Supplementary cementitious materials (SCMs) provide a variety of benefits to fresh and hardened concrete. These materials can be found in naturally occurring substances or from by-products or co-products of a variety of industries. However, some of the industries that have been a large source of SCMs over past decades are not as prevalent today and therefore are causing a decrease in availability of popular SCMs, particularly fly ash. The main reason for the decreases in production have been concern over the environmental impacts that the mechanical process to derive fly ash, coal burning, is causing. Research has now turned to the identification of new SCMs that provide the same performance benefits as materials such as fly ash but without the environmental impacts. Evaluation of an alternative SCM produced as a byproduct of the phosphorous industry for use in concrete is the goal of this project. The material being tested in the following research project is a co-product of producing phosphoric acid called J-Rox, produced by a phosphoric acid producer in Florida. The material was tested at 15% and 25% rates in paste, mortar, and concrete samples to determine the benefits it could provide as a SCM compared to the benefits of samples that did not use an SCM and samples that had a 20% replacement of fly ash. Through the process of testing the paste and mortar samples, different variations were created based on results of previous versions. This was done to determine which versions would potentially perform the most similar to fly ash when used in concrete. The versions determined best for concrete use were J-Rox 3 and 4. The main concerns for similar performance among J-Rox and other SCMs like fly ash was the differences in chemical composition and fineness. J-Rox was found to have a higher P2O5 percent weight which could potentially affect its performance. However, despite these differences J-Rox performed very similarly to the control samples. Compressive strength test results for J-Rox mortar and concrete were lower than control samples at the 28 day test period, but the J-Rox mixtures continued to show late age strength gain, reaching values similar to those of the controls at later ages. J-Rox concrete mixtures showed resistivity gain in late age testing similar to that which is seen in fly ash mixture, and therefore may provide durability benefits. No notable issues with concrete performance due to the higher P2O5 content were observed for the mixtures and tests performed as part of this study. For all mixtures prepared as part of this work, shrinkage values were moderate to relatively high among all samples. However, this could be adjusted through the use of a lower w/c ratio, should be used in mixtures produced during future testing. Since this material is targeted for use in Florida, the addition of the chloride diffusion test to the experimental program of future work may also be beneficial.