Placing Concrete

Topic 3 – Placing Concrete

Key Competencies

The NOA for Carpenter (2013) identifies the required competencies (skills) for the task of placing concrete. These are:

1. Plan pour taking into consideration factors such as weather conditions, location of equipment, starting point, sequence of pour and rate of pour and drop
2. Select additives such as plasticizers, hardeners, accelerators and curing agents according to weather conditions and project requirements
3. Ensure slump on concrete before starting pour to maintain integrity of desired mix design
4. Select and use placement methods such as using concrete pump, crane and bucket, wheelbarrow, and chute according to accessibility to location and size of job
5. Vibrate concrete to consolidate and eliminate voids around locations such as beam pockets, chases, and bucks, while avoiding over-vibrating, segregation and blowouts
6. Recognize signs of an impending blowout such as deformation, deflection and leakage and take remedial measures
7. Place joints in poured concrete such as expansion, isolation and control joints
8. Double check after concrete is placed for straightness and dimensions of wall and column forms, and make adjustments to achieve plumb, level and square formwork (NOA, p. 42-43).

Concrete can be transported from the truck or mixer by various equipment:

1. Concrete pump
2. Crane and bucket
3. Wheelbarrow/handcart
4. Conveyor
5. Chute

https://www.flickr.com/photos/mtacc-esa/8343390252/

Tools for placing and consolidating concrete include:

1. Shovels
2. Rakes
3. Come-alongs
4. Screeds/Straightedge
5. Bull Floats/Darby
6. Hand Float
7. Jointer
8. Vibrator

Source: https://commons.wikimedia.org/wiki/File:Heurechen_haeringer_rechen.JPG

For additional information review:

• Principles and Practices of Commercial Construction, “Placing, Mixing, and Transportation of Concrete”
• Carpentry, “Placing Concrete” up to the section on “Consolidation of Concrete”

Review Instruction Sheet (IS) on Brightspace:

CONC 100/122, p. 42 – 69:

• IS 1.2 Transporting Concrete
• IS 1.3 Tools for Placing Concrete

Review Questions – 9.01.3

1. Why is a square nose shovel better for placing concrete than a spade?
2. Describe “striking off” concrete
3. Describe “wet screeding”
4. What is the purpose of the bullfloat?
5. How deep must a control joint be cut?
6. How must the grade below a slab-on-grade be prepared?
7. Wood formwork that will hold concrete should be:
8. Give the proper method of placing concrete in wall forms
9. What is the difference between a drop chute and a tremie?
10. Describe dangers to your skin when exposed to concrete.