- 973 - SECTION 1080 -- WARM MIX ASPHALT
1080.01 Description
1.The Contractor has the option to use Warm Mix Asphalt (WMA) meeting the following requirements.
1080.02 Material Requirements
1.Warm Mix Asphalt (WMA)
a.Warm Mix Asphalt mixtures shall follow the requirements of Superpave Asphaltic Concrete and all ot her applicable sections with the following exceptions:
1.The Contractor shall request the use of a WMA additive in writing when submitting the Job Mix Formula. The requested additive shall be an approved Level I or II production product or combination thereof. The manufacturer’s recommended additive ra tes, specifications, and all other pertinent information shall be included in the requests. All requests must be approved by the Engineer prior to their use.
1080.03 Construction Methods
1.Level I Production
a.Level I WMA additives are as follows: water injection devices. b. Hydrated Lime at 1.25% by weight of virgin aggregate is required for all mixtures.
c.The allowable drop in temperature shall be a maximum of 40°F below the producer’s recommended production temperature for Hot Mix Asphalt (HMA), or less as required during production to achieve proper laydown and compaction properties. Plant production temperatures shall not drop below 230°F.
2.Level II Production a. Approved Level II WMA additives are listed on the Department’s Approved Products List.
b.For amine based WMA additives, 25% of the additive must be considered an amine based anti-stripping agent, unless Poly-Phosphoric Acid (PPA) is used. If PPA is used in the binder, the WMA shall be a non- amine based WMA, specifically fo r use and compatible with binders containing PPA. WMA additives and anti-strips shall be terminal blended by the binder supplier. For all other warm mix technologies hydrated lime shall be added at a minimum rate of 1.25% by weight of virgin aggregate, including the weight of limestone. Hy drated Lime shall not be used on Level II WMA mixtures when the WMA additive is an Amine based additive or when the Amine WMA additives are used in combination with Level I water injection. The minimum rate for amine based WMA additives shall be 0.7%. The dosage rate of anti-strip sh all not exceed manufacturer’s recommendations.
c.The drop in temperature shall be a maximum of 90°F from the producer’s recommended production temperature for HMA. Plant production temperatures shall not drop below 215°F.
3.Other WMA additives shall not be used unless otherwise approved by the Engineer.
1080.03 Warm Mix Asphalt
- 974 - 4. WMA additives may be used in combination by approval of the Engineer.
5.Asphalt mixes shall be tested for TSR on the first lot of production and then on randomly selected lots thereafter.
6.Field samples shall be heated and compacted using the following table unless otherwise approved by the Engineer. Mix Type % RAP Compaction Temp °F SPS 0-25 270 ± 5 26-65 280 ± 5 SPR 0-35 280 ± 5 36-55 290 ± 5 SPH 0-35 300 ± 5 SLX 20-35 280 ± 5 SRM 35-65 290 ± 5
7.The Engineer may suspend or eliminate the use of WMA on a project if any of the following conditi ons occur: rutting, segregation, surface voids, tearing, irregular surface, low density, raveling, stripping, or if pavement does not meet an y other design criteria.
1080.04 Method of Measurement and Basis of Payment
1.Warm Mix Asphalt (WMA) additives will be measured and paid for directly by the unit of each for the item “Hydrated Lime/Warm Mix Asphalt” for each ton of hot mix asphalt produced. - 975 - SECTION 1081 -- ASPHALT DENSITY GAUGE
1081.01 Description
1.An Asphalt Density Gauge may be used for Quality Control when determining the in-place density of asphaltic concrete.
1081.02 Material Requirements
1.The device must be approved by the Engineer. 1081.03 -- Testing Method
1.The Contractor shall establish the method of testing in the preconstruction conference. All testing shall be in accordance with AASHTO T-343 and as directed in this provision.
2.The first 3 (three) density locati ons of the project shall be cored in accordance with AASHTO T166 to calibrate the asphalt density gauge. Prior to coring, the Contractor shall calibra te the device at each core location.
3.Calibration: A correction factor shall be established for the first 3 (three) cores by calculating the difference between the average density measurement of the asphalt density gau ge and the roadway core density. All readings taken with the gauge shall ha ve the correction factor set at zero. The necessary corrections will be adju sted in the Department Superpave Software. The correction factor shall be verified with another core for every 15 density readings that are to be recorded.
4.Density Reading Procedure: Place the asphalt density gauge on the asphalt mat over the area to be tested. Record the density reading, and repeat this process for a total of 5 (fiv e) readings, as detailed in Figure 1. An average of the 5 (five) readings will be used as the density reading for each location. For densities taken less than 6 (six) inches from the edge of the lift, density readings shall be taken as shown in Figure 2. The span between density reading locations in each direction shall be no greater than 12”.
Source: Nebraska Standard Specifications for Highway Construction, 2017 Edition. Pages 1007–1008 of 1,048.