Might be tricky but can you not 'chase' the concrete out under the joists?
I enclose chase in '' because you clearly can't use a grinder if the joists are sitting on the concrete, so maybe grind out a small square either side of the joist then angle drill underneath?
I would angle the outer edge of each side so you have an almost boat like shape running under the joists so you don't have 90 degree bends in the cable.
I enclose chase in '' because you clearly can't use a grinder if the joists are sitting on the concrete, so maybe grind out a small square either side of the joist then angle drill underneath?
I would angle the outer edge of each side so you have an almost boat like shape running under the joists so you don't have 90 degree bends in the cable.