26 AGGREGATE BASES
26-1 General
26-1.01 General
26-1.01A Summary
Section 26 -1 includes general specifications for placing aggregate base.
26-1.01B Definitions
Reserved
26-1.01C Submitt als
Submit an aggregate base QC plan.
26-1.01D Quality Assurance
26-1.01D(1) General
Aggregate samples must not be treated with lime, cement, or chemicals before testing for durability index. Aggregate from untreated reclaimed processed AC, PCC, LCB, or CTB is not considered treated.
26-1.01D(2) Quality Control
26-1.01D(2)(a) General
Reserved
26-1.01D(2)(b) Quality Control Plan
Reserved
26-1.01D(2)(c) Qualifications
Reserved
26-1.01D(2)(d) Quality Control Testing
AB quality control must include te sting the quality characteristics at the frequencies shown in the following table: QC Testing Frequencies Quality characteristic Test method Sampling location Minimum frequency R-value California Test 301 Stockpiles, transportation units, windrows, or roadways 1 test before starting work and every 2,000 cu yd thereaftera Aggregate gradation California Test 202 Stockpiles, transportation units, windrows, or roadways 1 per 500 cu yd but at least one per day of placement Sand equivalent California Test 217 Stockpiles, transportation units, windrows, or roadways Durability indexb California Test 229 Stockpiles, transportation units, windrows, or roadways 1 per project Relative compaction California Test 231 Roadway 1 per 500 sq yd on each layer aAdditional R -value frequency testing will not be required when the average of 4 consecutive sand equivalent tests is 29 or greater for Class 2 AB or 25 or greater for Class 3 AB. bApplies if section 26 -1.02 contains an applicable requirement for durability index .
26-1.01D(3) Department Acceptance
The Department accepts AB based on aggregate gradation, R -value requirements, durability, and sand equivalent requirements specified in section 26 -1.02. The Department accepts AB based on percent relative compaction specified in section 26 -1.03E tested under California Test 231. The Engineer takes aggregate base samples for R -value, aggregate gradation, sand equivalent, and durability index from any of the following locations: SECTION 26 AGGREGATE BASES
1.Windrow
2.Roadway If the aggregate gradation test results, sand equivalent test results, or both comply with the Contract compliance requirements but not the operating range requirements, you may continue placing AB for the remainder of the workday. Do no t place additional AB until you demonstrate to the Engineer the AB to be placed complies with the operating range requirements. If the aggregate gradation test results, sand equivalent test results, or both do not comply with Contract compliance requiremen ts, remove the AB or request a payment deduction. If your request is authorized, $2.00/cu yd is deducted. If AB is paid by weight, the Engineer converts tons to cubic yards for the purpose of reducing payment for noncompliant AB left in place. Each aggrega te gradation and a sand equivalent test represents no more than 500 cu yd of AB or 1 day's production, whichever is smaller.
26-1.02 Materials
26-1.02A General
Aggregate must be clean and consist of any combination of the following:
1.Broken stone
2.Crushed gravel
3.Natural rough -surfaced gravel
4.Sand
5.Processed reclaimed asphalt concrete, PCC, LCB, or CTB Use either 1 -1/2-inch or 3/4 -inch maximum aggregate gradation unless otherwise specified. Do not change your selected aggregate gradation without authorization.
26-1.02B Class 2 Aggregate Base
Aggregate gradation must be within the percentage passing limits for the sieve sizes shown in the following table : Aggregate Gradation Sieve size Percentage passing 1-1/2 inch maximum 3/4 inch maximum Operating range Contract compliance Operating range Contract compliance 2" 100 100 -- -- 1-1/2" 90–100 87–100 -- -- 1" -- -- 100 100 3/4" 50–85 45–90 90–100 87–100 No. 4 25–45 20–50 35–60 30–65 No. 30 10–25 6–29 10–30 5–35 No. 200 2–9 0–12 2–9 0–12 The aggregate quality characteristics must comply with the requirements shown in the following table: Aggregate Quality Characteristics Quality characteristic Requirement Operating range Contract compliance Resistance (R -value, min) -- 78 Sand equivalent (min) 25 22 Durability index (min) -- 35
26-1.02C Class 3 Aggregate Base
Aggregate gradation must be within the percentage passing limits for the sieve sizes shown in the following table : SECTION 26 AGGREGATE BASES Aggregate Gradation Sieve size Percentage passing 1-1/2 inch maximum 3/4 inch maximum Operating range Contract compliance Operating range Contract compliance 2" 100 100 -- -- 1-1/2" 90–100 87–100 -- -- 1" -- -- 100 100 3/4" 50–90 45–95 90–100 87–100 No. 4 25–60 20–65 40–70 35–75 No. 30 10–35 6–39 12–40 7–45 No. 200 3–15 0–19 3–15 0–19 The aggregate quality characteristics must comply with the requirements shown in the following table: Aggregate Quality Characteristic Quality characteristic Requirement Operating range Contract compliance Resistance (R -value) (min) -- 50 Sand equivalent (min) 21 18
26-1.03 Construction
26-1.03A General
Apply water to the AB as needed for compaction.
26-1.03B Subgrade
Immediately before spreading AB, the subgrade must comply with the specified compaction and elevation tolerance for the material involved and be free from loose or extraneous material. You may use AB to fill areas of the subgrade that are lower than the grade established by the Engineer.
26-1.03C Placing Geosynthetic Materials
Geosynthetic materials include filter fabric and biaxial geogrid. If filter fabric is shown, place it on the subgrade. Before placing geosynthetic materials, remove sharp objects that may come in contact with the material. Place the material :
1.Under manufacturer's instructions
2.Longitudinally along the roadway alignment
3.Without wrinkles Overlap adjacent edges of geosynthetic material at least 2 feet. Overlap the ends of the rolls at least 2 feet in the direction AB is spread. You may fold or cut geosynthetic material to conform to curves. If material is cut, overlap it at least 2 feet. You may hold material in place with mechanical ties, staples, pins, or small piles of AB. Do not place stockpiles on geo synthetic material or place more material than can be covered in 72 hours. Do not operate equipment or vehicles directly on filter fabric. Do not operate equipment or vehicles directly on geogrid unless one of the following conditions is met:
1.Vehicles a nd equipment are: 1.1. Equipped with rubber tires SECTION 26 AGGREGATE BASES 1.2. Operated under 10 mph 1.3. Operated to avoid sudden braking and sharp turns
2.At least 0.35 ft of AB has been placed, spread, and compacted on the material Repair or replace any damaged geosynthetic material by placing a new piece of material over the damaged area with at least 3 feet of overlap.
26-1.03D Spreading
Deliver uniform mixtures of AB to the roadbed. Deposit AB in layers or windrows. Spread and shape the AB to such thickness that after watering and compacting, the completed AB is within the tolerances specified in section 26 -1.03E. When AB is spread and compacted the moisture content m ust be uniform and sufficient to obtain the required compaction. Avoid material segregation. AB must be free from pockets of coarse or fine material. If the subgrade is cohesionless sand, you may dump AB in piles and spread it ahead in sufficient quantitie s to stabilize the subgrade, if authorized. If the AB thickness shown is 0.50 foot or less, spread and compact the AB in at least1 layer. If the thickness shown is more than 0.50 foot, spread and compact the AB in at least 2 approximately equal layers in t hickness. The compacted thickness of any one layer must not exceed 0.50 foot. At locations inaccessible to spreading equipment, spread and compact AB by any means that will attain the specified requirements.
26-1.03E Compacting
Compact each AB layer to at least 95 percent relative compaction. If biaxial geogrid is shown, compact AB with either (1) a smooth -wheeled roller or (2) a rubber -tired roller. Do not use vibratory devices during compaction. The finished AB surface must not vary more than 0.05 foot from the grade established by the Engineer. Correct areas of AB that do not comply with the described thickness or request a payment deduction if AB is paid for by volume. If your request is authorized, the Engineer calculates the deduction by multiplying:
1.Deficient thickness less allowable tolerance
2.Planned width
3.Longitudinal distan ce of the deficient thickness
4.$17.00/cu yd or the item bid price adjusted for cubic yards, whichever is higher
26-1.04 Payment
If aggregate base is paid for by volume, the payment quantity is determined from the dimensions shown. The payment quantity does not include the volume of aggregate base used to fill low areas of the subgrade. If the basement material is imported borrow, aggregate base placed to fill low areas is not measured or paid for as imported borrow. If aggregate base is paid for by weig ht, the Engineer deducts the weight of the water at the time of weighing in excess of the optimum moisture content plus 1 percent from the weight of the aggregate base. The Engineer determines the optimum moisture content under California Test 216.
26-2 26-10 Reserved
Source: California Standard Specifications, 2024 Edition. Pages 407–410 of 1,372.