A specialized mix and a strict pour schedule for the TTC

Working alongside Buttcon, Dufferin Concrete completed a job for the Toronto Transit Commission (TTC) on the Patten Building, providing not only innovative products, but ensuring quality service and technical support.

Having worked with the TTC on numerous occasions, our team is familiar with their requirements on schedule dates, health and safety, security controls and of course quality products and services. During construction, the building remained completely functional with the exception of the ground parking level, where the new concrete reinforcement was added. Due to the reduced working area and limited space to delimit a construction zone, all concrete pours were scheduled for Saturdays, leaving no room for error.

Our team worked to design a completely new Self Consolidated Concrete (SCC) mix that would meet the TTC’s strict specifications. The concrete was pumped from an offsite location across from the job site and had to flow through the forms between two layers of rebar and stir-ups. The complex formwork needed to remain completely water tight and valves and ports were installed to release air and eliminate air pockets. As an extra measure of care, camera ports were added to confirm that all voids were filled. There were three scheduled days to complete the six phases of the pour in a designed sequence in order to reduce the stress of the structure and possibility of voids. The largest of these phases was 50+/-m3. Two testing companies, comprising of 35 testers and monitors, were on site to perform several tests on each load of SCC going into the pour. The compressive strength was achieved on average three to five days after pouring. TTC and Buttcon were pleased with the technical support as well as the excellent quality of the concrete, workability, uniformity and performance of the SCC mix supplied by Dufferin Concrete and have indicated that this would be a preferred mix for future similar TTC projects.