PART A - MATERIALS
To construct a concrete-block wall, you will need concrete blocks and the basic ingredients for mortar
(cement, lime, sand, and water). Other ingredients that speed up or slow down the curing time of mortar
are called admixtures.
1-1. Blocks. When storing concrete blocks, use good storage techniques. Never allow the blocks to get
wet before you lay them. Excess moisture in concrete blocks will cause shrinkage when drying.
Stockpile the blocks on a raised platform to prevent the absorption of ground moisture. At the end of the
workday, cover the stockpile of blocks with a waterproof tarpaulin to protect them from the rain.
1-2. Mortar (cement). Specifications for the types of portland cement are covered by the American
Society for Testing and Materials (ASTM) and include types with the following characteristics:
Type I is a general purpose cement and the most commonly used. It is generally used in
Types II is used in concrete.
Type III is a high early-strength cement. Although Type III takes as long as Type I to set, it
will achieve its full strength much sooner. It is sometimes specified for cold weather because
it requires shorter protection time. Type III is generally used in mortar.
Types IV and V are used in concrete.
1-3. Lime. Cement provides the strength of mortar while lime acts as a plasticizing agent providing
smoothness and workability. Lime also increases the water-holding capacity of mortar without it, the
mixture would be stiff and unworkable.
1-4. Sand. Sand used in mortar must be clean and free of organic materials; individual particles should
be well-graded as to size. In a good mortar, all sand particles are completely coated with cemetitious
material (paste). This permits the separate ingredients, or aggregates (sand and stone or gravel), to roll
over each other and produce a plastic, workable mortar.
1-5. Water. Water used
in mortar should
of acids, alkalies,
salts, and organic matter.
As a general rule, drinking water is suitable for making mortar.