Section 311 — Stabilized Aggregate Surface Course
Description
311.01This work consists of constructing a stabilized aggregate surface course.
Material
311.02Conform to the following Subsections: Calcium chloride, magnesium chloride, and lignosulfonate 725.02 Surface course aggregate 703.05(c) Water for construction 725.01(c)
Constru ction Requirements
311.03Proportioning. Determine the maximum density and optimum moisture content according to AASHTO T 180, Method D for the surface course aggregate with and without calcium chloride at the target percentage. Use the proctor with calcium chloride to monitor yield and final compaction of the mixture. The target calcium chloride content is 1.85 percent by dry mass of aggregate. The target water content is from 2 percent below the optimum moisture content to optimum moisture content.
311.04General. Set target values within the gradation ranges shown in Table 703-1, grading G. Store calcium chloride in closed, weatherproof containers. Conduct a pre -stabilization preparatory phase meeting at least 7 days before the start of stabilization operations according to Subsection 153.06(a) . Prepare the surface on which the stabilized aggregate surface course is placed according to Section 204 or 303, as applicable. Start the placement of surface course aggregate within 5 days of completing roadway reconditioning, unless otherwise approved.
(a)Weather requirements. Start application or mixing operations when the following conditions are met:
(1)The mean daily temperature is not expected to fall b elow 40 °F for a 7- day cure period after the calcium chloride is incorporated;
(2)The ambient air temperature is 40 °F or above, and is not expected to fall below 40°F within 48 hours; (3) No precipitation is occurring or forecast to occur within 24 hours; and
(4)The underlying surface is not frozen or muddy.
(b)Control of mixture. Continuously monitor calcium chloride content, moisture content, and aggregate yield according to Section 153 during production and placement. Stop production and provide immediate corrective action if yield calculations, moisture content measurement, or other observations indicate specifications are not being met. Report moisture content and calcium chloride yield twice daily. Adjust operations as approved to ensure an accurate yield is maintained. Maintain the accuracy of the quantities of calcium chloride, aggregate, and water content within the following tolerances during pugmill or in -place mixing and placement:
(1)Calcium chloride. 1.85 percent ±0.15 percent by dry mass of aggregate. Use an independent measuring device with display, accurate to ±0.05 percent of the mass of calcium chloride.
(2)Water. ±1.0 percent by mass (maintain moisture content from 2 percent below optimum to optimum).
(3)Aggregate. ±2.0 percent by mass. Calculate the calcium chloride yield according to the following formulas: 𝑇𝑇𝑇𝑇𝑛𝑛𝑠𝑠𝑓𝑓𝑓𝑓� = (𝑇𝑇× 0.95 ×𝛾𝛾×𝑊𝑊×𝐷𝐷) 2000 𝑃𝑃𝑇𝑇𝑃𝑃𝑛𝑛𝑃𝑃𝑠𝑠𝑈𝑈𝑄𝑄𝑆𝑆𝐷𝐷� = (𝑇𝑇× 0.95 ×𝛾𝛾×𝐷𝐷) × 9 Where: T = Target calcium chloride content in decimal percent γ = Maximum dry density of aggregate, lb/ft3 W = Width of calcium chloride application, ft D = Depth of mixing calcium chloride, ft Incorporate calcium chloride using pugmill mixing as described in Subsection 311.05 or in -place mixing as described in Subsection 311.06.
311.05Pugmill Mixing.
(a)Calcium chloride mixing. Use a stationary pugmill with weighing or metering equipment that can accurately control the material entering the mixer. Interlock the metering controls for the aggregate feed with those of the calcium chloride and water to ensure uniform introduction of material into the mixer. Take calcium chloride yield samples using an approved method at least twice daily during production. If yield test results indicate a rate outside the contract tolerances, correct the rate and perform additional yield testing. Do n ot produce more treated aggregate than can be placed within 7 days, unless approved. Do not produce treated aggregate when precipitation is anticipated before the treated aggregate can be placed. Do not use treated aggregate that has been exposed to precip itation before placement without approval.
(b)Placement. Follow the requirements of Subsection 311.06(a) .
311.06In- Place Mixing.
(a)Surface course aggregate placement. Transport and place the surface course aggregate after preparatio n of the surface and approval of the surface. Process the aggregate to full depth and width with a motor grader into a uniform windrow within one hour of delivery on the roadway, adjusting the moisture content to obtain a homogenous mixture with a moisture content within 2 percent below the optimum moisture content to optimum moisture content. Spread the material on the prepared surface in a uniform lift. Shape the road to the required cross -section. Compact according to Sub section 311.07 by the end of the shift. Do not allow hauling vehicles to drive on the placed aggregate before windrow processing except where required to allow traffic to pass or to dump subsequent loads.
(b)Calcium chloride mixing. Incorporate calcium chlori de within 14 days of placement of surface course aggregate, unless otherwise approved. Apply calcium chloride in a uniform layer across the full width of the surface to be mixed. Use distributor equipment that can meter the application rate from the operator’s cab accurate to ±0.05 percent of the mass of calcium chloride. As an alternative, rotary mixing machines that can closely meter calcium chloride and additional mixing water into the mixing process may be used if the required application rates are met and the application rates can be continuously controlled from the operator’s cab accurate to ±0.05 percent of the mass of calcium chloride. Verify the application rate by performing calcium chloride weight yield tests twice daily for each distributor. If yield test results indicate a rate outside the contract tolerances, then correct the application rate and perform additional yield testing. The CO may increase the test frequency. Do not spread more calcium chloride than can be incorporated within one hour. Use rotary mixing equipment to uniformly incorporate the calcium chloride and additional mixing water into the surface course aggregate or surface course aggregate and existing aggregate to a compacted depth of 4 inches +0.0 inch/-0.5 inch. Mix the materi al one- lane at a time.
(c)Processing. After mixing is complete, ensure a uniform product free of segregation, streaking, and inconsistent moisture content by processing the treated material with a motor grader to full depth and width. Shape the road to the re quired cross- section. To the extent practical prevent hauling equipment from traveling on recently placed calcium chloride treated aggregate. If not practical route hauling equipment uniformly over the full width of the surface to minimize rutting or uneve n compaction.
311.07Compacting and Finishing. Maintain the moisture content from 2 percent below optimum to optimum. Compact each lift full width. Roll from the sides to the center, parallel to the centerline of the road. Along curbs, headers, walls, and places not accessible to the roller, compact the material with approved tampers or compactors. Provide pneumatic tired rollers for initial compaction that have a minimum ballasted weight of 15 tons and have a minimum tire overlap of 1.5 inches. Provide single smooth drum rollers for final compaction to provide a smooth and uniform finished surface.
(a)Pugmill mixed. Compact each lift of treated surface course aggregate to at least 95 percent of maximum dry density according to the proctor performed with calcium chloride. Meet compaction requirements for sections of roadway before the end of the work shift. Determine the in- place density and moisture content according to AASHTO T 310 or other approved test procedures.
(b)In-place mixed. Compact the untre ated surface course aggregate placed each shift to at least 95 percent of maximum dry density of the respective proctor by the end of shift. The CO may approve alternative test procedures if requested and if calcium chloride is to be incorporated within 2 days of aggregate placement. After calcium chloride incorporation, compact each layer to at least 95 percent of maximum dry density as determined in Subsection 311.03 for aggregate combined with calcium chloride. Meet compa ction requirements before the end of the work shift. Determine the in -place density and moisture content according to AASHTO T 310 or other approved test procedures.
(c)Finishing. Finish the mixture to produce a surface that is smooth, dense, and free of compaction planes, ridges, or loose material. Compact the aggregate foreslopes to ensure they are dense and recoverable. Shape the surface to the required template and check the surface with a 10 -foot metal straightedge. Defective areas are surface deviations more than ½ inch in 10 feet between two contacts of the straightedge with the surface, or noticeable dips, bumps or other undulations identified through visual inspection or vehicle ride inspection. Correct defective areas by loosening the material full de pth, adding or removing material as required, adjusting moisture content, reshaping, and compacting. Submit alternative methods of correction, including patching or filling of potholes for approval.
311.08Acceptance. See Table 3 11-1 for sampling, testing, and acceptance requirements. Calcium chloride will be evaluated under Subsections 106.02 and 106.03. Aggregate gradation, plasticity index, fractured faces, and l iquid limit will be evaluated under Subsection 106.05. Other aggregate quality properties will be evaluated under Subsections 106.02 and 106.04.
(a)Aggregate gradation. The upper and lower specification limits are equal to the calculated mean of all test results plus or minus the allowable deviations shown in Tables 703-1 and 703-2, except as follows:
(1)If the calculated mean value for a tested sieve exceeds the maximum gradation range value shown in Table 703-1, then the upper specification is equal to the maximum gradation value in Table 703-1 plus or minus the allowable deviation in Table 703-2.
(2)If the calculated mean value for a tested sieve is less than the minimum gradation range value shown in Table 703-1, then the lower specification is equal to the minimum gradation value in Table 703-1 plus or minus the allowable deviation in Table 703-2.
(b)Fractured faces. If aggregate is produced from a gravel source, use the specification limit shown in Subsection 703.05.
(c)Liquid limit. The specification limit is shown in Subsection 703.05.
(d)Plasticity index. The specification limit is shown in Subsection 703.05. Aggregate stabilization construction will be evaluated under Subsections 106.02 and 106.04. Compaction of surface course aggregate will be evaluated under Su bsection 106.04. Preparation of the surface for placement of surface course aggregate will be evaluated under Section 204 or 303, as applicable.
Measurement
311.09Measure the Section 311 pay items listed in the bid schedule according to Subsection 109.02 .
Payment
311.10The accepted quantities will be paid at the contract price per unit of measuremen t for the Section 311 pay items listed in the bid schedule, except the stabilized aggregate surface course contract price will be adjusted according to Subsection 106.05. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05 . Table 311-1 Sampling, Testing, and Acceptance Requirements
Material or
Product
(Subsection) Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Source
Surface course
aggregate quality (703.05 ) Measured & tested for conformance (106.04 & 105) LA abrasion (coarse) – AASHTO T 96 1 per
Type but
not less than 5 per source of material(2) Source of material Yes Before using in work Not required if using
Government
-furnished sources
Soundness
using sodium sulfate ( coarse & fine) – AASHTO T 104 " " " " "
Durability
Index ( coarse & fine) – AASHTO T 210 " " " " "
Accelerated
weathering – WFL W DMSO " " " " "
Surface course
aggregate (703.05 ) Process control (153.03 ) Gradation – AASHTO T 27 & T 11 1 per 6 hours of production but not less than 2 per day per stockpile Flowing aggregate stream (bin or belt discharge) or conveyor belt Yes End of shift " Fractured faces – ASSHTO T 335 " " " " " Liquid limit – AASHTO R 58 & T 89, Method A " " " " – Plasticity index – AASHTO R 58 & T 90 " " " " " Table 311- 1 (continued) Sampling, Testing, and Acceptance Requirements
Material or
Product
(Subsection) Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Proportioning
Proportioning
(311.03) Measured & tested for conformance (106.04 ) Moisture - density − AASHTO T 180, Method D(1) 1 per mixture & change in material Processed material before incorporating in work Yes, if requested Before using in work Report proportion of aggregate, calcium chloride, & water
Production
Surface course
aggregate (703.05) Statistical (106.05) Gradation – AASHTO T 27 & T 11 1 per 1000 tons but not less than 3 In-place mixing: from windrow immediately after processing
Pugmill
mixing: flowing aggregate stream (bin or belt discharge) or conveyor belt before adding stabilizer Yes, if requested 4 hours − No. 4 I No. 40 I No. 200 I
Other II
Table 311- 1 (continued) Sampling, Testing, and Acceptance Requirements
Material or
Product
(Subsection) Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Production (continued)
Surface
course aggregate (703.05 ) Statistical (106.05) Liquid limit II AASHTO R 58 & T 89, Method A 1 per 1000 tons but not less than 3 In-place mixing: from windrow immediately after processing
Pugmill
mixing: flowing aggregate stream Yes, if requested 4 hours – Fractured faces I ASSHTO T 335 " " " " – Plasticity index I AASHTO R 58 & T 90 " " " " –
Mixture
(311.03) Process control (153.03) Moisture content of aggregates – AASHTO T 255 2 per day minimum " No "
Measured &
tested for conformance (106.04) In-place density & moisture content – AASHTO T 310 or other approved procedures 1 per 500 tons or 3000 yd2 In-place after compaction No 4 hours – (1)At least 5 points per proctor. (2)Submit at least five reports, but at least one repo r t per rock type for each source. Submit r eports dated within 1 year of intended use. Obtain samples representative of aggregates being provided. Include rock type and sample location on test reports.