This session will focus on the specific challenges of the constructability of mass concrete placements. Presentations will highlight case studies, reviews of best practices, and real-world examples ranging from cold-weather SCC optimization in nuclear construction, to slag-rich shotcrete for underground transit stations, to high-strength mass placements in extreme heat. Additional talks will address specification challenges, performance-based approaches, and the practical impacts of thermal control measures such as cooling pipes. Collectively, these case studies will provide attendees with a deeper understanding of constructability challenges in mass concrete, including effective measures to control heat development, the effect of thermal control on project schedules, and strategies for balancing performance, compliance, and field execution.
Learning Objectives:
(1) Identify constructability challenges in mass concrete placements, including those arising from conservative or conflicting specification requirements;
(2) Evaluate thermal control measures and their effects on temperature management, constructability, and overall project schedules;
(3) Compare prescriptive specifications, industry standards, and performance-based approaches to determine their impact on constructability, compliance, and project delivery;
(4) Apply best practices and lessons learned to develop practical strategies for planning, sequencing, and executing mass concrete placements under challenging site conditions.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Optimization of SCC Mixture for use in Mass Concrete During Cold Weather in New Nuclear Construction
Presented By: Boris Haranki
Affiliation: Baker Concrete Construction, Inc.
Description: Working with SCC in cold weather poses significant challenges, as low temperatures can slow down the hydration process and can lead to bleeding, segregation, and surface settlement due to delayed setting times. This case study presents stability issues experienced in SCC in mass concrete applications during cold weather and how the mixture was optimized, in part, by using an accelerating admixture. A thermal analysis was performed to assess heat development, and a thermal control plan was developed.
Low-Carbon 70% GGBFS Shotcrete for Mass Underground Walls at Mount Pleasant Station
Presented By: SHAUN RADOMSKI
Affiliation: Thurber Engineering Ltd.
Description: Mount Pleasant Station on Toronto’s Eglinton Crosstown LRT Line marked a world-first use of 70% GGBFS (slag) shotcrete to construct 1.5 m thick, heavily reinforced underground walls using a “hybrid” shoot-and-vibrate method. This presentation highlights the structural design requirements and rigorous preconstruction process used to qualify the mixture, equipment, and crew.
Full-scale mock-ups were evaluated through wire saw cuts, strength and durability testing, and thermal analysis to confirm performance around dense reinforcement and waterproofing membranes.
The hybrid method enabled placement around up to four layers of 35M rebar—unprecedented for shotcrete. Construction incorporated full-time inspection, testing of every truck for temperature, slump, and air content, as well as core strength testing and real-time thermal monitoring.
This case study showcases a sustainable, high-performance approach to mass concrete construction using shotcrete in challenging underground conditions.
Mass Concrete in Practice: Bridging Standards and Field Experience
Presented By: Justin Torkilson
Affiliation: Kiewit Engineering Group, Inc
Description: Mass concrete (or thermally controlled concrete) commonly requires means and methods to reduce maximum temperature, mitigate temperature difference, among others project specific requirements. Temperature limits can affect mix design selection, reinforcement details, construction operations and even compliance to specifications for mass concrete related work. Many of today’s specifications typically limit temperatures to conservative default values usually referred in industry standards; however, it can be recognized that current standards for mass concrete often do not reflect the current state of knowledge on performance or experience from field practitioners. This frequently results in unfortunate challenging and difficult scenarios during design and construction of mass concrete placements. This presentation focuses on the implementation of today’s knowledge, industry standards and best practices for mass concrete with an overview of design to construction challenges and opportunities in projects from a field practitioners’ perspective. A special emphasis will be given to the updates provided for mass concrete requirements and guidance published in the CSA A23.1.
Approaches to Overcome Challenging or Impossible Specification Requirements for Mass Concrete
Presented By: Scott Cumming
Affiliation: WSP Canada Inc.
Description: Presentation will provide an overview of development of performance-based approaches for mitigation of thermal stresses in mass concrete when prescriptive specification requirements are challenging and/or impossible to achieve. Presentation will also provide guidance for mitigation measures including use cooling pipes and cryogenic cooling of plastic concrete to overcome spec requirements that may be excessively conservative
10,000 PSI Mass Concrete in the Texas Heat
Presented By: Jacob Borgerson
Affiliation: Wiss, Janney, Elstner Associates, Inc.
Description: This presentation will explore the constructability challenges with placing a 10,000 psi 15-foot-thick pile cap during the hottest recorded summer in Houston. Due to the high cementitious materials content of the concrete and the record-breaking summer heat, it was determined that the pier cap's internal temperature could potentially reach 200°F, and a cooling pipe system was necessary to control internal temperatures and temperature differentials. Given the amount of reinforcement in the pile cap, reinforcement locations had to be adjusted to ensure that the fresh concrete could be reasonably placed within the element. This presentation will include the methods for managing the heat of hydration, the logistical challenges, and the large-scale concrete placement strategy.
Typical Challenges of Mass Concrete Constructibility
Presented By: Jonathan Poole
Affiliation: MJ2 Consulting, PLLC
Description: