Lime or calcium carbonate works slowly to loosen clay soil by changing the ph or acidity of the soil. You can apply \"Super Sweet\" calcium in a granular form to your soil twice a year in fall in spring for the first two years and then every year apply at least once. Follow the amount on the label of the type of limestone or calcium or start with 5 pounds spread over 1,000 square feet of lawn. Moss is a sign that your lawn has poor drainage and poor fertility. Aerate the lawn in May, and feed with a slow release lawn food after aeration. Keep growing, Marianne Binetti