Benefits to the Owner
Owners are primarily interested in owning a structure constructed within budget and schedule and will provide the expected service life with minimal maintenance. Owners are generally not interested in the means and methods and details of construction materials used. If there is a sustainability goal, the owner is interested in achieving this at a minimal increase in cost without compromising other objectives.
Performance specifications attract knowledgeable stakeholders who have assigned responsibility consistent with expertise and who support the owner’s interests. For concrete construction, this translates to optimized mixtures, improved quality, and adoption of innovation. This results in reduced time and project costs, mixtures that comply with specified performance, and better partnering of stakeholders for reduced problems during the project. In summary, performance specifications assure performance, support sustainability, and are more likely to deliver a project on time and within budget.
Benefits to the Designer
Designers (architects and engineers) design the space, aesthetics, and structural system to the owner’s requirements and budget. They need to evaluate the required performance for each portion of the structure to comply with the Building Code and service life expectations. This has to be translated to project specifications that are reasonable and achievable at the project location. While establishing requirements for concrete that are consistent with the Code, the designer may consider including other performance requirements of mixtures for some members based on exposure and design requirements, such as permeability to water or chemicals, shrinkage, resistance to alkali aggregate reactions, modulus of elasticity, etc.
Concrete material technology, and in particular concrete mixture development and optimization to meet the desired performance is in the realm of expertise of the concrete producer and the material suppliers they work with. In a prescriptive specification, the designer assumes responsibility for the performance of concrete. Minimizing prescription and evolving to performance benefits the designer whereby the responsibility to optimize and meet the performance requirements is with the contractor and concrete producer. Evolving to performance specifications also minimizes conflicts between prescriptive and performance requirements or factors that impact constructability. Performance tests and criteria ensure that the supplied concrete meets the performance. Prescriptive specifications and criteria may not ensure that the required performance is achieved or may cause problems with constructability. If sustainability goals are important to the owner, the engineer can set a carbon budget for all concrete to be used on the project based on a defined Life Cycle Assessment (LCA). Performance specifications incentivize the ability to optimize mixtures, improve quality and minimize overdesign, and assign responsibility to the applicable expertise. These features typically attract more proficient stakeholders that will be technical resources to the designer to meet project objectives. This can help conform to the project schedule and budget.
Benefits to the Contractor
The contractor is interested in obtaining concrete that is consistent between loads and responds appropriately to constructability requirements that can include fresh concrete characteristics and early-age rate of strength gain. Their goal on the project is to complete the project in accordance with the contract documents and meet the owner’s schedule. There are several characteristics of concrete for constructability that are not covered in project specifications. Further, some specified requirements could cause conflicts with constructibility.
Performance specifications are more likely to draw knowledgeable producers who can technically support the contractor’s requirements. This can lead to reduced time and cost to address project problems that may arise. Performance specifications provide an opportunity for the producer and contractor to partner together to set requirements that address the constructibility expectations.
Benefits to the Producer
With a performance specification, the concrete producer can optimize concrete mixture proportions as constraints such as limits on supplementary cementitious materials content, maximum water-to-cementitious materials ratio (w/cm), and minimum cementitious content are removed. Performance specifications also allow for increased investments to reduce the variability of strength and reduce the strength over design. Innovations in concrete mixtures can be more rapidly introduced. The concrete producer will be included as an important stakeholder in the construction project who can offer technical solutions to the designer and the contractor that satisfy their needs. Producers for long have felt that they lacked the authority to make changes to the mixtures but were held responsible for the performance of the concrete. With a performance specification, the responsibility for performance is aligned with the authority to adjust mixtures.