Case study: St. Joseph Seminary
Edmonton’s St. Joseph Seminary was opened in 2010, after the existing seminary lands were annexed by the provincial government to allow expansion of the St. Albert Trail and Anthony Henday Ring Road. The chapel component was modelled on the floorplan and shape of ancient Roman basilicas, with a direction from the Bishop of the Edmonton Archdiocese for a permanent structure reflecting the history of the Catholic Church and the permanence of the religion for future generations.
With that in mind, the chapel is formed from one of the largest installations of white self-consolidating, self-levelling concrete in North America. This concrete was cast as a single pour, using four pump trucks and two standby pumps in a continuous operation lasting almost 36 hours. The walls are 11 m (36 ft) high by 450 mm (18 in.) thick, and supported by falsework and custom-fabricated formwork.
The success of the AESC was directly attributable to establishing early communications between the concrete supplier, formwork fabricator, concrete placers, construction manager, and the architects and engineers with DIALOG (the design firm for the project). The members of the construction team were brought together a year in advance of any concrete being placed to discuss conditions that could affect its placement and appearance.
Everything that could have an effect on the final outcome was put on the table for discussion, including:
- appearance of form liners—there was a requirement for the finish to look like the rough fabric robes traditionally worn by the seminarians, which consequently helped dissipate air bubbles and voids on the finished surfaces;
- methods of placement and porting within the formwork, to allow for dissipation of formwork pressure;
- time of year—late spring was chosen to even out temperature and humidity swings; and
- length of time formwork was left on the completed concrete.
The concrete supplier cleaned out its storage silos to control the appearance of the concrete and ensure the aggregates and cement were consistent in colour and appearance throughout the mixing and placing operations. The construction manager co-ordinated all trades immediately affected by concrete placement, as well as those responsible for subsequent work associated with part of the finished appearance (e.g. stained glass windows, electrical lighting, sculpting).
Once all contributing trades and design team members had compiled a list of controllable criteria, the project specification was written to capture the various procedures and quality control mechanisms. Describing the work results involved the concerted efforts of the structural engineers, design architects, and contract administrators, so each discipline was aware of the consequences for enforcing the performance requirements associated with materials and workmanship.
Several sample installations of the concrete mix were tested during installation of other concrete components, and were well-hidden within elevator shafts and basement walls. Mockups were created and used as part of the final site signage, all in an effort to show repeatability and that the specified quality controls provided a consistent concrete appearance at each different installation.
Even with the amount of control effort, there were still surprises, such as a sudden cold snap and late-season snowstorm that dramatically altered the environmental conditions, and which could have greatly affected the appearance of the exposed concrete. The construction manager had insulated blankets and heaters on standby, which were almost deleted from the specifications because of the time of year (April to May). A lot of tension and sleepless nights resulted after the concrete trucks had departed, since the final esthetic finish could not be determined until the forms were removed seven days after completion of the pour. The whole team was elated to see the concrete in its pristine form—a resounding success.
The only condition the team failed to describe—and which subsequently almost ruined the material’s final appearance—was the concrete worker that patched and repaired bug holes and voids in the surface using standard cement-based mortar. The concrete specification failed to reference the same white cement and titanium oxide colour admixtures used in the concrete mix, resulting in very visible grey smears and spots. Fortunately, this ended up being in an area invisible in the final installation.
To paraphrase Robert Burns, the best-laid plans of mice and men often go awry. No matter how carefully a project is planned, something may still go wrong, so the more the project parameters are discussed and communicated to an educated and trained team, the better controls can be put in place to offset the unknown.
Chris Bennett, CSI, is a concrete consultant for commercial projects in North America. He specializes in document creation, contractor training and technology testing for MasterFormat Divisions 03, 07, and 09. He can be reached via e-mail at email@example.com.
Keith Robinson, FCSC, FCSI, RSW, LEED AP, has worked as a specifications writer since 1981, and is an associate at DIALOG in Edmonton. A past-president of Construction Specifications Canada’s (CSC’s) executive council, he sits on several standards review committees for ASTM and the National Fire Protection Association (NFPA). Robinson works closely with the Concrete Floor Contractors Association (CFCA) to address specification requirements for floor flatness and levelness. He is a member of the editorial advisory board of Construction Canada. Robinson can be reached via e-mail at firstname.lastname@example.org.
Rae Taylor, PhD, holds a doctorate in civil engineering and materials science from the University of Leeds, and a post-graduate certificate in technology management from the Open University. Her principal research interests lie in the field of materials science and improving the environmental impact of construction materials, with a focus on the effect of cement replacement materials and additives on cement microstructure. Taylor has published on the topic of cement in numerous academic journals and conferences, such as the Journal of the American Ceramic Society, American Mineralogist, and Cement and Concrete Research. She can be reached at email@example.com.