6-188 SECTION 673 - WET CAST SMALL LANDSCAPE BLOCK WALL
673.01 Description The work under this item shall consist of t he design, fabrication,
furnishing and construction of a Wet Cast Small Landscape Block Wall in accordance with these specifications and in conformance with the lines and grad es shown on the Plans, or established by the Resident. The Wet Cast Small Landscape Bloc k Wall shall consist of blocks made of Structural Precast concrete made from Portland c ement, water, chemical admixtures, and aggregates, supported on concrete leveling pads , and if required, geosynthetic reinforced backfill. The concrete blocks used in this system should have dimensions 18 inches or less wide and 6.125 inches high at the face, with a pattern to simulate small stones or cobbles. Included in the scope of the wall construction are ; geotechnical design of any wall with an exposed height greater than 2.5 feet or as specified on the Plans, all grading necessary for wall construction, compaction of the wall foundat ion soil, backfill, piped drainage, construction of leveling pads, and concrete wall unit installation. The top of the upper row of concrete wall units shall be at or above the top o f the face elevation shown on the Plans.
673.02 Quality Assurance The wall system shall be one of the approved
combinations of facing block and soil reinforcement systems not ed in the Plans or on the Department’s Qualified Products List (QPL). Alternate wall sys tems will not be considered for this item. All design calculations and Shop Drawings shall be signed, che cked, and sealed by a Professional Engineer licensed in the State of Maine. The Contractor shall require the wall design-supplier to provi de an on-site, qualified experienced technical representative to advise the Contractor c oncerning proper installation procedures. The technical representative shall be on-site duri ng initial stages of installation and thereafter shall remain available for consultation as neces sary for the Contractor or as required by the Resident.
673.03 Materials Materials for walls shall meet the requireme nts of the following
sections of Division 700: G r a v e l B o r r o w 703.20 C r u s h e d S t o n e , ¾ - I n c h 703.13 U n d e r d r a i n P i p e 706.06 or 706.09 Reinforcing Steel 709.01 Structural Precast Concrete Units 712.061 Reinforcement Geotextile 722.01 Drainage Geosynthetic 722.02 The Contractor is cautioned that all of the materials listed a re not required for every Wet Cast Small Landscape Block Wall. The Contractor shall furn ish the Resident a 6-189 Materials Certification Letter certifying that the applicable m aterials comply with this section of the specifications. Materials shall meet the follow ing additional requirements: 673.031 Concrete Units The Materials Certification Letter desc ribed above shall contain the date of concrete casting, a lot identification number, comp ressive strength results, and entrained air results. All prefabricated concrete units shall c onform to the requirements of 712.061 Structural Precast Concrete with the following exceptio ns: Materials. Materials are modified as follows: The maximum water cement ratio shall be 0.42, use of calcium ni trite is not required, and the minimum 28 day compressive strength shall be 4600 psi. The third paragraph of Materials is not applicable to this Sect ion. Quality Control and Quality Assurance. Quality Control and Qua lity Assurance is modified as follows: delete the paragraph which begins with “Th e contractor shall provide a private office…” Curing. Curing requirements are modified as follows: Replace the first sentence in the paragraph which begins “Forms shall remain …” with the following: The forms shall remain in place until the concrete has gained sufficient strength such that removal of the forms and subseque nt handling will not damage the units. Add the following paragraph at the end of the Curing section: Face texture of the units shall be a formed finish on all expos ed surfaces. Pigment shall be added during the casting process of the concrete unit to ach ieve a consistent shade of gray or other color as determined by the Resident. Concrete Testing. Concrete testing requirements are modified a s follows: Replace the paragraph which begins “A minimum of 8 ….” With the following: The Contractor shall make and test at least one set of cylinder s for every 50 yd3 of production concrete used to cast the concrete units. Replace the paragraph which begi ns “At least once …” with the f ollowing: The Contractor shall make four cylinders for use by the Departm ent for every 200 yd 3. Tolerances. Maximum dimensional deviation of formed unit dime nsions shall not vary more than 1/2-inch or 2 percent or the manufacturer’s published tolerances, whichever is less. Units not meeting the specified tolerances will be rejec ted.