Permanent Deformation Behavior Research Articles

Permanent and resilient deformation behaviour of recycled concrete aggregates from different sources, in pavement base and subbase

This paper presents an investigation on the permanent and resilient deformation behaviour as well as the shear and physical properties of different RCA, sourced from demolished buildings (RCAB1 and RCAB2) and concrete pavement (RCAP). Monotonic triaxial tests and repeated load triaxial tests (RLTT) were performed to determine respectively their failure resistance and the cyclic behaviour, modelled with the Boyce model and the DBGSP model. In addition, the physical properties and water absorption kinetics of aggregates were studied and compared with the existing standard. The results indicated that all RCA have admissible physical properties and can be used in pavement base and subbase layer. However, the RLTT revealed that the use of concrete wastes with low strength and containing high amount of rounded particles (RCAP in this study) can lead to poor performance of pavement, which should be limited in the pavement construction.

Estimation of permanent deformation behaviour of crushed waste rocks using multistage repeated load triaxial and CBR tests

ABSTRACT Crushed waste rocks (CWR) are widely used to build mine haul roads. However, the permanent deformation in waste rocks layers can result in surface rutting. Realistic prediction of pavement rutting requires models that can accurately capture the permanent deformation behaviour under repeated loading. However, such models are usually based on advanced laboratory apparatus such as multistage (MS) repeated load triaxial (RLT) tests. In this study, a new approach, using MS repeated load California Bearing Ratio (RLCBR) tests, was proposed to estimate the permanent deformation behaviour of CWR. MS RLCBR tests are faster, easier and more often available than MS RLT tests. A series of MS RLCBR and MS RLT tests for different stress levels were therefore carried out on the same material to characterise CWR permanent deformation behaviour. Results showed that Rahman and Erlingsson model that modified by time hardening approach could satisfactorily capture CWR permanent deformation behaviour for MS RLT tests. A new model was proposed and fitted on MS RLCBR test results to predict CWR permanent deformation behaviour. This model performed well in describing MS RLCBR test results and predicting the CWR permanent deformation behaviour. Results indicate that MS RLCBR tests could be an effective alternative to MS RLT tests for estimating the permanent deformation behaviour of CWR.

Permanent Deformation Behavior under Repeated Load of Recycled Material Stabilized with Bitumen Emulsion

Permanent Deformation Behavior under Repeated Load of Recycled Material Stabilized with Bitumen Emulsion

Repeated Load Triaxial Testing of Recycled Excavation Materials Blended with Recycled Phyllite Materials.

Recycled Excavation Materials (REM) are becoming viable alternative construction resources due to their economic benefits. However, REM may be composed of weak rocks, e.g., phyllites, limiting the use in a base layer. The present paper attempts to further the knowledge of the mechanical performance of REM by performing Repeated Load Triaxial Tests (RLTT). REM are mixed with Recycled Phyllite Materials (RPM) in systematic blends of 0%, 25%, 50%, and 100%. The batches’ resilient modulus (MR) and permanent deformation (PD) characteristics were assessed to establish the maximum RPM allowed into REM while maintaining the required performance. Hicks and Monismith’s and Uzan’s models were used to characterize the stiffness behavior. A wide variation in the stiffness between the two materials was observed. Batches comprised of 0% RPM–100% REM and 25% RPM–75% REM showed high stiffness performance. The Coulomb model assessed the PD behavior, and the results showed a similar response for all batches. Unlike the stiffness, blended mixtures did not show sensitivity to increased RPM content in the PD. This study may help end-users to understand the performance of REM given the documented threshold on the allowable quantity of RPM in REM.

Resilient and Permanent Deformation Behavior of Expandable Foam Grout Under Repeated Loading

Resilient and Permanent Deformation Behavior of Expandable Foam Grout Under Repeated Loading

Strength and permanent deformation properties of demolition wastes, glass, and plastics stabilized with foamed bitumen for pavement bases

Foamed bitumen (FB) stabilization is an in-place soil improvement technique that has become popular in recent times. Nevertheless, a lack of understanding exists about the strength and deformation responses of FB stabilized recycled demolition wastes in pavements. This paper aims to introduce the application of FB stabilized recycled demolition waste blends with glass and plastic in the pavement base layer. A suite of laboratory tests was undertaken to evaluate the indirect tensile strength, unconfined compressive strength, California bearing ratio, and permanent deformation behavior of FB stabilized blends. Recycled concrete aggregate (RCA) was blended with recycled glass (RG), recycled plastic (RP), and reclaimed asphalt pavement (RAP) in various percentages and the performance of the FB stabilized blends were characterized through extensive experimental testing. A multi-stage repeated load triaxial (RLT) testing procedure was adopted to evaluate the permanent deformation behavior of the unbound and FB stabilized blends under various stress levels. The ITS, UCS, and CBR values exhibited decreasing trends with increasing the RAP, RG, and RP contents. The permanent deformation of the blends was found to be reduced as a result of FB stabilization, most notably for the blends with higher percentages of RAP, RG, and RP. The permanent deformation responses of the blends were ranked using the shakedown concept that indicated the FB stabilized demolition wastes exhibited relatively stable responses under cyclic loads. The deformation response of the blends with 50%RAP and 7%RP changed from incremental collapse to plastic creep as a result of FB stabilization. The results indicated that the FB stabilization of recycled aggregates is a suitable practice for developing more sustainable roads with enhanced ductility and resistance to rutting.

A geomechanics classification for the rating of railroad subgrade performance

The type of subgrade of a railroad foundation is vital to the overall performance of the track structure. With the train speed and tonnage increase, as well as environmental changes, the evaluation and influence of subgrade are even more paramount in the railroad track structure performance. A geomechanics classification for subgrade is proposed coupling the stiffness (resilient modulus) and permanent deformation behaviour evaluated by means of repeated triaxial loading tests. This classification covers from fine- to coarse-grained soils, grouped by UIC and ASTM. For this achievement, we first summarize the main models for estimating resilient modulus and permanent deformation, including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters. This is followed by the procedure required to arrive at the geomechanical classification and rating, as well as a discussion of the influence of environmental factors. This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.

Effect of Glass Cullet Size and Hydrated Lime—Nanoclay Additives on the Mechanical Properties of Glassphalt Concrete

In this study, the use of glass waste as aggregate in asphalt mixtures was investigated. Maximum glass aggregate size options of 0.075, 2.00, 4.75 and 9.5 mm. were selected. Conventional bitumen, nanoclay-modified bitumen and hydrated lime-modified bitumen were used. Dense graded asphalt mixtures were designed according to the Marshall method. Mixtures were evaluated for low-temperature cracking, resistance to water damage, fatigue, and permanent deformation behavior with repeated creep, indirect tensile strength, indirect tensile fatigue, modified Lottman and Hamburg wheel tracking tests. Increasing glass aggregate size reduced the water damage resistance of asphalt mixtures because of the smooth surface of the glass particles and nanoclay and hydrated lime modification improved the mechanical properties of the asphalt mixtures. Using 2.00 mm sized maximum glass aggregate showed relatively less water damage and deformation properties due to higher internal friction which is due to the greater angularity of the glass particles. In addition, there was a significant correlation between repeated creep test, modified Lottman methods and Hamburg Wheel tracking test from the viewpoint of deformation and water damage assessments.

Characterizing the permanent deformation Response-Behavior of subgrade material under cyclic loading based on the shakedown theory

Coarse-grained soil is widely used as a filling material in the railway subgrade to provide foundational support to the long-term effects of dynamic (cyclic) train loads transmitted by the track structure. Despite this wide usage, there is limited literature on its permanent deformation behavior characterization under different magnitudes of dynamic stress. The GDS (Geotechnical Digital System) dynamic triaxial tests were presented in this paper to characterize and quantify the dynamic response-behavior of coarse-grained railway subgrade soils when subjected to dynamic loading. Based on the shakedown concept, the patterns of accumulated axial plastic strains for the coarse-grained soil under different magnitudes of dynamic stress were classified into three categories, namely plastic shakedown, plastic creep, and incremental collapse. As a result, the critical dynamic stresses for plastic shakedown and plastic creep state could easily be determined. The experimental test results indicated that whilst the critical dynamic stress of the coarse-grained soil increased with an increase in the effective confining pressure, it correspondingly decreased as the loading frequency increased from 1.0 to 3.6 Hz, respectively. From the regression fitting-analysis of the experimental test results, an empirical model is proposed in this paper, which denotes the critical dynamic stress of coarse-grained subgrade soils as a function of the effective confining pressure. As a contribution to the literature and potential engineering applications, the proposed models may provide theoretical significance for the subgrade state evaluation and settlement control.

Consideration of the permanent deformation of soils used in flexible pavement design

The decreasing supply of soils with geotechnical parameters suitable for pavement designs is a problem. To establish more efficient designs and adequate construction criteria, it is essential to understand the performance of materials. In this work, the permanent deformation (PD) of soils used in pavement layers was studied using prediction models of PD and modulus of resilience in addition to the design of pavement structures using mechanistic–empirical and empirical methods. The multistage repeated load triaxial test was used along with numerical analyses of stresses and displacements using the CAP3D program. The results showed that both the test procedure and the prediction models satisfactorily obtained the PD behaviour. Moreover, designs using the methods adopted resulted in distinct structures (i.e. different thicknesses of granular pavement layers). From the results of this study, it was concluded that both the model and the test procedure show significant potential for characterising and modelling the PD of granular materials.

Fines content, plasticity index and dust ratio influencing the modulus and permanent deformation behavior of aggregates

Resilient modulus (Mr) and permanent deformation (PD) characteristics of unbound aggregates under repetitive traffic loads dictate the structural response and performance of pavement base and subbase layers. Aggregate material behavior is dependent on the amount of fines in particulate matrix, also referred to as fines content (percent passing number 200 sieve), as well as plasticity index, dust ratio (percent passing number 200 sieve to percent passing number 40 sieve), material type, aggregate gradation/packing and the interactions of these properties with each other. In this study, repeated load triaxial tests were conducted on crushed limestone and crushed gravel aggregates. Fines content and plasticity index were varied from 5% to 12% and 5% to 9%, respectively. Two most typical gradations of aggregates used in roadway construction in Illinois were utilized with dust ratios ranging from 0.4 to 1.0. The results of these tests were analyzed using the shakedown theory for evaluating typical base/subbase permanent deformation or rutting trends linked to practical design considerations. Charts were also established for the modulus and deformation characteristics of unbound aggregates to designate the material quality with performance trends. Such guiding charts were compared with others developed in previous studies by authors for determining aggregate behavior under monotonic loading tests such as California Bearing Ratio (CBR). The comparisons provide valuable insights on how each aggregate property influences strength, modulus and permanent deformation behavior under different loading conditions.

Impact of Graphene Oxide on Zero Shear Viscosity, Fatigue Life and Low-Temperature Properties of Asphalt Binder.

This study has investigated the impact of graphene oxide (GO) in enhancing the performance properties of an asphalt binder. The control asphalt binder (60/70 PEN) was blended with GO in contents of 0%, 0.5%, 1%, 1.5%, 2%, and 2.5%. The permanent deformation behavior of the modified asphalt binders was evaluated based on the zero shear viscosity (ZSV) parameter through a steady shear test approach. Superpave fatigue test and the linear amplitude sweep (LAS) method were used to evaluate the fatigue behavior of the binders. A bending beam rheometer (BBR) test was conducted to evaluate the low-temperature cracking behavior. Furthermore, the storage stability of the binders was investigated using a separation test. The results of the ZSV test showed that GO considerably enhanced the steady shear viscosity and ZSV value, showing a significant contribution of the GO to the deformation resistance; moreover, GO modification changed the asphalt binder’s behavior from Newtonian to shear-thinning flow. A notable improvement in fatigue life was observed with the addition of GO to the binder based on the LAS test results and Superpave fatigue parameter. The BBR test results revealed that compared to the control asphalt, the GO-modified binders showed lower creep stiffness (S) and higher creep rate (m-value), indicating increased cracking resistance at low temperatures. Finally, the GO-modified asphalt binders exhibited good storage stability under high temperatures.

Dynamic modulus and damping ratio of compacted loess under long-term traffic loading

Previous studies have centred on the long-term permanent deformation behaviour of soil under traffic loading while neglecting the dynamic parameters as it is affected by cycle number. In this study, forty tri-axial dynamic tests were conducted to assess the effects of cycle number, confining pressure, and dynamic stress on the dynamic modulus and damping ratio of compacted loess. Empirical models of both parameters were established and examined, from which emerged a nearly linear relationship between the dynamic stress-strain points when dynamic stress fell below a given threshold value. The representative dynamic modulus in the linear range initially increased and then decreased. The maximum representative dynamic modulus linearly increased as confining pressure increased, while confining pressure had no clear effect on the damping ratio. As the dynamic stress increased, the damping ratio was initially stable and then gradually increased until becoming stable again at a higher level.

Permanent Deformation Behavior of Foamed Bitumen Stabilized Mixes

AbstractThis paper investigated the deformation (dynamic creep) behavior of foamed bitumen stabilized mixes (BSM-foam) that incorporates recycled asphalt pavement (RAP) material. The influence of t...

Towards a unified performance based characterisation of bitumen and mastic using the DSR

A laboratory study was done on three bitumen of penetration grade 50/70 from three sources and three corresponding mastics made using these three base bitumen and one filler – Limestone. The tests were all done using the Dynamic Shear Rheometer (DSR), including frequency sweeps for rheology, single stress creep recovery test (SSCR) for permanent deformation behaviour, Dresden cryogenic test (DDCT) for low temperature performance, and fatigue testing using column specimen. The frequency sweep data was modelled using the 2 Spring-2 Parabolic-1 Dashpot (2S2P1D) rheological model. Selected tests were carried out on unaged and aged bitumen and mastic samples to investigate the sensitivity of the materials to ageing. Performance diagrams were made which could enable in bitumen and mastic selection based on specified desired criteria. It was found that bitumen from different bitumen producers and provenances had different performance behaviours. Furthermore, the addition of the limestone filler also affect the ranking based on specified behaviours.

Discussion of “Permanent Deformation Behavior of Compacted Loess under Long-Term Traffic Loading” by Zhiping Hu, Rui Wang, Xiang Ren, Xueni Wei, and Qiang Wang

Discussion of “Permanent Deformation Behavior of Compacted Loess under Long-Term Traffic Loading” by Zhiping Hu, Rui Wang, Xiang Ren, Xueni Wei, and Qiang Wang

The effect of weathering on the engineering properties of laboratory compacted unbound granular materials (UGMs)

Unbound Granular Materials (UGMs) are extensively used in pavement construction practice. These materials are uncoated, and their durability can be easily affected by the frequent variations of moisture content in the service life of the pavement. To this end, the effect of Wetting and Drying (W-D) cycles on the performance of two sources of andesite aggregates are investigated by conducting California Bearing Ratio (CBR) alongside Repeated Load Triaxial (RLT) tests. One source of aggregate characterised to be of high quality, indicates premium aggregates, and the other of more marginal in terms of engineering performance. It is observed that CBR results of Marginal aggregates are more dependent to moisture content. Additionally, W-D cycles have a damaging effect on CBR values of Marginal aggregates (up to 55% reduction in CBR results after 16 cycles of W-D), whereas, CBR results of Premium aggregates show a subtle increase after conditioning. The W-D cycles also affect the properties of fine portion of both aggregates and control the swelling trend of Marginal materials. Application of 16 cycles of W-D result in 64% and 29% increase in the proportion of fine materials in Marginal and Premium aggregate, respectively, and almost 60% increase in Clay Index (CI) test results of both sources of aggregates. Moreover, W-D cycles have been shown to have a considerable effect on permanent deformation behaviour and resilient modulus of aggregates in the RLT test. W-D process could potentially result in more than 40% increase in overall permanent deformation of aggregates. In addition to that, the permanent deformation performance of Marginal aggregates considerably depends on the state of stress and variation in moisture content. Overall, in order to achieve more sustainable use of available aggregates it is essential to incorporate the ageing characteristics of UGMs into selection procedure of road materials.

Investigation of Permanent Deformation Behavior of Steel Slag Asphalt Mixture under Indoor Simulation

Previous studies have indicated that steel slag can be used as a substitute for natural aggregates in asphalt mixture, while little attention has been paid to systematic investigation of the influences of various external environmental factors on deformation resistance of steel slag asphalt mixture. In order to understand the service behavior of steel slag asphalt mixture, its permanent deformation under different condition was investigated based on an indoor simulation test. The chemical composition, microscopic structure, surface texture, and volume stability of steel slag were firstly characterized. The uniaxial repeated loading test and standard wheel‐tracking test were applied to evaluate the effect of temperature, stress levels, and water damage on the permanent deformation of AC‐16 and AC‐20 steel slag asphalt mixtures. The results indicate that a higher content of alkaline oxide and high‐grade texture index existing in steel slag contribute to its strong absorptivity and adhesion of asphalt. The steel slag demonstrates fine volume stability due to its lower free‐CaO (f‐CaO) content, autoclave chalked ratio, and immersion expansion ratio. The permanent deformation of steel slag asphalt mixtures increases rapidly under higher stress and temperatures in contrast to lower increment at lower stress and temperatures. Asphalt mixtures at higher stress and higher temperatures and water condition exhibit larger rutting deformation and inferior rutting resistance. AC‐16 steel slag asphalt mixture has superior resistance to permanent deformation than AC‐20 asphalt mixture. Rutting factors show different degrees of impact in a decreasing order of temperature, water damage, and stress levels. The findings have significant implications for providing a theoretical basis for reusing steel slag in pavement construction and facilitating engineering application of steel slag asphalt mixture.

Dynamic characterization of recycled glass-recycled concrete blends using experimental analysis and artificial neural network modeling

This study investigates the deformation properties of recycled concrete aggregate (RCA) when blended with up to 70% of recycled glass (RG) for pavement base applications. A multi-stage repeated load triaxial (RLT) testing procedure was proposed and utilized for evaluating the permanent deformation behavior of RCA/RG blends. The resilient modulus (Mr) of the blends was examined by performing RLT test in different stress combinations using a proposed testing protocol. The shear strength response of the blends was also investigated. Shakedown theory was utilized to classify the permanent deformation behavior of the blends. Except for the RCA30/RG70 blend, all other blends exhibited either Range A or Range B response in the investigated stress levels. There was an increase in the permanent strain and a decrease in the Mr of blends as the RG content increased. The shear response of the blends exhibited a strain-hardening behavior in the post-peak zone when the RG content was more than 10%. Artificial neural network (ANN) models were developed for predicting the deformation properties of the blends and examining the effect of test variables on the deformation properties. The developed ANN models for prediction of permanent strain and Mr were converted to practical equations for pre-design purposes. Results of numerical modeling indicated that ANNs were robust for predicting the deformation properties as well as identifying the impact of input variables on the deformation properties of RCA/RG blends.

Shakedown analysis of PET blends with demolition waste as pavement base/subbase materials using experimental and neural network methods

Recycling and reusing construction and demolition (C&D) wastes for civil engineering construction activities has been identified as an energy-saving and sustainable solution. The purpose of this study is to evaluate the deformation behavior of two types of C&D waste materials, namely recycled concrete aggregate (RCA) and crushed brick (CB) when mixed with polyethylene terephthalate (PET) plastic waste. RCA and CB were mixed with 1%, 3%, 5%, and 7% of PET, and the permanent deformation behavior of the blends was evaluated using repeated load triaxial (RLT) test. The shakedown criterion was utilized for identifying the deformation behavior of blends. Most of the PET/RCA and PET/CB blends exhibited Range B (plastic creep) and Range C (incremental collapse) response, respectively, in the investigated stress levels. Shakedown analysis of the test results indicated that up to 3% PET could be mixed with RCA for base/subbase applications, while CB should be mixed with 1% PET, in the subbase layer. Artificial neural network (ANN) method was next used to simulate the permanent strain and shakedown behavior of the blends with consideration of the physical properties and stress states. The ANN model was found to be highly efficient for simulating the permanent strain graph and identifying the shakedown behavior of the blends. A sensitivity analysis was subsequently performed to investigate the impact of input variables on the permanent deformation behavior and the results indicated that number of cycles and confining stress were the most important factors.