**CONSTRUCTION SPECIFICATION**

**[204. CONCRETE MASONRY UNITS]{.underline}**

1.  **[SCOPE]{.underline}**

The work shall consist of furnishing, placing, and finishing concrete
masonry units (CMU's) as required to build the structures described in
Section 15 of this specification.

2.  **[MATERIALS]{.underline}**

Concrete blocks shall be 8-inch hollow load bearing concrete masonry
units, Grade N, Type II units conforming to ASTM C90-81.

Masonry units shall have been air-dried for not less than 28 days prior
to being placed in the structure. Wetting of the block units shall not
be permitted.

# Mortar shall conform to the requirements of ASTM C270-89 or shall be proportioned based on laboratory or field experience to provide the required strength and workability.

> [Grout]{.underline} shall be mixed in the ratio, by volume, of one
> part Portland cement, up to 1/10 part lime, 2-1/4 parts minimum to 3
> parts maximum damp loose sand and up to 2 parts coarse aggregate. The
> grout shall be of a fluid consistency suitable for placing without
> segregation.
>
> [Cement]{.underline} shall conform to ASTM C150-86 Type I, IA, II, or
> IIA.
>
> [Hydrated Lime]{.underline} shall conform to ASTM C150-86 Type II.
>
> [Aggregate]{.underline} shall be clean, hard and well graded, free of
> injurious amounts of dust, lumps, shale alkali, surface coatings, and
> organic matter.
>
> [Admixtures]{.underline}, such as fly ash or other flowability
> improving and water retention agents, may be used in the grout mix.
>
> [Water]{.underline} used in mixing and curing concrete shall be clean
> and free from injurious amounts of oil, salt, acid, alkali, organic
> matter or other deleterious substances.

3.  **[WORKMANSHIP]{.underline}**

All masonry shall be laid in running bond, true, level, plumb and neatly
finished in accordance with the dimensions shown on the drawings.

There shall be no visible grout or mortar stain on the finished interior
or exterior wall surfaces.

4.  **[INSPECTION]{.underline}**

The Contracting Officer's Technical Representative shall have free entry
to the proper facilities to inspect and sample the units at the place of
manufacture from the lots ready for delivery. Sampling and testing of
units shall be conducted in accordance with ASTM C140. Total linear
drying shrinkage shall be based on tests of concrete masonry units made
with the same materials, concrete mix design, manufacturing process, and
curing methods, conducted in accordance with ATSM C426 and not more than
24 months prior to delivery.

5.  **[HANDLING OF CONCRETE MASONRY UNITS]{.underline}**

Materials shall be stockpiled and batched by methods that will prevent
cracking, chipping and breaking of the concrete masonry units. CMU's are
to be stacked to a height of eight-block layers maximum. CMU's shall not
be stored on the ground and shall be protected from mud, dirt, and other
contaminants.

> Five percent of a shipment containing chips not larger than 1 in.
> (25.4 mm) in any dimension, or cracks not wider than 0.02 in (0.5 mm)
> and not longer than 25% of the nominal height of the unit is
> permitted.

6.  **[MIXING OF MORTAR AND GROUT]{.underline}**

After all ingredients are in the batch mixer, they shall be mechanically
mixed for not less than three minutes. Hand mixing may be used when
approved by the Engineer.

7.  **[MORTAR]{.underline}**

The starting joint on foundations shall be laid with full mortar
coverage on the bed joint, except that the area where grout occurs shall
be kept free from significant accumulations of mortar so that the grout
will contact the foundation.

Allow mortar joints to stiffen to "thumbprint hardness" before tooling.
All tooling shall be done with a tool that compacts the mortar, pressing
the excess mortar out of the joint rather than dragging it out. Remove
mortar protrusions or droppings from the face of the masonry. Allow
mortar to achieve an initial set prior to removal to avoid smearing
mortar into masonry, but do not leave mortar droppings on masonry for an
extended time.

Exterior and interior wall surfaces shall have joints tooled with a
round or V-shaped bar to produce a dense, slightly concave surface well
bonded to the block at the edges.

The horizontal and vertical mortar joints shall be 3/8" thick with full
mortar coverage on the face shells and on the webs.

Mortar may be retempered with water as required to maintain proper
plasticity. Retempering on mortar boards shall be done only by adding
water within a basin formed within the mortar and the mortar reworked
into the water. Any mortar, which is unused after 1-1/2 hours from the
initial mixing time, shall be discarded.

8.  **[GROUT]{.underline}**

The coarse aggregate used in grout shall comply with the following:

> [Size of Smallest Space to be Grouted]{.underline} [Maximum Coarse
> Aggregate Size]{.underline}
>
> 3/4-inch wide none
>
> 3-inches wide 1/2 inch
>
> 4-inches wide 3/4 inch

Reinforcing steel shall be secured in place and inspected before
grouting starts.

> There shall be no bridging or honeycombing of the grout. Slump of the
> grout shall be no greater than 11 inches. The grout is to be placed in
> lifts not to exceed 5 feet.
>
> Grout shall be placed within 1.5 hours after water is first added to
> the batch. Grout not used within the allotted time is to be discarded.
>
> Significant accumulations of detrimental mortar droppings shall be
> removed from the grout space. No grout shall be placed until the NRCS
> Technical Representative has inspected the grout space, and approved
> it for grouting.
>
> All grout shall be rodded or vibrated into place. Vertical cells to be
> filled shall have accurate alignment to maintain a continuous
> unobstructed cell area not less than 2" by 3".
>
> Grout of beams over openings shall be done in one continuous
> operation.
>
> Anchor bolts cast in walls shall be solidly grouted in place.

9.  **[PREPARATION OF SUBGRADE]{.underline}**

Prior to placement of concrete masonry units, subgrade shall be free of
chips, sawdust, debris, water, extraneous oil, mortar, or other harmful
substances. Earth surfaces shall be firm and damp. Placement of concrete
masonry units on mud, dried earth or un-compacted fill will not be
permitted.

> Items to be embedded in or placed on the concrete shall be positioned
> accurately and anchored firmly. The top surface of the concrete
> foundation shall be clean, free of laitance and the aggregate shall be
> exposed, but not undercut, before the initial masonry course is
> placed.

10. **[PLACING]{.underline}**

Concrete masonry units shall not be placed until the subgrade, forms,
steel reinforcement, and embedded items have been inspected and
approved. The Contractor shall give reasonable notice to the Engineer
each time he intends to place concrete masonry units. Such notice shall
provide sufficient time for the Engineer to inspect the subgrade, steel
reinforcement and other preparations for compliance with the
specifications. Other preparations include but are not limited to the
finishing, schedule of work, or workforce. Deficiencies are to be
corrected before concrete masonry units are to be placed.

11. **[CONSTRUCTION]{.underline}**

Excessive mortar smears and droppings shall be avoided.

Prevent rain from entering walls by covering the tops of walls at the
end of each working day. Within a day or two of that a smear occurs, use
a stiff fiber brush and water (with or without sand) to scrub mortar
smears off the masonry surface.

All walls over 8 feet shall be braced. If conditions are or expected to
be excessively windy, the contractor is responsible for adequate
bracing, irrespective of wall height.

12. **[FINISHING]{.underline}**

Cleaning of the CMU's shall only be by scrubbing or as suggested by the
manufacturer. Scrubbing efforts shall be focused on the unit surfaces,
not the mortar joints. Pressure water spraying and acid cleaning are not
acceptable.

Masonry walls shall be protected from saturation or other factors that
may cause efflorescence during construction and until they are weather
proofed. If efflorescence occurs prior to weather proofing, it shall be
removed.

Over cleaning of masonry shall always be avoided.

13. **[REMOVAL AND REPLACEMENT OR REPAIR]{.underline}**

When concrete masonry units are damaged or otherwise defective, the
Contractor shall remove and replace the structure or structural member
containing the defective concrete masonry units or, where feasible,
correct or repair the defective parts. The Engineer will determine the
required extent of removal, replacement or repair. Prior to starting
repair work the Contractor shall obtain the Engineer's approval of his
plan for effecting the repair. The Contractor shall perform all repair
work in the presence of the Engineer.

14. **[MEASUREMENT AND PAYMENT]{.underline}**

[Method 1]{.underline} For items of work, for which specific unit prices
are established in the contract, concrete masonry units installed will
be measured to the nearest unit. Payment for each item of concrete
masonry units will be made at the contract unit price for that item.
Such payment will constitute full compensation for all labor, materials,
equipment, transportation, tools, falsework, bracing and all other items
necessary and incidental to the completion of the work, except items
listed for payment elsewhere in the contract.

[Method 2]{.underline} Payment for each item of concrete masonry units
will be made at the lump sum established in the contract. Such payment
will constitute full compensation for all labor, materials, equipment,
transportation, tools, falsework, bracing, and all other items necessary
and incidental to the completion of the work, except items listed for
payment elsewhere in the contract.

> [All Methods]{.underline} Compensation for any item of work described
> in the contract but not listed in the bid schedule will be included in
> the payment for the item of work to which it is made subsidiary. Such
> items and the items to which they are made subsidiary are identified
> in Section 15 of this specification.

15. **[ITEMS OF WORK AND CONSTRUCTION DETAILS]{.underline}**

> Items of work to be performed with this specification and the
> construction details therefore are:

a.  **[Bid Item 4, Concrete Masonry Units (CMU's)]{.underline}**

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(1) This item shall consist of the masonry work required to construct
    the storage building and columns as shown on the drawings.

(2) All CMU's shall be laid with a 3/8" thick mortar bed between block
    layers.

(3) All cells of the CMU's shall be filled with 3000-psi concrete grout.

(4) In Section 15, [Measurement and Payment]{.underline}, will be by
    Method 2.

(5) The item of work subsidiary to this bid items is:

## Steel Reinforcement, Construction Specification 34