Answers
Home/Answers/Page 55Do you need to remove the ads? Get the paid membership
Join TheConstructor to ask questions, answer questions, write articles, and connect with other people. When you join you get additional benefits.
Log in to TheConstructor to ask questions, answer people’s questions, write articles & connect with other people. When you join you get additional benefits.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
What is the difference between UTM and WGS in GIS software ?
Soumyadeep Halder
A map will have only one coordinate system, either Geographic or Projected in our software’s terminology. For example, the “WGS projection” is a geographic one. A UTM projection is a projected one. Either of these will use only one datum. However, the data on the map could have come from multiple soRead more
A map will have only one coordinate system, either Geographic or Projected in our software’s terminology. For example, the “WGS projection” is a geographic one. A UTM projection is a projected one. Either of these will use only one datum. However, the data on the map could have come from multiple sources, all with unique projections and therefore datums
See lessFoundation Issue
Pranta Narula
My plot of land is low lying and needs to be earth filled for approximately 1 to 1.5 metre. Now my question is that Can i start foundation of a 2 storey building on the ground without excavation ? after that we can filled the rest of the plot with earth.
My plot of land is low lying and needs to be earth filled for approximately 1 to 1.5 metre. Now my question is that Can i start foundation of a 2 storey building on the ground without excavation ? after that we can filled the rest of the plot with earth.
See lessHow to prepare post construction checks, concrete checklist, form work checklist, reinforcement, height work permission, other checklist, etc ?
Soumyadeep Halder
i am showing all types of checklist that may help you in future. EXCAVATION & P.C.C. Final plinth levels of all buildings. Strata as per consultant’s specifications. Size of pits is more than size of P.C.C., & depth as desired. Shuttering provided, if required. Uniformity & thickness ofRead more
i am showing all types of checklist that may help you in future.
EXCAVATION & P.C.C.
FOOTING & PLINTH BEAM
BACKFILLING
COLUMNS
General & reinforcement
Checking of shuttering for columns
Checking of column before concreting
Checking of column while concreting.
Checking of columns after concreting.
SLAB & BEAMS
Checking of shuttering material
Checking of reinforcement for Beams.
Steel for slab.
Care to be taken before / after casting of slab
Management before / after casting of slab.
Checklist after concreting
BRICK MASONRY
PLASTERING INTERNAL PLASTER ITEMS TO BE CHECKED: –
AFTER PLASTERING
EXTERNAL PLASTER
WATERPROOFING
CHECKLIST FOR ‘BOX TYPE’ WATERPROOFING
CHECKLIST BEFORE WATERPROOFING FOR TOILET
CHECKLIST FOR ‘BASE COAT’ FOR TOILET / BATHROOM WATERPROOFING
CHECKLIST FOR ‘BRICKBAT COBA’ COAT FOR TOILET / BATHROOM WATERPROOFING
CHECKLIST FOR TOPPING COAT FOR TOILET/ BATHROOM WATERPROOFING
CHECKLIST FOR TERRACE WATERPROOFING PREPARATION CHECKS
CHECKLIST FOR BRICKBAT COBA COAT FOR TERRACE WATERPROOFING
Compound.
CHECKLIST OF FINAL COAT OF TERRACE WATERPROOFING
CHECKLIST FOR CHAJJA WATERPROOFING (before plastering work) Ensure & confirm:
CHECKLIST FOR SLOPPING TERRACE WATERPROOFING (before any other architectural treatment) Ensure & confirm:
CHECKLIST FOR PLUMBING
CHECKLIST FOR DOORS & WINDOWS DOORS
Ensure & confirm:
ALUMINUM WINDOWS
Ensure & confirm:
CHECKLIST FOR PAINTING
Internal wall painting Ensure & confirm:
Oil paint
For M.S. Windows, doors, gates, grills & railings etc. Ensure & confirm:
For wooden Doors
EXTERNAL WALL PAINTING (CEMENT PAINT)
Ensure & confirm:
CHECKLIST FOR ELECTRICAL WORK
Ensure & confirm:
CHECKLIST FOR ELEVATORS (LIFTS)
Ensure & confirm:
a) ladder for pit
b) weld mesh guard to the motor
c) weld mesh guard to the window to avoid entry of the birds.
d) all safety indicators working properly
e) Effective key operations
f) Emergency key operations
g) Instruction plates for the passengers’ guidance
h) Earthing done properly.
CHECKLIST FOR STORM WATER SYSTEM
Ensure & confirm:
Ensure & confirm:
-
- The approved drawings, customer changes with N.O.C.
- The material for the approved specifications prior to placing the order.
- The material as per specifications.
- a) Diagonal/Angles b) plumb c) Design d) joints welding e) Grounding of joints
- Painting a) primer coat b) paint as per specification
- Any damages created during erection, to be rectified.
- Final touch ups.
See lessWhat is the Procedure to Design the Double Angle Tension Member in Steel Structures with formulas?
Amit Bhuriya
As per Section 6 (Design of Tension Members) of IS 800:2007 – Code of Practice for Construction in Steel, The design strength of the tension member is the minimum of following, Design strength due to yielding of the gross section (Tdg) (Clause 6.2 of IS 800:2007). Design Strength Due to Rupture of CRead more
As per Section 6 (Design of Tension Members) of IS 800:2007 – Code of Practice for Construction in Steel,
The design strength of the tension member is the minimum of following,
Let’s take an example to understand the designing of double angle tension member:
Data Known:
Service Load, T = 200 N/mm2
STEP 1:
Factored Load, Tu = Tdg = 1.5 x 200 = 300 N/mm2
Considering the tension member fails due to yielding of gross section, determine the gross area of angles required.
Tdg = AgFy/ꙋm0 → Ag = Tdgꙋm0/Fy
Ag = (300 x 103 x 1.1)/250 = 1320 mm2
The total gross area of tension member (Ag) required is 1320 mm2. Remember this is the area of two angle sections. Therefore,
Gross area of single angle section (Ag1) = (Ag)/2 = 1320/2 = 660 mm2
From steel table (SP 6-1), choose an angle having gross area of single angle about 25% to 40% more than computed above.
Taking Rolled Steel Equal Angle ISA 60x60x8 having following properties,
Sectional Area, A= 896mm2
Total Gross Area, Ag0 = 2×896 = 1792 mm2 > 1320 mm2 (O.K)
STEP 2:
Designing Connections: – We can provide either bolted or welded connections, so let us provide bolted connections.
Total thickness of angles having outstanding legs placed back to back,
ta = 8+8 =16mm
Let us provide 20mm diameter bolts of grade 4.6 and Steel of grade Fe415,
Diameter of bolt, d = 20mm
Diameter of bolt hole, dh = 20 + 2 = 22mm (Table 19 of IS 800:2007)
Fu = 410 N/mm2
Fub = 400 N/mm2
Fy = 250 N/mm2
Kb = 0.606
= 2 x (Fub/√3) x (Anb/ꙋmb) where, Anb = 0.78 x (πd2/4)
= 2 x (400/√3) x ((0.78 x (π(20)2/4))/1.25)
= 90.545 KN
= (2.5 Kb d t Fub)/ ꙋmb
= (2.5 x 0.606 x 20 x 16 x 400)/1.25
= 155.136 KN
Therefore, Bolt Value = Least of (90.545, 155.136) = 90.545 KN
No. of bolts required, N = (Tu/Bolt Value) = (300/90.545) = 3.31 ≈ 4 nos
STEP 3:
Check of Strength due to rupture of critical section,
The design strength,
Tdn = 0.9Ancfu/ꙋm1 + βAgofy/ ꙋm0
Where,
β = 1.4 – 0.076(w/t)( fy/fu)( bs/Lc) ≤ (fu ꙋm0/fy ꙋm1)
≥ 0.7
w = outstand leg width = 60mm
t = total thickness of angles = 16mm
w1 = end distance = 40mm
bs = shear lag distance = w + w1 – t = 60 + 40 – 16 = 84mm
Lc = length of end connection = 3 x 60 = 180mm
β = 1.4 – 0.076(60/16)(250/410)(84/180)
= 1.4 – 0.081
= 1.319 ≤ (410×1.1/250×1.25) = 1.4432 (OK)
≥ (0.7) (OK)
Anc = (60+60-2 x 22) x 8 = 608mm2
Ago = (60 x 16) = 960mm2
Tdn = 0.9Ancfu/ꙋm1 + βAgofy/ ꙋm0
= ((0.9 x 608 x 410)/1.25) + ((1.319 x 960 x 250)/1.1)
= 179481.6 + 287781.81
= 467343.6 N
= 467.34 KN > 300 KN (O.K)
STEP 4:
Check for Strength Due to Block Shear (Tdb),
Tdb = [(Avgfy)/(√3ꙋm0) + (0.9Atnfu)/( ꙋm1)] or [(0.9Avnfu)/(√3ꙋm1) + (Atgfy)/(ꙋm0)]
Avg = 220 x 16 = 3520 mm2
Avn = (220-3×22-(22/2)) x 16 = 2288 mm2
Atg = 40 x 16 = 640 mm2
Atn = (40-(22/2)) x 16 = 464 mm2
Tdb = [((3520×250)/ (√3x1.1)) + ((0.9x464x410/1.25)]
= 461880.22 + 136972.8
= 598853.02 N
= 598.85 KN
Tdb = [((0.9x2288x410)/ (√3x1.25)) + ((640×250/1.1)]
= 389952.53 + 145454.54
= 535407.07 N
= 535.41 KN
Tdb = min (535.41, 598.85) = 535.41 KN > 300 KN (O.K)
Therefore, the selected section is safe.
So, Provide 2 ISA 60x60x8 angles placed in such a way that outstanding legs are placed back to back and attached with 20mm diameter bolts of grade 4.6. Edge distance and End distance is 40mm and pitch is 60mm.
See lessWhat are the different Types of Concrete Mixers available in the market for Construction.?
Soumyadeep Halder
Concrete mixers can be divided into two broad categories: Batch Mixer Continuous Mixer 1. Batch Mixer Batch mixers can be further divided into two types: i) Drum Mixer Tilting Drum Mixer Non-Tilting Drum Mixer Reversing Drum Mixer ii) Pan Mixer 2. Continuous Mixer
Concrete mixers can be divided into two broad categories:
1. Batch Mixer
Batch mixers can be further divided into two types:
i) Drum Mixer
Tilting Drum Mixer
Non-Tilting Drum Mixer
Reversing Drum Mixer
ii) Pan Mixer
2. Continuous Mixer
See lessWhat is OSHA Compliance in Construction Field?
Abhishek Singh
The Occupational Safety and Health Administration(OSHA) is an agency of the United States Department of Labor. To ensure health and safety at workplace there are certain standards and rules have been made for working men and women at workplace under OSHA Act(1970). So an employer must provide a workRead more
- The Occupational Safety and Health Administration(OSHA) is an agency of the United States Department of Labor.
- To ensure health and safety at workplace there are certain standards and rules have been made for working men and women at workplace under OSHA Act(1970).
- So an employer must provide a workplace which is free from hazards and comply with standards and regulations as per OSHA Act.
- So OSHA compliance means adhering to all the standards and rules developed under OSHA Act.
See lessWhat are the Standard Sizes of Tiles available in the market?
Abhishek Singh
Nowdays tiles are available in a wide range of sizes. Some popular sizes for floors are 300×600 mm, 600×600 mm.
Nowdays tiles are available in a wide range of sizes. Some popular sizes for floors are 300×600 mm, 600×600 mm.
See lessWhich types of chemicals and admixtures used in the construction industry for normal conditions as well as seismic conditions?
Rohan Chaugule
Definition of Concrete Admixtures As per BIS (IS – 9103: 1999) Page No.1, Concrete Admixture is defined as a material other than water, aggregates and hydraulic cement and additives like Pozzolana or slag and fiber reinforcement, used as on ingredient of concrete or mortar and added to the batch immRead more
Definition of Concrete Admixtures
As per BIS (IS – 9103: 1999) Page No.1, Concrete Admixture is defined as a material other than water, aggregates and hydraulic cement and additives like Pozzolana or slag and fiber reinforcement, used as on ingredient of concrete or mortar and added to the batch immediately before or during its mixing to modify one or more of the properties of concrete in the plastic or hardened state.
Reasons for Using Admixtures (ACI Committee Report Page – 298)
Admixtures are used to modify the properties of concrete or mortar to make them more suitable for the work at hand or for economy or for such other purposes as saving energy.
Some of the important purposes for which admixtures are used are:
To modify properties of fresh concrete, mortar and grout to:
To modify the properties of hardened concrete, mortar and grout to:
When Concrete Admixtures Used?
How to Use Concrete Admixtures?
Types of Concrete Admixtures (Additives)
Types of admixtures as per American Concrete Institute Committee report and IS 9103: 1999 are:
Classification of admixtures according to the book of “Concrete Admixtures: Use and Applications” edited by M. R. Rixom are given in the forward pages.
1. Air Entraining Admixture
These are generally used to improve workability, ease of placing, increased durability, better resistance to frost action and reduction in bleeding. The common Air-Entraining agents are natural wood resins, neutralized vinsol resins, polyethylene oxide polymers and sulfonated compounds.
Mechanism of Air Entraining Concrete Admixtures
These are anionic, because the hydrocarbon structures contain negatively charged hydrophilic groups, such as COO, SO3 and OSO so that large anions are released in water. Conversely, if the hydrocarbon ion is positively charged, the compound is cation active or cationic.
In other words, anionic surface active agents produce bubbles that are negatively charged, cationic charged cause bubbles to be positively charged, surface active agents of all classes can cause air entrainment in concrete, but their efficiency and characteristics of air-void system vary widely.
Properties of Air entraining Admixtures
2. Accelerating Admixtures
Accelerating admixtures are used for quicker setting times of concrete. It provides higher early strength development in freshly cast concrete.
Main uses of Accelerating Concrete Admixtures
Disadvantages of Accelerating Concrete Admixtures
3. Water Reducing Admixtures
Chemical Types for Water Reducing Admixtures
Mode of Action
The principal role on mechanism of water reductions and set retardation of admixtures are usually composed of long-chain organic molecules and that are hydrophobic (not wetting) at one end and hydrophilic (readily wet) at the other.
Such molecules tend to become concentrated and form a film at the interface between two immiscible phases such as cement and water, and alter the physio-chemical forces acting at this interface.
The mechanism by which water reducing admixture operate is to deflocculated or to disperse the cement agglomerates into primary particles or atleast into much smaller fragments.
This deflocculating is believing to be a physio chemical effect whereby the admixture is first of all adsorbed on to the surface of the hydrating cement, forming a hydration “sheath”, reduces the antiparticle separated from one another.
The presence of water reducing admixture in a fresh concrete results in:
Why Water Reducing Admixtures are used?
a) Concrete having greater workability be made without the need for more water and so strength losses are not encountered
b) By maintaining some workability, but at a lower water content, concrete strengths may be increased without the need for further cement addition
c) While maintaining the same w/c ratio and workability concrete can be made to a given strength as in the reference concrete at lower cement content.
Effect on durability
The straight addition of admixtures of this type does not came any increase in permeability and indeed where the admixture is used to reduce the w/c, then permeability is considerably reduced.
Effect on shrinkage
Admixture of this type when used as workability aids on water reducers do not adversely effect the shrinkage.
Effect on creep
Materials of this type of admixture have no deleterious effect on the creep of concrete.
Detrimental effect
a) While using water reducing agent. Care must be taken in controlling the air content in the mix. Most water-reducing agent entrain air due to their surfactant properties.
b) At high dosages of lignosulphonate material, retardation of the mix occurs.
Applications of Water Reducing Concrete Admixtures
The application of the type of admixtures are as follows —
a) When concrete pours are restricted due to either congested reinforcement or this sections.
b) When harsh mixes are experienced such as those produced with aggregates (crushed). Then considerable improvement in the plastic properties of concrete can be obtained.
c) When required strengths are difficult to obtain within specified maximum cement content and where early lifting strengths are required.
d) By addition of this admixture in concrete cement economics of about 10% can be obtained.
4. Retarding Concrete Admixtures
The function of retarding concrete admixture is to delay or extend the setting time of cement paste in concrete. These are helpful for concrete that has to be transported to long distance in transit mixers and helpful in placing the concrete at high temperatures, specially used as grouting admixture and water reducers results in increase of strength and durability.
Chemical type for Retarding Concrete Admixture
a) Unrefined lignosulphonates containing sugar, which of course the component responsible for retardation.
b) Hydroxyl carboxylic acid and their salts
c) Carbohydrates including sugar
d) Soluble zinc
e) Soluble borates etc.
Mode of action
It is thought that retarding admixtures are absorbed on to the C3A phase in cement forming a film around the cement grains and presenting or reducing the reaction with water. After a while thus film breaks down and normal hydration proceeds. This a simple mixture and there is a reason to believe that retards also interact with C3S since retardation can be extended to a period of many days.
Why Retarding Concrete Admixtures are used?
To delay in the setting time of concrete without adversely effecting the subsequent strength development.
Advantage of Retarding Concrete Admixture
a) The hydroxyl carboxylic acid type admixture normally produces concrete having a slightly lower aim content them that of a control mix.
b) Materials of this class (lignosulphonate containing sugar and derivatives of hydroxyl carboxylic acid) in some cases have a much higher dispersing effect and hence water reducing capacity.
c) Durability increases.
Detrimental effect
a) When lignosulphonate based material used, then the air content might be 0.2 to 0.3% higher unless materials of the tributyle phosphate type are added.
b) As the water content increases, so there is a tendency for drying shrinkage.
Applications of Retarding Concrete Admixture
Retarding admixtures are used
a) Where long transportation of ready mixed concrete is required then premature setting can be usefully avoided by this type admixture.
b) When concrete is being placed or transported under conditions of high ambient temperature.
c) In case of large concrete pours
d) Concrete construction involving sliding formwork
5. Super Plasticizers or High Range Water-Reducing Admixtures in Concrete
These are the second generation admixture and also called as Superplasticizers. These are synthetic chemical products made from organic sulphonates of type RSO3, where R is complex organic group of higher molecular weight produced under carefully controlled condition.
The commonly used superplasticizer are as follows:
i) Sulphonated melamine formaldehyde condensate (S M F C)
ii) ii) Sulphonated napthalene formaldehyde condensate (S N F C)
iii) iii) Modified ligno-sulphonates and other sulphonic esters, acids etc.,
Chemical type
a) formaldehyde derivatives such as melamine formaldehyde and napthalene sulphonate formaldehyde.
Mode of action of Super Plasticizer Admixtures
This admixture acts as the same way as that of a water reducing admixture acts. It disperses the cement agglomerates when cement is suspended in water and adsorbed on to the surface of cement, causing them mutually repulsive as a result of the anionic nature of super plasticizers.
Why Super Plasticizer Admixtures are used?
a) At a given w/c ratio, this admixture increases the workability, typically by raising the slump from 75 mm to 200 mm.
b) The second use of this admixtures is in the production of concrete of normal workability but with an extreme high strength (super plasticizer can reduce the water content for a given workability by 25 – 35 percent compared with half that value in the case of conventional water reducing admixtures).
Advantages of Super Plasticizer Admixtures
a) The concrete using this admixture can be placed with little or no compaction and is not subject to excessive bleeding or segregation.
b) They can be used as high dosages became they do not markedly change the surface tension of water.
c) It does not significantly affect the setting of concrete except that when used the cements having a very low C3A content.
d) They do not influence shrinkage, creep modulus of elasticity or resistance to freeing to thawing.
Disadvantage
The only real disadvantage of superplasticizer is their relatively high cost.
Applications of Super Plasticizer Admixtures
a) In very heavily reinforced sections, in inaccessible areas in floor or road slabs.
b) Where very rapid placing is desired.
6. Mineral Admixtures for Concrete
Mineral admixtures are finely divided materials which are added to the concrete in relatively large amounts, usually of the order of 20 to 100 percent by weight of Portland cement.
Source of Mineral Admixtures
a) Raw or calcined natural minerals
b) Industrial by products
Reasons for using mineral admixtures
a) In recent years’ considerable efforts have been made by the cement industry world wide to reduce energy consumption in the manufacture of Portland cement. Therefore, a partial replacement of Portland cement by mineral admixtures which can be of the order of 50 – 60% by weight of total cementitious material, represents considerable energy savings.
b) The ability of cement and concrete industries to consume mithions of tons of industrial byproducts containing toxic metal would qualify these industries to be classified as environmentally friendly.
c) Since natural Pozzolana and industrial by products are generally available substantially lower costs than Portland cement, the exploitation of the Pozzolanic and cementitious properties of mineral admixtures are used as a partial replacement of cement can lead to a considerable economic benefit.
d) Possible technological benefits from the use of mineral admixtures in concrete include entrancement of impermeability and chemical durability, improved resistance to thermal cracking and increase in ultimate strength.
Classification of Mineral Admixture
Mineral admixtures may be classified as follows —
a) Pozzolanic — Siliceon or siliceons and admixtures material which itself possesses little or no cementitious value but is the presence of moisture chemically react with CalOH2 at ordinary temperature to form compounds possessing cementitious properties.
b) Pozzolanic & Cementitious — The materials which have some cementitious properties in itself.
ASIM specification C618 recognizes the following three classes of mineral admixtures.
a) Class N — Raw or calcined natural pozzolanic such as diatomaceous earths, clay and shales, tuffs and volcanic ashes.
b) Class F — Fly ash produced from burning anthracite or bituminous coal.
c) Class C — Ash normally produced from lignite or sub-bituminous coal which may contain analytical CaO higher than 10%.
7. Silica Fume as Concrete Admixture
Although the use of silica fume (SF) in concrete has increased significantly in the past few years, its beneficial properties were not well realized until comprehensive research was undertaken in the late 70’s and early 80’s at the Norwegian Ins. of technology to study the influence of SF on concrete properties.
Production of Silica Fume
Silicon, ferrosilicon or other alloys are produced in so-called “submerged are electric furnaces”. There are two types of electric furnaces one is with heat recovery system and the other is without heat recovery system.
Types of Alloys Produced in Submerged Arc Electric Furnaces
a) Ferrosilicon of various Si contents
– FeSi – 50% with a 43 to 50% Si content
– FeSi – 75% with a 72 to 78% Si content
– FeSi – 90% with a 87 to 96% Si content
b) Calcium silicon
c) Ferrochromium Silicon
d) Silicomanganese
Specific Gravity and Specific Surface Area of SF
The specific gravity of SF is generally equal to that of amorphous silica which is about 2.20. However, depending on its chemical composition, the specific gravity of SF particle can be as high as 2.40 and 2.55, as in the case of FeGSi.
The specific surface area of SF is measured by nitrogen absorption is given below.
However, regardless of the differences in chemical composition, color and carbon content, all types of SF share a certain number of common, yet important physio chemical characteristics, which make them effective supplementary cementitious materials to cement concrete. these properties are as follows —
a) SF originates from the condensed SiO vapors and generally has a high content of silica of 35 to 98%
b) SF is an amorphous material
c) SF is composed mostly of fine spheres with a mean diameter of 0.1 to 0.2 mm.
Filler and Pozzolanic effects of Silica Fume
The unique characteristics of SF that make it suitable for use as supplementary cementitious materials are its fineness, highly amorphous in nature and elevated content of SiO2.
The small SF spheres act as fillers since they occupy some of the space between the relatively coarser cement grains which can be otherwise occupied by water. This results also in a denser matrix with a better gradation of fine particles.
Bache stated that in a super plasticized, low w/c ratio concrete, small SF spheres can displace water entrapped between the flocculated cement grains, thus increasing the amount of free water in the paste which enhances fluidity.
Several researchers have studied the pozzolanic properties of SF. The resulting reactions between SF and Ca(OH)2 increases the volume of CSH and reduces the total volume of capillary pores in the cement paste. The pozzolanic reactions of SF with Ca(OH)2 reduces the amount of Portlandite in the hydrate cement paste.
Mehta explained that the absence of large Portlandite crystals in a SF mixture can be due to the fact that each SF particles can act as a “nucleation site” for precipitation of Ca(OH)2. As a result, numerous small crystals of Ca(OH)2 can form rather than a few large ones.
This absence of large and week crystals of Portlandite enhance the mechanical properties of concrete.
The beneficial action of SF has also been attributed to the reduction of the porosity of the transition zone between the cement paste and aggregate which increases the strength and impermeability of the concrete. In or conventional concrete, the transition zone can have large and oriented Portlandite crystals which form weak zones in the concrete.
The thickness of the transition zone can be drastically produced by adding SF to the concrete since SF reduces bleeding and the amount of water accumulation under aggregate. As a result, it decreases the porosity of the transition zone and it also reduces the concentration of oriented Ca(OH)2 crystals.
Selection of Concrete Admixtures
Concrete admixtures shall be selected carefully as per the specifications and shall be used as recommended by the manufacturer or by lab testing report. The quantity of admixtures to be used for specific application of admixtures are recommended by the manufacturers.
For use in large construction projects, the quantity of the admixture to be used shall be obtained from tests reports for concrete mixed with admixtures at various percentage admixtures use. These tests are conducted to understand the behaviour of admixtures on the desired quality and strength of concrete at different quantity of admixtures used. Thus, the optimum quantity of admixtures can be selected for specific application based on results.
The selection of specific admixtures for use in concrete to alter properties of concrete should be selected carefully as per requirement of concrete works. Concrete admixtures should be used judiciously according to specification and method of application to avoid adverse effect on concrete properties at fresh and hardened state.
After selecting the admixtures product, one should carefully choose the supplier with quality product, timely service and at competitive price. The admixture supplier should be with good history and should possess the staff with efficient and professional experience to guide on effective application/use of admixture in right way.
Concrete admixtures should be accepted with test certificate, manufacturing date and its chemical composition, should comply specifications given by the authorities.
See lessHow to Determine the Specific Gravity of Chemicals using Pycnometer?
Rohan Chaugule
Steps PROCEDURE Clean and dry the density bottle wash the bottle with water and allow it to drain. Wash it with alcohol and drain it to remove water. Wash it with ether, to remove alcohol and drain ether. Weigh the empty bottle with stopper (W1) Take about 10 to 20 gm of oven soil sample which is cRead more
Steps
PROCEDURE
under constant temperature water baths (Tx0 ).
OBSERVATIONS
2
3
4
Weight of density bottle + dry soil (W2 g)
Weight of bottle + dry soil + water at temperature T x0 C (W3 g)
Weight of bottle + water (W4 g) at temperature Tx0 C
INTERPRETATION AND REPORTING
Unless or otherwise specified specific gravity values reported shall be based on water at 270C. So the specific gravity at 270C = K�Sp. gravity at Tx0C.
See lessWhat is the Cost of Construction Equipments Mobilization?
Soumyadeep Halder
Mobilization and demobilization costs can vary greatly depending on the type of work being performed and what level of costs and logistics will be required to get the job rolling. So, there isn’t really one rule of thumb to follow on all projects. But, mobilization should represent the actual costsRead more
Mobilization and demobilization costs can vary greatly depending on the type of work being performed and what level of costs and logistics will be required to get the job rolling. So, there isn’t really one rule of thumb to follow on all projects.
But, mobilization should represent the actual costs of accumulating and coordinating all the necessary equipment, tools, materials, etc. – it shouldn’t typically be made up independently and without a sound basis. With that being said, mobilization costs tend to be under 10% and even as low as 2%. And as mentioned above, that should be pretty tightly tied to the actual costs of mobilizing and demobilizing the job.
See less