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Wednesday, December 12, 2018

Details about R-value and U-value of Concrete Slab

The conduction of heat regarding the materials utilized in its construction is measured with the thermal conductivity coefficient alias k-value (W/m.K), of the materials used in its construction. It belongs to the rate at which heat moves through a material among points at dissimilar temperatures.

The thermal resistance alias R-value (m2K/W), is computed by dividing the thickness of the material (in metres) with the k-value. From this the thermal transmittance alias U-value (W/m2.K) concerning a building material is measured like the inverse of the sum of the R-values of the component parts and adjoining air layers.

R-value stands for the estimation of concrete slab (or other material) strength to counter heat flow i.e. it calculates the potency of insulation or thermal resistance. However, U-value stands for the estimation of heat transmission throughout concrete slab from ground into the closed space or oppositely.

Since, thermal insulation fluctuates contrariwise with density, lower density concrete offers superior insulation as compared to greater density concrete. With the purpose of determining the strength of the reinforced concrete slab to withstand heat transfer, it is necessary to estimate R-value and U-value of the reinforced concrete slab under consideration.

The method for estimating R-value for Concrete Slab: A perfect R-value for a normal concrete slab is computed with an R-value, the thermal resistance per inch of thickness, among 0.1 and 0.2 and multiplying it times the slab thickness. The value of R is determined with the following equation provided by ASTM C 168:

Here, the temperature variation (among exterior and interior of concrete slab) is provided in degrees Fahrenheit, the area is given in square feet, the time in hours, and the heat loss in Btus.

ASTM C 168 also offers two supplementary expressions to measure R-value and is available in ASTM C 168 document.

The R-value imperial unit and metric unit are given below:

Computation of u-value for Concrete Slab

The U-value for a concrete slab (and any other building material) stands for the inverse of its R-value and is computed with the formula given below:

The U-value unit is the inverse those of R-value:

Note: There is difference among the American Standard and European Standard for R-value and U-value. Therefore, to transform an American R-value into a European U-value, divide 1 with the R-value, then multiply the result by 5.682 whereas transforming a European U-value to an American R-value, multiply with 0.176, then divide 1 by the result.

Details about R-value and U-value of Concrete Slab

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Published By
Rajib Dey

Tuesday, December 11, 2018

How to design rectangular and T shape beam

Beams are defined as members which are exposed to flexure. So, it is important to give attention to the analysis of bending moment, shear and deflection.

When the bending moment operates on the beam, bending strain is created. The resisting moment is formed with internal stresses. Under positive moment, compressive strains are developed in the top of the beam and tensile strains in the bottom.

Concrete is weak against tensile strength and it is not perfect for flexure member by itself. The tension side of the beam will collapse prior to failure of compression side when beam is exposed to a bending moment devoid of the reinforcement. To resolve this issue, steel reinforcement is provided on the tension side. The steel reinforcement withstands all tensile bending stress as tensile strength of concrete is zero when cracks are formed.

Rectangular beam

Accept the depth of beam with the ACI code reference, least thickness until the deflection is considered.
Accept the beam width (ratio of width and depth is approx 1:2).

Calculate self-weight of beam & design load.
Work out factored load (1.4 DL + 1.7 LL).
Calculate design moment (Mu)
Work out maximum possible nominal moment for singly reinforced beam (φM n ).

Determine reinforcement type by making comparison between the design moment (M u ) and the maximum possible moment for the singly reinforced beam (φM n ). If φM n remains under Mu, the beam should be designed as a doubly reinforced beam otherwise the beam should be designed with tension steel only.

Find out the moment strength of the singly reinforced section (concrete-steel couple).

Calculate the necessary steel area for the singly reinforced section.
Determine an essential residual moment, deducting the total design moment and the moment capacity of the singly reinforced section.
Calculate the extra steel area from the required residual moment.
Calculate the total tension and compressive steel area.
Design the reinforcement with the selection of the steel.
Verify the actual beam depth and assumed beam depth.

T-shape Beam

Calculate the design moment (Mu ).
Presume the effective depth.
Choose the effective flange width (b) depending on ACI criteria.

Workout the practical moment strength (φM n ) anticipating the total effective flange is supporting the compression.

When the practical moment strength (φM n ) is greater than the design moment (Mu ), the beam is measured as a rectangular T-beam with the effective flange width b. If the practical moment strength (φM n ) is not more than the design moment (Mu ), the beam will operate as a true T-shape beam.

Determine the approximate lever arm distance for the internal couple.
Work out the approximate required steel area.

Design the reinforcement
Verify the beam width
Calculate the actual effective depth and analyze the beam

How to design rectangular and T shape beam

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Published By
Rajib Dey

Friday, December 7, 2018

How to calculate quantity of earthwork in road

In this civil engineering video tutorial, you will learn step-by-step guidelines for measuring the quantity of earthwork (soil) in road, railway, canal work with the help of mean area method.
For explanation, the solution is given on the following example :-
Example – Calculate the quantity of earthwork for an embankment with length 120 m and width 10 m at the top. Side slope is given as 2:1 and depths at each 30 m distance are 0.4, 0.6, 1.4, 1.2 and 0.8 m.
The calculation is done through a table. The table contains various heads like Road station, depth, centre area, side area, total area, mean area, intervals and quantity.
The work of road will start from 0 point. So, in road station column in the table, the values will be given as 0, 30, 60, 90, 120 (as distance is given as 30 m).
In depth column, provide the values as 0.4, 0.6, 1.4, 1.2 and 0.8 m
To calculate center area, the following formula will be used :-
B x d = Breadth or width x Depth
After putting the values, we get the following result :-
10 x 0.4 = 4 meter
In this way, the other values can be determined easily.
To determine the side area, the following formula will be used :-
Sd2, here S denotes slope and d denotes depth.
After putting the values, we get the following output :-
2 x 0.42 = 0.32 m2 (as sloe is given by 2:1)
In this way, the other values can be determined easily.
Total area will be calculated with the following formula :-
Bd + Sd2 = Center Area + Side area
To determine the mean area, first, sum up the first two rows of total area and then divide it with 2 i.e. 4.32 + 6.72 /2 = 5.52 meter. In this way, other values can be calculated.
The value of intervals is given as 30 meter.
Finally, the total area will be calculated as follow :-
Mean area x Intervals
After putting the values, we get the following result :-
5.52 x 30 = 165.6 m2
In this way, the other values can be calculated.
Total filling or embankment will be determined by summing up all the quantities and it will be 1389.6 m3
So, the total quantity of soils for filling or embankment of the road = 1389.6 m3
To get more clear ideas, go through the following video tutorial.

Published By
Rajib Dey

Thursday, December 6, 2018

Uses and benefits of dry pack mortar in job site

Dry pack mortar also known as deck mud or floor mud, is formed by blending sand, cement, and water. It’s application is found in repairing small spots, developing thick bed mortar for tile and brick placement, and bed shower setting up.

The proportion of the mixture is done with one part of cement to four part of sand, and sufficient water is required to form mortar that bind together while it is molded into a ball manually.

After being added, the ball shall not decay due to low water quantity and should not slump because of to high-water proportion. This mixture is supposed to produce a compressive strength of 21 MPa.

Dry Pack Mortar – usages and benefits

Mixture Proportion: It is found that one part of cement to four part of sand, desirably sharp clean sand, is sufficient. Further, mix proportions like one to two and half, and one to five or even six are recommended.

Mixture Proportion: It is found that one part of cement to four part of sand, desirably sharp clean sand, is sufficient. Further, mix proportions like one to two and half, and one to five or even six are recommended.

In terms of quantity of water, it is based on the moisture content of the sand being utilized. When moisture of sand is low, larger quantity of water is required in respect to where moisture content is high.

1. Developing ordinary thick mortar beds.
2. Leveling of concrete surfaces up to 51 mm thick.
3. Suitable for floating shower bases.
4. It is directly connected or applied as a isolated floating mortar bed over a cleavage membrane or waterproofing membrane.
5. Suitable for both residential and commercial applications in dry and wet areas.

6. The purpose of dry pack mortar is to fill deep holes in a concrete wall. When the dry pack mortar components are blended, it should be arranged in layers of 10mm and then compressed with hammer, stick, or hardwood dowel. Instead of wooden stick, the metal stick should be utilized to compress dry pack mortar since metal stick produces greater compaction and as well as bond. Besides, it is direct tamping should be employed at an angle to the sides of the hole to maintain good compaction at the sides of the hole.

Benefits of Dry Pack Mortar

1. Applicable for Interior and Exterior applications
2. Mixing of sand and cement in construction site is not necessary
3. It is easily tamped, compacted, and sloped
4. It ensures a consistent mix on large jobs

Uses and benefits of dry pack mortar in job site

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Published By
Rajib Dey

Wednesday, December 5, 2018

The role of Viscosity Modifying Admixture (VMA) in Concrete

Viscosity Modifying admixtures or VMAs belong to the admixtures which are applied to modify various properties of fresh concrete ranging from viscosity, workableness, cohesiveness etc.
The functionality and uses of VMA for several types of concrete are given below.

Function of Viscosity Modifying Admixture (VMA) in Concrete

The prime objective of viscosity modifying admixture in a concrete mix is to modify the rheological properties of concrete- particularly the plastic viscosity of fresh concrete. If VMA is added to concrete mix, the plastic viscosity of concrete is raised and a slight surge in yield point is observed.

Yield point is another rheological property of concrete that should also be improved together with the plastic viscosity to attain perfect concrete rheology. The yield point of concrete is not impacted with VMA.

Therefore, besides, VMAs plasticizers or super plasticizers are also included to modify the yield point of concrete mix.

Advantages of Viscosity Modifying Admixtures (VMAs)

Given below, the details of various types of concretes which show different behavior with the inclusion of viscosity modifying admixture to their design mixes:

1. Self-compacting Concrete, 2. Pumped Concrete, 3. Under Water Concrete, 4. Light weight concrete, 5. Semi-dry Concrete, 6. Sprayed Concrete, 7. Porous Concrete, 8. Concrete with Poorly Graded Aggregates

1. Self-compacting Concrete: When Self-compacting concrete blends with less powder content, it remains unsafe against moisture variations and as a result segregation may take place.

Inclusion of viscosity modifying admixture to self-compacting concrete raises the segregation resistance as well as enhances the strength to moisture variations.

VMAs improve the strength of self-compacting concrete mixes.

VMAs also minimize bleeding from concrete mix.

Pumped Concrete

a. Obstacle of aggregates at bends in pipe is the issue found in general that occurs for pumped concrete.
b. When Viscosity modifying admixture is included, pumped concrete turns out to be more consistent and segregation while pumping can’t occur.
c. The friction among pump-wall and concrete mix while pumping is minimized by lubricating effect resulting from VMA.

Sprayed Concrete
a. Use of viscosity modifying admixture reduces the rebound of aggregates from sprayed concrete by enhancing the cohesion of concrete mix.

Porous Concrete
a. Viscosity modifying admixtures resist the discharge of cement paste from porous concrete mix.
b. VMA makes the bond better among cement paste and aggregate thereby raises the strength of concrete.

To get more details, go through the following link

The role of Viscosity Modifying Admixture (VMA) in Concrete

Published By
Rajib Dey

Tuesday, December 4, 2018

Types and construction process of compound wall

The purpose of a compound wall is to contribute elegant look, privacy and security to any building. It checks movements of unessential objects in the building. It is erected to detach any building from other building and arrange proper segmentation to your property.

Types Of Compound Walls: Based on the appearance & construction material applied, various types of compound walls are found in building.

In this construction article detail information is given on masonry compound wall and precast compound wall.

Masonry Compound Wall: Red clay bricks / Fly ash bricks, steel and cement mortar are considered as the major components for masonry compound walls construction. The compound wall is built up from 2 ft. below ground level to provide perfect anchorage to the wall.

Toward Individual House Construction, the height of the masonry compound wall is normally kept among 5-6 feet and the thickness is normally150mm.

Once excavation work is completed, a PCC of 100 mm thick and 600 mm wide is provided to develop an even surface on which the compound wall can be placed.

A rubble masonry having 450 mm width and up to 2 feet height is arranged underneath the brick wall to disperse the load of the structure constructed above.

Over rubble masonry, a RCC Coping of 4″ thick is formed for making the surface smooth as well as transmitting the loads of the compound wall to the substructure underneath.

Over RCC coping, masonry compound wall is built up with 6”Red clay bricks or 4” Red clay bricks / fly ash bricks. Intermittent brick columns with dimension 300mm X 230mm are erected at a distance of 7 ft to 10 ft center to center and at the corners of the plot.

Once the curing of this masonry wall is completed, cement plaster is employed on both the sides of compound wall and paint is used.

The cost of a standard masonry compound wall that is normally applied in residential buildings averages to Rs. 1200/Rft along with a 8 Feet wide MS Gate on the front size. The cost may fluctuate +/-10 % based on the accessibility of local materials like bricks, rubble etc.

Bonus Tip: To enhance the elegant look of the wall, the grooves can be included with the plaster.

Precast Compound Wall: Currently, precast compound wall is mostly found in different areas since they can be set up simply and finished within very short span. But the strength and stability of the compound are not up to the standard.

To create perfect precast compound walls, the consideration should be given on developing proper foundation to the structure and the walls.

As the precast compound walls are factory made and are transmitted to site, the overall cost is considerably less with regard to masonry compound wall. Based on the design and necessary customization, the cost fluctuates significantly.

The cost of a precast compound wall normally commences from Rs. 60 per sqft (i.e., roughly Rs 400 per Rft). This cost is exclusive of the cost of foundation, painting, gate, any other finishing etc. Therefore, while measuring the cost of precast compound wall, all these should be contained in overall costing.

Types and construction process of compound wall

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Published By
Rajib Dey

Monday, December 3, 2018

Definition and benefits of column starter

This construction video tutorial provides detail information on column starter. You will learn the process for casting of starter as well as advantages of column starter.

Starter is generally a casting of concrete material with equivalent width and length of column section and comparatively smaller height of around 10 cm. It is cast in such a manner that equal cover is left encircling the reinforcement bars of column and then shuttering of column is provided. The main purpose of starter is to fine-tune the form work of a column vertically to maintain sufficient gap among column reinforcement and shuttering.

To retain the exact position of the columns in the below slab as well as retain the column lines in number of floors easily, starter is marked.

Given below, the major benefits of a starter :

a. It is easier to set up & check the center line of the starter as compared to that of the column.
b. With the existence of the starter is exact place, fixing the column becomes stronger. Sometimes, the column form work turns out to be skew. With starter, this issue is reduced completely.
d. Once the shuttering for column is completed, bracing or supports are settled ,the verticality is examined on two sides (adjacent faces ) with a plumb bob and alignment is examined through a cotton or nylon thread.

e. The column is casted as soon as all checks are finished with the certified concrete mix.
f. The column shuttering is eliminated next day and the curing should be started. Based on the climate (temperature and humidity ), the curing is performed either by spraying water at intermediate intermissions or covering column by hessian clothe to keep it wet.

To get more clear ideas, go through the following video tutorial.

Definition and benefits of column starter

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Published By
Rajib Dey