The cement used shall be an established brand of Portland Cement, which shall meet all the requirements of the Standard Specifications for Portland Cement of the American Society for Testing Materials, as adopted August 16, 1909, such tests being made in accordance with the methods prescribed by the Committee on Uniform Tests of Cement of the American Society of Civil Engineers adopted January 21, 1903, with all subsequent amendments thereto, or to such tests as the Engineer may make.

Contractors are advised that in the absence of adverse reasons, cement will be accepted upon the satisfactory passing of the tests for specific gravity, fineness, time of setting and the seven-day tensile tests, but in the event of failure or unsatisfactory performance will be held for the full twenty-eight (28) day period.

The cement shall be delivered, in suitable packages with the brand and name of the manufacturer plainly marked thereon.

The Contractor shall keep in store a sufficient quantity of cement to allow time for the twenty-eight ('28) day tests to be made without delay to the work. The Contractor shall notify the Engineer when deliveries are to be made a sufficient time in advance so as to allow the Engineer to have a representative present to sample cement; or he shall re-handle the cement in the store-house for the purpose of obtaining samples as directed by the Engineer. The cement shall be so stored as to make it convenient to label or identify each lot in case of its rejection or the necessity for further tests. Cement kept in storage several months may be subjected to repeated tests, if required.

Should the Contractor so elect, he may secure cement from previously tested lots in the stock of a supply dealer, provided the packages are properly labeled for identification, or he may furnish cement which has been tested at the mill and certified to by a reputable testing bureau acceptable to the Engineer, provided the cement is delivered under seal. The Engineer reserves the right to retest such cement and reject the same, if it fails to pass the required tests.

The use of cement which has not been tested or which has failed to pass the above tests is prohibited.

Sand used for concrete shall be clean and sharp, free from organic matter, and shall not contain more than five (5) per cent by volume of clay and loam and no clay shall be artificially added. and all material shall be acceptable to the Engineer. The sand shall be a well graded material, containing no particles larger than one-quarter ( 1/4) inch in diameter and not more than three (3) per cent of fine material shall pass a standard sieve with one hundred (100) meshes to the inch.

Portland Cement and sand mixed in the proportion of 1 to 3 to form a mortar, shall show a tensile strength of at least ninety (90) per cent of the tensile strength of 1 to 3 mortar made up of the same cement and standard Ottawa sand.

Coarse Aggregate for concrete shall consist of crushed stone or clean washed gravel; whether of crushed stone or of gravel, it shall be free from seamy or scaly material, shale, soapstone, loam or dirt, and must be substantially equal in hardness and durability to sound native blue limestone.

All coarse aggregate shall be well graded material, with the proper proportions of the various size pieces varying from the minimum diameter of one-quarter (1/4) inch in all cases, to the maximum diameter allowable for the different classes of concrete and the varying conditions of the work. In every case the coarse aggregate shall be thoroughly screened free from all material which will pass a wire sieve of one-quarter (1/4) inch square holes. The maximum size will vary from three-quarters (3/4) inch to one and one-half (1 1/2) inch for Class 1 concrete; from one (1) inch to two and one-half (2 1/2) inches for Class 2 and Class 3 concrete. The maximum size to be used for each' particular piece of work will be specially specified in each case.

Water used in the mixing of the concrete or mortar or for wetting concrete or brick shall be clean, and free from oil, acid, strong alkalies, vegetable matter, or sewage.

Classification. - Concrete will be divided into three classes, which will differ in the proportions by volume of cement, sand and stone or gravel as follows:

Class 1. - Consisting of one (1) part cement, two (2) parts sand and four (4) parts stone or gravel.

Class 2. - Consisting of one (1) part cement, two and one-half (2 1/2) parts sand and five (5) parts stone or gravel.

Class 3. - Consisting of one (1) part cement, three (3) parts sand and six (6) parts stone or gravel.

Proportioning. - The concrete shall be composed of Portland cement, sand and crushed stone or gravel, mixed with clean water in the proportions specified. All proportioning of materials must be done by means of a carefully gauged wheelbarrow or other apparatus of capacity which shall be determined by the Engineer. The method of measuring shall be one which will insure uniformity at all times in all measurements of proportions. A sack of cement weighing not less than 94 pounds shall be considered to have a volume of one (1) cubic foot.

Mixing. - The ingredients shall be thoroughly mixed in approved batch mixers. The use of continuous mixers will not be allowed.

Concrete is not to be mixed by hand, except by special permission, and then only on watertight platforms. The batches so mixed shall not exceed one cubic yard each. The measured cement shall be spread over the proper amount of sand on the platform, and shall be thoroughly mixed dry until an even color. Sufficient water shall then be added while this mixing is continued until a mortar of proper consistency and uniform texture is produced. The measured quantity of stone, having been previously wet, shall then be distributed evenly over the mortar and the whole turned over three (3) times, during which operation more water will be added by sprinkling until of the proper consistency.

Retempering, or mixing additional water with mortar or concrete that has partially set, will not be permitted.

Consistency. - The materials shall, unless otherwise ordered, be mixed wet enough to produce concrete of a consistency which will flush readily under light tamping, which can be handled without causing a separation of the coarse aggregates from the mortar and which will not creep or sag out of place when deposited and lightly tamped.

Placing and Finish. - Immediately after mixing, the concrete shall be transported rapidly without loss of mortar to the place of final deposit, and for mass work shall be spread in approximately six (6) inch layers. The use of concrete that shall have undergone initial set will not be permitted.

In placing, all concrete must be joggled or tamped sufficiently to expel air and to make the mortar flush to the surface. Where forms are used, the concrete forming exposed faces shall be spaded sufficiently to prevent honeycombing.

Working or walking on green concrete will not be allowed. Such concrete shall be sprinkled or protected from the weather if deemed necessary. Concreting in freezing weather will not be allowed without special permit therefor.

Special finishes for concrete surfaces will be specified as required.

For Pavement Base. - The top of the concrete must be brought, by means of screeds or templates, to a grade which shall) not depart more than one-quarter

(1/4) inch from a grade exactly parallel and at the proper depth below the finished surface of the pavement.

In the case of asphalt and bitulithic pavements the surface of the concrete shall be roughened by tampers with lugs or other approved methods to obviate the liability of shoving of the pavement.

No hauling of any kind will be allowed on the concrete base until eight days after laying or longer, if the Engineer so directs. In the case of brick, wood block and granite streets, the paving may proceed after the elapse of such period, not less than 72 hours, as the Engineer may prescribe, but the sand and cement for the cushion must be got onto the work without hauling over the concrete.

Where street railway tracks are being laid or relaid, the Street Railway Company will furnish and place concrete up to the required sub-grade of the street. In cases where the old concrete base is being re-concreted the Street Railway Company will bring the concrete to the top of the ties.

Concreting Over Old Base. - This applies only to such work where it is the intent of the City to utilize for the proposed new pavement, the existing concrete base with such additional concrete applied, as specified below. Such intent will be stated in a synopsis of the proposed work given elsewhere in these specifications.

In these cases, the existing concrete base will not be disturbed except where necessary to lay drain pipe, water pipe, conduits, street railway tracks, set new curbs or reset old curbs and perform any other underground work ordered by the City.

Where new tracks are to be laid the Traction Company will, after the installation of their tracks, bring their concrete level with top of the ties. All other trenches and openings made in the old concrete base shall be re-concreted by the Contractor, who shall also apply a layer of concrete to the entire area between curb sufficient to form a paving base --------- inches below and parallel to the proposed finished surface of the roadway, but before placing the concrete the Contractor shall see that all cuts through the old base are dug out to the full depth of six (6) inches and to the full size, and shall thoroughly clean off the old concrete base by the use of brooms and hose.

Concrete placed by the Contractor will be measured and paid for in accordance with the following:

1st - For re-concreting of trenches over sewers, drain pipes and water pipes laid under this contract; allowance will be made for the full widths and lengths of the trenches by a depth of six (6) inches. This concrete will be paid for at the price bid under Item ------.

2nd - Where new curbs are set or old curbs are reset, allowance wilt be made for a width of six (6) inches by a depth of six (6) inches.. This concrete will be paid for at the price bid under Item ------.

3rd - Where larger radii corners are installed or roadway otherwise widened, allowance will be made for actual widened area by a. depth of --------- (------) inches. This concrete also will be paid for at the price bid under Item

4th - For cuts other than those above specified, allowance will be made for actual area by a depth of six (6) inches, but this concrete will not be included in the work to be paid for under this contract, but will be paid for directly by the Street and Sewer Repair Department at the uniform price of $6.00 per cubic yard.

5th - In addition to the above the Contractor will be paid at the price bid under Item ------ for a layer of concrete over the entire pavement area of the depth necessary for the required paving surface, as previously specified.

Payment. - The amount of concrete to be paid for will be that actually placed in accordance with orders. The price per cublic yard will include all forms, work and material necessary or incidental to furnishing and placing the finished concrete as specified.