Common Mistakes Pouring Concrete

COMMON MISTAKES IN SITE ENGINEERING

Pouring Concrete

• The common mistake usually seen in a site is the contractors pouring concrete using chutes.

• It is poured usually directly from Transit mixer and the same shall be avoided.

• According 456 -2000 the maximum height for pouring of concrete without segregation is 1.5 m and for pump able mix Concrete shall not be placed from a height more than 2.0 m

• Concrete shall be placed within 60 minutes after mixing of it. Strictly prohibit addition of extra water at batching plant, during transit or at site. Mix without proper slump or cohesion shall not be used.

• The amount of concrete requited shall be correctly estimated to avoid wastage

Site Preparation:

If the site is not level or doesn’t have the correct grade to it, it could cause water to run down.

Weather:

• Pouring concrete on a nice day is very different from pouring it in any other weather, especially if there’s going to be any type of precipitation or if it’s going to get very cold.

• During extremely hot weather, you’ll actually need to use sprinklers to keep the water in the concrete from evaporating too quickly.

• Checking the weather before concrete is important

Other Site Mistakes to avoid

• The construction materials like sand, bricks, aggregates, etc, are not washed and are full of deleterious material and dust

• Polythene bag and hand glows were found buried with concrete

• The cement-sand mix in the mortar and brick masonry is made quite early, prior to its use and in larger quantities than required

• Concrete stopper was not proper and few concrete get way during casting of plinth beam

• Shear key was not prepared on top of column

• The bottom strata of the foundation is not compacted properly.

• Honeycomb was observed in concrete

• In trapezoidal footings concrete is not vibrated properly

• Column concreting in usually not mechanically vibrated and machine mixed.

• Cover blocks are not provided to reinforcement in columns, beams and slab

• Proper care for uplift pressure in black cotton soil is not taken

• Rectification of misaligned columns at higher levels causing eccentricity

• Damp proofing course is not properly cast

• The plinth filling is not carried out in layers nor compacted

• Joints with RC surface is never roughened and hacking is not deone before plastering

• All joints in formwork shall be sufficiently tight to prevent leakage of grout.

• Mixing ratio of cement mortar is never measured and maintained

• Rebound materials are never handled instantly causing serious issues in removing them

• Corner reinforcement is not provided in two-way slabs leading to uplift of corners.

The following preventive/remedial measures are suggested for improvement in the quality of construction for low cost residential buildings.

• The total civil work is executed mainly by labor, masons and carpenters. A workshop or training schedules shall be arranged for training them. The training will also improve their approach towards quality work.

• Civil contractors who have undergone civil engineering education shall be preferred.

• Time and cost factor also affects the quality of construction. Proper coordination shall be ensured between different agencies

• Prior testing of construction materials like sand, yellow earth, bricks, aggregate, cement and reinforcement steel also helps to improve the quality of construction.

• Overall, a good supervision by the civil contractor is essential during the execution of construction.

PREVENTION IS BETTER THAN CURE