Sustainable pavement applications utilizing quarry by-products and recycled/nontraditional aggregate materials

Quarry By-Products;Accelerated Pavement Testing;Life Cycle Assessment;Life Cycle Cost Analysis;Sustainability;Mechanistic Modelling;Pavement;Stabilized;Aggregates;Transportation Geotechnics;Nontraditional Aggregates;FRAP;FRCA

Qamhia, Issam I.A.

关键词: Quarry By-Products;    Accelerated Pavement Testing;    Life Cycle Assessment;    Life Cycle Cost Analysis;    Sustainability;    Mechanistic Modelling;    Pavement;    Stabilized;    Aggregates;    Transportation Geotechnics;    Nontraditional Aggregates;    FRAP;    FRCA;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/104851/QAMHIA-DISSERTATION-2019.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Quarry By-products (QB), usually less than 0.25 in. (6 mm) in size, are the residual deposits from the production of required grades of aggregates and are often stockpiled in excess quantities at the quarries. More than 175 million US tons of QB are produced every year from the 3,000 operating quarries around the US. QB pose environmental and economic challenges as they accumulate in large quantities in landfills or interfere with quarry operations. With recent focus on sustainable construction practices and the scarcity of natural resources, more common and sustainable uses of by-product materials such as QB are becoming imperative.This dissertation focuses on the introduction and evaluation of new sustainable applications of QB and/or QB mixed with other marginal, virgin or recycled aggregate materials in pavements. The selected QB applications were evaluated through the construction of full-scale pavement test sections utilizing QB in targeted sustainable applications, and testing them with heavy wheel loads through Accelerated Pavement Testing (APT). The QB applications studied included both unbound and bound (chemically stabilized) pavement subsurface/foundation layers. The studied QB pavement applications were in five categories: (1) Using QB for filling voids between large stones as aggregate subgrade on soft subgrades; (2) increased fines content (e.g. 15% QB fines passing No. 200 sieve) in dense-graded aggregate subbase over soft subgrade soils; (3) using QB as a cement or fly ash-treated subbase (e.g., in inverted pavements); (4) using QB as a cement-treated base material; and (5) for base course applications, blending QB with coarse aggregate fractions of recycled materials and stabilizing the blends with 3% cement or 10% class C fly ash.In preparation for the field evaluations, several laboratory studies were conducted to finalize the designs of intended QB applications. The main laboratory studies were: (1) A packing study of QB with recycled coarse aggregates to determine the optimum blending ratio; (2) a packing study to aid the construction of large aggregate subgrade with QB materials filling the inherent voids; and, (3) Unconfined Compressive Strength (UCS) tests for chemically stabilized QB samples. Fifteen full-scale pavement test sections utilizing QB applications and one conventional flexible section were constructed in three ‘Test Cells.’Cell 1 had four paved and four unpaved test sections to study construction platforms and low volume road applications of QB. Cells 2 and 3 studied chemically stabilized QB applications for base and subbase layers. Construction activities included engineering the top 305 mm (12 in.) of existing subgrade to a California Bearing Ratio (CBR) = 1% for Cell 1 test sections and to a CBR = 6% for all the pavement test sections in Cells 2 and 3. Subgrade modification was achieved through moisture adjustment and compaction. The construction of the QB layers were successfully achieved and extensively monitored. The data for nuclear density measurements and moisture contents indicated that nearly all the test sections were constructed at or near the targeted optimum moisture contents and achieved proper densities. A Lightweight Deflectometer (LWD) was used to assess the stiffness of the constructed layers after the construction of each lift. It was also used to monitor the increase in stiffness of the chemically stabilized layers. The increase in stiffness of the chemically stabilized layers was the highest for cement-stabilized test sections and usually lower for fly ash-stabilized sections. Following the paving of test sections with Hot Mix Asphalt (HMA), Falling Weight Deflectometer (FWD) tests were conducted on all finished surfaces. Significantly low deflection values were measured for the sections with cement-stabilized QB and QB blends with recycled aggregates. APT was conducted using the Advanced Transportation Loading Assembly (ATLAS). A constant unidirectional wheel load of 10 kips (44.5 kN), a tire pressure of 110 psi (760 kPa), and a constant speed of 5 mph (8 km/h) were assigned. The exceptionally good performance of some of the stabilized QB applications in Cells 2 and 3 necessitated trafficking in excess of 100,000 passes; an increased wheel load/tire pressure combination of 14 kip (62.3 kN)/ 125 psi (862 kPa) was adopted for the additional 35,000 passes. Four of the test sections in Cells 2 and 3 were instrumented with soil pressure cells on top of the engineered CBR = 6% subgrade. Data collected from these pressure cells showed that significantly low vertical pressures were transmitted to the subgrade for sections with stabilized bases/subbases.Measurements for rutting progression for the construction platform and HMA-paved test sections in Cell 1 showed good performance for the sections constructed with 15% nonplastic fines and with blends of large aggregate subgrade rocks with QB. Measurements of rutting progression in Cells 2 and 3 indicated exceptionally good performance of sections with blends of QB and recycled coarse aggregates stabilized with cement. Generally, sections stabilized with cement accumulated lower rutting than those stabilized with fly ash. No significant differences in rutting performance were detected for sections with QB from two different aggregate sources. For the inverted section with a cement-stabilized QB subbase, measured rut amounts were significantly lower than those in the test section with the fly ash-stabilized QB subbase. None of the stabilized sections showed any signs of cracks.Additional testing and forensic analyses were conducted after the APT study to better assess the performance of the constructed sections. These tests included: (1) FWD testing before and after APT; (2) HMA coring; (3) Dynamic Cone Penetrometer (DCP) testing for the aggregate subbase/base layers; (4) flooded tests for the aggregate subgrade/QB test sections; and (5) trenching to assess uniformity of construction and determine as-constructed layer thicknesses. Results from these forensic tests further supported the conclusions from the APT study indicating the overall quite satisfactory performance for the studied sustainable QB applications. Mechanistic analysis was conducted using GT-PAVE axisymmetric finite-element program to analyze the FWD results, and to calculate response benefits based on resilient FWD deflection for various design thicknesses and material properties. Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) studies were conducted to assess the environmental impacts and cost benefits for the studied QB applications. LCA and LCCA results for three scenarios, i.e. as-constructed and as-designed pavement thicknesses studied though APT and newly proposed pavement sections for low volume pavement alternatives, indicated that chemically stabilized QB and QB blended with recycled coarse aggregates could be successfully used to construct sustainable, resilient, and low cost pavements. Particularly, pavement structures with a low 3% cement-stabilized QB applications created high stiffness base/subbase layers in this study; they exhibited significant response benefits due to low FWD measured and predicted surface deflections and can withstand higher traffic volumes over pavement life.