Marake Matjila resigned on Tuesday, Business Day reported.
Raubex said Matjila considered it appropriate to resign to prevent any perceived conflicts of interests given that the company was involved in national roads privatisation projects.
City Press reported on Sunday that Kopano Ke Matla had shares in Raubex, which won a tender to build the R21, which forms part of the Gauteng Freeway Improvement Project. These roads will be tolled to pay for their construction.
Raubex received R800 million for the project.
Kopano Ke Matla holds 3% of Raubex, so it would have received R24m as a result, according to the weekly. This would mean that the Congress of SA Trade Unions (Cosatu), which had been vehemently against the toll roads, stood to benefit from them.