Quarry By-products Research Articles

From quarry by-products to a zeolites-based Zn fertilizer with increased resistance to rain leaching

In the face of an extensive literature on the use of zeolites for the removal of metals from water for environmental purposes, it is seldom considered that some metals are also essential nutrients for life and that zeolites could be profitably used to dose their release. Among these, Zn is a key micronutrient, and when its demand by crop is not fully balanced by adequate accessibility, fertilization must be provided using Zn salts that can be, however, easily leached and partly wasted in the environment.In an attempt to solve this critical problem, a new controlled-release formulation of Zn using zeolite-containing geomaterials was designed, prepared, characterized, and tested by applying a sequential, multi-method approach. Different formulations were trialed, and the most effective included 30 wt% pumice by-product and 70 wt% clinoptilolite-rich zeolitized tuff, with about 20 mg/g of exchangeable Zn2+. The enrichment process reached equilibrium after about 8 h, a timing well-tuned with technology transfer. Desorption kinetic tests in a weekly acid environment revealed gradual Zn release, with about 4.28 wt% released after 6 h. When tested as a foliar fertilizer on Vitis vinifera, this formulation demonstrated superior resistance to leaching under simulated rainfall conditions compared to conventional ZnSO4·6H2O fertilizer, maintaining the initial level of Zn (130 mg/kg of dry leaves), while about 22 % of the Zn applied with ZnSO4·6H2O was loss. This outcome was plausibly due to mineral particle adhesion to leaf. Preliminary cost estimates suggest that the product designed here can be placed in the market with competitive sales prices.

Freeze–Thaw Performance Trends of Short-Term Cured Cement-Stabilized Aggregate Quarry By-Product Materials

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.

Strategy for the Mix Design of Building Earthen Materials Made of Quarry By-Products

The use of quarry by-products can enable the commercialization of a clay building material (reconstituted earth) thanks to minimal valorized and perennial stocks of materials. This study shows that quarry by-products can be used to mix design a clay-based building material for the manufacture of CEB. These soils are composed of quarry tailing and clayey muds. Proctor and dry compressive strength tests have shown that the proportion of mud that achieves the highest possible compressive strength is a balance between increasing density through the aggregate arrangement, increasing clay activity, and decreasing density through the increase in water content. These tests resulted in the formulation of materials with compressive strengths of 5.8 MPa and 8.4 MPa at densities of 2135 kg/m3 and 2178 kg/m3. The influence of mud incorporation on the material granulometry and on its characteristics was also studied. Moreover, a model allowing us to link the compressive strength, the clay activity, and the dry density is proposed for the materials composed of quarry by-products. This model enables us to facilitate the mix design and the standardization of the earth material.

Life Cycle Assessment of Aggregate Quarry By-Product Fines in Pavement Applications

Quarry by-products (QB) pose a major environmental challenge for quarries as they accumulate in large quantities, and their beneficial uses are continually sought out. Research at the Illinois Center for Transportation introduced seven applications to utilize QB in chemically stabilized base/subbase pavement layers. These applications were evaluated for field performance through accelerated pavement testing. This paper presents results for the environmental benefits and trade-offs of including QB or blends of QB with recycled materials in pavements. The seven QB applications and a control section were evaluated in terms of environmental impacts using life cycle assessment (LCA). The LCA was conducted in accordance with the International Standard Organization ISO 14044:2006 guidelines. The life cycle impacts were calculated in terms of energy consumption and global warming potential. Three scenarios for (1) as-constructed thicknesses, (2) as-designed thicknesses, and (3) thinner sections for local roads were considered. LCA analysis results were interpreted in terms of the normalized impacts and the response benefits based on falling weight deflectometer resilient deflections to reflect on the impacts due to relative service life expectancy. It was shown that cement-stabilized QB pavement layers, particularly those having QB blended with recycled pavement materials, can have lower environmental impacts when normalized over pavement life and anticipated traffic (i.e., when pavement life expectancy is considered).

Aggregate Subgrade Improvements Using Quarry By-Product Fines: A Case Study

This paper presents a case study for constructing aggregate subgrade improvement (ASI) layers using quarry by-product aggregates (QBA)—a quarry mix of large primary crushed rocks (PCR) and sand-sized quarry fines. The construction took place at Larry Power Road in Bourbonnais Township in Kankakee County, Illinois, where the Illinois Department of Transportation (IDOT) placed two QBA mixes for performance evaluation. The first mix (QBA_M1) consisted of 45% quarry by-products (QB) and 55% railroad ballast-sized PCR. The second mix (QBA_M2) consisted of 31% QB and 69% PCR. Two conventional ASI sections with only PCR were also constructed. All sections consisted of a 229 mm (9 in.) QBA/PCR layer topped with a 76 mm (3 in.) thick dense-graded capping layer. Laboratory studies preceded the construction to recommend optimum QB percentages for the QBA materials and construction practice. The quality and uniformity of the construction was ensured through field testing using dynamic cone penetrometer (DCP), lightweight deflectometer (LWD), and falling weight deflectometer (FWD). The segregation potential of the QBA mixes was monitored by visual inspection, aggregate stockpile sampling, and image analysis techniques. Short-term field evaluation of the constructed QBA layers, particularly QBA_M2 with 31% QB, showed no evidence of major segregation. The QBA ASI layers had slightly lower but comparable strength and stiffness profiles to the conventional ASI sections. The use of QBA materials in ASI was therefore field validated in this case study as a sustainable construction practice to provide stable pavement foundation layers.

Environmentally safe release of plant available potassium and micronutrients from organically amended rock mineral powder

The staggering production of rock dusts and quarry by-products of mining activities poses an immense environmental burden that warrants research for value-added recycling of these rock mineral powders (RMP). In this study, an incubation experiment was conducted to determine potassium (K) and micronutrients (Zn, Cu, Fe and Mn) release from a quarry RMP to support plant nutrition. Four different size fractions of the RMP were incubated with organic amendments (cow dung and legume straw) under controlled conditions for 90 days. Samples were collected at different intervals (7, 15, 30, 45, 60 and 90 days) for the analysis of available K and micronutrients in the mineral-OM mixtures and leachates. There was a significant (p <0.05) increase in pH of leachates from the mineral-OM mixtures. The K release was significantly higher from the finer size fraction of RMP. About 18.7% Zn added as RMP was released during the incubation period. Zn release increased from 4.7 to 23.2% as the particle size of RMP decreased. Similarly, Cu release from RMP increased from 2.9 to 21.6%, with a decrease in the particle size. Fe and Mn recovery from RMP recorded 11.2 and 6.6%, respectively. Combined application of OM and RMP showed significantly higher nutrient release than other treatments. This study indicates that effective blending of RMP with organic amendments could be a potential source of K and micronutrients in agriculture without posing a risk of toxic element contamination to the soil.

Mechanistic Analyses and Modeling of Pavement Sections Utilizing Sustainable Aggregate Quarry By-Product Applications

This paper presents a modeling study based on finite element (FE) analysis to mechanistically evaluate flexible pavements constructed with quarry by-products (QB). Twelve pavement test sections, a control section, and 11 others incorporating QB as unbound subgrade replacement and chemically stabilized base/subbase applications were evaluated for field performance using accelerated pavement testing (APT). First, falling weight deflectometer (FWD) deflection basin parameters were calculated and compared with critical pavement responses to evaluate the structural adequacies of the QB pavement sections. The moduli of the constructed pavement layers were then backcalculated from the FWD deflections using the GT-PAVE FE analysis program with nonlinear and cross-anisotropic layer characterizations. For stabilized QB applications, the layer properties calculated from this analysis for the base/subbase layers were used to calculate critical pavement responses. The sections were compared using a response benefit parameter, defined as the ratio of maximum resilient surface deflection in a conventional pavement, as the control section, to that obtained for each section having a certain QB application in consideration. According to the results obtained from the APT sections and the mechanistic FE analyses, the measured and calculated FWD deflection basins were successfully matched with individual sensor errors not exceeding 5% for all 12 test sections. The calculated response benefits indicated significant advantages for using cement-stabilized QB applications over fly ash-stabilized QB applications and conventional flexible pavement sections. Considering the pavement structural response benefits and good performance trends observed, major cost benefits can be realized by routine use of these sustainable QB applications.

Durability Aspects of Chemically Stabilized Quarry By-Product Applications in Pavement Base and Subbase

Recent research conducted at the Illinois Center for Transportation evaluated sustainable applications of quarry by-products (QB) or QB blended with coarse recycled aggregates in chemically stabilized base and subbase layers in flexible pavements and proved that stabilized QB pavement applications show satisfactory pavement performance. This paper investigates the durability aspects of the evaluated QB applications, particularly in relation to freezing–thawing cycles during winter and wetting–drying conditions. Durability tests were conducted on samples extracted from field test sections previously evaluated with accelerated pavement testing (APT) as well as on new samples prepared in the laboratory with the same QB types and material combinations. Field-extracted samples were exposed to multiple cycles of freezing and thawing and wetting and drying throughout APT. Both sets of samples were evaluated by AASHTO T 135 and AASHTO T 136 for wet–dry and freeze–thaw durability, respectively. The results of durability testing indicated that cement-stabilized QB materials benefited from the long-term curing in the field, whereas fly ash-stabilized QB materials were less durable after exposure to multiple freeze–thaw and wet–dry cycles in the field. Field samples compacted at or near the maximum dry density (i.e., having higher relative densities) consistently showed better performance for durability. Further, durability samples made with QB materials from dolomitic aggregate sources, having higher magnesium oxide content in chemical composition, showed better field performances than those with limestone QB having high calcium oxide content. This was possibly linked to cementation observed in the dolomitic QB applications after being exposed to freeze–thaw cycles in three winters.

Trace metal leaching from quarry by-product-stabilized marine sediments

Millions of cubic meter of sediments are dredged annually to open channels for navigation of ships in ports and harbors. Beneficial reuse of these dredgings is typically possible upon their stabilization with calcium-rich amendments. A series of long-term laboratory column leaching tests and contaminant transport models were employed to study metal leaching behavior of bottom-sea dredged material (DM) and their blends with quarry by-products in the natural environment. Column leach tests yielded generally low or non-detectable metal concentrations. The results of the transport modeling indicated that the analyzed metals leached from the DM and the blends were below the national water quality limits at the point of entry to surface water or upon reaching groundwater. Model results showed a significant reduction in leached porewater concentrations due to adsorption and natural attenuation onto a simulated natural formation located between the DM or treated DM and the body of surface water. The overall findings showed that dredged sediments can be considered for reuse following amendment with quarry by-products.

Engineering Characteristics and Stabilization Performance of Aggregate Quarry By-Products From Different Sources and Crushing Stages

Quarry by-products (QB), usually less than 1/4 in. (6 mm) in size, are the residual deposits from the production of required grades of aggregate. This paper provides findings of a detailed laboratory study with the objective of characterizing the engineering properties of QB materials produced in the primary, secondary, and tertiary aggregate production stages from four different quarries operating in Illinois. Property tests were conducted for determining aggregate gradation, morphological shape characteristics, compaction properties (moisture-density), chemical composition and strength properties of QB samples. Since the unconfined compressive strength for QB materials is relatively low, chemical admixture stabilizers such as Portland cement and Class C fly ash were used to improve the strength properties. This study aims at evaluating properties governing the untreated and stabilized strength of QBs such as source variation, compacted density, chemical composition, gradation, particle shape and angularity, as well as the uniformity of distribution and the effectiveness of stabilizer. QB samples treated with 2% cement or 10% Class C fly ash by dry weight were found to be 10 to 30 times stronger than the virgin QB samples. Such significant increases in the strength of stabilized QB materials observed may indicate suitability of QBs for sustainable pavement applications.

Evaluation of Chemically Stabilized Quarry Byproduct Applications in Base and Subbase Layers through Accelerated Pavement Testing

Research conducted at the Illinois Center for Transportation evaluated sustainable applications of quarry byproducts (QB) or QB blended with coarse recycled aggregates in chemically stabilized base and subbase layers in flexible pavements. In total, eight full-scale test sections, including one conventional flexible pavement with no QB as the control section, were constructed over a subgrade with an engineered strength of 6% California bearing ratio. The test sections were stabilized with either 3% Type I Portland cement or 10% Class C fly ash by dry weight. Fractionated reclaimed asphalt pavements and fractionated recycled concrete aggregates were also used as the recycled coarse aggregates. Based on laboratory tests conducted to determine strength properties of the chemically stabilized samples, QB and recycled aggregates were blended in a ratio of 70% to30% by weight, respectively. A lightweight deflectometer was used to evaluate the quality of the construction and the curing of the test sections. The constructed test sections were then evaluated for performance through accelerated pavement testing (APT) and frequent measurement of surface deformations. The results of APT showed quite a satisfactory rutting performance of all the evaluated QB applications with no observed surface cracking after 135,000 cycles. Four of the test sections were also instrumented with soil pressure cells to measure the wheel load deviator stress on top of the subgrade. The pressure measurements indicated subgrade pressures 3−5 times lower for the stabilized QB sections compared with that of the conventional flexible pavement control section.

Environmental impact and potential use of coal fly ash and sub-economical quarry fine aggregates in concrete

The Israeli quarry industry produces 57 Mt of raw material and ∼4–6Mt of associated sub-economical by-products annually. These sub-economical quarry fines are not used because production and transportation costs considerably exceed their retail value. Therefore these by-products, are stored in large piles of fine grain size particles, create environmental risks to their surrondings.This paper evaluates the possibility of mixing the sub-economical quarry by-products of two Israeli quarries with sub-economical Class F coal fly ash (<20wt.% CaO) to form an economical aggregate sand substitute to be used as a concrete filler product.To study the feasibility of the aggregate as partial substitute to sand in concrete several analyses, including leaching experiements (EN12457-2), analytical techinques (SEM-EDX, ICP-MS, ICP-AES, and XRD), as well as an analysis of the mechanical and chemical properties of the concrete aggregate (strength, workability, and penetration) were performed. Scrubbing quarry waste with coal fly ash was found to be very effective for reducing the leaching rate of potentially harmful trace elements. In addition, adding fly ash with quarry fines as partial substitute to sand enhanced the performance of the concrete mixture and the properties of the fresh and harden concrete.

Sustainable Application of Unbound Quarry Byproducts in Pavement Construction through Aggregate Gradation Optimization

Unbound aggregates are becoming increasingly scarce and expensive due to the loss of rock quarries and gravel mines to other land uses; therefore, it is important to engineer and optimize aggregate gradations for the targeted end-performance. This paper is aimed at validating in the laboratory a newly introduced gradation design concept intended for controlling structural assembly strength (stability) and drainage characteristics (field drainability). Aggregate gradation optimizations were studied for blending and mixing proportions of fine granite tailings (FGT), a typical crushed granite mining byproduct that has long been considered “waste” materials, and coarse crushed granite aggregates (CCGA). To this goal, one of the common quarry byproduct wastes (i.e., FGT), was mixed with CCGA in varying percentages to explore their potential use for building pavement foundations. Large-scale monotonic triaxial compression tests were performed to investigate the effects of blending proportions on the stress-strain behavior. Based on the test results, the optimum aggregate gradations recommended by the new gradation design concept provided enhanced stability without compromising drainability. The new gradation design concept, hence validated in this study with produced optimum gradations, is expected to achieve sustainable and beneficial unbound aggregate applications for cost-effective longlife pavements.

SUSTAINABILITY AND INTEGRATION BETWEEN MINERAL RESOURCES AND C&amp;DW MANAGEMENT: OVERVIEW OF KEY ISSUES TOWARDS A RESOURCE-EFFICIENT EUROPE

Sustainability and integration are becoming keywords in many European Union policies, including ones that are directly or indirectly related to mineral resources and waste management. Moreover, life cycle thinking (LCT) is core to many of these policies. The European Union has recently issued two Communications on A resource efficient Europe and Roadmap to a Resource Efficient Europe, the stated goal of which is to reconsider the whole life cycle of resource use so as to make the European Union a circular economy, one based on recycling and the use of waste as a resource. Construction and Demolition Waste (C&DW) is a possible source of unconventional aggregates, which are recognised as essential and valuable resources for the economic and social development of humankind. The objective of this paper is to give an overview on some key issues relevant to the integration between mineral resources and C&DW management, in urban areas, towards a more resource-efficient Europe. The paper starts from a definition of Sustainable Supply Mix (SSM) of aggregates, i.e. a selected blend of natural aggregates, quarry by-products and recycled waste that minimizes total negative impacts and maximizes overall benefits to society. Then it turns on available technologies for C&DW recycling and technical quality requirement of recycled aggregates. Finally, it focuses on assessment tools and metrics that are currently used to understand and enhance eco-efficiency.

Laboratory validation of a gradation design concept for sustainable applications of unbound granular materials in pavement construction

Unbound aggregates are becoming increasingly scarce and expensive due to the loss of rock quarries and gravel mines to other land uses; therefore, it is important to engineer and optimize aggregate gradations for the targeted end-performances. This paper is aimed at validating in the laboratory a newly introduced gradation design concept intended for controlling structural assembly strength (stability) and drainage characteristics (field drainability). Aggregate gradation optimizations were studied for two applications: (1) unbound permeable aggregate base (UPAB) and (2) mixing proportions of blending fine granite tailings (FGT), a typical crushed granite mining by-product that has long been considered “waste” materials, with coarse crushed granite aggregates (CCGA). To this goal, five representative gradations were first selected according to the current Minnesota DOT UPAB gradation band, and the effects of different UPAB gradation designs on the shear strength properties and particle breakage potential were investigated using a large-scale direct shear test device. In the second application, one of the common quarry byproduct wastes (i.e., FGT), were mixed with CCGA in varying percentages to explore their potential use for building pavement foundations. Both laboratory permeability and large-scale monotonic triaxial compression tests were performed to investigate the effects of blending proportions on the stress–strain behavior. Based on the test results, the optimum aggregate gradations recommended by the new gradation design concept provided enhanced stability without compromising drainability. The new gradation design concept, hence validated in this study with produced optimum gradations, is expected to achieve sustainable and beneficial unbound aggregate applications for cost-effective long-life pavements.

Utilization of quarry by-products for reduction of expansion due to alkali-aggregate reaction

The replacement of normal fine aggregate with high fines limestone screenings is a technique to reduce waste from crushed stone operations, while potentially improving the durability and performance of concrete. The main objective of this research is to evaluate varying percentages of high fines limestone screenings as a partial weight replacement of reactive fine aggregate (similar to limestone sweetening) in mortars to assess reductions in the expansion due to alkali-aggregate reaction (ASTM C 227, ASTM C 1260, and modified ASTM C 1105). Fresh and hardened properties have been evaluated to assess the effects of limestone screenings on performance criteria. Environmental scanning electron microscopy (ESEM) was performed to visually observe and confirm alkali-aggregate reaction products and associated damage. From the physical testing and microstructural analysis, it was found that 50% or more of limestone screenings significantly reduce expansions due to alkali-aggregate reaction, attributed to the preference for monocarbonate formation in the presence of limestone and/or reactive silica dilution. Replacements less than 50% did not significantly reduce expansion.

Cement-Treated Bases Containing Reclaimed Asphalt Pavement, Quarry By-Products, and Fibers

A laboratory study was conducted to demonstrate that sustainable cement-treated base courses can be achieved through the application of waste quarry by-products (QB) and fractionated reclaimed asphalt pavement (FRAP). Aggregate packing tests were performed on blends of QB and FRAP to determine an optimal blend that would minimize the void content of the aggregate structure while achieving acceptable strengths. The optimal aggregate packing proportions were found to be 70% QB with 30% FRAP. Modified Proctor samples were prepared to determine the moisture–density relationship with several cement contents (2% to 4% by total volume) on dolomite or FRAP coarse aggregate mixed with QB and 0.4% synthetic macrofibers. Mixture design performances were evaluated through strength (compression and split tension) and modulus tests. As expected, higher cement content increased both the strength and elastic modulus for all mixes tested. Mixtures containing virgin aggregates with QB yielded statistically greater elastic moduli than mixtures with FRAP and QB. Fibers did not have a statistical effect on strength or elastic modulus but did provide residual shear capacity across cracks. The QB and FRAP or virgin mixtures with 3% to 4% cement content exceeded the strengths for typical cement-stabilized base materials in the literature. The measured strength and elastic modulus properties show that QB, together with FRAP or virgin aggregates, can be successfully applied as a cement-treated foundation layer.

The influence of water content on the Dynamic Cone Penetration Index of a lateritic soil stabilized with various percentages of a quarry by-product

Laterites and lateritic soils have been a source of good pavement material in tropical countries for a long time. However, increasingly it is becoming difficult to find lateritic material that meets the required specification within economic haulage distances of roads under construction. This has necessitated, among other things, the need for stabilization of lateritic soils of high fines content with quarry by-products. The use of such marginal material however requires that they be properly compacted in order to improve their engineering properties. For low volume roads there is the need for simple, rapid and economical methods of compaction quality control. This study builds upon previous ones on using the Dynamic Cone Penetrometer (DCP) for compaction verification and seeks to account for post-compaction water content changes. The use of the DCP for compaction verification starts with the establishment of a correlation between the Dynamic Cone Penetration Index (DPI) and the relative level of compaction. However, the DPI is sensitive to water content changes even at constant dry density. The objective of this study is to investigate how the DPI of a lateritic soil determined at the optimum moisture content changes when the water content varies and the fines content reduces. The results show that small changes in water content can lead to significant effects on DPI.

Using alkali-activated natural aluminosilicate minerals to produce compressed masonry construction materials

This paper documents research that explores the possibility of alkali activating the aluminosilicate minerals reclaimed from recycled quarried soil products to produce compressed masonry construction materials. The objective of the research is to identify and optimize the principal variables affecting geopolymerization of a common quarry by-product containing montmorillonite and alkali feldspars and other minerals. The key variables optimized in the research were: type and concentration of alkali activator, optimum moisture content for compaction and geopolymerization, and curing temperature and duration. Geopolymerization of natural aluminosilicate minerals exhibiting low reactivity typically require supplementary cementitious materials to achieve high strength. In this case, however, the use of supplementary cementitious materials was eliminated by promoting nucleation in the geopolymerization reaction. The addition of 4wt.% of nanocalcite or 0.25wt.% of synthetic nanoaluminosilicates significantly improved the 1- and 7-day compressive strengths of test specimens. Finally, the total porosity and pore-size distribution of the microstructure of certain specimens were characterized. The results were correlated with water absorption and drying shrinkage performance. The results demonstrate the feasibility of alkali activating commonly-occurring, natural aluminosilicates in the soils to produce compressed masonry blocks that exhibit reliable mechanical performance without the use of Portland cement or supplemental cementitious materials.

Characterization and Stabilization of Quarry Byproducts for Sustainable Pavement Applications

Increased emphasis in the construction industry on sustainability and recycling requires production of aggregate gradations with lower dust and smaller maximum sizes, leading to increased amounts of quarry byproducts (QB). Constituted of particles usually less than ¼ in. in size, QB is the residue deposit from the production of required grades of aggregate often stockpiled in excess quantities. This paper provides findings of an industry survey of Illinois aggregate producers on the annual production rate, excess QB generated, and the current application areas of QB. The current uses of QB in Illinois were limited to applications with low amounts of QB, and, therefore, excessive amounts of QB may remain in the stockpiles. A detailed laboratory study conducted to characterize the engineering properties of QB materials produced in the primary, secondary, and tertiary aggregate production stages examined aggregate gradation, shape characteristics, and mineralogical analysis. Differences in shape and gradation of QB materials produced in each crushing stage were observed. Strength tests, including unconfined compressive strength (UCS) and direct shear, were conducted. Because the UCS for QB materials is very low, chemical admixtures such as portland cement and Class C fly ash were used to improve their strength properties. In general, treated QB materials were 10 to 30 times stronger than the virgin QB samples. In the case of 10% Class C fly ash-treatment, UCS values achieved were as high as 340 psi. Such significant increases observed in the strength of stabilized QB materials may indicate suitability of QB for sustainable pavement applications.