Geowestern, Inc.'s Earth Retention Products

CONSTRUCTION AND MATERIAL SPECIFICATIONS

FOR MODULAR CONCRETE BLOCK RETAINING WALLS WITH GEOSYNTHETIC REINFORCED SOIL

Download these Specifications: ama-specific.doc (19KB)

Revised: December, 1996

These guidelines have been developed to aid in the preparation of construction and material specifications for a specific project. These guidelines should be modified to:

Incorporate Specific Geosynthetic Reinforcement Criteria
Incorporate Any Special Project Requirements
To Delete Any Unnecessary Requirements
To Provide Format And Wording Consistent With Other Project Specifications
To Provide Consistency With Construction Drawings

SECTION 1. SCOPE

1.1	These Specifications set out requirements for the design and construction of the Amastone Retaining Wall System. Contract work consists of furnishing materials and installation of Amastone units in accordance with details shown on the project plan.
1.2	Bidders attention is called to the fact that Amastone modular block retaining wall units are the basis for this Specification. Other modular block wall systems may require alterations to the project design.
1.3	Amastone Retaining Wall System Component Details are incorporated into and made part of this Specification.
1.4	These specifications do not purport to be a full engineering analysis of the Amastone Retaining Wall System. Such an analysis can be performed by a qualified engineer as required.

SECTION 2. MATERIALS

2.1	AMASTONE BLOCKS
2.1-1	Individual Amastone units shall be designed so that they can be subject to handling without being damaged.
2.1-2	DESIGN MIX
	A qualified materials laboratory shall prepare a design mix specifying relative quantities of cement, water, aggregate, and admixtures necessary to obtain required minimum concrete strength and durability. This mix design shall be available from manufacturer at all times.
	A sample mix design is as follows: Unit weight of block - 59 lbs. (approx.) Aggregate - sand & gravel Aggregate P.M. - 3.70
	Batch Design Sand - 4,100 lb. Gravel - 3,270 lb. Portland - 700 lb.
	Cement / Aggregate Ratio 1 part cement to 10.5 aggregate
	Add-mixture - Addiment Block W - 84 oz
	Amastone Standard units shall have a minimum 28 day compressive strength of 3,000 psi in accordance with AASHTO. The concrete shall have adequate protection for freezing and thawing with a maximum moisture absorption rate of 5.50%.

SECTION 3. CONSTRUCTION

3.1	ACCEPTANCE OF UNITS ON SITE
3.1-1	All units shall be subject to final acceptance on site. Where the contract includes the construction of the wall, it shall be the Contractor’s responsibility to ensure that all units are erected in an undamaged condition.
3.1-2	The Project Engineer’s representative may carry out such tests or measurements as deemed necessary to be satisfied that the units delivered to the site are equal in quality to the approved specification and design. Where the tests are of a destructive nature and the units prove acceptable, the cost of the units as delivered to the site of testing will be charged to the contract.
3.1-3	Units which do not satisfy the material requirements of the dimensions and tolerances of this specification will be liable to rejection.
3.1-4	Units with cracks or other imperfections which, in the opinion of the Project Engineer, are unacceptable shall not be placed in the wall.
3.1-5	Rejected units shall be removed from the site and shall be replaced with acceptable units at no extra cost to the contract.
3.2	WALL LAYOUT
3.2-1	Amastone Retaining Wall construction shall be in reasonably close conformity to the lines, grades, design and dimensions shown on the plans and as established by the Project Engineer by means of surveyed staking.
3.2-2	The Contractor shall obtain the Project Engineer’s approval of wall alignment before placing granular bedding, concrete leveling pad or placing any Amastone units.
3.3	EXCAVATION
3.3-1	A bench excavation to sound material shall be made for the base of the wall. Unless shown otherwise on the project plans, the benches shall be horizontal in the line of the wall. The depth of the excavation shall be a minimum of 1.0 feet below the proposed finished ground level at the front face of the wall, or as shown on the project plans.
3.3-2	Contractor shall call for and obtain the Soils Engineer’s inspection and approval of the excavated foundation prior to casting any concrete or placing any Amastone units.
3.3-3	Finished base excavation to within 0.5 inches of the base elevation and shall include vertical steps in 8" increments where plans indicate base of wall is to step.
3.4	GRANULAR BEDDING
3.4-1	Unless specified by the Project Engineer or project plans, a concrete leveling pad is not required.
3.4-2	After verification by the Soils Engineer of base soil adequacy, a granular bed may be utilized below the base course of Amastone units. Before placement of the granular bedding, It is recommended that the base soil be compacted to a minimum 95 percent of Standard Proctor. It is recommended that a minimum of 4 inches of 3/4 inch crushed rock be used for the granular bedding. The wall is initiated by placing the first course of Amastone units directly onto granular bedding.
3.4-3	It is essential that the granular bedding be protected. Ensure that the Amastone retaining wall is buried at least 1.0 feet below the proposed finished ground level at the front face of the wall, or as directed by the project engineer.
3.5	CONCRETE LEVELING PAD
3.5-1	For portions of the wall where the bearing pressures exceed 2,500 psf, a cast-in-place concrete leveling pad with a minimum thickness of 3 1/2 inches and a minimum width of 24 inches may be constructed. This pad shall be placed so that the wall is constructed centrally to the pad. The leveling pad may require rebar or fiber mesh reinforcement for higher walls that exert bearing pressures greater than 4,000 psf. Concrete leveling pads shall be manufactured and placed in accordance with ASTMC and shall have a minimum compressive strength of 3,000 psi at 28 days.
3.6	AMASTONE BLOCK PLACEMENT
3.6-1	The units shall be handled and placed in such a manner that they are not cracked or chipped and so that no damage is caused to the seating areas.
3.6-2	The first course of units shall be placed side by side on the granular bedding (3/4" crushed rock) or concrete leveling pad. Care shall be taken in the placement to ensure firm bedding against the base.
3.6-3	The units in the base course shall be checked for level and alignment.
3.6-4	The units shall be placed in a uniform pattern as shown on the drawings or as approved by the Project Engineer.
3.6-5	Where required by project plans, steel rebar may be placed in the dowel notch at the back of the Amastone units in such a way that the steel spans three blocks and that the geosynthetic reinforcement interlocks with the steel rebar. The steel shall be #4, grade 40 rebar and a minimum of 24 inches in length.
3.6-6	When capstones are used on the top course of the wall, they shall be epoxied in place on a clean, dry surface.
3.7	GEOSYNTHETIC REINFORCEMENT
3.7-1	Geosynthetic Reinforcement shall be the type shown on the drawings or that which conforms to a structural stability analysis design for a specific project.
3.7-2	If required, the geosynthetic reinforcement manufacturer shall provide certification that the selected reinforcement meets the design requirements of the project’s retaining wall stability calculations.
3.7-3	Geosynthetic reinforcement shall be laid horizontally on compacted fill at the specified elevations and patterns shown on the construction drawings or the structural stability analysis. Proper orientation of the geosynthetic reinforcement shall be verified by the contractor.
3.8	BACKFILL MATERIALS
3-8.1	BACKFILL BEHIND WALL Backfill material used behind the wall shall conform to structural stability calculations.
3.9	FILL PLACEMENT IN UNITS
3.9-1	Backfill materials within the wall shall be placed in layers corresponding to the height of the blocks. It is recommended that fill within units be comprised of 3/4" crushed rock. Insure that each course is completely filled prior to proceeding to the next course. Material immediately behind the block should be compacted using only hand-operated compaction machinery.
3.9-2	Concrete grout can be used to fill the Amastone units if required by the plans or Project Engineer. Concrete grout may be placed with or without steel reinforcement as per the plans. No more than three courses should be grouted per pour. Care should be taken not to alter the block alignment during grouting.
3.10	FILL PLACEMENT FOR GEOSYNTHETIC REINFORCEMENT
3.10-1	Fill placed in areas reinforced with geosynthetic reinforcement shall be placed in 12 inch lifts and compacted to 90 - 95 percent of standard proctor. Care should be taken not to disturb the alignment of the units during backfilling and compaction operations.
3.10-2	Backfill shall be placed from the block backwards to insure tautness, and shall be placed in such a manner as to minimize both the development of wrinkles in the reinforcement and the movement of the reinforcement.
3.10-3	Only hand operated compaction equipment shall be allowed within 3 feet of the wall face. Special care should be taken when operating heavy equipment on fill over the geosynthetic reinforcement. No equipment shall be operated directly on the reinforcement.
3.10-4	Compaction tests should be measured no less than 24 inches from the back of the block.