UNITED STATES DEPARTMENT OF AGRICULTURE

NATURAL RESOURCES CONSERVATION SERVICE

OREGON

[CONSTRUCTION SPECIFICATION]{.underline}

[CS-42 REINFORCED CONCRETE FOR MINOR STRUCTURES]{.underline}

42.1 [SCOPE]{.underline}

The work shall consist of proportioning, forming, placing, finishing,
and curing Portland cement concrete for minor structures. A minor
structure is defined as one of low hazard where strength control is not
critical for function and safety.

The structures shall be constructed to the line and grades as shown in
the plan.

42.2 MATERIALS

Cement shall be Type II or Type IIA Portland cement. Cement that is
partially hydrated or otherwise damaged shall not be used.

Concrete aggregate is defined in Material Specification, MS-201. Fine
aggregate shall be between 35 and 45 percent and course aggregate shall
be between 55 and 65 percent of the total aggregate volume by weight.
The aggregate shall not contain more than 1 percent clay lumps and a
total of 4 percent of material smaller than the 200 sieve.

Maximum size of the course aggregate shall not exceed:

1 inch - Concrete thickness of 4 inches or less

1-1/2 inch - Concrete thickness of 4 inches or more

Reinforcing steel shall be woven wire fabric or deformed steel bars as
described in Material Specification MS 213, Steel Reinforcement.

Water shall be of a potable quality free from harmful chemicals.

42.3 [DESIGN OF CONCRETE MIX]{.underline}

The person in charge of construction shall be responsible for designing
a high quality concrete mix conforming to this specification. The
concrete mix shall be approved by the NRCS technician prior to
placement.

The mix shall contain no more than 6 gallons of water per 94 pound bag
of cement, and at least 6 bags of cement per cubic yard of concrete.

The air entrainment shall be between 4 and 7 percent by volume, and the
slump shall be between 3 and 5 inches.

The following table is a guide for developing a satisfactory mix
intended to produce approximately 3000 PSI compressive strength for air
entrained concrete:

Max. Size Gal. Water Cement Pounds Fine Pounds Coarse

Aggregate per sack per CY Aggregate per Aggregate per

Inches of cement Sacks Sack Cement Sack Cement

1 6.0 6.0 190-200 300-310

1-1/2 6.0 6.0 180-190 330-340

Measurement of materials shall be by weight where suitable scales are
available. Volume measurements may be used provided volume-weight
relationships are carefully determined. Admixtures including calcium
chloride or antifreeze compounds shall not be used.

42.4 [FORMS]{.underline}

Forms shall be made of wood, plywood, or metal. The form surfaces are to
be clean and free from holes and other irregularities. The type, size,
shape, quality and strength of forms will be subject to approval by the
NRCS technician. The forms shall be moist when the concrete is placed.
Forms shall be mortar tight and non-yielding. All form work shall be in
place for at least 24 hours after concrete placement.

Metal ties that break off below the surface of the concrete shall have
removable cones that permit their removal without damage to the
concrete.

42.5 [REINFORCING STEEL]{.underline}

The reinforcement shall be the size and grade shown on the drawings and
securely fastened in place to prevent movement during placement of the
concrete. The reinforcing steel in slabs on grade shall be supported on
blocks or chairs. All blocks shall have a strength equal to or greater
than the 28-day compressive strength of the concrete.

42.6 [PLACING CONCRETE]{.underline}

**[The NRCS technician shall be notified a minimum of 24 hours prior to
the placement of concrete to inspect the reinforcing steel, forms,
subgrade, preparation for curing, and vibrating
equipment.]{.underline}**

Concrete shall be placed in final position within one and one-half hours
after mixing with cement. Concrete may be consolidated by either hand
spading and tamping or mechanical vibration.

All concrete placed on earth shall be placed on clean, damp surface,
free of frost, ice, or running water.

Concrete shall not be dropped more than 5 feet vertically unless
suitable equipment is used to prevent segregation.

Uniformed exposed surfaces in the completed work shall have a wood float
or broomed finish. Concrete edges shall be chamfered 3/4 inch or
finished with molding tools.

42.7 [CURING CONCRETE]{.underline}

The air temperature shall be between 40 and 90^o^F. During the curing
period, the concrete shall be kept moist or covered for at least 7 days
after placement.

An approved curing compound may be used provided it is applied by
pressure sprayer at a uniform rate of not less than 150 sq. ft per
gallon.

42.8 [DEFECTIVE CONCRETE]{.underline}

Honeycombed areas and other voids in concrete will be promptly repaired
with mortar patching immediately upon discovery.

Concrete subjected to damage and/or other violations of this
specification will be rejected.

42.9 [DELIVERY TICKETS]{.underline}

The delivery tickets shall identify the mix delivered to the site and
all ingredients in the mix by weight or volume. If additional water is
added at the job site it shall be identified.

A copy of the delivery ticket for each truckload of ready mix concrete
shall be available for review by the NRCS technician.

42.10 [ACCEPTANCE]{.underline}

The acceptance of concrete made under this specification will depend
upon adherence to the procedures set forth herein and the appearance of
the finished structure.

11. [ITEMS OF WORK AND CONSTRUCTION DETAILS FOR THIS
    PROJECT]{.underline}