CATEGORY 900 MATERIALS SECTION 926 — FOAMED ASPHALT STABILIZED BASE COURSE MIX
926.01 Mix Requirements
Develop a mix consisting of Reclaimed Asphalt Pavement (RAP), Recycled Portland Concrete (RC), aggregate, and foamed asphalt binder. Include lime, Portland cement, and fly ash as necessary to increase the fines to meet the design parameters in Table 926 A and Table 926 B. Select a PG 64-22 asphalt binder that provides the required asphalt foaming characteristics and mix properties. Do not use polymer modified asphalt binders. Table 926 A - Aggregate Blend Requirements GRADATION (T 27) Sieve Size Percent Passing 1 1/2 in. (38 mm) 100 3/4 in. (19 mm) 65 – 100 No. 4 (4.74 mm) 50 – 70 No. 200 (75 µm) 1 – 8 OTHER PI (T 90) < 10 % Table 926 B - Foamed Asphalt Stabilized Base Course Mix Requirements DESIGN PARAMETERS VALUE Aggregate Blend Compaction: T 180D, Max Dry Density, pcf ≥120 Specimen compaction: Marshall compaction: T 245 - number of blows per face, or 75 Gyratory compaction: T 312 - number of gyrations 30 Indirect Tensile Strength: modified T 283 Minimum Wet Tensile Strength, psi 45 Minimum Wet Tensile Strength, psi, for material stockpiled >2 days Minimum Tensile Strength Ratio (TSR), % 55 Foamed Asphalt Expansion Characteristics @ 160, 170, & 180 C Minimum Half-Life of Foamed Expansion, sec (1) Minimum Expansion Ratio (2) 8 Note 1: Total time for foamed asphalt to settle to half of the maximum foamed volume. See Section A.1.3.4 of the Wirtgen Cold Recycling Technology Manual (2010) for the half-life test procedure. Alternate suitable equipment can be substituted for the Wirtgen WLB 10 S laboratory unit. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS Note 2: Maximum foamed asphalt volume divided by non-foamed asphalt volume. See Section A.1.3.4 of the Wirtgen Cold Recycling Technology Manual (2010) for the expansion ratio test procedure. Alternate suitable equipment can be substituted for the Wirtgen WLB 10 S laboratory unit. Submit job mix formulas for approval at least 30 days prior to production to the Office of Materials Technology, Soils and Aggregate Division. Job mix formulas must meet the requirements of Table 926 A and Table 926 B. Work will not be allowed to commence without approved job mix formulas. Perform the following tests for each job mix formula:
a.Aggregate. T 2. Sample 50 lb of material representing the RAP, RC, and aggregate to be used in the job mix formula. Test as specified in 901A and 901B.
b.Performance Graded Asphalt Binder. M 322. Provide five 4-quart samples of the asphalt binder.
c.Water. 921.01
d.Lime, Cement and Fly Ash. Determine the percentage of lime, cement and fly ash required to meet the mix design parameters.
926.02 Mix Design
Prepare a minimum of four Marshall or four gyratory compactor specimens at 0.5 percent increments for a range of asphalt contents; with at least one specimen above and one below optimum to determine the job mix formula. The moisture content of the specimens shall be within 1.5 percent of the optimum moisture content of the aggregate blend. For gyratory specimens, obtain a 2 in. thick test specimen cut from the middle of each compacted cylinder.
926.03 Foamed Asphalt Expansion Characteristics
Test the asphalt binder according to Table 926 B for the following:
a.Measure the expansion ratio and foam half-life of the asphalt binder over a range of water contents for the three temperatures.
b.Plot expansion ratio and half-life vs. water content. The optimum foaming water content for a given temperature is the average of the two water contents that meet the respective minimum expansion ratio and half-life requirements.
926.04 Indirect Tensile Strength (Idt)
T 283.
a.Place the samples to be soaked in a 77 F water bath for 24 hours. Dry the samples to constant mass at 104 +/-2 F. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
b.Graph IDT strength versus foamed asphalt content for both dry and soaked specimens. Graph TSR versus foamed asphalt content.
c.For wet IDT strength vs. foamed asphalt content curves exhibiting a maximum value, select the design foamed asphalt content corresponding to the maximum. Otherwise, select a design foamed asphalt content that meets the wet IDT strength and TSR requirements in Table 926 B.
d.In no case shall the design foamed asphalt content be less than 2 percent or greater than 3.5 percent.
926.05 Foamed Asphalt Cement Content
Once the foamed asphalt content of the Job Mix Formula has been determined, prepare a minimum of 5 compacted specimens based on the Job Mix Formula. These specimens must meet the design parameters according to Table 926 B. Calculate the mean, standard deviation of the Indirect Tensile Strength results (modified T 283, according to Table 926 B). These values must be reported in the FASBC Mix Design for the Administration’s approval. The Contractor shall also submit five bag samples representative of the aggregate blend of the Job Mix Formula and five bag samples representative of the Job Mix Formula with the added foamed asphalt as part of the mix approval process. These sample bags shall contain at least 20 lb of FASBC material. The samples will be tested to develop an ignition oven correction factor and a base reference for the foamed asphalt cement content for acceptance purposes. The Office of Materials Technology will evaluate the suitability of the material and proposed job mix formula. If the job mix formula is not approved, submit a new job mix formula as directed. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 927 — OPEN GRADED FRICTION COURSE MIX 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS CATEGORY 900 MATERIALS SECTION 927 — OPEN GRADED FRICTION COURSE MIX Open Graded Friction Course (OGFC) shall conform to the applicable sections of 901 and PP 77, except as specified. GRADATION: *Mix Control Tolerance not applicable to this sieve for this mix.
a.Less than Design Level 4 (ESAL).
b.Porous European Mix (PEM) – Design Level 4 (ESAL). (c) Conduct drain-down test on loose mix at a temperature 15 C higher than anticipated production temperature. Crushed glass, roofing shingles, RAP, or other recycled materials are not allowed in OGFC mixes. PHYSICAL PROPERTIES: TEST TEST METHOD LIMITS Asphalt Bindera M 332 64E-22 Tensile Strength Ratio (TSR) T 283b ≥85% Permeabilityc MSMT 408 300 ft/day (100m/day)
a.Mineral Fibers used at 0.4% of total mix, Cellulose, 0.3% of total mix, or other approved stabilizer systems as specified in 904.05.04. Design Gradation Limits, % Passing Sieve Size Mixture Control Tolerance, % 9.5 mm OGFCa 12.5 mm OGFCa 12.5 mm PEMb 3/4 in. (19 mm) ±0.0 100* 100* 1/2 in. (12.5 mm) ±6.0 100* 85-100 80-100 3/8 in. (9.5 mm) ±5.5 85-100 55-75 35-60 No. 4 (4.75 mm) ±6.0 20-40 15-25 10-25 No. 8 (2.36 mm) ±4.5 5-10 5-10 5-10 No. 200 (75 µm) ±2.0 2-4 2-4 1-4 Range for % AC ±0.4 6.0-7.25 5.75-7.25 5.5-7.0 Drain-down (D6390), %c <0.3 <0.3 <0.3
Source: Maryland Standard Specifications for Construction and Materials, 2025 Edition. Pages 1064–1066 of 1,113.