Concrete Construction.

(1) 

Materials.

(a) 

Composition of Aggregate. Concrete aggregate shall consist of natural sands, gravels, crushed rock, air-cooled blast furnace slag or other inert materials having clean, strong, durable particles and shall meet the approval of the Building Inspector. Aggregate containing soft, friable, thin, flaky, elongated or laminated particles totaling more than three percent (3%) by weight or containing shale in excess of one and one-half percent (1-1/2%) or silt and crushed dust finer than No. 100 standard sieve in excess of two percent (2%) shall not be used. These percentages shall be used on the weight of the combined aggregate as used in concrete. When all three (3) groups of these injurious materials are present in the aggregate, the combined amounts shall not exceed five percent (5%) by weight, of the combined aggregate. Aggregate shall not contain strong alkali or organic material which gives a color darker than the standard colorimetric test of the American Society for Testing Materials.

(b) 

Size of Aggregate. The maximum size of the aggregate shall not be larger than one-fifth (1/5) of the narrowest dimension between forms of the member for which the concrete is to be used, not larger than three-fourths (3/4) of the minimum clear spacing between reinforcing bars, or between bars and forms. Maximum size of aggregate is defined as the clear space between the sides of the smallest square opening through which ninety-five percent (95%) by weight of the material can be passed.

(c) 

Mixing. Course aggregate and fine aggregate shall be delivered separately and mixed in the proper proportion with the cement and water on the job, except that ready mixed concrete may be used.

(d) 

Other Requirements. Concrete materials shall in no case be placed on the ground and then placed in the mixer, but shall be deposited on a material platform of wood or concrete.

	Water used in mixing concrete shall be clean and free from injurious amounts of oil, acid, alkali, organic matter or other harmful substance.
	Storage of cement and aggregate shall be in such manner as to prevent deterioration or the intrusion of foreign matter. Any materials which have been damaged shall be immediately and completely removed from the work.

(2) 

Test of Materials. On concrete or reinforced concrete work, the Building Inspector shall have the right to require the owner or his agent to make tests of the concrete from time to time to determine whether the materials and methods in use are such as to produce concrete or reinforced concrete of the quality specified for use in the design of the building or structure. The tests shall be made when ordered by the Building Inspector, by the owner or his authorized representative and no responsibility for the expense of these tests shall be attached to the City of West Allis. All such tests shall be made by competent persons approved by the Building Inspector and copies of the results shall be kept on file in the office of the Building Inspector for a period of not less than two (2) years after the acceptance of the structure. Specimens of such tests shall be taken at the place where the concrete is being deposited and shall be taken, cured and tested in accordance with the standard specifications C31-66, Part 10 and C39-66, Part 10, of the American Society for Testing Materials.

(3) 

Quality of Concrete.

(a) 

Mixing. Provisions for the design of structures embodied in this section are based on the presumption of concrete of certain strength. To produce concrete of the required strength, the proportion of the mixing water to the cement shall be accurately controlled, except that the ratios of water to cement suggested in this subsection shall not apply to gunite.

(b) 

Strength. The strengths of concrete indicated in the following table are the minimum ultimate strengths that may be expected of Portland cement concrete when using the tabulated ratios of water to cement and when the concrete is cured and tested as specified in paragraph (c), but in all cases the strength used in design shall be the ultimate measure and determining factor. Water or moisture contained in the aggregate must be included in determining the ratio of water to cement.

(c) 

Concrete Mixtures. Assumed Strengths and Quantities of Materials for Concrete Mixtures:

	Water Cement Ratio No. of gal. (U.S.) Water per sack of cement (94 lb.)	Approximate Quantities of Material per sack of cement Dry volumes of aggregate			Assumed Strength at 28 days at 70° F. lb. per sq. inch
		Cement	Sand	Course Aggregate
	8 1/4	1	3	5	1500
	7 1/2	1	2 1/2	4	2000
	6 3/4	1	2	3 1/2	2500
	6	1	2	3	3000
	5	1	1 3/4	2 1/2	3750
	4	1	1 1/2	2	5000

	All of the concrete shall be governed by the foregoing table and the approximate quantities of materials as listed shall serve as a basis for estimating and designing concrete mixtures for the various strengths of concrete as specified.
	In no case shall the quantities of aggregates be increased so that the sum of the separate volumes of aggregate actually used exceed the sum of the separate volumes contained in the aforesaid table. The amount of mixing water used shall at all times be held to the smallest quantity which will produce a workable mixture which will not segregate nor be honeycombed.

(d) 

Structural Drawings. All structural drawings and plans submitted for approval shall show the proposed strength of concrete to be used and the water cement ratio assumed to produce that strength, but the concrete produced and used shall develop a strength in twenty-eight (28) days not less than that shown on the plans and assumed in the design.

(e) 

American Concrete Institute Regulations. Questions of concrete used and design not covered by this Code shall be governed by the building regulations for reinforced concrete of the American Concrete Institute. (ACI-1318-63.)

(4) 

Proportions.

(a) 

The proportions of aggregate to cement for concrete of any water cement ratio shall be such as to produce concrete that will work readily into the corners and angles of the form and around the reinforcement without excessive puddling or spading and without permitting free water to collect on the surface. The proportion of coarse to fine aggregate shall stay within the following limits:

	Maximum Size of Coarse Aggregate Inches	Minimum	Ratio of Coarse to Fine Aggregate on Basis of Dry and Rodded Volumes Maximum
	3/8	0.4	0.8
	3/4	0.6	1.5
	1 and over	1.0	2.0

(b) 

The amount of coarse aggregate shall not be such as to produce harshness in placing or honeycombing in the structure.

(c) 

When forms are removed, the faces and corners of the members shall be smooth throughout.

(d) 

Admixtures of lime or finely pulverized inert materials may be added, but not in excess of six percent (6%) by volume of the cement used.

(5) 

Control of Proportions. The methods of measuring concrete materials shall be such that the proportions of water to cement can be accurately controlled during the progress of the work and easily checked at any time by the Building Inspector or his authorized representative. A tolerance of one-fourth (1/4) gallon of water per sack of cement in any batch of concrete will be allowed, provided that the average of any ten (10) consecutive batches does not show a water content greater than that shown in the table and on plans as specified in this section.

(6) 

Mixing and Placing Concrete.

(a) 

Mixing. The concrete shall be mixed until there is a uniform distribution of the materials and the mass is uniform in color and homogeneous. In machine mixing, only batch mixers shall be used. Each batch shall be mixed not less than one minute after all the materials are in the mixer and must be completely discharged before the mixer is recharged. Machine mixers shall have a peripheral speed of approximately two hundred (200) feet per minute.

(b) 

Cleaning Forms and Equipment. Before concrete is placed, all equipment for mixing and transporting the concrete shall be cleaned, all debris shall be removed from the spaces within the forms to be occupied by the concrete, forms shall be thoroughly wetted (except in freezing weather) or oiled, and masonry that will be in contact with concrete shall be drenched (except in freezing weather). Reinforcements shall be thoroughly cleaned and held securely in position. Concrete shall not be placed until the forms and reinforcement shall have been inspected and accepted by the Building Inspector.

(c) 

Removing Water from Excavations. Water shall be removed from excavations before concrete is deposited, unless otherwise directed by the Building Inspector. Any flow of water into an excavation shall be diverted by other approved methods which will avoid washing the freshly deposited concrete. Water vent pipes and drains shall be filled by gravel, crushed rock or otherwise, after the concrete has thoroughly hardened.

(d) 

Transporting Concrete. Concrete shall be handled from the mixer to the place of final deposit as rapidly as practicable by methods which shall prevent the separation or loss of the ingredients. It shall be deposited as nearly as practicable in the final position to avoid rehandling or flowing. Under no circumstances shall concrete that has attained its initial set be used.

(e) 

Placing. Concrete shall be thoroughly compacted with suitable tools. When necessary, openings shall be provided in the forms to permit the placing of concrete in such a manner as to avoid accumulations of hardened concrete on the forms or reinforcing bars. The concrete shall be thoroughly worked around the reinforcement.

(f) 

Curing. Exposed surfaces of concrete shall be kept moist for a period of at least seven (7) days after being deposited.

(g) 

Depositing in Cold Weather. When depositing concrete at freezing temperatures, the concrete shall be maintained at a temperature of at least fifty degrees Fahrenheit (50° F.), but not more than one hundred twenty degrees Fahrenheit (120° F.), the concrete shall be maintained at a temperature of not less than fifty degrees Fahrenheit (50° F.), for not less than seventy-two (72) hours after placing. When necessary, concrete materials shall be heated before mixing. Dependence shall not be placed on salt or other chemicals for the prevention of freezing.

(h) 

Bonding Fresh and Hardened Concrete. Before new concrete is deposited on or against concrete which has set, the forms shall be retightened, the surface of the set concrete shall be roughened, cleaned of foreign matter and laitance and thoroughly wetted but not saturated. The cleaned and wetted surface of the hardened concrete, including vertical and inclined surfaces, shall first be slushed with a coating of 1:2 cement mortar against which the new concrete shall be placed before the mortar has attained its initial set.

(7) 

Forms and Details of Construction.

(a) 

Design of Forms. Forms shall conform to the shape, lines and dimensions of the member as called for on the plans and shall be sustained and sufficiently tight to prevent leakage of mortar. They shall be properly braced or tied together so as to maintain position and shape. If adequate foundation for shores cannot be secured, trussed supports shall be provided.

Forms shall be so designed, braced and aligned as to keep the finished columns of the building plumb with not more than an error of one to one thousand (1,000) in the height of the exterior columns, or of columns adjacent to elevators. Temporary openings shall be provided at the base of column and wall forms, and at other points where necessary to facilitate cleaning and inspection.

(b) 

Removal of Forms. Forms shall not be disturbed until the concrete has hardened sufficiently to permit their removal with safety. Shoring shall not be removed until the member has acquired sufficient strength to support safely its own weight and the load upon it. Members subject to additional loads during the construction shall be adequately shored to support both the members and construction loads in a manner that will protect the member from damage.

(c) 

Cleaning and Bonding Reinforcements. Metal reinforcement, before being placed, shall be thoroughly cleaned of loose mill and rust scale and of other coating that will destroy or reduce the bond. Reinforcements shall be carefully formed to the dimensions indicated on the plans. Cold bonds shall be made around a point having a diameter of not less than four (4) times the least dimension of the bar.

Metal reinforcement shall not be bent, straightened or handled in a manner that will injure the material. Bars with kinks or bends not shown on the plans shall not be used. Heating of reinforcement will be permitted only when approved by the Building Inspector.

(d) 

Placing Reinforcement. Metal reinforcement shall be accurately placed and secured and shall be supported by chairs, spaces or hangers. The minimum clear distance between parallel bars shall be one and one-half (1-1/2) times the diameter for round bars or one and one-half (1-1/2) times the diagonal for square bars. The minimum clear distance between bars and forms shall be the diameter of round bars and the diagonal of square bars. If the ends of bars are anchored, the clear spacing may be made equal to the diameter of round bars or to the diagonal of square bars, but in no case shall the spacing between bars be less than one inch, nor less than one and one-third (1-1/3) times, the maximum size of the coarse aggregate. The main longitudinal slab steel shall be spaced not more than two and one-half (2-1/2) times the slab thickness. Not less than two-tenths of one percent of transverse steel shall be provided. (Note: For example, consider a slab eight (8) inches thick. A strip of twelve (12) inches wide has a cross-sectional area of eight (8) times twelve (12), or ninety-six (96) square inches. Two-tenths of one percent is 0.002 x 96 or 0.192 square inches of steel required for every foot width of slab. A one-half (1/2) inch round bar has a cross-section area of 0.1963 square inches. Therefore, a slab eight (8) inches thick shall have a one-half (1/2) inch round rod every twelve (12) inches placed at right angles to the main reinforcement.)

(e) 

Reinforcement Splices and Offsets. In slabs, beams and girders, splices or reinforcement shall not be made at points of maximum stress without the approval of the Building Inspector. Splices, where permitted, shall provide sufficient lap to transfer the stress between bars by bond and sheer. In such splices, the bars shall be spaced at the minimum distance specified in the preceding paragraph.

Where changes in the cross-section of a compression member occur, the longitudinal bars shall be sloped for the full length of the member or offset in a region where lateral support is afforded. Where offset, the slope of the inclined portion from the axis of the member shall not be more than one in six (6).

(f) 

Construction Joints. Joints not indicated on the plans shall be so made and located as to least impair the strength of the completed structure. Where a joint is to be made, any excess water and laitance shall be removed from the surface after concrete is deposited. Before depositing of concrete is resumed, the hardened surface shall be treated as specified in paragraph (h) of subsection (6) of this section.

	At least one hour must elapse after concrete is deposited in the columns or walls before depositing in beams, girders or slabs supported thereon.
	Haunches and column capitals shall be considered as part of, and to act continuous with, the floor.
	Construction joints in floors shall be located near the middle spans of slabs, beams or girders, unless a beam intersects a girder at this point, in which case the joints in the girder shall be offset a distance equal to twice the width of the beam. Provision shall be made for shear by use of reinforcement inclined in both directions across the joint.