Resin Modified Pavement Demonstration Project.pdf

Chapter 5 – Conclusions from Construction and Early PerformanceUltra-Thin WhitetoppingAs the data in Table C7 of Appendix C indicates, the smoothness of the Ultra-ThinWhitetopping test section is less than satisfactory. Undoubtedly this amount ofroughness will impact the service life of the pavement. For future projects utilizingUltra-Thin Whitetopping, adequate smoothness incentive/disincentive specificationsshould be utilized to insure proper care and construction techniques are employed by thecontractor. One step in the right direction would be to disallow the use of small “bull”floats for the finishing of the concrete surface.Resin Modified PavementIt cannot be stressed enough that care must be taken to insure proper quality control is inplace to successfully construct the Resin Modified Pavement. The gradations of the opengraded asphalt mix must be carefully controlled to insure the target 30% air void level isobtained. Should the mat have less than the target 30%, the ability of the grout topenetrate the entire 2” thickness is compromised.The grout must be agitated continuously once the PL7 latex additive has been introducedinto the mix. If proper agitation is not provided, the grout will become too viscous,which will hamper its ability to penetrate the entire 2” thickness of the mat.Planning quantities of grout that will be needed are difficult to calculate. Due to thenature of the pavement system, there are many variables which influence the amount ofgrout that will be required for a project. If air voids vary from the target 30%, the amountof grout required to fill the open graded mat will increase or decrease. On inlaysituations, if the milling depth varies and the thickness of the open graded asphalt matvaries, the quantity of grout required will also change.Since the PL7 latex additive is so expensive (approximately $1000 per 55 gallon drum)and it is imported, a limited amount of PL7 was available for this project. Attention togrout usage must be monitored during construction. Measures should be taken to insurethat too much grout is not wasted by overflowing the mat. During this project when itappeared that grout usage was higher than planned, 225’ of the Resin Modified Pavementtest section was eliminated to insure that the quantity of available PL7 would not beexhausted prior to the completion of the test sections.The difficulty of constructing this pavement system is best exemplified by this project.Even with all of the above listed “attentions to detail” provided during construction, therestill was a 75’ section of the pavement that had to be removed due to a lack of groutpenetration of the mat. For an unexplained reason, a 75’ section of one of the ResinModified Pavement test sections “capped off”, with only approximately the top 1” of the2” thick mat receiving the proper amount of grout. A review of the air voids in the mat ofthis area and the grout flow times don’t indicate any problems. The same constructiontechniques that were employed in the successfully constructed portions of the test section31