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.
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.
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, firstname.lastname@example.org.
© National Ready Mixed Concrete Association, 2013