AASHTO M156-97 pdf free download
AASHTO M156-97 pdf free download.Requirements for Mixing Plants for Hot-Mixed, Hot-Laid Bituminous Paving Mixtures.
1. Replace Section 4.2.4 with the following: A sampling tap and valve shall be provided in the bituminous storage tank or in the feedline between the pump and the return line discharge. The sampling valve shall be readily accessible and free from obstructions. An acceptable sample valve detail is shown in AASHTO T 40, Figure 3. 2. Add the following sentence to Section 4.3: Baghouse fines recirculated into the mix shall be considered as a mineral filler. 3. Add the following sentence to Section 4.5: Leave no visible unburned oil or carbon residue on the aggregate when discharged from the dryer. 4. Change the first sentence of Section 4.8.1 to read: Plants located in areas regulated by emission standards shall have a dust collection system. 5. Change Section 4.9 to the following: 4.9.1 Bins or silos may be provided for surge or storage capacity of mixtures. 4.9.2 Bins or silos used for surge capacity during mixing and delivery periods shall be such that the mixture discharged into delivery units meets the requirements of the paving mixture specifications. The surge bin or silo shall be emptied at the cessation of each mixing and delivery period. 4.9.3 Storage of mixtures between periods of production shall be permitted for silos which meet the requirements of Section 9.
9. STORAGE OF MIXTURES 9.1 Conditions of Use: 9.1.1 A plant may be permitted to store hot-mixed bituminous concrete in a silo after prior evaluation and approval by the Engineer. Use will be in conform- ance with all limitations on retention time, type of mixture, heater operation, silo atmosphere, mix level or other char- acteristics set forth in the applicable specifications. Affixed to each silo and visible to the loading operator shall be an indicating device, which will be activated when the material drops below the top of the sloped portion of the silo. 9.2 Approval Procedure: 9.2.1 An evaluation of a unit will determine the degree of mix composition uniformity, temperature characteristics, and degree of asphalt cement hardening of mixture processed through the unit. Approval will be granted for operation that consistently results in mixtures hav- ing gradation and temperature properties of no less quality than specified mixtures discharged directly from the plant’s mix- ing operation and resulting in asphalt hardening properties which do not ex- ceed the limits specified in Section 9.3. Mixtures which the Engineer determines visually to be segregated will be rejected. 93. Limits for Storage of Asphalt Mix. 9.3.1 Dense-graded Asphalt Mix will not exceed eighteen (18) hours in storage. Open-graded Asphalt Mix will not ex- ceed two (2) hours in storage.”The indicated storage times may be reduced by the Engineer if it is deter- mined that asphalt absorption is a prob- lem. Storage of open-graded mixtures will not be allowed if it is determined that migration of asphalt during the storage period is excessive.’ 9.3.2 Samples for penetration or vis- cosity tests shall be taken from trucks loaded from the storage unit or mixing operation, chilled immediately and main- tained at a temperature below 0°C (32″F) until tested. 9.4. Changes in System: 9.4.1 In the event that an approved storage unit is charged or altered, the Engineer shall be notified of the modifi- cations. Any departure from the ap- proved unit will necessitate reevaluation. 9.5 Temporary Use of Unapproved Silos: . 9.5.1 In the event that a unit is per- mitted to be used prior to evaluation and approval, the maximum storage times to be used are shown in the table entitled “Maximum Storage Times.”‘ NOTE 3- -Treated with Dow Corning Fluid DC-200 at a rate of approximately 30 ml (one fluid ounce) per 18.9 kl (5,000 gal- lons) of asphalt.AASHTO M156-97 pdf download.
