506.01 506-1 SECTION 506 RIPRAP DESCRIPTION
506.01 This work consists of the construction of riprap per these specifications and in
conformity with the lines and grades shown on the plans or established. MATERIALS
506.02 Riprap shall consist of hard, dense, durable stone, angular in shape and resistant to
weathering. Rounded stone or boulders shall not be used as riprap material. The stone shall have a specific gravity of at least 2.5. Each piece shall have its greatest dimension not greater than three times its least dimension. Material used for riprap may be approved by the Engineer if, by visual inspection, the rock is determined to be sound and durable. The Engineer may require the Contractor to furnish laboratory results if, in the Engineer's opinion, the material is marginal or unacceptable. At the request of the Engineer, the Contractor shall furnish laboratory test results indicating that the material meets the requirements for abrasion resistance or compressive strength as indicated in Table 506- 1. Table 506 -1 RIPRAP MATERIAL TEST REQUIREMENT S Test Description Test Method Specification Requirement Abrasion Resistance by Los Angeles Machine ASTM C535 50% Loss, max. Unconfined Compressive Strength of Drilled Core Specimen AASHTO T 24 2500 psi, min. Riprap shall conform to the gradation requirements given in Table 506 -2. 506.02 506-2 Table 506 -2 RIPRAP GRADATION REQUIREMENTS Pay Item Stone Size d50* (Inches) Percent of Material Smaller Than Typical Stone # Typical Stone Dimensions^ (Inches) Typical Stone Weight + (Pounds) Riprap 6 70-100 50-70 35-50 2-10 12 2 85 0.4 Riprap 9 70-100 50-70 35-50 2-10 15 3 160 1.3 Riprap 12 70-100 50-70 35-50 2-10 21 4 440 Riprap 18 100 50-70 35-50 2-10 30 6 1280 Riprap 24 100 50-70 35-50 2-10 42 9 3500 Table 506 -2 Notes: *d50 = nominal stone size #based on typical rock mass ^equivalent spherical diameter +based on a specific gravity = 2.5 Nominal stone size and total thickness of the riprap shall be as shown on the plans. Control of gradation will be by visual inspection. The Contractor shall provide two samples of rock at least 5 tons each, meeting the gradation specified. One sample shall be provided at the construction site and may be a part of the finished riprap covering. The other sample shall be provided at the quarry. These samples will be used as a reference for judging the gradation of the riprap supplied. When it is determined necessary, conformance of the gradation will be verified by dumping and checking the gradation of two random truckloads of stone. Mechanical e quipment, a sorting site, and labor needed to assist in checking gradation shall be provided at the Contractor’s expense. 506.03 506-3 CONSTRUCTION REQUIREMENTS
506.03 Stones with typical stone dimensions that are equal to d50 and larger shall be placed at
the top surface with faces and shapes matched to minimize voids and form as smooth a surface as practical. Dumping and backhoe placement alone is not sufficient to ens ure a properly interlocked system. The material may be machine- placed and then arranged as necessary by use of an excavator with a multi -prong grappling device or by hand to interlock and form a substantial bond. Excavation for toe or cut -off walls shall be made to the neat lines of the wall. Allowance will not be made for work outside the neat lines. METHOD OF MEASUREMENT
506.04 Riprap of the sizes specified in the Contract will be measured by the ton or by the
cubic yard. Cubic yards will be by the method of average end areas based on dimensions shown on the plans or ordered. BASIS OF PAYMENT
506.05 The accepted quantities of riprap will be paid for at the contract unit price per cubic
yard or per ton. Payment will be made under: Pay Item Pay Unit Riprap (___inch) Cubic Yard or Ton Structure excavation will be measured and paid for per Section 206. RIPRAP (GABIONS) AND SLOPE MATTRESS DESCRIPTION
506.06 This work consists of the construction of riprap in wire mesh gabions and in wire mesh
slope mattresses per these specifications and in conformity with the lines and grades shown on the plans or established. MATERIALS
506.07 The wire, wire mesh, cages, anchor stakes and riprap shall conform to subsection
712.09. CONSTRUCTION REQUIREMENTS
506.08 Gabions and Slope Mattresses. Gabions and slope mattresses shall be placed to conform
to the plan details. Riprap material shall be placed in close contact in the unit so that maximum fill is obtained. The units may be filled by machine with sufficient han d work to accomplish requirements of this specification. 506.09 506-4 Where the length of the unit exceeds its horizontal width, the gabion is to be equally divided by diaphragms, of the same mesh and gauge as the body, into cells whose length does not exceed the horizontal width. The unit shall be furnished with the necessary diaphragms secured in proper position on the base section in such a manner that no additional tying at this juncture will be necessary.
a.Gabions. All perimeter edges of gabions are to be securely selvedged or bound so that the joints formed by tying the selvedges have approximately the same strength as the body of the mesh. The gabion bed shall be excavated to the width, line, and grade as staked by the Engineer. The gabions shall be founded on this bed and laid to the lines and dimensions required. Excavation for toe or cut -off walls shall be made to the neat lines of the wall. All gabion units shall be tied together each to its neighbor along all contacting edges in order to form a continuous connecting structure.
b.Slope Mattresses. Slope mattresses shall be filled with angular or fractured stone. Rounded boulders will not be permitted. Before the mattress units are filled, the longitudinal and lateral edge surfaces of adjoining units shall be tightly connected by means of wire ties placed every 4 inches or by a spiral tie having a complete loop every 4 inches. The lid edges of each unit shall be connected in a similar manner to adjacent units. The slope mattress shall be anchored as shown on the plans. The Contractor shall determine whether the holes for the soil anchor stakes are to be drilled or whether the stakes may be driven. Care shall be taken to avoid drilling holes to a greater depth than is necessary to place the top of the finished stake slightly above the top of the finished mattress. The Contractor will be allowed to assemble, partially fill, and tie together mattress -units on the subgrade provided they can be placed on the slope without abrading the zinc coating on the wire mattress or permanently distorting the shape of the mattress in transporting and installing the units on the slope. All prefabrication procedures shall be subject to approval. METHOD OF MEASUREMENT
506.09 The quantity to be measured under this item will be the number of cubic yards of
riprap required to fill the gabions and slope mattresses per the dimensions shown on the plans or ordered. BASIS OF PAYMENT
506.10 The accepted quantity measured as provided above will be paid for at the contract
unit price per cubic yard for “Riprap (Gabions)” or “Slope Mattress” as the case may be. Payment will be made under: Pay Item Pay Unit Riprap (Gabions) Cubic Yard Slope Mattress Cubic Yard Structure excavation and structure backfill will be measured and paid for per Section 206. 507.01 507-1 SECTION 507 SLOPE AND DITCH PAVING DESCRIPTION
507.01 This work consists of the construction of slope and ditch paving per these specifications
and in conformity with the lines and grades shown on the plans or established. MATERIALS
507.02 Concrete Slope and Ditch Paving . Concrete shall conform to the requirements of
Section 601. Concrete shall be Macro Fiber -Reinforced Class B Concrete.
507.03 Dry Rubble Slope and Ditch Paving . Stone shall conform to the material requirements
of subsection 506.02. Size of stone and total thickness of paving shall be as shown on the plans.
507.04 Grouted Rubble Slope and Ditch Paving . Stone shall conform to the material
requirements of subsection 506.02. Size of stone and total thickness of paving shall be as shown on the plans. Mortar shall consist of one part portland cement and three parts of fine aggregate by volume thoroughly mixed with as much water as is necessary to obtain the required consistency. Materials shall meet the requirements specified in the following subsection s: Hydraulic Cement 701.01 Fine Aggregate 703.01 Water 712.01 Mortar shall be used within 45 minutes after mixing and shall not be re- tempered. Class B concrete, conforming to the requirements of Section 601, may be substituted for mortar.
507.05 Grouted Riprap Slope and Ditch Paving . Concrete mortar for grouted riprap slope
and ditch paving shall meet the requirements of Section 601 and the following: Table 507 -1 GROUTED RIPRAP CONCRETE MORTAR REQUIREMENTS Field Compressive Strength (28 days) (Not a specification requirement) 2000 psi Minimum Cement Content 560 lb/cu yd Air Content 6-9% Slump, AASHTO Designation T -119 5-9 inches Fine Aggregate, AASHTO M -6 65-75% Coarse Aggregate, AASHTO M -43 3/8" nominal maximum size Polypropylene Fibers (1" fiber length or equivalent) 1.5 lb/cu yd
Source: Colorado Standard Specifications for Road and Bridge Construction, 2023 Edition. Pages 469–472 of 943.