Chip Seal Specification Revisions

Transcription

1 46 th Annual Idaho Asphalt Conference October 26, 2006 Chip Seal Specification Revisions Idaho Transportation Dept. Mike Dehlin,, P.E. Pavement Development Engineer Not a chip seal expert Overview - Chip Seal Problems & Causes - Chip Seal Team - McLeod Method - ITD Chip Seal Specification Review - s - Choke Sand - Chip Seal Payment by Square Yard Chip Seal Problems Summer 2003 Chip Seal Team Various reasons / causes - Chip sealed too late in year - High traffic volume locations - Non-rubberized / non-polymerized - non-uniform chip size - One sized chip defined as less than 5% passing two adjacent sieves. - Non-polymerized / non-rubberized s were prohibited for chip sealing - Consider McLeod method for chip seal design McLeod Method - One stone thick, 70% voids filled with - Design Procedure - Median Particle Size - Average Least Dimension (includes Flakiness Index) - Loose Weight of Cover Aggregate - Voids in Loose Aggregate 1

2 McLeod Method (continued) - Design Procedure (continued) - Aggregate Absorption - Traffic Volume - Traffic Whip-off - Existing Pavement Condition McLeod Method (continued) Results - Cover Coat Aggregate Application Rate - Binder Application Rate - McCleod Method was added to ITD Standard Specifications (as optional) and will be incorporated into Idaho T-60T Specification Review Mr. Newton Jackson, P.E. Nichols Consulting Engineers Climate Previous Specification - Unless otherwise approved, no seal coat shall be applied before June 15 or after September 1. - No seal coat shall be applied before June 15 or after September 1. Pneumatic Tire Roller Speed - Allowed max speed of 8 mph for first roller and 16 mph for subsequent rollers. - Maximum speed for all rollers is 8 mph Photo courtesy of Newton Jackson, P.E. 2

3 Chip Application Time Immediate chip application? - Referred only to immediately applying cover coat aggregate Photo courtesy of Newton Jackson, P.E. Chip Application Time - To avoid exposure of for more than three minutes length of spread of shall not exceed that which trucks w/ cover coat aggregate can immediately cover. Moisten Chips Previous procedure - Most ITD Residencies were requiring cover coat material to be moisture conditioned at the time of placement on the roadway. Previous Specification - None Moisten Chips (continued) Purpose - Eliminate or reduce dust coating of the aggregate. - Incorporated into the standard specification. Rolling Time - Required 4 roller passes (as a compromise between 3 and 5 passes) with no time limit. Revised specification - Uses 3 roller passes within 5 minutes of spreading chips. 3

4 Choke Sand Current Standard Specification - Blotter specification including 0 to 15 % passing #200 sieve Proposed to Specification Committee - Choke sand uses 0 to 5 % passing #200 sieve - One or two roller passes to orient chips - Apply choke sand - Complete rolling Not incorporated as standard procedure yet. Benefits of Choke Sand - Successful at preventing chips from overturning and exposing underlying - Beneficial for reducing noise Chip Sealing by Square Yard - Optional for ITD Districts - Asphalt is paid for by the ton - Approaches are paid for per Each - Chip Sealing is paid for by square yard - Tends to reduce overapplication of chips Chip Sealing by Square Yard (continued) - Square yard payment includes: - Cleaning pavement surface - Provide and place Cover Coat Material - Rejects / Choke Sand (Chip Seal Maintenance) - Water for Dust Abatement - Brooming Benefits of Chip Sealing by SY - Reduces paperwork (fewer pay items) - Reduces excessive application of chips - Reduced quantities of chips does not seem to be a problem. 4

5 Results to Date and Conclusion - Concern has been expressed with one chip seal (Summer 2006) - No other problems have been reported Questions? 5