Table of Contents
In this article, we will discuss checklist for concrete placement.
Concrete is a composite material that is composed of a mixture of fine and coarse aggregates bonded together with biding material which hardens over time. The binding material mostly includes fluid cement paste, lime putty, lime, etc.
1. Checklist for Concrete Placement
Here we have 3 checklists for concreting work that needs to be fulfilled:
a. Equipment and Material Preparation
Aggregate for concrete material:
√ Extreme dust is screened out from coarse aggregate.
√ The size of aggregates is acceptable as per specification.
√ Stone chips must be prepared of crushed stone or boulder
√ Both coarse and fine aggregates are free from all organic and deleterious materials.
√ Aggregates are well stored on a brick flat.
√ The percent wear of stone chips is below 30% sampled by Los Angles Abrasion test.
√ The compressive strength of stone aggregate shall not be smaller than 36.1 MPa or 5240 Psi.
√ Laboratory tests ensure the specifications noted in Sl. No. (8) and (9)
Grading of coarse aggregates:
√ 19mm sieve size- passing 95-100% is confirmed.
√ 9mm sieve size- passing 25-55% is confirmed.
√ No. 4 (4.76mm) sieve size- passing 0-10% is confirmed.
√ No. 8 (2.38mm) sieve size- passing 0-5% is confirmed.
√ Sieve analysis is done and the report confirms the above criteria
Cement for concrete:
√ Types of cement are CEM-1 as per specification.
√ The quality of cement is satisfied as per specification.
√ Cement is well stored, not in a moist environment.
√ The laboratory test is done and the report verifies the above standards.
Other materials for concrete:
√ Admixture as per specification is given.
√ Water should be free from salt and other types of impurities.
√ Spare Vibrator machines and vibrator nozzles are obtainable.
√ Proper leveling Instrument is obtainable at the site.
√ Aggregate measuring boxes and sand filters are available at the site.
√ Slump testing apparatus is available at the site
√ Cylinder testing equipment is available and in acceptable shape.
b. During Construction
The mix proportion is inspected by the expert:
a) Volume of concrete is calculated and the target time is fixed.
b) Admixture is utilized as per design specification.
Manpower for concreting
a) Site Engineers are available on-site while mixing and placing concrete.
b) Work assistant at the mixing point is deputed to count and maintain the batch as per the concrete pouring slip and load count slip.
c) Manpower for mixing is sufficiently involving the volume of work
d) During casting good shuttering men are kept for constant watch on the prop.
Adequacy of materials
a) Mixing ratio of cement, aggregates, and sand is analyzed as per design specification.
b) Adequate Materials such as cement, aggregates, and sand are given regarding the volume of work.
c) Aggregates are adequately soaked.
d) Aggregates are well-graded.
Preparation at the site for concreting:
a) For adhesion with old concrete, the edges of old concrete are to be split to provide a firm bonding.
b) Grouting is utilized for construction joints. Electrical conduit is provided in the appropriate place.
c) Rain protection is placed. Clear covers are observed before setting concrete.
d) Casting sequences are selected as per the consent of the engineer in command.
Adequacy of equipment:
a) Chutes and concrete buckets are washed and prepared for use.
b) Good Vibrator nozles are inspected and prepared for use.
c) Tower crane for vertical lifting is delivered.
d) Thickness checking device is delivered.
Mixing of Concrete:
a) Measured quantity of materials as per proportion are dumped in the drum of mixture machine.
b) Mixing is completed with the needed quantity of water for not less than 2 minutes after all materials including the water are in the drum.
c) Proper water-cement ratio is provided by measuring slump as noted below:
Footing, pile cap, mass concrete 2″ ultimate
Precast pile, column, beam, slab 2.5″ ultimate
Ready mix concrete (with admixture) 4.0″ ultimate
After mixing concrete:
a) Workability of concrete is acceptable (slump is proper).
b) Cubes/ Cylinders are taken from the mixing for testing.
c) Slump test is performed and seen OK.
Placing of concrete:
a) Water is poured on the surface of the shutter/ steel shutter.
b) Concrete is put within 30 minutes after mixing the water.
c) Height of free-fall concrete is within 3 feet.
d) Concrete is passed from one end, then constantly moved to the other end.
e) Fresh concrete is deposited against concrete that is in place within 45 minutes.
f) Thickness is capped at a 3’-0’’ interval over the concrete slab.
g) Regular movement of laborers/others over reinforcement is bypassed during casting. Usage of the plain sheet as a walkway for carrying concrete at the place.
h) During casting, quick remedial measures are considered in case props get loosened.
Compaction of Concrete:
a) For beam and column, concrete compaction is accomplished correctly by the vibrator.
b) Compaction is performed within 15 minutes after the fresh concrete is kept in position.
c) Vibrating is ended as soon as the laitance of mortar seems on the surface. (More vibration segregates the mix.)
d) Vibrating is managed properly in the vertical placement of the vibrator.
e) Vibrating is performed without touching the re-bar.
f) Proper surface vibration of slab surface with thick & plain wooden plank.
c. After concreting
a) Movement over a concrete surface is avoided within 24 hours.
b) Concrete surface is kept wet with water till the removal of formwork.
c) Keys in the column lift are provided for subsequent concreting in the proceeding days.
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