End-Result Specifications for Hydraulic Cement Concrete: Phase II

About the report:

A study was undertaken to develop an end-result specification (ERS) for hydraulic cement concrete to be used by the Virginia Department of Transportation (VDOT) in transportation structures to obtain a uniform, consistent, quality product.  The study was done in two phases.  In the Phase I study, an ERS special provision was developed and applied to two pilot bridge projects, one each in two of VDOT’s nine districts.  In the current Phase II study, the ERS special provision developed in Phase I was updated and applied to more projects: of VDOT’s nine districts, eight provided strength and permeability data for Class A3 concrete, eight provided strength data for Class A4 concrete, and seven provided permeability data for Class A4 concretes for bridge structures.  Two paving projects were also included.  The study addressed sampling, testing, quality characteristics, specification limits, bridge and paving concretes, and pay factors.  VDOT’s current specifications were applied for acceptance and rejection of all pilot projects, and pay adjustments were not applied.

VDOT’s ERS has three parts.  The first part covers process control measures.  The contractor is responsible for the concrete design and is required to provide a quality control plan. The plan addresses all elements that affect quality, including mixture designs, aggregate sources, ingredients, tests and testing frequency, fresh and hardened concrete properties, and control charts.  The second part covers the mixture design approval by VDOT.  The third part covers project acceptance, which includes pay adjustments depending on the results of tests conducted under the first part.

In the current study, the first two parts of the ERS were well received and enabled innovations, minimized waste of materials, and provided green initiatives by reducing cement consumption.  The third part dealing with pay adjustments had strong opposition from the industry and needs further evaluation.  Thus, the study recommends that the first two parts of the ERS be implemented for use with bridge structures and the third part be deferred until more projects are evaluated.  In addition, pilot projects for pavements should be initiated as was done for bridges.

 A new, single class of concrete for both decks and substructures is planned for bridges that will provide the same high-quality concrete throughout the structure.  This new class of concrete will enable more samples for ERS testing since there will not be more than one type of concrete in the structure.  Projects with this new type of concrete should be included in further pilot tests of VDOT’s ERS.

Authors