Impact of impurities in water on concrete properties

If the water applied for concrete preparation contain impurities, the properties of concrete is influenced in the following manner:

a) The strength & longevity of concrete is decreased because of the existence of the impurities in the mixing water. It is found that water with extreme amount of dissolved salts weakens the compressive strength by 10 to 30% as compared to potable water.
b) The setting time of cement is modified. Existence of Zinc chlorides delays the setting of concrete to significantly so that no strength test can be done at 2 and 3 days.Contrary, the existence of calcium chloride speeds up the setting and hardening.
c) Existence of extreme chlorides leads to dampness, surface efflorescence & raise the corrosion of reinforcing steel.
d) Existence of algae in water decreases the bond among aggregate & comet paste & as a result the strength of concrete is reduced significantly.

e) Existence of sugar up to 0.15% by weight of cement delays the setting of cement and the early strength is decreased. When the quantity of sugar is raised to 0.2% by weight of cement ,setting is expedited.
f) The existence of vegetable oils provides detrimental effect on the concrete strength, specifically at later ages.

Name of Impurities – Allowable limit
1.Organic matter – 200 mg/lit
2.Inorganic matter – 3000 mg/lit
3.Sulfates ( as SO2 ) – 400 mg/lit
4.Chlorides (as Cl)
a) For plain concrete – 2000 mg/lit
b) For R. C. C. – 500 mg/lit
5.Suspended matter – 2000 mg/lit

Impact of impurities in water on concrete properties

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Arka Roy


A wide array of reinforced concrete design examples

This construction article is based on various reinforced concrete design examples. You will be familiar with flexural analysis of beam.

Given below, various examples and their solutions :-
Make proper calculation for the following reinforced concrete sections :-

Example 1 : The balanced steel reinforcement: The maximum steel reinforcement area for a tension-controlled and transition section per ACI code 318-11.

The location of the neutral axis and the depth of the equivalent compressive Whitney stress block for the tension-controlled section in B.

Here, the compressive strength is given as f’c = 4 ksi and yield strength is given as Fy = 60 ksi

ACI code 318-11 is followed

Example 2 : Examine the adequacy of a rectangular tension controlled section on the basis of dead and live loads.

A 10 ft long cantilever beam contains a rectangular section and reinforcement. The beam bears a dead load of 2 k/ft (along with self weight) and a live load of 1 k/ft.

The compressive strength is provided as f’c = 4 ksi and yield strength is fy = 60 ksi, verify if the beam has sufficient strength to bear the provided loads with ACI Code 318-11.

Example 3 : Work out the design moment strength and the location of the neutral axis of a rectangular section containing two rows of tension reinforcement.

b (width) is given as 13 inches
d is given as 23.5
h (through depth of the section) is given as 27 inches
dt (distance from the extreme compression fibre to the location of the extreme tension reinforcement) is given as 24.5

f’c (the compressive strength) is given as 4 ksi
fy (the yield strength) is given as 60 ksi

Example 4 : Work out the design moment strength and the position of the neutral axis of a rectangular section with compression reinforcement that yields.

The following properties are included in the rectangular section :-
Width = b = 12″
Effective depth = d = 22.5″
Tension reinforcement = (6) no. 9 bars
Compression reinforcement = (2) no. 6 bars

Compute the design strength of the beam if f’c = 4 ksi and fy = 50 ksi with ACI Code 318-11.

To get the solutions of the above-mentioned problems, go through the following link.

A wide array of reinforced concrete design examples

Published By
Arka Roy

Combined Pad Foundation Design Spreadsheets

Combined Pad Foundation Design Spreadsheets comprise of a series of spreadsheets which can be used for stability analysis and structural design of a combined rectangular pad foundation.

The spreadsheets evaluate the loadings input by the user and work out the best possible pad size to transmit these loads into an tolerable bearing pressure into the soil.

Unique Pad Sizing and Eccentricity Charts simplify the process for the designer to opt for the best pad dimensions.

As soon as the pad size is set, the spreadsheets then workout the design bending moments and the necessary reinforcement in both X and Y directions for sagging and hogging. The designer can then indicate the perfect reinforcement arrangement with unique recommended reinforcement chart which demonstrates graphically the existing reinforcement arrangements to fulfil both necessary cross sectional area and spacing requirements.

Then a summary page is formed and a reinforcement drawing is produced to provide the perfect reinforcement arrangements which the user has indicated.

The suite comprises of a total of 4 spreadsheets :

• A simple combined pad design spreadsheet to make analysis of a simple combined pad foundation depending on two axial loads where the consequential load must operate through the centroid of the base.

This spreadsheet is ideal for most cases and facilitates making design rapidly for straight forward situations.

• A complex integrated pad design spreadsheet that can easily analyze any combined rectangular pad foundation on the basis of axial, horizontal or moment loadings.

These spreadsheets contain all the tools to design complicated issues or where close attention should be given to detail. It can deal with any size rectangular pad and rectangular columns to where space is restricted in one direction. The spreadsheet also arranges the base for being loaded eccentrically in any arrangement required by the designer.

It comprises sliding analysis to rationalize any horizontal loads. It involves design charts to make brief analysis of shear and punching shear loads, and comprises of bending moment and shear force diagrams to facilitate the designer to design the reinforcement in as much detail.

Both simple and complex spreadsheets are available to abide by either British Standards BS8110 & BS8004 or Eurocodes BS En 1992 & BS En 1997.

Download Combined Pad Foundation Design Spreadsheets

Combined Pad Foundation Design Spreadsheets

Published By
Arka Roy

How concrete is mixed in different ways

Concrete belongs to a composite material formed by cement, sand, coarse aggregate, water and chemical admixtures (if necessary). To maintain the superior quality of concrete, the materials of the concrete should be blended properly so that the quality of concrete is not impacted.

A well-mixed concrete is formed on the basis of the following conditions:

• The color of the concrete should be consistent.
• Admixture of all concrete materials like cement, fine aggregate, coarse aggregate and water should be uniform.
• Cement paste should wrap all the surface of the aggregate.
• Segregation should not happen as soon as the mixing of concrete is completed.

Mixing concrete is dependent on the following three options:

• Hand mixing (Mixing concrete devoid of a mixer)
• Machine mixing (Mixing concrete with a mixer)
• Ready mix concrete

Hand mixing (Mixing Concrete without a Mixer): Hand mixing stands for the method of mixing the different materials of concrete by hand. Mixing concrete devoid of a mixer is suitable for small works. Mixing of materials is executed on masonry platform or flat iron sheet plates.

The hand mixing concrete is performed as follow:

• Expand the measured quantity of sand on the platform, and then unload the cement on the sand.
• The sand and cement should be blended thoroughly with the help of shovels in the dry state.
• The measured amount of coarse aggregate should be extended, and the mixture of sand & cement should spread on it and mixed in an exact manner.
• Depression is provided at the centre of the mixed materials.

• Include 75% of the required quantity of water in the depression and blend well by the shovels.
• Include the leftover amount of water and the mixing method should be carried on unless a uniform colour and consistency of concrete is procured. Time of mixing concrete should not be in excess of 3 minutes.
• The mixing platform should be washed at the end of the day’s work.

Machine Mixing (Mixing Concrete with a Mixer): Machine mixing is mostly suitable for bigger projects where huge masses of concrete are necessary. The machine mixing can retain the persistent uniformity of concrete. Besides, the machine mixing can significantly reduce the mixing time. In recent times, different types of concrete mixers are available which run with petrol/diesel or electricity.

The machine mixing is performed in the following ways:

• Initially, the concrete mixer should be drenched inside of the drum.
• After that Cement, sand and coarse aggregate should be arranged in the portable concrete mixer in desired ratio.
• The dry materials should be blended in the mixing machine. After this, exact quantity of water should be added slowly when the machine is running.
• The concrete should be blended for minimum two minutes after placing all materials in the drum.
• If segregation occurs, the concrete should be remixed after unloading from the mixer.

Ready Mix Concrete: Ready Mixed Concrete (RMC) is developed in the factory or in a batching plant and supplied in a ready-to-use manner. The quality of the consequential concrete is superior as compared to the site-mixed concrete.

Less time is necessary for ready mix concrete as compared to site mixing (hand or machine mixing) and quality of concrete is also greater than the site mixing.

for more:

How concrete is mixed in different ways

Published By
Arka Roy

Various types of measuring units found in building construction

Types of measuring units used in the following items of Building Construction.

Earth Work in Excavation and Filling, Brick Flat Soling, Mass Concrete Work, RCC Work, Plaster and Pointing Work, Patent Stone and DPC, Mosaic and Tiles Work, Wood Work, Lime Terracing and Water Proofing on Roof, White Washing, Color Washing, Distempering, Painting and Varnishing.

1. Mining Work Unit: The measurement for soil digging is performed in cubic feet. It means three-dimensional quantity can be found if you multiply the length, width and height or depth. Unit = cubic feet alias “cft’’.

2. Soil Filling Work Unit: The measurement of soil filling is done in cubic feet alias “cft’’.

3. Brick Flat Soling Work Unit: Flat soling in brickwork is measured in square feet, or “sft”.

4. Concrete Work Unit: The measuring unit of concrete work is provided in cubic feet alias “cft’’.

5. RCC Work Unit: The measuring unit of RCC work is given in cubic feet alias “cft’’.

6. Brick Work Unit: Single brick or more bricks work is calculated in cubic feet alias “cft’’. Partition walls or half-brick walls are measured in square feet alias “sft”.

7. Plaster And Pointing Work Unit: The measuring unit of plaster and pointing work is given in square feet, or “sft”.

8. Patent Stone and DPC Unit: The measuring unit is provided in Square Feet, or “sft”.

9. Mosaic and Tiles Work Unit: The measuring unit for mosaic and tiles work in given in square feet, or “sft”.

10. Wood Work Unit: The volume of the door and window frames work is estimated in cubic feet alias “cft’’.

The door and the window panels wood work is estimated in square feet alias “sft”.

11. Lime Terracing Work Unit: The measuring unit of time terracing work is given in square feet alias “sft”

12. The Working Unit of Finishing: Surface finishing works are calculated in the following units:

i. White Washing Unit= Square Feet, or “sft”.
ii. Color Washing Unit= Square Feet, or “sft”.
iii. Distempering Unit= Square Feet, or “sft”.
iv. Painting Unit= Square Feet, or “sft”.
v. Varnishing Unit= Square Feet, or “sft”.

Various types of measuring units found in building construction

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Rajib Dey

Checklist of Concrete Formwork at Construction Site throughout Concreting and Striking

Concrete formwork stands for a temporary supporting structure for concrete. It is arranged at the job site to retain the concrete in perfect position and shape unless it becomes solidified.

Ensure that formwork should be done prior to start of concreting work, throughout concreting and after elimination of formwork. Concrete formwork contains both quality and safety threats. If the formwork is improper for the concrete and work is accomplished at height, safety issue may occur.

If the formwork is imperfectly organized and does not have good resistance capacity against leak, the quality of concrete may hamper. If the concrete formwork is stored sufficiently, the cost of the project is reduced significantly.

Checklist of concrete formwork in construction site:

Formwork Checklist for Walls:

1. Make sure lateral bracings rigidly supports the forms at all points of support.
2. Layout (stop end) braced to withstand vertical and lateral loads.
3. Form panels are sufficiently braced and attached with each other.
4. Formwork corners shall be adequately attached so that leakage, bulging and spreading of concrete do not occur.
5. Make sure there is adequate length for wall ties as well as necessary strength and spacing as necessary.

6. Verify wales to maintain proper spacing and joints and they should be staggered from one tier to the next.
7. In double member wales, one member remains continuous over the location of form ties.
8. Wall ties and bolts are tightened properly.
9. In case of double member, wales are utilized and both wales should contain similar depths.

10. Verify that sufficient lap exists among forms and previously cast concrete.
11. Make sure that there is no grout leakage at joints among panels and joints connecting old concrete and panels over them.
12. Examine the provision of resistance against uplift for sloping faces of concrete formwork.

13. Make sure that the installation of wall forms and placement of concrete should be done at the construction site in the presence of an experienced supervisor.

To get more details, go through the following construction article

Checklist of Concrete Formwork at Construction Site throughout Concreting and Striking

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Arka Roy

How to create rate analysis of civil works

Each construction project is segregated into various numbers of activities. Each activity is supported with types of civil or construction works.

As for instance, when a building is constructed there are various activities like excavation or earthwork, concrete work, masonry work, wood work such as doors and windows, plumbing, flooring, waterproofing, finishing work like plastering, painting and distempering.

The Activity earthwork is segregated into different types depending on depth and type of soil. As for instance, an excavation of 1.5m deep in soft soil, an excavation of 3m deep in hard soil. Similarly, concrete work is segregated into several types on the basis of its mix proportions and its placement.

As for instance, M25 reinforced concrete is suitable in foundation, M30 reinforced concrete work in columns, slabs etc. Similarly, there are various small civil works in each construction project.

The construction project cost is estimated on the basis of each works related to each construction activity. Thus it is necessary to compute the cost of each small works.

Rate analysis of Civil Works or Building Works is the determination of cost of each construction work per unit quantity.

This cost includes the cost of materials, labors, machinery, contractors profit and other diverse insignificant expenses essential for the specific work that should be executed in unit quantity.

As for instance, cost of 1 cubic meter of M20 RCC work in slab, Cost of 1 cubic meter of excavation in soft soil of 1.5m depth, cost of 1 square meter of plastering of 20mm, cost of 1 square meter of painting work with specified paint in 2 layers or 3 layers as necessary.

Compute the cost of materials in rate analysis as composite of cost of material at origin, its transportation costs, taxes. The rate of labor is set with skill of the labor, like skilled labor, semi-skilled and unskilled labor. The cost of materials and labors differ from place to place. Thus, the cost of each construction work fluctuates from place to place.

How to create rate analysis of civil works

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Published By
Arka Roy

Specification of M50 concrete mix design

Concrete mix design belongs to the method of determining the ratios of concrete mix in terms of proportions of cement, sand and coarse aggregates.

As for instance a concrete mix of proportions 1:2:4 signifies that cement, fine and coarse aggregate are in the ratio 1:2:4 or the mix comprises of one part of cement, two parts of fine aggregate and four parts of coarse aggregate.

The concrete mix design proportions are both by volume or by mass. The water-cement ratio is normally stated in mass.

The mix design M-50 grade (with Admixture –Sikament) presented here is for reference purpose only. Actual site conditions may fluctuate and consequently, this should be modified as per the location and other factors.

M50 Grade concrete is mostly suitably in heavily reinforced structures to withstand dynamic loading.

Given below the specifications of M50 Concrete Mix Design

Grade Designation = M-50
Type of cement = O.P.C-43 grade
Brand of cement = Vikram ( Grasim )
Admixture = Sika [Sikament 170 ( H ) ]
Fine Aggregate = Zone-II
Sp. Gravity
Cement = 3.15

Fine Aggregate = 2.61
Coarse Aggregate (20mm) = 2.65
Coarse Aggregate (10mm) = 2.66
Minimum Cement (As per contract) =400 kg / m3
Maximum water cement ratio (As per contract) = 0.45

Mix Calculation: –
1. Target Mean Strength = 50 + ( 5 X 1.65 ) = 58.25 Mpa

2. Selection of water cement ratio:-
Suppose water cement ratio = 0.35

3. Calculation of water: Estimated water content for 20mm max. Size of aggregate = 180 kg /m3 (As per Table No. 5 , IS : 10262 ). As plasticizer is projected, water content is decreased by 20%.

Water content is taken as 180 X 0.8 = 144 kg /m3

For more details, click on the following link

Specification of M50 concrete mix design

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Published By
Arka Roy

How to use Staad Pro computer program to analyze a continuous beam with various types of loading

This is another exclusive tutorial from Unite Coaching. The tutorial is based on estimating with Staad Pro. Staad Pro is a globally recognized computer program for effective structural analysis and design. It is compatible with all Indian and all international codes.

With STAAD.Pro, the structural engineers will get the ability to analyze and design different types of structures virtually. In this tutorial, one will learn how to analyze a continuous beam that has to withstand various types of load.

A continuous beam is defined as a statically indeterminate multispan beam that is supported by various columns. Here three beams are supported by columns in a straight line.

The end spans may belong to cantilever, may be freely supported or fixed supported. As a minimum one of the supports of a continuous beam should contain the ability to grow a reaction along the beam axis.

How to use Staad Pro computer program to analyze a continuous beam with various types of loading

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Published By
Arka Roy

Detailed process for measuring weight of steel

This is a useful video for construction professionals. The video will teach you how to estimate weight of steel. In this video, two diverse formulas are applied – Density Method and D square /162 Method.

Density refers to the mass of an object that is divided with its volume. Density frequently contains units of grams per cubic centimeter (g/cm3). Keep in mind, grams mean a mass and cubic centimeters mean a volume (the identical volume as 1 milliliter).

As density is mass per unit volume, the density of a metal is measured by submerging it in an identified amount of water and computing how much the water increases. It is the volume of the metal. Its mass is calculated with a scale. The unit for density is gm/cm3.

Detailed process for measuring weight of steel

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Published By
Arka Roy