Q.: We generally keep a supply of bagged cement on hand in our storage shed, and sometimes we hold some of this on the jobsite for extended periods of time. Although the bags are usually covered with a tarpaulin or plastic sheet, even when we store them indoors, we frequently find that after a few months the cement contains lumps and sometimes it is even hard. Is this to be expected with all brands, and if so, is there any way to prevent it?

A.: The virtue of cement its ability to harden by reaction with water is in this case its weakness. It must be protected not only from water but from dampness. The bags in which cement is packed seal out some moisture for limited periods but not all moisture, and, of course, after a protracted period of time an undesirable amount of water vapor can get through the bag. Liquid water should not be allowed to come in contact with the bag.

It is best to store bags of cement on pallets to keep them off the floor or off the ground. Waterproof covers or enclosures should be used to protect them as well as possible against rain, snow, mist, or accidental sprinkling. Even in a storage building there may be a certain amount of water vapor in the air, so the bagged cement may not last indefinitely. When bags are trucked from one place to another in rainy weather they should not only be protected on the top and sides, but also on the bottom to protect against rain splashing up under the pallet .