1905.3.5 Field Changes to Concrete Proportions

Based on test data and observations during the course of construction, the following changes described in Sections 1905.3.5.1 and 1905.3.5.2 are permitted without requiring additional trial mixtures or field strength test records, provided:

1. There are no changes to the type and source of materials described in Section 1905.3.4;

2. Documentation of these changes are maintained by the concrete producer and the concrete contractor;

3. The changes described in Section 1905.3.5 cannot be used for the submission of an initial mix design to demonstrate that a previously prepared mix design meets strength or air content requirements that differ from the required concrete properties without new field strength test records or new trial mix designs;

4. Where required in Section 1905.3.5, documentation of these changes shall be submitted for acceptance to the registered design professional of record for the structural design by the concrete producer prior to use;

5. Copies of the revised mixtures shall be maintained at the construction site and provided to the licensed concrete testing laboratory performing the acceptance testing of concrete in accordance with Item 4 of Table 1704.4 of this code; and

6. The documentation required by Items 2 and 5 above shall be made available to the commissioner upon request.

The following admixture modifications to concrete proportions can be made without requiring prior acceptance by the registered design professional of record:

1. Air-entraining admixtures. Air-entraining admixture dosages can be increased or decreased as needed to obtain the air content specified in the construction documents.

2. Water reducing admixtures. Water reducing admixture dosages can be increased or decreased to produce the specified workability, provided that the design water is not exceeded and the changes do not segregate the concrete mix.

The following modifications to concrete proportions can be made only with prior acceptance by the registered design professional of record. Any added materials and the final mix proportions shall be indicated in a revised mix design submitted to the registered design professional of record prior to use:

1. Retarding and accelerating admixtures. Retarding and accelerating admixtures may be added to concrete mixtures or the dosage may be modified as needed to maintain practical set times.

2. Pigment. Pigment dosage may be adjusted to maintain uniform concrete color.

3. Fibers. Synthetic, glass or natural fibers may be added to the mix within the manufacturer recommended range. Any loss in workability shall be compensated with a water reducer.

Exception: Steel fibers may not be added to a concrete mixture without the performance of a new mix design.

4. Corrosion inhibitor. Corrosion inhibiting admixtures may be added, provided the corresponding adjustment of mix water remains within the limits of the required water/cementitious material ratio. The added materials and the revised design mix shall be submitted for review by the registered design professional of record for the structure prior to use.

5. Cementitious content and water-cementitous material ratio (w/cm). The cementitious content may be increased by a maximum of 12 percent, or the w/cm ratio may be decreased while maintaining the same cementitious content, but the w/cm and air content shall not be increased. Aggregate quantities shall be adjusted, as required, to maintain the mix proportion and yield.