Shingle Roof Research Articles

Investigation of the proposed solar-driven moisture phenomenon in asphalt shingle roofs

Unvented attics are an energy-efficiency measure to reduce the thermal load of the conditioned space and decrease the space conditioning energy consumption by about 10%. This retrofit is usually done by spraying polyurethane foam underneath the roof sheathing, and on the gables and soffits of an attic to provide an air barrier and a thermal control layer. Unvented attics perform well from this perspective, but from a moisture perspective sometimes homes with unvented attics have high interior humidity or moisture damage to the roof. As homes become more air tight and energy efficient, a better understanding of the hygrothermal dynamics of homes with energy-efficient envelopes becomes more important. One proposed reason for high unvented attic humidity has been that moisture can come through the asphalt shingle roof system and increase the moisture content of the roof sheathing and attic air. This has been called “solar-driven moisture.” Oak Ridge National Laboratory investigated this proposed phenomenon by examining the physical properties of a roof and the physics required for the phenomenon. Results showed that there are not favorable conditions for solar-driven moisture to occur. Oak Ridge National Laboratory also conducted an experimental study in a home with an unvented attic and compared the humidity below the roof sheathing before and after a vapor impermeable underlayment was installed. There was no statistically significant difference in absolute humidity before and after the impermeable underlayment was installed. The outcomes of the theoretical and experimental studies suggest that solar-driven moisture does not occur in any significant amount.

Investigation on the Effect of Recycled Asphalt Shingle (RAS) in Portland Cement Mortar

Tear-off roofing shingle, referred to as Reclaimed asphalt shingle (RAS), is the byproduct of construction demolition and it is a major solid waste stream in the U.S. Reuse of this byproduct in road construction sector can contribute to the success of materials sustainability as well as landfill conservation. Ground RAS has similar particle distribution as sand and its major component includes aggregate granules, fibers, and asphalt. To promote the beneficial utilization of RAS, this study evaluates the effect of RAS in cement mortar when used as replacement of sand. In addition, the study investigates how cellulose fibers from RAS behave under high alkaline environment during cement hydration process, which may significantly affect mortar’s strength performance. The laboratory study includes measurements of physical, mechanical, and durability behaviors of cement mortar containing RAS replacing sand up to 30%. It was found that the optimum mixture proportions are 5% and 10% for compressive strength and toughness, respectively.

An Assessment of the Asphalt Shingle Roofing Process for Residential Buildings

Asphalt shingle roofing is performed by specialty contractors in the construction industry with the roofing crew performing tasks in different areas on the roof simultaneously. While asphalt shingle roofing materials have improved, the roofing construction process has not changed significantly over the past 70 years.This paper describes the process, factors that affect the productivity of the workers, and methods for calculating productivity in terms of man-hours worked and cost per unit output. Safety is also a concern in roofing. While falls from roofs are a major cause of injuries on the construction job site, other injuries common to roofers include sprains and strains to the back, knees and ankles. The trend of constructing steep roofs, common in Texas high end residential homes, are implicated in these injuries. Safety plans and worker safety climate are low priorities for financially strapped construction companies. Designing out the hazard would be more effective than Personal Protective Equipment (PPE) in preventing accidents in the roofing industry.The paper concludes that research and development are needed to improve roofing construction methods to provide a safe and healthy environment for the worker and reduce costs of construction.

Experimental characterisation of base asphalt binder used for shingles production under static and dynamic loading

Significant fluctuations in asphalt binder cost and limited budget for road construction, as well as growing needs for saving natural resources, have contributed to the increased use of recyclable materials in asphalt pavement industries. During the past decades, many transportation agencies in the USA have investigated the effect of adding different types of recycled asphalt shingle (RAS) on the asphalt mixtures performance, while limits were proposed on the maximum amount of RAS that can be recycled. However, not many studies in the USA and Europe have addressed the possibility of directly using base roofing shingles binders for preparing asphalt mixture despite this binder is relatively less expensive than conventional asphalt binders. In this paper, the mechanical performance of base asphalt binder used for roofing flux and shingle production was evaluated with two experimental test methods: bending beam rheometer creep test and dynamic shear rheometer complex modulus test. Based on experimental data, creep stiffness, m-value, thermal stress, critical cracking temperature and complex modulus were calculated and then compared graphically and statistically with the same parameters obtained from two conventional binders commonly used for asphalt pavements. The comparison between the three binders indicates that the shingle binder presents reasonable low and high temperature performance even though the base binder may have different consistency and performance grade compared to the conventional ones. The statistical analysis suggests that the base binder for shingle production can be successfully incorporated into asphalt mixture and that any current specification limiting the content of shingles binder in asphalt mixture should be more asphalt binder type and mix design specific.

The Home Front, 1942–1945

The Home Front, 1942–1945 Robert Lacy (bio) WORLD War ii was good for us. In the months leading up to it, mother was working in a sawmill commissary in Kilgore for eleven dollars a week. But following the attack on Pearl Harbor, word quickly reached East Texas that the shipyards down in Houston were hiring and paying good money, and that there were plenty of jobs for all. Mother and her younger brother, John Allen, decided to roll the dice. Within weeks our two families—mother and I, John Allen, his wife Doris, and their two kids, Roger and Gay—were installed in a small frame house on Common Street in a rundown section of Houston. The little house had two bedrooms: a small one for mother and me, and a larger one for Johnny and his brood. There was also a living room, bathroom, and kitchen. The kitchen came equipped with a stove and an icebox. Not a refrigerator, an icebox—for which an iceman had to deliver a big gray block of ice one or more times a week. I remember this icebox particularly well because Roger and I turned it over one night while wrestling on the kitchen floor. I remember the milk spilling out of it onto him and me, the general mess the icebox’s contents made on the linoleum-covered floor, and, most of all, the spanking we each got soon after the icebox had been placed upright again and the floor mopped up. I was six when this happened; Roger was five. There were two big shipyards in Houston at the time. One was called simply Houston Shipyard and the other was called Brown Shipyard. Johnny went to work as a welder’s helper at Houston Shipyard and mother went to work as an “expediter” at Brown. They were each paid about forty dollars a week as I remember it, a huge improvement over the prevailing wage back up in Kilgore. Brown Shipyard was a war-time spinoff of Brown & Root Construction, whose owners would become in later years big financial backers of Lyndon Johnson. I’m still not sure what an expediter was, but I think it had something to do with making sure all the various parts required in building a ship got to the right place at the right time and in a suitable number—something like that. [End Page 629] They were making small, fast boats called destroyer escorts, or de’s, at Brown, and turning them out by the dozen. Somebody had to keep track of what was going on. And mother, with her high-school education, became one of the ones who did. A photographer for the Houston Chronicle newspaper came out to the shipyard one afternoon and took a picture of her seated up on a stack of de materials. She was holding a clipboard in one hand and a pencil in the other and appeared to be checking off items destined to become part of yet another de. She looked perky and cute as could be—sort of a cross between Rosie the Riveter and a Hollywood glamour-gal—perched up there in her coveralls, her hardhat pushed back on her head. We kept a copy of that picture around the house for years afterward, but finally misplaced it in one of our many moves. I wish I still had it. Most of my memories of Houston are sketchy and rather dim. It was many years ago and I was only six. I remember that there were several large boardinghouses across the street from us, and that they were two-story, frame, and in need of paint. I remember waiting out a hurricane in the front room of the little house on Common Street, watching roofing shingles being ripped off the boardinghouses across the way and being frightened by both the high wind and heavy rain, and by the fireballs off the electricity transformers that went rolling gaily down the street. I remember getting hit in the head by a rock on a playground, but I don’t remember who threw it, or why. I remember Roger, who had a quick temper, chasing me...

Application and validation of an asphalt shingle roofing damage estimation method

Asphalt shingle roofing that is widely used in US has been observed to be prone to wind damage. Also roofing damage often creates the opening that leads rain water into the building and may cause significant further loss to interior contents. Correctly estimating wind damage for asphalt shingle roofing has its significance from the perspective of wind loss mitigation and wind risk management. This paper focuses on the application and validation of the asphalt shingle roof damage estimation method presented in the previous paper (Huang et. al, 2015, “Data-based probabilistic damage estimation for asphalt shingle roofing.” J. Struct. Eng., http://dx.doi.org/10.1061/(ASCE)ST.1943-541X.0001300, thereafter denoted as DBPDE method). Firstly, the DBPDE method is employed to estimate the asphalt shingle roofing damage for a single residence. Secondly, the estimation procedure is extended to a group of residences in an area. Finally, the shingle resistance estimation and the validation of the damage estimation method are conducted using field survey data.

Data-Based Probabilistic Damage Estimation for Asphalt Shingle Roofing

AbstractAsphalt shingles on residential building roofs are susceptible to damage, and often blow off, during windstorms. The loss of shingles can also result in damage to the content in the interior of a residence by allowing the penetration of rain. This paper presents the data-based probabilistic damage estimation procedure to predict wind-induced damage on asphalt shingle roofing, using wind pressure data from wind tunnel testing. First, the probability distribution of peak wind pressure over a certain period for pressure data associated with each measurement tap is estimated. Then, the failure probability of the shingle associated with each tap and the damage ratio for the entire roofing shall be determined. Finally, a neural network is adopted to predict the wind-induced damage ratio for asphalt roof shingles considering multiple contributing factors such as wind speed, wind angle of attack, building sizes, roof slope, and terrain roughness.

Investigation on the microstructure of recycled asphalt shingle binder and its blending with virgin bitumen

Recycling waste roofing shingles into pavement construction has attracted more attention due to their high content of usable bitumen. Waste roofing shingles have gone through an air-blowing process during production and are exposed to severe weather for many years during service life, which yields extremely aged asphalt binder. The difference in nature between virgin binder and binder from recycled asphalt shingle (RAS) has led to concerns over binder blending and compatibility of asphalt paving mixtures containing RAS. Therefore, usage of RAS has been commonly limited to a maximum of 3–5% incorporation. Currently, there is very little information in the literature that has addressed the RAS–virgin binder blending issues. This paper used atomic force microscopy (AFM) to characterise microstructural properties of the selected virgin, post-manufactured RAS and post-consumer RAS (tear-off) binders, as well as the temperature dependence of microstructure in one type of tear-off RAS binder. Meanwhile, the mode of interaction while bringing together virgin and RAS binders, that is, the extent of mixing or blending, was first observed in this study. According to the observations, AFM proved to be capable of differentiating virgin binder from RAS binder in terms of microstructure. The microstructure of tear-off RAS binder was found to be temperature dependent at moderate temperatures, but changed very little between 60°C and 180°C. Virgin binders selected in this study could not blend through an RAS-binder layer of 300 µm within 30 min at 180°C. Based on the observations, RAS binder was found to interact with virgin binder through “mixing” rather than “blending”, in a mixing zone of 25–30 µm.

New Approach to Recycle Glass Cullet in Asphalt Shingles to Alleviate Thermal Loads and Reduce Heat Island Effects

AbstractAs an approach to mitigate the harmful effects of urban heat islands (UHI), the use of glass cullet in the production of asphalt roof shingles has the potential to be employed as a cool roof strategy. The objective of this study was to test the hypothesis that the use of recycled glass cullet increases the solar reflectance index (SRI) without affecting the performance of asphalt roof shingles. In order to evaluate the feasibility of using recycled glass cullet in this new application, the engineering properties of glass cullet were measured and compared to conventional aggregates used in the production of asphalt roof shingles. Laboratory shingle specimens were then prepared in order to measure solar reflectance properties and strength characteristics of conventional and recycled glass roof shingles. Results show that while the use of recycled glass cullet as a replacement to standard ceramic coated black roofing granules on the top surface of asphalt shingles increased the SRI, the addition of w...

Wind Uplift Resistance of Artificially and Naturally Aged Asphalt Shingles

AbstractDamage assessment surveys performed following the 2004 and 2008 hurricane seasons indicate that the vulnerability of shingle roofs to wind-induced damage increases with age. This paper presents two interrelated experiments on the wind uplift resistance of asphalt shingle seals. The objective is to identify whether and to what extent aging reduces the wind uplift capacity. In the first experiment, asphalt shingles were artificially aged, and the mechanical uplift resistance was measured at discrete intervals. In the second experiment, mechanical uplift tests were performed in situ on ≥9-year-old shingle roofs installed on four central Florida homes. Results from the first experiment demonstrate that heat exposure can reduce uplift resistance along its sealant strip in some products; however, the excess capacity in the bond may be sufficiently large to prevent the mechanical resistance from dropping below the design requirement. Inclusion of ultraviolet and water in the heat-exposure tests did not a...

The influence of unsealing on the wind resistance of asphalt shingles

This paper addresses the wind-induced tearing and blow-off of asphalt roofing shingles, which are the most frequently observed forms of residential building damage in hurricanes. Field surveys indicate that in-service asphalt shingle sealant strips can lose adhesion along their leading edge over time, leaving the shingle partially unsealed and susceptible to wind uplift. Two interrelated studies presented in this paper show that unsealing is a naturally occurring process and that unsealed shingles are a contributing cause of shingle roof cover damage in high winds. The first study quantified the number, location, and failure mode of laminate and three-tab style shingle systems installed on residential buildings at 30 sites in Florida and Texas. Systematic patterns of partially unsealed field shingles found on 22 of the 30 roofs resembled spatial patterns of wind-induced shingle damage observed in post-hurricane building performance assessments. As expected, older roofs generally contained more unsealed shingles than newer roofs. The results of the second study link blow-off to partially unsealed shingles. Seventeen ASTM D7158 Class H asphalt shingle roofs were aged outside for nominally one year at the Insurance Institute for Business & Home Safety Research Center and then evaluated in full-scale wind tunnel tests. Partially unsealed field and hip shingles frequently exhibited damage during wind testing, while fully sealed shingles were not damaged unless adjacent, unsealed shingles failed first.

Measured temperature reductions and energy savings from a cool tile roof on a central California home

Abstract To assess cool-roof benefits, the temperatures, heat flows, and energy uses in two similar single-family, single-story homes built side by side in Fresno, California were measured for a year. The “cool” house had a reflective cool concrete tile roof (initial albedo 0.51) with above-sheathing ventilation, and nearly twice the thermal capacitance of the standard dark asphalt shingle roof (initial albedo 0.07) on the “standard” house. Cool-roof energy savings in the cooling and heating seasons were computed two ways. Method A divides by HVAC efficiency the difference (standard − cool) in ceiling + duct heat gain. Method B measures the difference in HVAC energy use, corrected for differences in plug and window heat gains. Based on the more conservative Method B, annual cooling (compressor + fan), heating fuel, and heating fan site energy savings per unit ceiling area were 2.82 kWh/m2 (26%), 1.13 kWh/m2 (4%), and 0.0294 kWh/m2 (3%), respectively. Annual space conditioning (heating + cooling) source energy savings were 10.7 kWh/m2 (15%); annual energy cost savings were $0.886/m2 (20%). Annual conditioning CO2, NOx, and SO2 emission reductions were 1.63 kg/m2 (15%), 0.621 g/m2 (10%), and 0.0462 g/m2 (22%). Peak-hour cooling power demand reduction was 0.88 W/m2 (37%).

Reflectometer measurement of roofing aggregate albedo

A solar reflectometer is commonly used to determine the albedo of roofing products. This study validates against pyranometer measurements of albedo three new methods for solar reflectometer measurement of the albedo of the irregular surface presented by a bed of roofing aggregate. Method A determines the albedo of an aggregate bed by averaging many reflectometer readings of a small sample of aggregate. Method B relates the albedo of the aggregate bed to reflectometer measurements of the albedo of an opaquely thick pile of finely crushed aggregate. Method C relates the albedo of the aggregate bed to reflectometer measurements of the albedo of a faux roofing shingle surfaced with finely crushed aggregate. When applied to the 17 specimens tested in this study, Method A worked well for all but the largest aggregates; Methods B and C worked well for all aggregates. The absolute mean error of each method was less than 0.01, and the RMS error of each method did not exceed 0.021.As an ancillary note, we find that beds of mineral particles have albedos that decrease with increasing particle size, up to sizes at which the particles become opaque to sunlight.

Mechanical characterization of asphalt tear-off roofing shingles in Hot Mix Asphalt

In the USA, asphalt tear-off roofing shingle is one of the largest productions in the municipal solid waste (MSW) stream. Applications into road construction materials can be an alternative to recycle these tear-off shingles. This paper discusses the beneficial use of tear-off shingles in Hot-Mix Asphalt (HMA) by presenting: (1) the physical properties of tear-off shingles and the extracted binder, (2) the mechanical behaviors and properties of shingle-mixed HMA, (3) an optimum mix design for the shingle used in HMAs. The tear-off shingles obtained from the states of Florida and Minnesota (but main study on the Florida’s shingles) were used for the sample preparation that involves varied amount of shingle addition (ranged from 0% to 6% with 1% increment) for three different virgin binder contents. Laboratory testing methods include a reflux extraction and recovery and penetration tests for the extracted binder and a modified Marshall stability, moisture susceptibility, and asphalt pavement analyzer (APA) tests for the mixtures. The shingle addition causes stiffer binder in the mixture, resulting in the increase of material stiffness, stability, and rutting resistance. A visual inspection of the fractured surface of samples was also conducted to investigate the location of the crack surface either through the aggregates or in the asphalt binder, which is a good indicator of sufficient level of asphalt film in the mixture. Testing results were used to identify the optimum mixing proportion of the tear-off shingle and asphalt binder in HMAs.

Design and performance of a novel building integrated PV/thermal system for energy efficiency of buildings

A building integrated multifunctional roofing system has been designed to harvest solar energy through photovoltaics (PVs) and heat utilization while minimizing PV efficiency loss and eliminating the material and labor redundancies of conventional PV systems. Silicon PV modules are embedded between a transparent protective layer and a functionally graded material (FGM) layer that is fabricated from a mixture of heat conducting aluminum and insulating high density polyethylene with water tubes cast within the FGM. Solar energy is collected by the PV modules in the form of PV electricity and heat energy. Due to high thermal conductivity of the upper part of the FGM, the heat in the PV modules is transferred into the FGM and is captured by the water flowing through the embedded tubes, so the modules’ temperature can be controlled and, thus, the PV efficiency can be optimized. The warm water can be used as it is gathered for heat supply in a radiant floor systems or it is heat can be extracted into a phase change material (PCM) storage unit, for use in nighttime heating or more efficient ejection during cooler evening hours. Due to the high thermal insulation of the lower part of the FGM and heat collection by water flow, excellent indoor thermal comfort can be achieved and building cooling needs minimized. A thermal resistive structural substrate is integrated into the composite system to provide structural support for FGM and PV elements. This holistic design will fulfill the basic functions of the building envelope: waterproofing, insulation, and structural strength and durability, while simultaneously producing energy and reducing energy consumption to achieve a high degree of energy efficiency and sustainability. A prototype study has proven the concept. The performance analysis indicates that the proposed solar roofing system provides significant advantages over the traditional asphalt shingle roof and PV systems without cooling.

Development of an atomistic-based chemophysical environment for modelling asphalt oxidation

Asphalt is the primary binding and waterproofing component in road pavements and roof shingles, and is expected to meet certain minimum performance requirements based on its rheological properties. With an optimum mixture design, desirable performance of asphalt can be ensured in its early service stage. However, being an organic end product of petroleum serving under the general open-to-air conditions, asphalt can lose the desired rheological properties with time due to oxidative hardening or aging that frequently leads to increase in viscosity, separation of components, and loss of cohesion and adhesion, and thereby becomes hardened. Oxidative hardening of asphalt can cause reduce mixture performance and eventually lead to failure of pavements and roof tiles. The study of asphalt oxidative hardening has thus far focused on the changes in the physical properties, mainly the viscosity and ductility of bulk asphalt. Such phenomenological approaches meet the direct engineering needs; however they do not contribute to understanding the fundamental physicochemical mechanisms of asphalt hardening. From this standpoint, this research study aims at exploring the chemical basis of asphalt oxidative hardening by establishing an ab initio quantum chemistry (QC)-based chemophysical environment in which the possible chemical reactions between asphalt ingredients and oxygen, as well as the changes in their physical behaviour can be readily studied. X-ray photoelectron spectroscopy (XPS) was used to validate the bulk asphalt model, of which the results showed high agreement to the model predictions.

Effectiveness of pre‐applied wetting agents in prevention of wildland urban interface fires

ABSTRACTThe purpose of the work described in this paper is to investigate the effectiveness of pre‐wetting structures, dead fuels, and landscaping plants in preventing fire spread from wildland fires to structures. Critical fluxes for fire growth were determined using intermediate‐scale testing for three wetting agents (water, type A foam, and gel) applied to 10 landscaping plants conditioned to 20% moisture, a mulch material, and four external structural materials (vinyl siding, plywood siding, asphalt shingle roofing, and cedar shake roofing). The critical flux for fire growth values was determined at 3‐min heat radiation exposure and simultaneous 300‐mm long flame exposure. Test specimens were exposed to various durations and intensities of drying prior to exposing them to heat radiation. Application of water or foam provided no noticeable protection. Gel was effective in providing protection even after 60 min of laboratory condition drying but was less successful when exposed to fire weather simulating accelerated drying. Some uncertainty is associated with the results of this work because of the variability of landscaping plants and gel wetting agent application uniformity. The intermediate‐scale test results were verified using full‐scale testing. Copyright © 2012 John Wiley & Sons, Ltd.

Field thermal performance of naturally ventilated solar roof with PCM heat sink

For decades, residential and commercial roofs have been considered a prime location for installation of building integrated solar systems. In climatic conditions of East Tennessee, USA, an experimental solar roof was tested during 2009/2010, by a research team representing Metal Construction Association (MCA), and a consortium of building insulation companies, photovoltaic (PV) manufacturers, and energy research centers. The main objective was to thermally evaluate a new roofing technology utilizing amorphous silicon PV laminates integrated with the metal roof panels. In order to mitigate thermal bridging and reduce roof-generated thermal loads, this novel roof/attic assembly contained a phase change material (PCM) heat sink, a ventilated air cavity over the roof deck, and thermal insulation with an integrated reflective surface. During winter, the experimental roof was expected to work as a passive solar collector storing solar heat absorbed during the day, and increasing overall attic air temperature during the night. During summer, the PCM was expected to act as a heat sink, reducing the heat gained by the attic and consequently, lowering the building cooling-loads.In this paper, field thermal performance data of the experimental PV-PCM roof/attic system are presented and discussed. Performance of the PV-PCM roof/attic is evaluated by comparing it to a control asphalt shingle roof. The test results showed about 30% heating and 50% cooling load reductions are possible with the experimental roof configuration.

Exposure Assessment Framework for Antimicrobial Copper Use in Urbanized Areas

Copper is used as an antimicrobial agent in building materials such as algae-resistant roofing shingles and treated wood products for decks, fences, and utility poles used in urbanized areas. Releases from these materials may pose risks to aquatic and terrestrial organisms. Copper exposures in surface water, sediment, and soil were estimated for a hypothetical urban setting using the TREX watershed model. Drainage and soil characteristics were based on an existing watershed. Urban landscape characteristics were developed from data regarding housing densities and copper use in building materials. This setting provides a spatially distributed, upper-bound assessment scenario. Release rates from algae-resistant shingles and treated wood were defined based on surface area and rainfall. Simulations for the urban landscapes were performed for a 10-year period. Simulation results were used to evaluate exceedences of benchmark concentrations for water, sediment, and soil. For algae-resistant shingles, exposures did not exceed benchmarks in any media. For treated wood, exposures did not exceed sediment and soil benchmarks, and surface water benchmarks were exceeded on 2 days in 10 years. Based on this analysis, copper use as an antimicrobial agent in algae resistant shingles and treated wood is not expected to pose significant adverse environmental risks on an individual use basis.

Performance Characterization of Half Warm Mix Asphalt Using Foaming Technology

The objective of this study was to evaluate the moisture susceptibility, rutting, and fatigue resistance of laboratory-made half warm mix asphalt (HWMA) mixtures containing moist aggregates and recycled materials such as manufactured roofing shingles and reclaimed asphalt pavement (RAP). The test properties evaluated in this study included weight loss (%), indirect tensile strength (ITS), tensile strength ratio (TSR), wet flow, wet toughness, percent toughness loss, rut depth of dry and wet conditioned specimens, rut index, and beam fatigue life. The experimental design in this study included the use of foaming technology and three hydrated lime contents (0, 1, and 2% by weight of aggregate), three aggregate sources (designated as A, B, and C), three fractioned RAP sources from the same aggregate sources, and one PG 64-22 binder. A total of 27 mixtures was designed, and a total of 120 ITS samples, 162 asphalt pavement analyzer (APA) samples, and 36 fatigue beams were tested in this study. Results indicated that the addition of recycled materials such as RAP or roofing shingles can be effectively employed in HWMA mixtures, which did not reduce wet ITS and TSR values, although the compaction temperature was only 85°C. The influence of the moist aggregate used in HWMA on rut depth can be neglected and even results in a better rut resistance when incorporating recycled materials. Stiffness values of mixtures with recycled materials were generally dependent on the aggregate type. Based on the statistical analysis for the selected aggregates, no significant difference in fatigue life was observed for mixtures with recycled materials and control mixtures.