A common dispute on a construction site involves the interpretation of specification requirements or enforcement of requirements that may not be required to achieve system performance in every situation

A typical example is the acceptance criteria for strength.  Many engineers argue that because the mechanical failure mode of slabs on grade is in flexure, then acceptance should be based on testing this parameter.  On the other hand, sample sizes and the difficulty of achieving an accurate result pose safety and uniformity concerns, whereas correlation with the more reliable compression test may achieve a better outcome.  Confounding the idea that many engineers assume the sample is representative of the in-place concrete is that samples extracted from the concrete usually exhibit different results from samples prepared at the time of placement and stored under controlled conditions. Moreover, some engineers and constructors argue that maturity or other methods may be a better and more reliable option to confidently accept in-place concrete pavement strength as meeting specification requirements.  This topic has been extensively researched in the past, but more work is needed to develop protocols and practices that are fair and minimize risk to all parties involved.

Planned work to address these types of issues includes:

• Interview owners, engineers, and contractors to develop a list of the most common specification provisions that cause disputes.
• Conduct research to find solutions to these ambiguous specification provisions.
• Prepare language to insert into specifications to clarify and resolve such problems.

The result of this may lead to further research to develop new acceptance criteria that will lead to better pavement performance at a reduced cost due to unnecessary disputes.

Cement manufacturers are developing new products in which cement clinker is being replaced with alternative materials like calcined clay, limestone, and pozzolans.  These materials will likely exhibit performance differences in concrete pavement in terms of:

• Set Time
• Air entrainment
• Bleeding
• Strength gain
• Modulus of elasticity
• Permeability
• Sulfate expansion
• Calcium oxychloride resistance
• Shrinkage

New protocols are needed to consistently characterize individual products and their impacts on concrete pavements. In addition, pavement structural models, design procedures, construction practices, and acceptance limits need to be modified to accommodate the differences. Research is needed to address these issues and to assess if recommended and appropriate changes are needed to FAA Advisory Circulars.