For a terrazzo topping, only cement and marble chips are used. Why no fines?
Because the mortar forms a part of the polished surface and I must have a similar abrasion resistance to that of the chips. If fines are included, more water is needed to make a workable mix, and thus the mortar matrix becomes weaker. Without fines the usual water/cement ratio is around 0.3; with fines it would need to be much higher. This doesn't completely avoid problems, however. A 1 to 3 mix must generally be used to ensure that there is sufficient mortar to fill the voids between the chips. A rich mix means that the terrazzo will be highly susceptible to cracking because of shrinkage on hardening. For this reason joints are necessary at 3- to 4-foot intervals in both directions.