A note on concrete pours


The way concrete pours work:

Before any concrete pour gets underway, forms, often made out of plywood, are set in place and steel rebar is put in place. required forming and rebar work must be completed. This frequently takes several hours or days.

Once the forming and rebar work is completed in one section of the building, the first step of any concrete work is the arrival of concrete trucks on site. This is always managed to minimize disruption to pedestrians and vehicles and ensure everyone’s safety. Concrete trucks do have to keep running at all times to ensure the concrete stays in liquid form, so the standard City of Toronto idling by-law does not apply to these trucks.

Concrete from the trucks is poured into large buckets that are lifted to the level of the building that is being built by the tower crane. A concrete pump may also be used. If it is used then concrete from the trucks is poured into the base of the pump and then pumped through a large pipe to the floor that is under construction.

Once concrete is poured it requires time to harden properly. This can take 1 to 3 hours and sometimes more, depending on the temperature.

Once the concrete has hardened and set, construction crews must finish the concrete. They use a machine that resembles a combination of a large fan and lawn mower. Crews then use the finishing machines to go over the concrete slab floor creating a smooth and level concrete surface.  This is an essential component of concrete work and the work is not completed until it has been ‘finished.’ While this work does generate some noise, it is not a particularly loud activity.

Note: columns and walls do not require ‘finishing’. 

Timing of concrete work:

The timing of concrete pours is dependent on the concrete supplier’s availability to deliver concrete to the site, the weather conditions, and the the section of the building that is going to be poured. 

In a large pour, for example for a major section of a floor slab, work may stretch into the afternoon or evening, even if work began in the morning. A lot depends on the amount of concrete that needs to be poured, the weather conditions, and the time it takes to pour and finish that section of concrete. 

Once underway it is not possible to safely stop a continuous concrete pour until it is properly completed.