A Shift to Performance-Based Specifications

For Concrete Focuses on innovation, quality

and customer satisfaction

Since the early days of the ready mixed concrete industry in the 1920s, technological advances, production capabilities and practices of concrete producers have evolved into an advanced science. Most modern ready mixed concrete production facilities have laboratories that incorporate rigorous quality control and product development programs, and expert concrete technologists to develop innovative concrete mixtures for any application—from houses to high-rises and sidewalks to superhighways. Unfortunately, typical project specifications are prescriptive in nature and stifle innovation by limiting the types and quantities of ingredients and material proportions. Prescriptive specifications are often overly conservative which can lead to higher costs and unexpected negative results, ultimately leading to unsatisfied customers. The concrete producer should be part of the team that delivers a quality constructed project since he is the expert on the material he manufactures and delivers. The same goes for the progressive contractor.

Industry stakeholders interested in promoting the P2P Initiative, click here.

Downloads:

• NEW Guide to Specifying Concrete Performance

• NEW Quality Management System for Ready Mixed Concrete Companies

• Research Report: Preparation of a Performance-based Specification for Cast-in-Place Concrete

• Research Report: Experimental Case Study Demonstrating Advantages of Performance Specifications

• P2P Online Learning Brochure

• P2P Article

• Summary of Performance-based Specification Research

• P2P Seminar

• Example Specification

• Specifying Concrete for Durability - Performance-Based Criteria Offer Best Solutions

• Performance Specifications for Durable Concrete

• Acceptance Criteria for Durability Tests

A shift to performance-based specifications is the next logical step in the evolution of the ready mixed concrete industry. Performance-based specifications provide details of required results such as strength and other mechanical properties along with requirements for durability and serviceability. The results are verifiable through measurement or testing to assure the product meets the desired requirements. And finally, performance-based specifications are free of process limitations such as mixture proportions and construction methods. Performance-based specifications encourage innovative products and construction methods along with rigorous quality management systems that lead to superior products and satisfied customers.

The ready mixed concrete industry recognizes customer needs will best be served through innovative concrete technology and improved quality—the outcomes of performance-based specifications. Led by the National Ready Mixed Concrete Association (NRMCA), the ready mixed concrete industry has established the P2P Initiative to promote a shift from traditional prescriptive specifications to performance specifications for concrete. P2P is an acronym for Prescription to Performance specifications. 

The P2P Initiative of NRMCA promotes a shift to performance-based specifications for concrete construction that includes highways and local roads.

The Research, Engineering and Standards (RES) Committee of NRMCA formed the P2P Steering Committee in October 2002 to develop a strategic roadmap for the P2P Initiative. The Steering Committee has collaborated with industry stakeholders including concrete contractors, material suppliers, engineers and architects to develop a set of goals and strategies to implement performance-based specifications.

The primary goal of the P2P Initiative is to improve the quality and competitive position of concrete by moving away from prescriptive requirements to those based on performance criteria. All stakeholders in the construction process must see a benefit to themselves. There is no intent to eliminate prescriptive specifications. These traditional modes of specifying concrete can work well in certain market areas and in certain established relationships. One effect could be that there will be an improvement in prescriptive specifications whereby some of the inherent conflicts are eliminated and responsibilities are more clearly defined.

Strategies for the P2P initiative include:

• Promote performance specifications as an alternative to current prescriptive specifications through education and communication

• Leverage the expertise of all stakeholders in the construction industry to improve quality and reliability of concrete construction

• Assist architects and engineers to address concrete specifications in terms of performance requirements, allowing concrete suppliers and contractors flexibility on the details of concrete mixtures and construction means and methods

• Elevate the performance level and credibility of the ready mixed concrete industry through training and certification

• Foster innovation and acceptance of new technology at a faster pace through research and development

Performance-based specifications foster innovation and acceptance of new technology such as high-strength concrete and self-consolidating concrete for high-rise construction.

P2P shifts the emphasis from prescribing the ingredients and their proportions in a concrete mixture to an emphasis on the performance properties of the combined materials. The details of a concrete mixture for the most part have little meaning to a contractor, design engineer or owner of a building or roadway. Concrete producers, on the other hand, have to maintain an expertise that allows them to optimize the mix for predictable performance, both in its plastic and hardened state. They have to know their ingredient materials and should be competent in mixture proportioning to compete and deliver a long-lasting product in a competitive environment. The P2P Initiative is a large undertaking with far-reaching implications throughout the construction industry that will require coordination with, and support from, project owners, government agencies, codes and standards organizations, engineers and architects, contractors and concrete producers. Eventually it should be considered an industry initiative rather than that of one group.

Who Benefits from Performance Specifications

Customers: The ultimate customer—building owners, government agencies, home builders, roadway users, just to name a few—will benefit from performance specifications since they empower contractor and producer teams to deliver a superior product that meets the customer’s needs.  Owners can expect improvements in quality and service life of concrete buildings and roadways.  Other benefits include accelerated construction schedules and potentially lower project costs.  With improved quality control systems and attention to functional requirements for concrete, owners can expect fewer call backs and construction conflicts.

Specifiers: Architects or engineers that represent the owner will benefit from performance specifications since they can focus their energy on aesthetic and functional design instead of the details of concrete construction and mixture proportioning.  Performance specifications will simplify the submittal review process.  Performance specifications reduce specifier liability since responsibility for mix design and construction means and methods is shifted to the ready mixed concrete producer and contractor.   In addition, specifiers can expect improvements in quality and consistency and potential reduction in project costs.

Contractors: For the most part, project specifications for concrete will focus on requirements of the hardened concrete.  However, since performance specifications encourage improved coordination between the contractor and producer, issues relating to placement and finishing will be addressed.  Contractors can expect enhanced placeability and finishability characteristics of plastic concrete, including improvements in product consistency.  Contractors will have flexibility on construction methods and more control over project schedule.

Concrete Producers: Performance specifications favor concrete producers that focus on quality control and innovation.  Progressive producers will be challenged to innovate and invest in product development and advanced quality control procedures.  Concrete producers can expect reduced conflicts within specifications.  They will have the ability to satisfy constructability and in-place requirements for concrete.  They will have control of the mix design and the flexibility to make adjustments to mix designs when material sources or weather conditions change.

What are the Challenges?

There are many challenges to implementing performance-based specifications.  Currently, there are no accepted model performance specifications in the United States that can be used as a guide for developing performance-based project specifications.  Most building codes and standards for concrete, including the American Concrete Institute (ACI) standards, ACI 318 and ACI 301, are predominantly prescriptive in nature.  Although they allow the use of performance specifications they don’t provide guidance on how they should be used or which criteria or test methods should be implemented.  Consequently, performance specifications are rarely used. 

For the most part, most state departments of transportation [DOT] employ prescriptive specifications for concrete.  Some state departments of transportation [DOT] have experimented with performance-based specifications on high-performance concrete especially for bridge applications where durability and long life are critical.  These applications are at the cutting edge of concrete technology, using a wide range of supplementary cementing materials and admixtures along with innovative construction techniques to minimize permeability and cracking.  The intent is to extend the life of structures beyond 100 years - which is significant in light of the harsh environments in which these structures reside.  The NRMCA P2P Steering Committee has invited state DOT engineers to draw on their experience with performance specifications to develop guide specifications.

The NRMCA P2P Steering Committee is conducting extensive research to develop a guide performance specification and propose changes to building codes and standards to better address performance specifications.  Researchers will perform a review of existing literature to identify where prescriptive requirements are built into the codes and reflected in specifications for concrete and propose new language to replace pertinent sections of ACI 318 and ACI 301.  Researchers will identify performance objectives for concrete including pre-qualification and acceptance tests.  Researchers will review existing performance-based standards from around the world including Canada, Europe and the U.S. Click here to download the Summary of Performance-based Specification Research.

The guide specification will allow designers to prepare concrete project specifications and contract documents that outline the performance requirements, submittal requirements, pre-qualification requirements and acceptance criteria.  The guide specification will identify consequences of non-performance and a resolution mechanism.  In addition to design requirements, the guide will include a mechanism whereby contractors can add construction requirements for installation and delivery.  Producers would then be able to use designer and contractor requirements to submit a bid showing levels of performance, cost, delivery rate, pre-qualification test results and plant certifications.

For some performance criteria, practical pre-qualification or field acceptance tests do not currently exist.  Tests that are expensive or take excessive time to conduct are not practical for construction.  The NRMCA P2P Steering Committee intends to conduct research to identify appropriate tests and, if required, develop new tests for use in performance specifications.

Specifiers, contractors and producers must be educated on the benefits and proper use of performance specifications.  The NRMCA P2P Steering Committee plans on educating producers, contractors and specifiers through seminars and distribution of guide specifications. In addition, NRMCA staff and members are working with national and local groups such as ACI and the American Society of Civil Engineers (ASCE) to communicate the benefits and proper use of performance specifications.

The P2P Steering Committee also intends to conduct a laboratory study designed to demonstrate the advantages of performance-based specifications over prescriptive specifications for concrete. Concrete specimens will be prepared using typical prescriptive specifications such as those in ACI 318 and tested for a variety of attributes including strength, scaling, sulfate resistance, corrosion and permeability. The results will be compared to specimens prepared using performance-based specifications.  Both fresh and hardened concrete properties will be quantified and compared. Click here to download the Summary of P2P Lab Study.

The P2P Steering Committee also realizes performance specifications will only be successful if ready mixed concrete producers are qualified to design and deliver concrete under the new standards.  They’ve undertaken a research project to prepare a QA/QC standard for ready mixed concrete to pre-qualify concrete producers to deliver concrete for projects employing performance-based specifications. The QA/QC standard will provide assurance to the purchaser that a concrete producer is capable of designing, producing and delivering concrete that is consistent and uniform. The QA/QC standard will establish guidelines for ready mixed concrete production facilities, equipment, personnel, management, testing, mix performance data and documentation. The QA/QC guidelines will be designed for projects of any size and scope and will be flexible enough to allow a producer of any size to adopt the program.

Although the challenges are many and the effort involved will be extensive, the NRMCA P2P Steering Committee feels the change is necessary to ensure continued growth and improvement of the ready mixed concrete industry.  Improved quality, innovation and customer satisfaction are at the core of the P2P Initiative. To get involved, contact Lionel Lemay, LLemay@nrmca.org.

Prescriptive Specification versus Performance Specifications (next page)