Many male African slaves in Muslim countries were made into eunuchs, a process with a roughly 90% mortality rate. The remainder were used as miners, soldiers, etc.
The females were mostly used as household labor.
The sexes were intentionally kept apart, so no native class of African blood grew up in these countries. Nevertheless, there are Arab countries with discernibly African minorities.
Historically speaking, in most slave societies the population of slaves was not self-sustaining and had to be constantly replenished with imports, as in the sugar islands and Roman Empire.
AFAIK, the American south is the only slave society in history to have a massive population explosion, indicating that conditions were probably less oppressive than the norm for such societies.
Edmund Morgan attributed the rise of white democracy in Virginia to 1) the population explosion in the colonies after 1715. 2) the arrival of the first significant numbers of African slaves whose numbers also increased exponentially as much naturally as from immigration. It had taken the English colonies about a hundred years to acclimate, and the Africans profited from the better living conditions. Birth rates rose to Bangladesh heights and the death rate plummeted among both blacks and whites. White servants continued to be brought to the new world, mainly convicts,