How do you dispose of Portland cement?

Answer 1

You should be able to spread a low concentration of unmixed portland cement over soil that needs to be more acidic, just as you would use ground limestone. You can use a home soil test kit; in many areas, the county extension service will test your soil for a reasonable fee.

The major constituents of portland cement are either materials (sand/silica) that don't affect soil chemistry or alkaline substances that reduce acidity. Many cements have gypsum which some people recommend adding to soil that is high in salt or low in calcium. Research has shown that dust from portland cement kilns is about as effective as ground limestone at reducing soil acidity. http://hubcap.clemson.edu/~blpprt/acid5.html. See http://ohioline.osu.edu/hyg-fact/4000/4026.html for recommended application rates (use the crushed limestone rate as an approximation, but realize the cement will reduce the acidity of the soil much more quickly). You could spread up to five 80-pound bags over a 0.2 acre yard.

Three cautions - 1. Cement can burn skin and plants until it's reacted with water. Apply it using the same precautions you would use in handling cement for mixing and avoid putting excessive amounts on lawns or desirable plants. If you have children or pets that could come into contact with the dust, if the wind is likely to blow the dust into areas where people or animals are, if you've applied it on grass or ground cover, or if you plan to work in the area right after applying, wet the area with a hose after spreading. It's a good idea to do this in any case.

2. The cement will affect the consistency of different soils differently. If you mix too much cement with soil that has a lot of clay, the mix may become like concrete. If you have any concerns, spread the cement over the area at half the recommended application rate (25 pounds per thousand square fee).

3. Some specialty cements will have different ingredients. You can find out what the ingredients of a particular brand are from the Material Data Safety Sheet (MSDS). Quikrete publishes its MDSDs at http://www.quikrete.com/OnTheJob/SpecData.asp.