A chemically setting acid-resistant cement product prepared from a mix comprising: (a) silica sand, (b) silicate of soda, (c) silica flour, (d) sodium silico fluoride coated with oil, and (e) a fully basic sodium phospate of the group consisting of sodium orthophosphate, sodium tripolyphosphate, sodium hexametaphosphate, the combined amounts of said sodium silico fluoride and said phosphate being effective to cause said acid-resistant cement product to set.