Taeyun Kong

Otta seal, a surface treatment method that typically employs locally sourced low-quality aggregates, has been recognized as a cost-effective and sustainable option for bituminous surfacing of low-volume roads. Because quarry by-products (QBs), sand-sized residues from quarrying operations, remain largely underutilized despite being readily available and exhibiting well-graded behavior, offering potential for use in Otta seal applications, a feasibility study on incorporating QBs into Otta seal design was conducted using adaptations of existing chip seal design methods: (1) modified McLeod; (2) modified Kearby; and (3) Austroads methods. The laboratory study on Otta-seal specimens incorporating QBs revealed that optimal lab-scale specimen preparation was achieved with a double-layer configuration where aggregates were separated using a No.8 sieve (2.36 mm). Using an optimized lab specimen configuration, three design methods were evaluated with two QBs and one typical Otta-seal aggregate as a control. Performance tests using sweep testing and a modified Hamburg Wheel Tracker (HWT) showed that specimens prepared with QBs demonstrated comparable or superior aggregate retention compared with those with typical Otta-seal aggregate, highlighting the feasibility of incorporating QBs in Otta seals. Among the design methods, the modified Kearby method consistently delivered the best performance, with an adequate binder/aggregate ratio resulting in the lowest aggregate loss in the sweep and modified HWT testing. Texture properties computed using close-range photogrammetry effectively captured the macro-surface texture of the Otta-seal specimens, accounting for the physical characteristics of QBs and typical Otta-seal aggregates and demonstrated an inverse relationship between surface roughness and aggregate retention.

This report evaluates through comprehensive laboratory testing the potential of utilizing quarry by-products (QBs) in Otta seal applications as a sustainable and economical alternative to conventional aggregates. An asphalt surface treatment used on low-volume roads, Otta seal consists of a relatively thick application of asphalt binder, covered with a graded aggregate layer that allows the use of locally available and marginal-quality materials. Commonly used chip seal design methods were modified to develop a rational design approach for Otta seal, as the conventional Otta seal design procedure is largely empirical. Material characterization was conducted to determine aggregate gradation, physical properties, and emulsion characteristics required for Otta seal design. A double-layer Otta seal configuration was selected based on laboratory optimization involving testing of various configurations and incorporating QBs. The effect of curing temperature and duration on performance was also investigated through weight-loss monitoring and post-curing sweep testing. The performance of laboratory-optimized, QB-based Otta seals was then evaluated and compared with typical Otta seal aggregate through multiple laboratory tests. Performance assessment included sweep testing to evaluate aggregate retention, a modified Hamburg wheel-tracking (HWT) test to evaluate aggregate retention under simulated braking conditions, and close-range photogrammetry to quantify surface texture. The QB-based Otta seal specimens showed performance trends comparable to those constructed with typical Otta seal aggregate. The best-performing design method was selected, and QB-based specimens were further evaluated for susceptibility to bleeding under repeated wheel passes using modified HWT, friction characteristics using a dynamic friction tester, and changes in composite modulus using a box-test setup with lightweight deflectometer testing. Results indicated that QB-based Otta seal provides adequate resistance to bleeding and sufficient friction for safe traffic movement, demonstrating strong potential as a sustainable and cost-effective pavement-preservation alternative for low-volume roads.

This study investigated the mechanical strength and freeze-thaw durability of carbonate-based aggregate quarry by-products (QBs) stabilized with cement alone and in combination with calcined clay (metakaolin, MK) for potential use in pavement foundation layers. The primary objective was to evaluate the chemical and physical characteristics of dolomitic and limestone QBs and determine how these factors influence strength development and durability under different stabilization conditions. Four QBs with varying carbonate compositions, ranging from highly dolomitic aggregates to nearly pure limestone, were examined. QBs were stabilized with 3% cement and tested under short- and long-term curing conditions. Short-term testing indicated the curing period was insufficient for the mineralogical properties of carbonate aggregates to fully manifest; instead, performance was governed primarily by physical characteristics, particularly particle packing. In contrast, long-term testing showed the effects of carbonate mineralogy became more pronounced, as the mineral components began contributing more noticeably to overall performance. Dolomitic QBs demonstrated superior strength and stiffness development along with higher retention of these properties after 10 freeze-thaw cycles due to the formation of hydrotalcite, a magnesium-aluminum layered double hydroxide phase. When cement was partially replaced with MK at the optimum MK-to-cement ratio of 1:4, both early-age and long-term performance improved relative to cement-only specimens. Chemical analyses showed that MK participated in pozzolanic and carboaluminate reactions, producing additional calcium-alumino-silicate-hydrate (C-A-S-H) gels and carboaluminate phases. Since MK rapidly consumed available calcium hydroxide to form C-A-S-H gel and carboaluminate phases, hydrotalcite formation was suppressed. This mechanism resulted in comparable long-term performance for all QBs, irrespective of carbonate types. The findings demonstrate that carbonate-based QBs can be transformed into high-performing, durable, and sustainable pavement foundation materials when their physical and mineralogical properties are considered properly and supplementary cementitious materials such as MK are incorporated effectively.

Recent research studies conducted at the Illinois Center for Transportation focused on sustainable applications of quarry-by-products (QB) as pavement foundation materials and demonstrated the superior durability performance of dolomitic aggregate materials exposed to long-term cementitious reaction and repeated freezing and thawing. This study investigated the influence of QB chemical composition on the strength of cement-stabilized samples exposed to freeze–thaw cycles. Dolomitic QB materials from different quarries in Illinois and with different magnesium oxide (MgO) content, and a control limestone sample were chemically characterized by X-ray fluorescence and X-ray diffraction techniques. The QB materials were then stabilized with 3% cement and subjected to a 7-day curing period, followed by freeze–thaw conditioning. Unconfined compressive strength and resonant frequency tests were conducted to examine how the percentage of MgO and dolomitic minerals could alter the strength/stiffness with freeze–thaw cycles. Optical microscopy analysis was also performed to observe the extent of microstructure damage with freezing and thawing. Over the course of the applied freeze–thaw cycles, no notable minerology effect on strength or stiffness characteristics was observed for the short-term curing. Instead, performance was predominantly governed by physical properties, such as the particle size distribution, which played a more significant role after short-term curing. Well-graded QB materials with optimum packing, following Talbot’s equation with a 0.45 exponent, consistently exhibited the highest strength after any freeze–thaw cycle. The next phase of research, focusing on long-term curing, is expected to provide more insights into the chemical and mineralogical effects of QB materials on durability performance.