Rationale

The purpose of this work item is to revise Appendix X1 and provision 8.4 of Test Method C900-23 on the pullout test. When Appendix X1 was developed, several sizes of pullout test inserts and reaction rings were being used in research and in practice. To compare test results among different systems, Appendix X1 provided a formula for calculating a fictitious nominal tensile stress perpendicular to the idealized conic frustum. Currently, only one pullout test geometry is commercially available, and the need for comparing test results among different systems is of secondary importance. However, the nominal tensile stress calculation is needed to determine the loading rate for pullout testing that is specified in 8.4. To allow for different test geometries, the loading rate is specified in terms of the rate of increase of the nominal tensile stress. The proposed change in Appendix X1 is to clarify how the equations are used to calculate the loading rate in terms of force to satisfy the stress rate requirement in 8.4. Other changes are proposed in 8.4 to clarify that the loading rate applies in the early part of the test before formation of extensive microcracks. This is similar to the requirements for compressive strength testing in Test Method C39/C39M, where the loading rate is allowed to decrease while approaching the ultimate strength.