.89/(1.145×1000)}]
= 0.69 cu.m.
Therefore Volume of Coarse Aggregate required = 64% of 0.69 cum. = (64/100)x0.69 = 0.442 cu.m.
 Now we know that
Total Volume of Aggregate = Volume of Coarse Aggregate + Volume of Fine Aggregate
Or Volume of Fine Aggregate = Total Volume of Aggregate – Volume of Coarse Aggregate
Therefore in our example Volume of Fine Aggregate = 0.690 – 0.442 = 0.248 cum.
Now we need to to convert their volume into mass as weight batching will be done.
Mass of Any Substance = (Specific Gravity of that Substance x 1000) x Volume of that Substance
Therefore we get,
Mass of Coarse Aggregate Required = (2.67×1000) x 0.442 = 1180.14 kg
Considering 55% 20mm Aggregate = 55% of 1180.14 = 649.1 kg
Considering 45% 10mm Aggregate = 45% of 1180.14 = 531.04 kg
 
Mass of Fine Aggregate Required = (2.62×1000) x 0.248 = 649.76 kg
 

STEP 8 – Arranging the Proportions of Different Ingredients :

Now the Proportions are to be computed of different ingredients of concrete as per the materials calculated in the previous steps.
 
Mix Proportions by Mass :
 
Cement = 394.33 kg [1]
Water = 157.73 kg (Water-Cement Ratio =0.40)
Fine Aggregate = 649.76 kg [1.648]
Coarse Aggregate = 1180.14 kg [2.993] (20mm = 649.1kg [1.646]  10mm = 531.04 kg [1.347] )
Admixture = 7.89 kg [2% by weight of Cement]
Hence Cement : Fine Aggregate : Coarse Aggregate = 1 : 1.648 : 2.993
 

STEP 9 – Final Adjustments for Moisture Contents in Aggregates :

The Aggregates which are used may contain some moisture in absorbed or both in absorbed and free surface moisture form. If necessary corrections in the quantity of mixing water and in the content of aggregates will not be adjusted then the Water-Cement Ratio in actual will increase and the Aggregate Content in actual will decrease due to the free water in the aggregates which will increase the water content, and at the same time which would occupy the volume of aggregate. Thus we have to make necessary corrections for this are to be made so that the calculated water content and aggregate content does not increase and decrease respectively.
In our example the coarse aggregate has 1% moisture in which 0.5% is absorbed into the aggregate it self, therefore the free water is (1%-0.5%) = 0.5%. And in the case of fine aggregate it has 4% moisture in which 1% is absorbed in it self, therefore free moisture is (4%-1%) = 3%.
It means that if we use the calculated value of coarse aggregate then it will include 0.5% of water by its weight and in case of fine aggregate the inclusion of water will be 3% of the weight of fine aggregate.
Total amount of inclusion of water from aggregates are (0.5% of Coarse Aggregate + 3% of Fine Aggregate) = [{1180.14x(0.5/100)}+{649.76x(3/100)}] = 25.39 kg
Therefore amount of water actually to be added at the time of mixing is = 157.73 – 25.39 = 132.34 kg
It also means that if we use the calculated value of coarse aggregate then it will not include 1% of coarse aggregate by its weight which have been occupied by water and in case of fine aggregate the non-inclusion of fine aggregate will be 4% of the weight of fine aggregate.
Thus the actual amount of Coarse Aggregate required at the time of missing will be (1180.14 + 1%) = [1180.14 + (1180.14*(1/100)}] = 1191.94 kg comprising of 55% of 20mm = 655.78 kg and 45% 10mm = 536.37 kg
Thus the actual amount of Fine Aggregate required at the time of mixing will be (649.76 + 4%) = [649.76 + {649.76*(4/100)}] = 675.75 kg
Therefore the Final Mix Proportions After all the Adjustments are as follows :
Cement = 394.33 kg [1]
Water = 132.34 kg (Free Water-Cement Ratio =0.40)
Fine Aggregate = 675.75 kg [1.714]
Coarse Aggregate = 1191.94 kg [3.023] (20mm = 655.78 kg [1.663]  10mm = 536.37 kg [1.360] )
Admixture = 7.89 kg [2% by weight of Cement]
Hence Cement : Fine Aggregate : Coarse Aggregate = 1 : 1.714 : 3.023
 
Now Trial Cubes are to be prepared and tested to see the results.
I hope I have been able to make the topic clear, easy and understandable. Please do share the Link of MyCivil – Civil Engineering Redefined which is  www.mycivil.engineer . And do leave Your Comments regarding this article. Any suggestions will be highly appreciated. Thank You and Have A Good Day.

 

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Home Made Waterproofing Compound

Today I’m here going to discuss about how to make waterproofing compound by self at the site during the construction with cheaply available materials. I know it has been a long time since my last article, and maybe you, who are following Techno Genome regularly know the reason behind that, anyways let us concentrate on today’s topic. First of all we have to understand what a Waterproofing Compound is, and why it is required in a Civil Engineering Construction works.

Waterproofing, Water Proofing Compounds, Waterproofing Methods
ENTRANCE OF WATER IN BUILDING
A Waterproofing compound is nothing but a chemical in the form of liquid or powder which when mixed with concrete or mortar during their preparation, makes that concrete or mortar impermeable to the moisture so that the moisture cannot penetrate through the fine pores of the concrete or mortar surfaces.

Now we must understand why a civil engineer should resort to water proofing compound, and what benefits it can provide for that extra expenditure which will be needed for using the water proofing compound or a water proffer.
See actually every concrete surface or mortar surface has got fine pores throughout its body, which are known as the capillary pores. No matter how rich the concrete mix is, no matter how well compacted it is, there will be capillary pores, which are simply unavoidable, so when ever you will give some water on the exposed concrete surface or mortar surface you will notice that the concrete or mortar surface will be absorbing the moisture. Now the fact is what is the problem which will occur if the absorption capabilities exists on concrete or mortar surface? The actual problem lies in the fact that concrete and mortar surface not only absorbs moisture but also carbon di oxide and also other gasses and acids which will penetrate through the surface of concrete or mortar surface and mixing with the moisture it will form the respective acids of them and thus mainly two things can happen depending on the fact that whether it is a Reinforced Concrete or Plain Concrete. Suppose it is a Plain Concrete without any reinforcements then what will happen that those acidic solutions will dissolve the hardened cement compounds and will decay the concrete, and if it is RCC that is Reinforcements are there within the concrete, then the moisture and oxygen which penetrates through the body will cause the rusting of the steel reinforcement. So to cope up with this problem the best way is that we must not allow the moisture to enter into the hardened concrete or mortar surfaces, and to resist the moisture from entering through the surface pores. In case the heavy moisture enters into mortar it may cause even electrical short circuit. A Waterproofing Technique also helps in proper curing of the concrete by preventing the moisture from escaping from the inside of the concrete to the atmosphere.


What a Waterproofing Compound does is that it seals off the pores on the concrete and mortar surface by producing some chemical substances which forms due to the reaction of Water Proofing Compound with the Water and the reaction products seals the pores with insoluble products and blocks the moisture from entering through the pores.
But the most important fact is that though this chemical, that is Waterproofing Compounds are required in small quantity about 2% but being costly in many unimportant cases or in cases where due to any reason it is not possible to use a Branded Waterproofing Compound at places where it must be used, then What will we do?????
Yes, We are going to make it by our self, in the following manner. I’ve arranged it in simple manner without any complexities, Let us see.

Ingredients :

  1. Cement : Sand = 1:2 by volume
  2. Pulverized Alum @ 120 N per cu.m. of sand that is 12 kg per cu.m. of sand
  3. Soft Soap @0.75 N or 75 gm. per Lit. of Water

Procedure :

  • Take Required Quantity of Cement and Sand in the proportions of 1:2 by volume.
  • Dry mix them well until a good texture is achieved which have to be judged by eyes that the mixing has been done enough.
  • Add Alum in Powder form which can be done by crushing the Regular Alum bought from Hardware stores, and add it to the dry cement-sand mix at the rate of 12 kg per cu.m. of the sand in that dry mix.
  • Now prepare the mixing water , first determine the amount of water required for producing a mortar of workable consistency, then add Soft Soap (Beauty Soap maybe used which are used for bathing) at the rate of 75 gm. per Lit. of water. and mix the water thoroughly with the soap.
  • Now use this soap water and add it to the dry cement-sand-alum mix and prepare the mortar.
  • Now this mortar has become a Waterproofing Mortar, use it on the surface of Concrete as a plaster or use for regular plastering works where Waterproofing is required.

But always remember it should be used in case only when it is not possible to use Branded Waterproofing Compounds, and on works which are not of major importance, as in adverse conditions it will not have the same power of resisting as a branded waterproofing compound.
Hope all of you would like this article, please do comment and share your thoughts on this article and on Techno Genome. and please do share the web address of Techno Genome that is www.technogenome.com in your circle of people and in your Social Networking pages to help in growing this site, Your one help may help others in finding these informative articles and also a growth to this site, or else these efforts are all wastes as it would not help others. Thank You for Your Visit. Keep Visiting Techno Genome for more and more like Articles, Have a Good Day.

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Brickwor Quality Control

Here I’ve listed the most important factors which are to be taken care of while doing Brickwork of any nature structural brickwork or face lifting works in brickwork for better appearance. These points mentioned below should always be taken care strictly in the site of construction for achieving a long lasting durable structure.

Brickwork
    • The bricks should be of 1st class quality for structural works, or atleast of 2nd class quality in unavoidable circumstances, but those 2nd class bricks must posses atleast 60% of the field quality checks of bricks.
    • The bricks should be immersed in water for a continuous period of 2 hrs for best results, or atleast 1 hr for satisfactory results, but anything less than this can cause total loss of bond strength of the mortar due to the absorption of water from the mortar to the water hungry dry bricks.
    • Brickwork should be done for a maximum height of 1.5 m in a day, and nest continuation should be started only after the brickwork previously done achieves sufficient strength to hold the load without squeezing out of the mortar from the newly prepared brick joints of brickwork.
    • In case of doing brickwork of half brick thick brick walls or construction of brick on edge like 5″, 3″ or 4″ wall construction H.B. Netting should be done on every third layer, or the wall may fall down.
    • Mortar should be of proper proportion and consistency as required for different types of brickwork.
  • The mortar which has been prepared must be used within its Initial Setting Time, that is  a period of 30 minutes for OPC and Blended Cements like PPC, PSC.
  • Brickwork should be cured well for a period of atleast 7 days for good results.
  • Brickwork should be raised in a manner of uniform level in height throughout its length, suppose  a wall is to be raised on the next layer of brickwork, then it should be done only after finishing the brickwork throughout the length in the current layer.
  • Brickwork should be done in proper bonding.
  • In Brickwork there must not be vertical joints in continuation, it must be be alternatively arranged by atleast overlapping one fourth portion of the brick above and below.
  • Nothing less than Half Bats shall be used
  • Connection between two walls of different alignment must be done with toothing in brickwork.

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