One local said he preferred to mix concrete in small batches using bags of cement, sand, stone etc mixed by hand or small machine, instead of ordering a whole truck of concrete. He felt that the concrete trucks used bulk cement that was treated with chemicals to prevent premature hardening or caking due to the very humid environment in the DR. He felt the chemical additives weakened the final product. The bagged cement made in smaller batches did not harden as quickly, since it has a plastic wrapper, compared to bulk cement which may be exposed to the elements. Seems logical but I have done a little research and I cannot find any chemical additive that prevents cement from hardening in high humidity environments. Does anyone know if they treat cement to prevent hardening? With what? Does it affect the final product so that if you retard hardening in the short run, will the treated bulk concrete have less strength than untreated bagged cement?