General. - Concrete pavement shall consist of one-course work with or without a finished and blocked surface, and with or without reinforcement. The depth will usually be seven (7) inches or six (6) inches at the sides and eight (8) inches in the center. It will be laid with either separate or integral curbs. The type to be used for each particular street will be indicated on the drawings and described under head of "Special Requirements."

Cement. - The cement shall meet the requirements of the specifications for cement as specified for concrete.

Sand. - Sand shall consist of natural sand or screenings from hard, tough, durable crushed rock or gravel, consisting of quartzite grains or other equally hard material graded from fine to coarse with the coarse particles predominating. Sand, when dry, shall pass a screen having four (4) meshes per linear inch; not more than twenty-five (25) per cent shall pass a sieve having fifty (50) meshes per linear inch, and not more than five (5) per cent shall pass a sieve having one hundred (100) meshes per linear inch. Sand shall not contain vegetable or other deleterious matter nor more than three (3) per cent by weight of clay or loam.

Sand shall be of such quality that mortar composed of one (1) part Portland cement, and three (3) parts sand, by weight, when made into briquettes, shall show a tensile strength (at seven [7] and twenty-eight [281 days) equal to or greater than the strength of briquettes composed of one (1) part of the same cement and three (3) parts standard Ottawa sand by weight. The percentage of water used in making the briquettes of cement and sand shall be such as to produce a mortar of the same consistency as that of the Ottawa briquettes of standard consistency. In other respects all briquettes shall be made in accordance with the Report of Committee on Uniform Tests of Cement of the American Society of Civil Engineers.

Coarse Aggregate. - Coarse Aggregate shall consist of clean, hard, tough, durable crushed rock or pebbles graded in size, free from vegetable or other deleterious matter, and shall contain no soft, flat or elongated particles. The size of the coarse aggregate shall be such as to pass a one and one-half (1 1/2) inch round opening and shall range from one and one-half (1%) inches down, not more than five (5) per cent passing a screen having four (4) meshes per linear inch, and no intermediate sizes shall be removed.

Aggregates. - Before delivery on the job, the Contractor shall submit to the Engineer a fifty (50) pound sample of each of the fine and coarse aggregates proposed for use. These samples shall be tested and if found to pass the requirements of the specifications similar material shall be considered as acceptable for the work. Aggregates containing frost or lumps of. frozen material shall not be used.

Water. - Water to be used shall be free from sewage, oil, acid, strong alkalies, or vegetable matter, and shall be reasonably free from clay or loam.

Subgrade. - The sub-grade shall be--------- (---------) inches below and parallel to the finished surface of the roadway. It will be prepared in accordance with the requirements for same, under item for "Grading" of these specifications. Immediately before any concrete is placed the sub-grade must be in a moist condition. Where the sub-grade is dry and of a porous nature the above mentioned condition shall be obtained by sprinkling.

Distribution of Materials. - Wherever it is possible to do so, the concrete material shall be stored outside of the portion of the roadway to be paved.

Proportions. - The ingredients of the concrete shall be mixed in the proportion of one (1) sack of cement to not more than one and one-half (1 1/2) cubic feet of sand and three (3) cubic feet of stone. A cubic yard of concrete in place between neat lines shall in no case contain less than seven (7) sacks of cement.

Measuring. - The concrete materials shall be measured by methods which will secure positive uniform proportions at all times. A sack of cement shall weigh not less than ninety-four (04) pounds net, and will be considered as one (1) cubic foot.

Mixing. - The materials shall be mixed in a batch mixer approved by the Engineer, and irrespective of the size of the batch and rate of speed used, mixing shall continue after all materials are in the drum for at least one (1) minute before any part of the batch is discharged from the drum. The drum shall be completely emptied before receiving material for the succeeding batch. The drum shall revolve at a rate of speed specified for the particular mixer used by the Contractor but not less than twelve (12) revolutions per minute. The volume of the mixed material used per batch shall not exceed the manufacturer's rated capacity of the drum in cubic feet of mixed material.

Retempering. - Retempering of mortar or concrete which has partly hardened, that is, mixing with or without additional materials or water, shall not be permitted.

Consistency. - The materials for the pavement shall be mixed with sufficient water to produce a concrete which will hold its shape when struck off with a template and so that there shall be no separation of the mortar from the coarse aggregate.

Forms. - Where forms are required, they shall be free from warp and of sufficient strength to resist springing out of shape. Wooden forms shall be not less than two (2) inch stock. Forms shall be well staked or otherwise held to the established line and grades. . Where the curb is to be constructed integrally with the pavement, the upper edge of the side forms shall conform to the top of the curb. All mortar and dirt shall be removed from forms before they are used.

Reinforcing. - The reinforcement shall have a weight of not less than twenty-eight (28) pounds per one hundred (100) square feet. The ratio of effective areas of reinforcing members at right angles to each other may vary from 1:1 to 4:1. The spacing between parallel lines of reinforcing members shall be not more than eight (8) inches. A reduction of three (3) pounds from the weight specified shall be allowed for those types of reinforcement not requiring extra metal at intersections.