Mortar is made by mixing to the consistency of soft porridge limes or cements with clean sands, the proportion of which depends upon the description of the lime or cement.

Proportion Of Sand

Rich and Poor Limes may be mixed with a large proportion of sand (3 or 4 measures of sand to 1 of lime), for in any case they make mortars with very little strength. Hydraulic Limes make a good mortar with 2 of sand to 1 of lime. Roman Cement Mortar should not have more than 1 or 1 sand to 1 cement, and is then a very weak mortar. Portland Cement will make a very strong mortar when mixed with 2 or 3 of sand, and even with 5 of sand - a mortar better than any of those made from lime.

Proportion Of Sand 200314

Fig. 406.

Grout is a weak mortar made liquid by the addition of water, and used to pour into joints and interstices which cannot be got at with the stiffer material.

Concrete is a conglomerate or thorough mixture of shingle, broken stones, or similar material, with lime or cement, sand and water, which form a mortar filling the interstices between the pieces of stone. The proportions of ingredients mixed determine the quality of this mortar, which in its turn governs the strength of the concrete.

Proportions Of Ingredients

Concrete is generally described with reference to the bulk (when dry) of the materials comprising it. Thus for an important work the concrete might be 1 Portland cement, 2 sand, and 5 of shingle or broken stone ; for less important work 1 Portland cement, 3 sand, and 8 shingle.

Laying Concrete

This should be carefully done in horizontal layers, about 12 inches thick, well rammed, the surfaces being kept clean, and the material not disturbed when setting.