Vital information on various component of construction

Vital information on various component of construction

Concrete:

What is concrete?
Ans:
It is mixture of sand, crush aggregate, Cement and water with different type of ratio.
Clause of concrete: 45/20, 40/20, 30/20, 20/20.
45 is compressive strength and 20 is the max size of aggregate.

What is concrete mix design?
Ans:
Design is blended of course/fine aggregate, water, cement and admixture. To achieve the required specify limit strength of concrete.

What are the constitute of concrete and what part each play in the quality in the concrete.
Ans:
Constitute of concrete are sand, aggregate, cement and water, sand and aggregate are play important rule in concrete.

What is curing of concrete and why it is necessity?
Ans:
To prevent loss of moisture from concrete .We need curing of concrete to keep the moisture in concrete for the hydration of cement to strength the concrete.
Curing Method: 1.Water curing method, 2-Membrane curing method, 3-Steam curing method.

Why do you compact concrete what are the different way of doing it.
Ans:
For proper placing and density, to avoid any defect like honeycombing, air holes etc, compaction is carried out by vibrator by mechanical or electromechanically poker viberator.
Slump test: which determines the consistency (strength) of freshly, mix concrete?

What are the main factors affecting the mix design?
Ans:

1-Workability,
2-Durability,
3-Economy.

How do you test quality of concrete and what are the effects of temperature on concrete?
Ans:
Compressive strength test is an important test to check quality of concrete.
Effect of temperature on concrete: The rate at which chemical reaction and hydration of cement take place is influenced by temperature. Within the limit the reaction takes place more quickly as the temperature is raised.

Write the different classes of concrete and their strength used on your most recent project?
Ans:
A=250kg/cm sq, B=190kg/cm sq, C=130kg/cm sq,

What is the purpose of doing of slump test?
Ans:
To measure the consistency (strength) of cement concrete mix.

Give reason of cracks in concrete?
Ans:
Bleeding, Steel mesh on surface, excess heating.

What is different test in aggregate?
Ans:
A. Course Aggregate:

1.Grading,
2-Content of clay lumps,
3-Soft fragments,
4-Sodium or Magnesium sulphate soundness,
5-Los Angeles Abrasion,
6-Aggregate crushing value,
7-Impact value,
8-Flakiness and Elongation index,
9-Chloride and sulphate content.

B.Fine Aggregate:
1-Grading,
2-Content of clay lumps,
3-Content of organic impurities,
4-Sodium or Magnesium Sulphalte soundness.

What is fineness modulus and how to determine it?
Ans:
It is a numerical number ,which outlines the grain size of material by fineness point of view, It is determined through sieve analysis by adding total percentage retained material on sieve size and dividing the sum by 100.

What is the flakiness index?
Ans:
It is the percentage by weight of aggregate particles whose least dimension thickness is less than .6 of their mean dimension. This is applicable to size larger than 6.3mm.

What is the Elongation index?
Ans:
It is the percentage by weight of particles whose greatest dimension or length is greater than the 1 and 4/5 or 1.8 times then their mean dimension. The elongation index applicable for size smaller than 6.3mm.

What is Aggregate crushing value?
Ans:
The strength of course aggregate may be assessed by aggregate crushing test .The aggregate crushing value provide a relative measure of resistance to crushing under gradually applied compressive load .To achieve a high quality pavement aggregate possession high resistance to crushing or low aggregate crushing value are performed.

What is workability?
Ans:
The consistence of concrete mix must be such that the concrete can be transported, placed and finished sufficiently easily and without.

Explain briefly about the trial mix of concrete to determine the concrete mix design?
Ans:
Preliminary laboratory test trial shall be carried out to determine the job mix design to satisfy the specification with approved material. 3 trial mixes shall not less than the mean strength. Trial mixed shall be tested to determine the following properties of mix.
1. Bleeding (None vibrating) not exceed 0.5%,
2. Drying shrinkage,
3. Air content,
4. Water, Cement ratio,
5. Workability,
6. Fresh and hardened concrete densities,
7. Compressive strength,
8. Water permeability max 10mm for 28 days and max 15mm for 7 days,
9. Chloride permeability,
10. Initial setting $ Hardening time
11. The variables which can be controlled are.
a-Water cement ratio
b-Maximum aggregate size
c-Aggregate grading
d-Aggregate/Cement ratio
e-Use of admixtures.

Write down concrete workability test?
Ans:

1-Slump test/Consistency of concrete,
2-Flow test,
3-V.B test,
4-Compaction factor

What is the general range of W/C ratio for the concrete?
Ans:
0.425 -.650

What are the tolerances in the different concrete structures?
Ans:

For all buried concrete = +25mm - 12mm,
For soffit edge beam and sides of parapet plinth =3mm
For all other concrete=6mm

What is the range of temperature of water for concrete?
Ans:
Min.5 degree centigrade Max.25 degree centigrade

General criteria for size of aggregate for concrete.
Ans:
Not less than 1/5 of the cover and not larger than the ¾ of the max spacing.

What will defects coming in concrete after pouring?
Ans:

1-Shrinkage cracks on top surface,
2-Honey combing,
3-Seggregation,
4-Bulging.

What is curing and purpose?
Ans:
To prevent to escape of mixing water required for hydration process and helps in development of strength.
Purpose:
1-To prevent cracks,
2-To increase strength.

What is different type of concrete curing?
Ans:

1-Water curing,
2-Steam curing,
3-Curing compound
Temperature: Concrete temperature max 32C
Ambient/Air temperature max 40C
Water temperature max 25 C and min 5 C
PH value of water 7-9

What is the function of admixture or retarder?
Ans:
To delay the setting time of concrete and increase concrete strength.

What is the final and initial setting time of concrete?
Ans:
Min 45 minutes, Max 48 hours

What is the type of admixture used in concrete?
Ans:

1-Plasticizers ,
2- Retarder,
3-Accelerator,
4-Plasticizer with retarding agent,
5-Plasticizer with accelerating agent,
6-Super Plasticizers ,
7-Super Plasticizers with retarding agent

What is function of retarder admixture in concrete mix?
Ans:

1-To delay the setting time of concrete about 1- 4 hours over normal setting time and reduce the mixing water by about 3-9 Kg/M cube and increase the compressive strength by about 10-15 %.
2-To reduce the setting time 1-4 hours.
3-To increase the strength 10-15 %.
4-To decrease the mix water 3-9 during Kb/m cubic.

How you will check a good quality of aggregate?
Ans:
Sp Gravity, ACV aggregate crushing value Soundness, LAA loss angles abrasion.

How you will design a concrete mix?
Ans:
Complete workout for quality test of aggregate both course and fine, lab trail, site trial and evaluation of job mix formula.

Plasticizers admixture
Ans: There are used to improve the concrete workability (increase the slump without increasing the water cement ratio.

Water proofing admixture.
Ans:
These admixtures play an important part in reducing the concrete permeability and thus increasing its density and directly increase the quality of concrete against leakage as for water tank concrete.

Retarder admixtures.
Ans:
This type is admixture is mainly used to increase the time of initial setting of the cement in concrete.

Write down 5 types of cement used in concrete.
Ans:

Cement type 1: OPC used for superstructure.
Cement type 2: This cement is Portland low heat cement as defined by BS.This type of cement if mainly suitable for concrete increase where chloride and sulphalte us existing and also used in massive concrete where heat is exerted due to chemical action.
Cement type 3: It is defined by Rapid hardening Portland cement .It is used for cold weather structure.
Cement type 4: It is equivalent to Rapid setting Portland cement and it is used for structure under water.
Cement type 5: It is define by Sulphate resistanting cement. It is mainly used for structures s Slump test: For workability
Cube test: For compressive strength.
Core test: Compressive strength.
W/C Ratio: Water diluted by the cement used in design per meter cubic.
Integrity test: To check the physical dimension continuity, cracks, buldging, and consistency, of material used in the pile concrete.


SUB-BASE:

What is sub-base?
Ans:
Sub-base shall consist of crushed mineral aggregate of the gradation and thickness specified as per project specification generally CBR should be 65 to 80 at 100% MDD.
Plasticity index in the range of 4 to 6.
Sand equivalent shall be not less than 35.
CBR should be 40 % minimum.
Compaction 95 % minimum.
Aggregate size 63mm down.
Placing of Sub base layer not exceed 200mm.
Tolerance of sub base +10mm and -20mm.

Road Base:

What is Road-base?
Ans:
Aggregate road base shall be consisting of uniform mixture of gravel with sand, silt and clay conforming to the specified gradation limits.
Road base mix at site and lay by grader.
Aggregate size should be 50mm down.
CBR 80 % min@ 98 % Compaction min.
Tolerance of road base +10mm and -10mm.

Physical properties test not exceed the following test values:
Liquid limit : 25% Water absorption : 2%
Linear shrinkage : 3% Aggregate crushing value : 25%
Plasticity index : 6% Flakiness index : 35%
Stone size : 50mm Elongation index : 35%
Sand equivalent not less than: 45 Soundness : 12%

Test standard:
Testing of sub base and road base shall be carried out in accordance with BS 812 and BS 1377.
Laboratory MDD test shall be carried in accordance with BS 1377.
Liquid limit shall be determined in accordance with part 2 of BS 1377.
Field density shall be determined in accordance with part 9 if BS 1377.
The acid soluble chloride in the sub base and road base shall not exceed than 3.5% and .8% by weight respectively.
The acid soluble sulphate in the sub base and road base shall not exceed than 2.0% and .5% by weight respectively.

Wet mix macadam:

What is Road-base?
Ans: Wet mix road base shall be crushed rock or crushed gravel material.
1. Wet mix mixed by plant and lay by paver.
2. Aggregate size should be 50mm and down.
3. CBR should be 80% min.
4. Compaction 100 % min.
5. Normal grading 70% aggregate and 30% sand.
6. Moisture content 4.5% to 6.5%.
7. Layer thickness not exceeds 150mm.
8. Tolerance of wet mix +10mm and -10mm.
Physical properties test same above mentioned Wet mix macadam test.


Prime Coat: Bitumen Kerosene oil:

What is medium curing prime coat i.e. MC-0MC-1, MC-2.
Ans:
Prime coat is low viscosity liquid bitumen material usually medium curing cutback asphalt.
Prime coat shall be medium curing cut back asphalt grade MC-70.
Prime coat is spray over road base or wet mix to seal the moisture content and penetration.
The rate of application should be between .7 to lit/m sq to 1.5 lit/m sq.
Curing time should be 48 hrs.
Temperature 60 degree to 80 degree.
There are three types for prime coat
MC-0 means medium zero viscosity.
MC-1 means medium curing on viscosity.
MC-2 means medium curing two viscosities.
1-MC-70 Medium curing -----Used kerosene oil.
2-SC -Slow curing -------- Oil of low vitality.
3-RC -Rapid curing ---------Gasoline.

Why is it necessity the prime coat must be fully dry.
Ans:
Because it is applied to water-bound absorbent surface. If prime coat is too wet then it cannot be absorbed properly.

What is prime coat/Tack coat quantity formula?
Ans:
Prime coat=Weight of prime coat ÷Area of board= Kg/m sq

Tack Coat:
What is medium curing prime coat i.e. MC-0MC-1, MC-2.
Ans:
Emulsified Asphalt (Diluted with an equal quantity of water 1:1) is called tack coat.
Temperature- 10 degree to 60 degree
Rate of application =0.30- 0.60 L/M sq
Curing time should be 2 hrs.
Temperature 10 degree to 60 degree.
Ambient temperature not less than 13 degree centigrade for both.

Why do we need tack coat or prime coat and what is difference among that.
Ans:
Before laying any asphalt material the existing surface should be clean and dry, any loose material on exiting surface can affect the compaction and bonding or asphalt layer on moisture on existing surface can cause crack in asphalt layer.

Why should you cut the joint straight/clean /apply tack coat.
Ans:
To obtain proper bonding with new asphalt to get neat joint.

ASPHALT WORK:

What do you understand by Bitumen mix or Asphalt concrete?
Ans:
Asphalt is use in the surface layer of road. The mix is composed usually of aggregate and asphalt cement. Some type of bituminous mixes is also used in base course.
The design of asphalt paving mix as with the design of other engineering material is largely a matter of selecting and proportioning constitute material to obtain the desired properties in the finished pavement structures.

What do you understand by Dense bitumen macadam/Asphalt concrete?
Ans:
Dense bitumen macadam is mixture of bitumen and course mineral aggregate.
Asphalt concrete is mixture of bitumen and well graded, high quality mineral aggregate laid and compact while hot.

What are the different types of pavements?
Ans:
There are two main types of pavement in road structure, flexible and rigid pavement.

What are the different types of asphalt?
Ans:
There are four main types of asphalt:
1- Hot mix asphalt concrete,
2- Warm mix asphalt concrete,
3-Cut-back asphalt concrete,
4-Mastic asphalt concrete.

What are the grades in asphalt?
Ans:
40/50, 60/70.

What is mean by traffic analysis?
Ans:
To determine present and future traffic volumes for pavement design purpose.

How the total thickness of asphalt pavement is determine.
Ans:
By Engineering design procedure, factors considered in the procedure are:
1-Traffic to be serve over the design surface life (i.e. the cumulative number of 80 KN standard Axles.
2-The strength of the prepared sub grade (i.e. CBR.value).

What is JMF?
Ans:
Job mix formula is combination of bitumen and blended aggregate with all specific requirements like voids, stability (strength), flow, density (compaction) for testing.

What is the job mix Design of Asphalt?
Ans:
Designing Asphalt paving mix is largely a matter of selecting and proportioning material to adequate obtains the desired qualities and properties in the asphalt finished construction.
The overall object is to determine an economical blend gradation of aggregates (within the specification limit) and corresponding asphalt content that yield a mix having the desired qualities as per the specification.
Brief description:
1. Preliminary lab test shall be carried out to determine the mixes to satisfy the specification with approved material.
2. Prior to finalization the proposed job mix with bitumen content
In base course 3.2 to 4.4 (by weight of total mix)
In Binder/Wearing course 3.4 to 4.4 (by weight of total mix)
3. Shall be compacted to refusal (400-600 blows) and the resulting voids in the mix shall not
be less than 2% for asphalt concrete and 3% for D.B.M.

What is Marshall Mix Design for Bituminous Materials?
The selection of the asphalt binder content with a suitable density which satisfies stability and range of flow values is called Marshall Mix Design method. The Marshall Mix Design method was originally developed by Bruce Marshall of the Mississippi Highway Department in 1939.

What are steps of Marshall Mix Design method?
Ans:

i) Determination of physical properties, size and gradation of aggregates.
(ii) Selection of types of asphalt binder.
(iii) Prepare initial samples, each with different asphalt binder content.
iv) Plot the following graphs.
(v) Determine the asphalt binder content.
(vi) Determine properties at this optimum asphalt binder content by reference with the graphs.
(vi) Evaluate the design with the design required.
The mix shall be tested in accordance with the following method:
1. Preparation and testing of Marshall Specimen: ASTM D1559 using 75 blows per face.
2. Aggregate greater than 25.4 mm shall be replaced with an equivalent weight of 19 to 25.4mm material.
3. Bulk specific gravity of specimens: ASTM C 1188.
4. The values for specific gravities of the aggregate to be used in calculating void shall be taken as the mean of bulk.
5. The adhesion of bitumen to aggregate shall be proven by comparing by stability of specimen cured in water and air for eight days at 18 degree C.
6. The course aggregate shall show no detrimental amount of stripping of bitumen when tested in accordance with ASTM D -1664.
7. Wearing course mix shall be subjected to further marshal test at 80 degree C after oven heating for a period 2 hours.
8. Mix with a bitumen content corresponding to the maximum allowable for the selected job mix shall be compacted to refusal and the resulting void in mix shall be not less than 3%.

Write the Marshall Test?
Ans:

1. Stability.
2. Flow.
3. VIM (voids in mix).
4. VMA (voids in mineral aggregate).
5. VFB (voids filled with bitumen).
6. GMB (bulk sp gravity of marshal).
7. Grading test carried out at the rate of one sample: every 200 ton produced.
8. Marshall test carried out at the rate of one sample: every 400 ton produced.
9. Core test carried out at the rate of one sample: every 500m sq.

Method Statement of Marshall test:
1-Asphalt sample collect from loaded truck at asphalt plant.
2- Asphalt sample temperature required: 142-147 C
3-Fill asphalt in 4 nos mould for sampling.
4-Compact filled material with hammer (weight 4.5kg) 75 blows each side.
5-Mould open after 24 hours.
6-Take sample dry weight.
7-Put sample in water for 3 minutes.
8-Take sample wet weight.
9-Take sample SSD weight (again dry with cloth).
10-Minimum density required: 2,000 kg/m3
Bulk Density: Sample wet weight –sample SSD weight/sample dry weight

Stability and Flow checking:
1-Keep sample into water bath in 60 degree C temperatures for 35 minutes.
2-Put out sample from water bath.
3-Check Stability and Flow through machine.
4-Minimum stability required: 1225N
5-Minimum Flow required: 8 TO 16.

What is difference in asphalt base course and wearing course?
Ans:
The base course in pavements is a layer of material in an asphalt roadway that is located directly under the surface layer.

What asphalt bitumen content is generally applied?
Ans:
5.5% to 7%

How will you approved an asphalt mix design?
Ans:

1-Complete work out of aggregate quality test,
2-Percentage of course and fine aggregate,
3-Percentage of filler and bitumen,
4-Trial in lab,
5-Trial at plant,
6-Trial at site with standard job mix formula.

Define different voids ratio for JMF and their limit?
Ans:

Base courseWearing Course

V.I.M (void in mix)​

7-11%​

6-9 %​

V.M.A (voids in mineral aggregate)​

14-20%​

14-20 %​

V.F.B (voids filled with bitumen)​

47-60%​

48-60 %​

Minimum stability kg mm​

1000​

1200​

Flow mm​

2-4​

2-4​

Bitumen content % of total mix​

3.3-4​

3.5-4.2​










What is the reason of segregation in asphalt?
Ans:

1.Improper cold feed,
2. improper batch mix,
3-Wrong bitumen content.
4-Wrong aggregate gradation.

What is the stripping (slip) of asphalt pavement explain some reason of stripping (slip).
Ans:

1-Smooth/Polished surface aggregate.
2-Dusty aggregate.
3-Wet aggregate.
4-Rooling mixture when too cold.
5-Inadequate rolling.6-Poor finisher operation.

Will we do compaction of asphalt more than 102% if not why?
No Life already consumed.
No allowance for future compaction.
Also due to less void.

What is the thickness allowance for laying of asphalt before compaction?
Ans:
20% extra thickness required with compacted thickness.

What is the function of asphalt wearing course.
Providing smooth riding surface with anti skid properties.
Waterproof and sloped to shed surface water to the road side.
To protect the course beneath it.
Resist distortion (bend) and wear caused by heavy traffic load.

What are essential properties of an asphalt paving mixture?
Ans:
The following desirable mix properties:
1-Stability (strength),
2-Flexibility (elasticity),
3-Durability,
4-Workability,
5-Impermeability,
6-Fatigue

Described briefly the method of production hot asphalt plant mix?
1. Cold aggregate storage at different cold bin.
2. Drying at hot dryer.
3. Screening over the screening unit.
4. Hot bins assembling and proportioning.
5. Pug mill mixing.
6. Hot asphalt storage.
7. Hauling to the paving site.

General notes of Asphalt:
The level of acid-soluble Chloride content in the Base course and Wearing course of pavement layer shall be not exceed .8% by weight.
The level of acid-soluble Sulphate (SO3) content in the Base course and Wearing course of pavement layer shall be not exceed .3% by weight.
During bitumen and aggregate mixing shall not be heated above 150 degree C and 163 degree C.
Compaction not more than 98% to 101.8%.
Re-rolling shall take within 72 hours.
If compaction not achieved as required compaction limit 20% reduction in the billed and asphalt passed otherwise remove and replaced in contractor cost.
Trial area minimum shall be 30m length.
Tolerance of vertical level alignment maximum +- 6mm.
Tolerance of thickness +5mm and – 3mm
Laser road surface testing machine to be used for ride ability of wearing course.
Laser road surface machine shall have an IRI (International Roughness Index) not exceeds the 400 m inspection: 1
The sampling and testing of bitumen macadam shall be carried out in accordance with the requirement of BS 598.
Core dia in base course 150mm.
Core dia in wearing course 100mm.