Much Portland cement is wasted, lost, is reduced in quality, or is made unusable, by careless or badly informed handling, transportation and storage. Though used all over the world for construction jobs from the largest to the smallest, and often taken for granted, Portland cement is in fact a high technology; quality assured manufactured product made to strict and carefully controlled international standards.
If Portland cement is to be properly used, it is important that certain basic rules be observed in moving it between its point of manufacture and point of eventual use to make Portland cement concrete.
The first and most important rule is: Keep the cement Dry.
Being a chemically active product which reacts with water (either in liquid or in vapour form), cement must be kept away from both wetness (actual water such as leaks, flooding, etc. which can be seen with the naked eyes) and dampness (water vapour in the air which cannot be seen, but which is always present to some extent). This water vapour can pass through the multi wall paper sacks and destroy the quality of the stored cement.
Some Practical points regarding storage of Cement in bags (Paper Sacks):
Do not cover cement bags stored on construction sites without first spreading a sheet of plastic OVER the ground UNDER the cement (to keep away dampness rising from the ground). If you are not sure that your concrete warehouse floor has a damp proof laver of plastic UNDER the concrete slab, do not store cement sacks directly on such a floor; first place a sheet of plastic on the floor BEFORE storing cement bags on top of it.
If not properly ventilated underneath, the wooden floor of a site office may allow enough dampness to pass through both the boards themselves (wood is porous) and the joints between boards (or sheets of plywood) to cause problems with stored cement.
Walls made of concrete blocks, clay blocks, rubble masonry, or even poured (cast) concrete may allow sufficient dampness to pass through them to cause problems to cement stored against them; if the wall is an external wall which can be wet by rain on its outside face, or if it is cast against earth (e.g. a basement wall), dampness may be a problem. Again, plastic sheet polyethylene ("polythene") is effective as a barrier to keep the cement from absorbing such moisture.
Cement which has become "lumpy" has already lost a significant portion of its strength, and should not be used for important structural work. Cement sacks can be torn or otherwise damaged by careless or rough handling, by sharp edges, by nails sticking out of the wooden pallets on trucks, by dropping from excessive heights, by the pallets of forklift trucks, etc. Cement sacks being transported on trucks should also be protected from rain, drizzle, sea spray on windward coasts, splashes from small roadside waterfalls and streams in well watered mountainous areas, splashes from water in puddles and potholes, etc.
Small amounts of cement remaining in opened sacks (or even full sacks of cement) can be stored for long periods (at least for several months) in undamaged plastic bags whose mouths are securely shut by twisting and then tying the twist with "wire ties", twine, etc. Large sized heavy-duty garbage bags are suitable, but any plastic bag will significantly extend the storage life of Portland cement packed in paper sacks only.
If sacks of cement are stored on pallets in a warehouse, there should be space for sufficient through ventilation to prevent a build up of damp air under or between the stacked cement. In damp or humid weather or during wet or rainy seasons, excessive stocks of cement should not be kept so as to reduce the tim