Extending The Nation’s Road Maintenance Dollars Nov 17 – 19, 2014 Hyatt Regency Baltimore, Maryland #ppra2014 Effects of Formulation Variables on Micro Surfacing Durability Andrew Bickford Product Development Platform Manager, Asphalt MeadWestvaco – Specialty Chemicals Division

Mix Design #ppra2014 PPRA FALL MEETING 2014 Purpose: Qualify materials and determine optimum ratios of components to achieve performance demands

Mix Design #ppra2014 PPRA FALL MEETING 2014 HMA Materials: Aggregate, binder (maybe modified), anti-strips Optimize ratio of aggregate to binder (hold anti-strip constant) Micro surfacing Materials: Aggregate, binder (w/ additives?), emulsifier, pH, mineral filler, latex polymer, mix additives, mix water Optimize ratio of aggregate to binder (all else constant)? Optimize ratio of aggregate to binder (allow others to vary)? Optimize (and limit within known ranges) all components?

Mix Design #ppra2014 PPRA FALL MEETING 2014 (1) Optimize aggregate/binder ratio (others constant)? Would be suitable if no variation was needed during application (2) Optimize aggregate/binder ratio (others vary)? Would be suitable if variation is required, and the variation has not appreciable effect on the micro surfacing performance (3) Optimize and range limit all components? Would apply if all of the components have positive/negative effects that must be known to predict performance

Mix Design #ppra2014 PPRA FALL MEETING 2014 Is variation needed? Why vary from the optimum design? Weather! Micro surfacing functions by a complex series of chemical reactions and environmental conditions Temperature impacts reaction speed Air temperature Radiative heating Humidity impacts ability of water to evaporate

Mix Design #ppra2014 PPRA FALL MEETING 2014 Conclusion: We must be allowed to vary from a single optimum design formulation The question: Can we vary, without limits, the other components of the mix?

This Study #ppra2014 PPRA FALL MEETING 2014 Alter an optimized design carried out at 77°F to allow field use at 100°F Determine the impact of common emulsion and mix component variations on “performance” Use 6 day soak WTAT as the performance measurement (durability) Mimics wear under traffic Predicts susceptibility to water damage

This Study #ppra2014 PPRA FALL MEETING 2014 Vary these components… Emulsifier content in the emulsion Water content in the mix Mix prewet additive content Mineral filler content, in combination with prewet retarders …to allow the system to be used under common but demanding field conditions... …and measure 6 day soak WTAT abrasion loss

This Study #ppra2014 PPRA FALL MEETING 2014 Emulsifier content in the emulsion (higher) Extra surfactant interacts with aggregate surface to pacify it Too much surfactant can create a “slip plane”, adhesion loss Water content in the mix Provides “space” between reactive components to help regulate reaction rates Excess water can cause the abrasion resistant or load bearing structure to form incorrectly (component segregation)

This Study #ppra2014 PPRA FALL MEETING 2014 Mix prewet additive content Pacifies the aggregate surface, can act as an adhesion agent Over-saturation creates an unreactive surface, poor adhesion Mineral fillers in combination with prewet additives Mineral fillers provide fines for mastic, may provide pH shift to enhance curing Some prewet retarders are reactive with mineral fillers Fillers and prewet additives together may be synergistic or antagonistic to long term performance properties

Control Formulation #ppra2014 PPRA FALL MEETING 2014 Emulsion 1.8% emulsifier 3.5% cationic latex 2.0 solution pH 62% PG 64-22

Control Formulation #ppra2014 PPRA FALL MEETING 2014 Micro surfacing mix ISSA type II aggregate (siliceous, SE=65) 1.0% type I portland cement 0% prewet additive 6.0% water 12.0% asphalt emulsion

Control Formulation #ppra2014 PPRA FALL MEETING 2014 Mix properties, lab conditions Workability (mixing time) = 180 seconds Wet cohesion – 30 minutes = 13N, 60 minutes = 17NS 6 day soak WTAT = 72 g/ft 2 loss Loaded wheel – not evaluated in this study At 100°F Workability (mixing time) = 60 seconds* *Mix water was increased from 6 to 7% to maintain proper mix consistency

Effect of Increasing Emulsifier % #ppra2014 PPRA FALL MEETING 2014 To maintain full workability at 100°F… Increase emulsifier to 2.1% at 0.5% cement content, or… Increase emulsifier to 2.4% at 1.0 cement content

Effect of Increasing Mix Water % #ppra2014 PPRA FALL MEETING 2014 To maintain full workability at 100°F… Increase mix water content by 4% (independent of mineral filler content)

Effect of Adding Prewet Retarder #ppra2014 PPRA FALL MEETING 2014 To maintain full workability at 100°F… Add 0.10% additive at 0.5% cement content, or… Add 0.18% additive at 1.0% cement content

Effect of Changed or Combined Mineral Filler (Cement and/or Alum) #ppra2014 PPRA FALL MEETING 2014 To maintain full workability at 100°F… Add 0.20% alum at 0% cement content, or… Add 0.10% alum at 0.5% cement content, or… Add 0.20% alum at 1.0% cement content

Summary #ppra2014 PPRA FALL MEETING 2014 In this system… Every common formulation adjustment for high temperature application had an effect on WTAT With two exceptions, all of the changes had a negative effect on WTAT Can it be concluded that every set of micro surfacing materials will react to change in the same way? No. Solution? Know your application conditions, and know your system.

#ppra2014 PPRA FALL MEETING 2014 Andrew Bickford Product Development Platform Manager, Pavement Preservation MeadWestvaco – Specialty Chemicals Division 5255 Virginia Avenue North Charleston, SC