Construction method of cement concrete road

The construction method of the road is started once the site is fully prepared. It involves the following steps :-

Formwork: Normally, wooden sheets, battens, plywood, fibre hard board, steel plates, angles, rope etc. are utilized for form work.

Prior to start the form work, check that there should not be any type of materials like dust, cement.

The concrete should be set in proper depth and for this purpose, 2.5 – 5 cm thick and 3 mtr long wooden sheeting should be applied.

The depth should be identical with the level of slab thickness.

Once 24 hours are passed, form work is moved to the next length of road.

Watering of base: If the base of the road is dry or the construction starts all through the summer seasons, then water should be sprinkled on concrete. Then, the concrete should be arranged.

Construction of joints

Normally, three basic joint types are utilized in concrete pavement which range from contraction, construction and isolation.
Besides, isolation joints, all joints are arranged to tie up slabs mechanically. The connection facilitates dispersing a load enforced on one slab onto slabs along its perimeter.
To arrange transverse and longitudinal joints, the wedges of woods, metals should be affixed on level of concrete.

Once concrete is set, it should be removed.
Material mixing & setting of concrete
The concrete is mixed through mixer with cement, concrete, sand and water. The following types of mixers are normally applied throughout construction.
Batch mixer – Suitable for small road construction
Continuous mixer – Suitable for large construction
If the distance is long from the job site, mix concrete is transmitted to the site within setting time.

Placing of concrete - The following processes are utilized for concrete placement :-

Alternative bay method: Under this method, the concrete is placed on both sides of road alternately similar to 1,3,5 part at one side and 2,4,6 part other side. This system contains slow process because of road traffic issues.

Continuous bay method: Built up one side of road continually and once construction of some portion of first side is completed then built up other side. This method contains rapid process devoid of any obstruction of traffic.

Compaction of concrete: The compaction is done to extract air from void and make concrete solidified. The compaction is performed with mechanically surface vibrator and manually hand tempers.

Then, floating, screeding or strike off, bull floating and brooming is performed according to finishing purpose of concrete pavement to make the top surface smooth.

Curing: Once the finishing operations are completed, the surface of the pavement should be fully covered with wet hessian cloth, burlap or jute mats.

Curing means the method of enhancing the hydration of cement. After setting, the curing method is performed till 14 to 28 days. 



Read Continue
~~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~~

Step for determining the quantity of bitumen & aggregates for road surface dressing

This construction video tutorial sheds light on the detail method to workout the quantity of bitumen and aggregates toward road surface dressing (Top Layer of the road).

The area of the road is taken as, Area = 20m2
The density of the road surface dressing on top should taken as 12 mm and it is demoted as TC

Here, the value of TL is unknown. TL denotes loose thickness that should be maintained after compaction

TL is based on the following factors :-
Initial Voids = 50% (existence or air or air pockets i.e. gaps in aggregates)
Final Voids = 20%
Wastage = 10%
Suppose that Bitumen will fill 60% of the final voids.
TC is defined as compacted thickness

To determine the thickness of TL, the following formula is used :-
TC = 50% in TL + 20% in TC
Now convert the value to decimal by dividing with 100 = 0.5 TL + 0.2 TC

TC – 0.2 = 0.5 TL = 0.8 TC = 0.5 TL

TL = 1.6 TC

putting the value of compacted thickness, we get 

TL = 1.6(12) = 19.2mm

So, loose depth is 19.2 mm

Now, after adding 10% wastage, we get = 19.2mm + 19.2(0.1) [convert to decimal value by dividing with 100]
= 21.12mm
So, loose thickness should be 21.12mm to attain 12mm compacted thickness

To get more details, watch the following video tutorial.

Video Source: F&U-FORYOU

~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~

Pros and Cons of ready-mix concrete

Ready-mix concrete belongs to a concrete that is formed in a batch plant, on the basis of a predefined engineered mix design. Ready-mix concrete is generally supplied in two ways i.e. the barrel truck or in–transit mixers.

This type of truck supplies concrete in a plastic state to the site. And the volumetric concrete mixer. It supplies the ready mix in a dry state and then blendes the concrete on site.

Given below some pros and cons of ready-mix concrete :-

Pros of ready-mix concrete:

a. With Ready Mix Concrete (RMC), the construction process becomes fast with programmed delivery at site, automated operation with subsequent economy.

b. The costs of labor and site supervision are decreased significantly.

c. RMC maintains uniformity in quality with perfect & computerized control of sand aggregates and water according to mix designs.

d. Formation of RMC facilitates reducing cement wastage because of mass handling.

e. While producing RMC, no pollution occurs.

f. By using RMC in project, project time is curtailed significantly and it leads to huge savings in all phases.

g. Perfect control and economy in applying raw material leads to saving of natural resources.

Cons of Ready-Mix Concrete

Following are the cons of ready-mix concrete:

1. The materials are batched at a main plant, and the mixing starts at that very plant. So the transition time from the plant to the site covers longer distances and becomes complicated. Some sites locate at too remote distance, which may cause risk for ready mix concrete to be useless owing to setting.

2. It will create extra road traffic. Normally, Ready Mix Trucks are bigger in size and may take huge space in the road that will obstruct other traffic. Besides, access roads and site access should have the capacity to bear the heavier weight of the ready-mix truck plus load. (Green concrete is approx. 2.5 tonne per m³.) This issue can be resolved by using so-called ‘mini mix’ companies which employ smaller 4m³ capacity mixers to visit more-restricted sites.

3. Concrete’s constrained time span among mixing and curing signifies that ready-mix should be arranged within 210 minutes of batching at the plant. The time span can be rectified with modern admixtures perfectly, though, the amount and type of admixture that is included with the mix is very crucial.

Read more

~~~~~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~~~~~