Dynamic Modulus Test Research Articles

Comprehensive Study on Dynamic Modulus and Road Performance of High-Performance Asphalt Mixture

Asphalt pavement durability significantly impacts the service life of roads, and hence, understanding the performance of high-performance asphalt mixtures is crucial. This study investigates the performance of four high-performance asphalt mixtures: heavy-load AC-20, high-viscosity AC-20, heavy-load SMA-13, and heavy-load SMA-10. Linear Amplitude Sweep (LAS) tests revealed that heavy-load asphalt mixtures exhibit superior fatigue resistances, with the fatigue life of heavy-load SMA-13 exceeding 1.5 times that of high-viscosity AC-20 under similar stress levels. Bending Beam Rheometer (BBR) tests at −6 °C, −12 °C, and −18 °C demonstrated that both heavy-load and high-viscosity asphalts had comparable low-temperature crack resistance, with heavy-load SMA-13 showing a stiffness modulus of 627 MPa at −18 °C. Marshall tests indicated that heavy-load AC-20 had the highest stability (14.3 kN) among the tested mixtures, while heavy-load SMA-13 exhibited the highest density (2.603 g/cm3). Dynamic modulus tests spanning a frequency range of 10−4 Hz to 105 Hz at various temperatures showed that heavy-load SMA-13 had a higher dynamic modulus than heavy-load SMA-10, particularly at lower frequencies (higher temperatures). Rutting tests at 60 °C indicated that heavy-load SMA-13 had the lowest rut depth (18.5 mm), outperforming other mixtures by up to 25%. The heavy-load SMA-13 asphalt mixture demonstrated the best overall performance, especially in terms of high-temperature stability, fatigue resistance, and rutting resistance. This study provides essential material performance parameters for the development of durable high-performance asphalt pavement structures.

Evaluation of SMA-13 Asphalt Mixture Reinforced by Different Types of Fiber Additives.

This research aims at systematically evaluating the properties of SMA-13 asphalt mixture reinforced by several fiber additives including flocculent lignin fiber (FLF), granular lignin fiber (GLF), chopped basalt fiber (CBF), and flocculent basalt fiber (FBF). Firstly, the thermal stability, moisture absorption, and oil absorption property of these fiber additives were analyzed. Secondly, the property of SMA-13 reinforced using four types of single fibers and two kinds of composite fibers (FLF + CBF and FLF + FBF) was comprehensively analyzed. Specifically, the high-temperature performance was evaluated using the uniaxial penetration test and the rutting test, the medium-temperature anticracking property was evaluated using the IDEAL-CT test, the low-temperature property was analyzed using the beam bending test, and the water stability was studied by the freeze-thaw splitting test. Thirdly, the dynamic mechanical response of different-fibers-modified SMA-13 was evaluated using the uniaxial compression dynamic modulus test. Finally, correlation analysis between the results of dynamic modulus and the high-, medium-, and low-temperature mechanical performance was carried out. The research results reveal that the stability of CBF and FBF under thermal action is better than that of GLF and FLF, and FBF shows the best thermal stability. The oil absorption property of FLF is better than that of GLF, followed by FBF and CBF. The comprehensive mechanical properties of CBF- and FBF-reinforced SMA-13 are better than those of FLF- and GLF-modified SMA-13. CBF can better reinforce the mechanical property of SMA-13 under low and medium temperature, while FBF can better reinforce the performance of SMA-13 at high temperature. FLF/CBF- and FLF/FBF-composite-modified SMA-13 show better high-temperature mechanical performance than that of the single-fiber-reinforced mixture, and FLF has some negative impact on the properties of FLF/FBF-composite-modified SMA-13 at low temperature. Fibers have no significant influence on the water stability of the mixtures. Meanwhile, the linear correlation between the mechanical performance of all the fiber-reinforced SMA-13 and the dynamic modulus result is good.

Impact of triaxial stress state at various pavement depths on the dynamic modulus of asphalt mixture

The mechanical characteristics of asphalt mixture are closely related with its stress state, temperature, and loading rate, therefore, the loading condition of the asphalt mixture's dynamic modulus test should be consistent with the actual temperature, loading frequency, and stress state that are applied to the mixture in actual pavement, thus can the test produce an objective result that can accurately reflect the actual stress-strain relationship for the asphalt mixture. However, due to limitations in the loading capacity of current dynamic modulus test equipment, the present modulus tester cannot yet set such a loading condition whose stress state is consistent with that of asphalt mixture in actual pavement. As a result, the modulus testing results of the current test may not accurately reflect the actual stress-strain characteristics of an asphalt mixture under real traffic loads. Therefore, this paper aims to figure out the impact of stress state on asphalt mixture’s dynamic modulus, and firstly conducts a numerical analysis to ascertain asphalt pavement’s triaxial stress state at different depth, then, utilizing the nonlinear elasticity theory of Soil Plasticity, proposes a theoretical model that can reflect triaxial stress state’s effect on asphalt mixture’s dynamic modulus, and then, arranges a series of triaxial dynamic modulus tests for asphalt mixture in different stress state to verify the model’s effectiveness, and meantime analyzes stress state’s influencing rule to asphalt mixture’s dynamic modulus. Their results indicate, the asphalt mixture of the actual pavement is in an obvious triaxial stress state, and that the higher the triaxial stress state, the larger the dynamic modulus, particularly for the mixture near the surface, whose high stress state will lead to their dynamic modulus to be significantly larger than that of the underlying course, while the model proposed in this paper can to a large extent reflect this impact.

Towards the high RAP dosage obtained by refined processing influence on comprehensive performance of recycled asphalt mixture

The severe agglomeration of Reclaimed Asphalt Pavement (RAP) particles not only leads to high gradation variability during recycling, but also impedes the miscibility between new-old binders. This phenomenon imposes significant limitations on maximizing the utilization of RAP with high content and value. This paper first realized the effective separation of asphalt milling material by the self-developed RAP refined processing equipment to obtain coarse RAP with low binder content and fine RAP with high binder content. The fine RAP with high binder content underwent a deep rejuvenation process, and the recovery efficiency of the asphalt mortar was evaluated by CT scanning test, microscope observation test, and dynamic shear rheology test. Moreover, to investigate the strength formation characteristics of recycled asphalt mixtures with high RAP content, specific tests including wheel tracking test, three-point bending test, Hamburg Wheel Tracking test, dynamic modulus test, and two-point bending fatigue test, were conducted. By using the refined processing equipment, the asphalt film on the RAP can be precisely removed, thereby addressing the issue of aged binder agglomeration. In the coarse RAP with low binder content, the binder content was reduced to 1.48 %, allowing it to be used as a direct substitute for new aggregate, whereas the binder content of fine RAP exceeded 10 %. It was found that the direct incorporation of unrefined RAP enhanced the high-temperature stability and dynamic modulus of recycled asphalt mixture, but impacted their low-temperature cracking resistance, moisture stability, and fatigue performance. After refined processing and differentiated recycling design, the agglomeration of aged binder was reduced and the miscibility of new-old binders was improved, effectively enhancing the comprehensive performance of the recycled asphalt mixture. It should be noted that the mixing homogeneity and miscibility decrease as the RAP content exceeds 75 %, resulting in the reduction of moisture stability, cracking resistance, and fatigue performance of recycled asphalt mixture.

Exploring the effects of waste plastic aggregate on styrene-butadiene-styrene-modified asphalt binders for sustainable rural pavements

In addressing the imperative need for sustainable and cost-effective solutions in rural pavement development, this study navigates the intricate balance of environmental and financial constraints to ensure the resilience of infrastructure in communities with limited resources. The focal point is the integration of waste plastic aggregate (WPA) into hot mix asphalt, augmented by the inclusion of styrene-butadiene-styrene (SBS) for an elevated level of performance. The findings underscore a gradual decrease in the tensile strength ratio, emphasizing a manageable impact, transitioning from 82.4% in the control to 73.7% at 6% WPA. Noteworthy is the observation of marginal reductions in indirect tensile strength and stiffness, particularly notable at higher WPA levels. Dynamic modulus testing highlights susceptibility to rutting at lower frequencies, while high-frequency results demonstrate stability up to 6% WPA. The Hamburg wheel tracking test signals heightened rutting at 3% and 6% WPA, indicating potential challenges in deformation resistance. Despite a slight dip in strength, the discernible magnitude of this reduction is not substantial. This affirms that the incorporation of WPA achieves a harmonious enhancement of sustainability without compromising critical mechanical properties.

Development and Validation of Asphalt Pavement Rutting Prediction Model with Transient Temperature Field Considered

This study developed a transient rutting analysis program based on the principles of heat transfer and the viscoelastic–viscoplastic theory of asphalt mixtures. Using the finite element model (FEM) model corresponding to the multi-layer pavement structure and the subprogram interface of ABAQUS software, along with Python programming, the program was designed to estimate rutting under transient temperature field conditions with climate conditions, traffic flow, and structure layer constitutive parameters of pavement considered. Subsequently, the program was used to validate the efficiency of the solution and analyze the influencing factors of internal temperature field and rutting depth within the asphalt pavement structure. Results showed that, based on meteorological data and recommended values of material thermal properties, the FEM of transient temperature field can accurately simulate the temperature field distribution of pavement structure. Based on loading information and dynamic modulus test, the transient temperature variable rutting with FEM proposed in this paper can simulate and calculate the rutting of pavement structure layer with some errors for different pavement conditions from 5% to 40%. Through parametric analysis of the influence factors of temperature field and rutting, the modified transient temperature field rutting prediction program can effectively simulate rutting of pavement structure, and the minor errors were less than 20%.

Evaluation on tension-compression anisotropic behavior of recycled asphalt mixture

The utilization of recycled asphalt pavement (RAP) is the effective way to improve resource conservation and reduce energy consumption. The asphalt mixture is a kind of typical anisotropic pavement materials due to its heterogeneity in composition and microstructure. This could lead to the differences of mechanical response between the tensile and compressive direction. However, there are limited researches to study the effect of RAP on the tension-compression anisotropic behavior of asphalt mixture. The strength, modulus and fatigue resistance tests are carried out and different loading modes are adopted. The results show that the tension-compression anisotropic behavior is more prominent with the increase of RAP content. The regenerant served as a kind of typical additive could alleviate this effect. In addition, the result of dynamic modulus test shows that the tension-compression anisotropic behavior has an increasing trend with the decrease of frequency and the increment of temperature. The ranking of fatigue life is opposite for the direct tensile and compressive loading mode, and the fatigue life ratio of compression to tension also show positive relation with the RAP content. Due to the difference in the stress mode, the fatigue life between the indirect tensile loading and four-point bending loading also show opposite trend, and the indirect tensile fatigue life has a larger discreteness.

Research on the Rheological Properties and Modification Mechanism of Epoxy Resin/SBS Composite-Modified Asphalt

Both epoxy resin (ER) and SBS are considered effective pavement materials for avoiding ruts. However, epoxy resin asphalt suffers from poor low-temperate performance and a high material cost in practical applications. Aiming to tackle these issues, a new type of composite asphalt modifier (ER-SBS) has been fabricated by combining epoxy resin with SBS. This work prepared modified asphalt with different doping amounts using the above composite asphalt modifier (ER-SBS), intending to explore the properties of composite-modified asphalt and the modification mechanism of the modifier. Furthermore, the effects of the composite modifier at different doping amounts on the viscoelastic property of asphalt were explored through rheological tests, and then the prepared composite-modified asphalt was compared with matrix asphalt and SBS-modified asphalt. In addition, the modification mechanism of the composite modifier was investigated by fluorescence microscopy and infrared spectroscopy. The difference in pavement performance between the composite-modified asphalt and SBS-modified asphalt was compared by a rut test and dynamic modulus test. The research results showed that the composite modifier improved the high- and low-temperature performances and viscoelastic property of matrix asphalt. When the doping amount was raised to 9%, the composite-modified asphalt exhibited better a modification effect than SBS-modified asphalt. The rut test results indicated that composite-modified asphalt demonstrated a stronger deformation resistance than SBS-modified asphalt. The dynamic modulus test showed that the composite-modified asphalt has better viscoelastic properties and temperature sensitivity. Fluorescence microscopy suggested that the crosslinking between the composite modifier and asphalt forms a mesh structure which greatly improves its resistance to deformation. From infrared spectroscopy, the composite modifier clearly functions as a physical modifier.

Feasibility Assessment of Mudstone Aggregate as an Alternative Material for Colored Asphalt Pavement in South Korea

Colored asphalt pavements have been implemented in South Korea to enhance visibility and lane distinction; however, color fading, accelerated deterioration, and increased pothole occurrence have been noticed. As a solution, alternative materials that can be used for the construction of colored asphalt pavements are being explored. This study evaluates the feasibility of using mudstone aggregate in constructing colored asphalt pavement in South Korea. Initially, aggregate quality tests were conducted on mudstone samples to assess their suitability compared to standard criteria. To enhance the visibility and color retention of colored asphalt, addition of pigment in the colored asphalt pavement mixture was considered and evaluated. The asphalt mixtures were evaluated for deformation, crack and viscoelastic properties using the Kim test, indirect tensile (IDT) strength test, and dynamic modulus test, respectively. Results showed that mudstone aggregate exceeded quality standards and the colored asphalt mixtures demonstrated superior deformation strength and crack resistance compared to typical SMA. However, the addition of pigment slightly reduced these properties. Overall, the findings suggest mudstone aggregate as a viable alternative for constructing colored asphalt pavements, offering potential improvements in durability and color retention.

Experimental Study on Pavement Performance of Warm High Modulus Mixture WHMM-13

In order to solve the dusting and rutting problems of hot mix asphalt mixture during construction and operation, rutting test, bending test, Marshall stability test, freeze-thaw splitting test, uniaxial compression dynamic modulus test, overlay test, and four-point bending fatigue life test are applied on WHMM-13 to study the high-temperature stability, low-temperature cracking resistance, water stability, anti-reflection crack performance and fatigue durability in comparison with HMM-13. The results show that, compared to HMM-13, the dynamic stability and dynamic modulus (45 ℃, 10 Hz) of WHMM- 13 are improved by 10.0% and 47% respectively, and the rutting depth is reduced by 27.3%, indicating that the high temperature stability of WHMM-13 has been greatly improved. As for low temperature cracking resistance, the bending failure strain, stiffness modulus, flexural tensile strength and rupture energy of WHMM-13 are slightly lower than those of HMM-13. As for water stability, the residual stability of WHMM-13 in immersion Marshall test is 87.5%, and the splitting strength is 82.3%, both higher than that of HMM-13. As for anti-reflection crack performance, the total tensile rupture energy of WHMM-13 is 2.32 times that of HMM-13, with cracking resistance index (CRI) increased by 25%, which shows that WHMM-13 has better strength, can effectively prevent the crack from spreading and effectively improve the cracking resistance capacity of asphalt pavement. As for fatigue durability, the fatigue life of WHMM-13 is 5.4% lower than that of HMM-13, with bending stiffness modulus and cumulative dissipation energy reduced by 11.3% and 2.8% respectively, indicating that the fatigue durability of WHMM-13 is slightly reduced.

Advancing the performance characteristics of rubber asphalt mixtures through the integration of Basic Oxygen Furnace (BOF) slag: A focus on static and dynamic mechanical enhancements.

To investigate the advantageous effects of incorporating industrial solid waste basic oxygen furnace (BOF) slag on the mechanical characteristics of warm-mixed rubber asphalt (WMRA) and hot-mixed rubber asphalt (HMRA) mixture, varying proportions of BOF slag were substituted for limestone coarse aggregates (0%, 25%, 50%, and 75%). Additionally, a 1.5% dosage of Sasobit warm-mixed modifier was introduced to prepare the rubber asphalt. Subsequent to preparation, both static mechanical tests (including Marshall and indirect tensile tests) and dynamic mechanical tests (including dynamic creep and elastic modulus tests) were conducted to evaluate the influence of BOF slag on the mechanical behavior of WMRA and HMRA mixtures across different substitution levels. Following testing, a two-way analysis of variance (ANOVA) was employed to dissect the impact of BOF slag content and Sasobit warm-mixed modifier on the static and dynamic mechanical properties of the rubber asphalt mixtures. The findings reveal that BOF slag exhibits commendable engineering aggregate properties, enabling substantial substitution of coarse aggregates in both HMRA and WMRA mixtures. As the proportion of BOF slag increases, it enhances the resistance of asphalt mixtures to permanent deformation and cracking under static and dynamic loading conditions, while broadening the range of elastic deformation for both WMRA and HMRA mixtures subjected to repeated loading. Moreover, a synergistic enhancement in the resistance of rubber asphalt mixtures to dynamic load-induced deformation is observed when employing both BOF slag and Sasobit warm-mixed modifier. The findings offer valuable insights for enhancing the performance of WMRA and HMRA mixtures, as well as broadening the utilization of BOF slag and waste rubber.

Statistical analysis of low-density and high-density polyethylene modified asphalt mixes using the response surface method

The common use of plastics in daily life has engendered gigantic amounts of waste plastics, which have a detrimental influence on the environment. Researchers have proposed several strategies for the recycling of waste plastics and their products. Among these, one strategy is to use them in the construction industry, particularly in asphaltic pavements. This study thus focused on the utilization of waste plastics, specifically Low-Density Polyethylene (LDPE) and High-Density Polyethylene (HDPE), as an additive in Asphalt Concrete (AC) mixes. Indirect Tensile Strength (ITS), Flow Time (FT), and Dynamic Modulus (DM) tests were used to investigate the moisture damage, permanent deformation, fatigue performance, and DM of the LDPE and HDPE modified AC mixes. According to the laboratory test results, the LDPE and HDPE modified AC mixes offer more resistance to moisture damage compared to the Control AC mixes. It was also concluded that asphalt mixes modified with the LDPE and HDPE attained 2.07 times and 1.26 times superior resistance to permanent deformation than the Control mixes. Furthermore, the LDPE and HDPE modified AC mixes outperformed the DM values of the Control mixes by 2.06 times and 1.41 times, respectively. In addition, it was determined that the LDPE and HDPE modified AC mixes exhibit 1.72 times and 1.39 times greater fatigue parameter values than their counterpart, suggesting superior fatigue resistance performance. The statistical models developed using Response Surface Methodology (RSM) revealed the highest values of the Coefficient of Determination (>0.80), adequate precision (>4.0), and lack-of-fit tests, indicating the model’s adequacy for predicting the response.

Mechanical and piezoresistive performance of polymethyl methacrylate modified with carbon nanotubes for sensitive road surface

Piezoresistive materials, known for their mechanical adaptability and sensing capacity, hold the potential to be used as the materials for the sensitive surface layer in the digital twin of road systems. This study aims to investigate the mechanical and piezoresistive performance of a novel pavement material, a composite that comprises Polymethyl methacrylate (PMMA) as the matrix and carbon nanotubes (CNTs) as the conductive filler. Firstly, the composition and preparation process of CNTs-modified PMMA (CMP) were optimized via investigation on curing time, dispersion methods, and initiator content. Subsequently, the piezoresistive responses of CMP were analyzed within a loading range of 0 to 10 MPa by conducting linear increase compressive stress tests. Additionally, dynamic modulus tests and dynamic creep tests were employed to assess the mechanical and piezoresistive responses of CMP under equivalent vehicle loads. Results show that optimal properties are achieved when using ultrasonic methods to disperse CNTs, with a curing period of 72 h and an initiator content of 1.6 wt%. PMMA exhibits a lower modulus, reduced elasticity recovery and temperature sensitivity after modification with CNTs. And varying the CNTs content from 0.8 wt% to 1.2 wt% does not significantly affect the viscoelastic properties of CMP. The piezoresistive response of CMP under equivalent vehicle loads occurs in the first stage of the fractional change in resistance curve and is exclusively correlated with the tunneling resistance of adjacent CNTs. In this stage, CMP demonstrates higher sensitivity to heavy loads at lower CNTs content. The developed piezoresistive model based on tunneling resistance aligns with the experimental results. This study provides a basis for the performance study of CMP as a piezoresistive material in pavements, contributing to the design and development of sensitive surface layers in road systems.

Mechanistic Fatigue Performance Evaluation of Stone Mastic Asphalt Mixtures: Effect of Asphalt Performance Grade and Elastic Recovery.

This study evaluates the crack performance of stone mastic asphalt (SMA) mixtures according to the performance of a modified asphalt binder, evaluated based on the asphalt performance grade (PG) and the elastic recovery of multiple stress creep and recovery (MSCR) according to AASHTO M 320 and T 350. The cracking performance of the mixture was evaluated using the asphalt mixture performance tester (AMPT) according to AASHTO T 378 and T 400 through dynamic modulus and direct tension cyclic fatigue tests. Furthermore, the recently developed viscoelastic continuum damage (VECD) theory was utilized to evaluate the cyclic fatigue index parameter (apparent damage capacity, Sapp) and the permissible heavy vehicle class. For performance evaluation, six modified asphalt mixtures were prepared and tested using SMA aggregate gradation with a nominal maximum aggregate size (NMAS) of 10 mm. The MSCR test results revealed that, of the six asphalt mixtures, the rubber-based PG76-28 exhibited the least initial strain and the highest elastic recovery. The dynamic modulus test results demonstrated that using a rubber-based modifier increased the elastic modulus at high temperatures and decreased it at low temperatures, thereby enhancing resistance to plastic deformation in the summer and reducing low-temperature cracking in the winter. Finally, the correlation between the Sapp performance index and the elastic recovery of modified asphalt and the number of direct tension cyclic loads until failure of the mixture was evaluated as 0.87 and 0.76, respectively.

Establishment and evaluation of dynamic viscoelasticity constitutive model for asphalt mixtures based on PCA model: Utilizing coal-based synthetic natural gas slag and phosphogypsum whisker as substitute fillers

To promote the secondary utilization of solid waste in asphalt pavement and reduce resource waste and environmental damage, the fine solid waste powder from the secondary treatment of solid waste was used as a substitute filler to prepare asphalt mixtures. To more precisely characterize the effects of filler type and substitution ratio on the dynamic viscoelastic mechanical characteristics of asphalt mixtures, the dynamic modulus test was conducted on asphalt mixtures, while the dynamic modulus master curve of asphalt mixtures was established based on the time-temperature equivalent principle and the Sigmoidal function. The improved generalized Sigmoidal (IGS) model, five-parameter fractional Zener (FFZ) model, six-parameter fractional Zener (SFZ) model and ten-parameter fractional Zener (TFZ) model were used to construct the shrinkage frequency curves of different asphalt mixtures under different constitutive relationships, whereas the applicability of the constitutive models was further evaluated by the principal component analysis (PCA) model. The research results showed that the dynamic modulus and phase angle of the mixture exhibited a similar change rule with the variation of temperature and frequency, and the use of solid waste-based fillers could effectively reduce the effect of frequency variation on the viscoelasticity of the mixture. The dynamic modulus master curve constructed by Sigmoidal function could accurately describe the functional relationship between the dynamic modulus with loading frequency and temperature, and the variation trend of dynamic modulus in a wider frequency range was flattened with the increase in frequency, and this change rule was not affected by the substitution ratio of the filler, while the use of solid waste-based filler could reduce the dependence of the mixture on the temperature. Compared to several fractional constitutive models, the IGS model exhibited a higher fitting accuracy for the dynamic viscoelasticity of several mixtures, and with the use of solid waste-based fillers, the deviation of fitting curves gradually decreased. A comparative study showed that the fractional constitutive model was difficult to accurately describe the dynamic viscoelasticity of the mixture, and the IGS model was preferred to be recommended as a calculation model to investigate the constitutive relationship on the dynamic viscoelasticity of the mixture.

Study on Dynamic Modulus Prediction Model of In-Service Asphalt Pavement

The dynamic modulus of in-service asphalt pavements serves as a critical parameter for the computation of residual life and the design of overlays. However, its acquisition is currently limited to laboratory dynamic modulus testing using a limited number of core samples, necessitating a reassessment of its representativeness. To facilitate the prediction of dynamic modulus design parameters through Falling Weight Deflectometer (FWD) back-calculated modulus data, an integrated approach encompassing FWD testing, modulus back-calculation, core sample dynamic modulus testing, and asphalt DSR testing was employed to concurrently acquire dynamic modulus at identical locations under varying temperatures and frequencies. Dynamic modulus prediction models for in-service asphalt pavements were developed utilizing fundamental model deduction and gene expression programming (GEP) techniques. The findings indicate that GEP exhibits superior efficacy in the development of dynamic modulus prediction models. The dynamic modulus prediction model developed can enhance both the precision and representativeness of asphalt pavement’s dynamic modulus design parameters, as well as refine the accuracy of residual life estimations for in-service asphalt pavements. Concurrently, the modulus derived from FWD back-calculation can be transmuted into the dynamic modulus adhering to a uniform standard criterion, facilitating the identification of problematic segments within the asphalt structural layer. This is of paramount importance for the maintenance or reconstruction of in-service asphalt pavements.

Durability analysis of metakaolin recycled concrete under sulphate dry and wet cycle

This study aims to enhance the durability, cost-effectiveness, and sustainability of recycled fine aggregate concrete (RFAC) subjected to the combined effects of wet-dry cycles and sulfate erosion. Dry–wet cycle tests were conducted in RFAC with different admixtures of biotite metakaolin (MK) and 15% fly ash (FA) mix (M) under 5% sulfate erosion environment. The effect of 0%, 30%, 60% and 90% recycled fine aggregate (RFA) replacement of natural fine aggregate on mass loss, cubic compressive strength, relative dynamic modulus test of RFAC, damage modeling and prediction of damage life of concrete were investigated. The results showed that the concrete cubic compressive strength and relative dynamic modulus were optimal for recycled concrete at 15% MK biotite dosing and 60% RFA substitution, and its maximum service life was accurately predicted to be about 578 cycles under 5% sulfate dry–wet cycling using Weibull function model. This study is pioneering in addressing the durability of RFAC under sulfate attack combined with wet-dry cycling, employing a novel approach of incorporating MK and FA into RFAC. The findings highlight the practical application potential for using MK and FA in RFAC to produce durable and sustainable construction materials, particularly in sulfate-exposed environments. This research addresses a critical challenge in the construction industry, providing valuable insights for developing more durable and eco-friendly construction materials and contributing to long-term sustainability goals.

A testing theory for simultaneously determining asphalt mixture’s dynamic modulus in compression and tension by use of IDT test

The compressive and tensile moduli of asphalt mixtures are not equal. As a result, in order to obtain reasonable response calculation results, asphalt pavement mechanical analysis should first determine the compressive and tensile moduli of asphalt mixtures separately. Then, it should assign an appropriate modulus to the FEM element based on the stress state of the element. However, conventional uniaxial compression modulus testing protocol is typically unable to determine the actual asphalt pavement's coring specimen due to the limitation that general dynamic modulus testing protocol requires a larger size of specimen and conventional coring specimen from field usually cannot meet the requirement in regard to specimen size. In this case, the dynamic modulus of the asphalt mixture can only be ascertained using the IDT test method.Nevertheless, the current IDT test protocol is unable to distinguish between the compressive and tensile moduli of asphalt mixtures, and the testing results are usually different from those obtained by using the conventional uniaxial compression or tension method. This is because the current IDT test method for determining the dynamic modulus of asphalt mixtures generally treats asphalt mixtures as a kind of ideal elastic material and considers its compressive modulus is equal to its tensile modulus.Consequently, this paper presents a new theory, based on Ambartsumyan's bi-modulus constitutive relation theory, that can use the IDT test method to simultaneously determine the dynamic modulus of an asphalt mixture in both compression and tension. This theory assumes that the stress-strain relationship of asphalt mixture complies with the bi-modulus constitutive relation, and obtains the vertical deformation or horizontal deformation of the IDT specimen by solving a definite integral for the displacement of a small segment on the vertical or horizontal axis, which utilizes the results of the mathematical analysis of the stress distribution of the IDT specimen under distributed strip load. Then, the specimen's dynamic modulus in compression and tension can be obtained via back-calculating method, if the specimen's vertical and horizontal displacement are measured by a physical test in the lab. Obviously, this theory addresses the limitation of the conventional IDT method that cannot reflect the distinction of compressive modulus with tensile modulus, and can be better utilized to simultaneously determine compressive and tensile modulus of cored specimen from field. The verification test also demonstrates, the dynamic modulus determined by this theory are in line with the results of the conventional uniaxial test and is highly practicable.

Impact of confinement condition of dynamic modulus test on the performance of flexible pavement structures

Impact of confinement condition of dynamic modulus test on the performance of flexible pavement structures

Evaluation of Fatigue Behavior of Asphalt Field Cores Using Discrete Element Modeling.

Fatigue cracking is one of the primary distresses of asphalt pavements, which significantly affects the asphalt pavement performance. The fatigue behavior of the asphalt mixture observed in the laboratory test can vary depending on the type of fatigue test and the dimension and shape of the test specimen. The variations can make it difficult to accurately evaluate the fatigue properties of the field asphalt concrete. Accordingly, this study proposed a reliable method to evaluate the fatigue behavior of the asphalt field cores based on discrete element modeling (DEM). The mesoscopic geometric model was built using discrete element software PFC (Particle Flow Code) and CT scan images of the asphalt field cores. The virtual fatigue test was simulated in accordance with the semi-circular bending (SCB) test. The mesoscopic parameters of the contacting model in the virtual test were determined through the uniaxial compression dynamic modulus test and SCB test. Based on the virtual SCB test, the displacement, contact forces, and crack growth were analyzed. The test results show that the fatigue life simulated in the virtual test was consistent with that of the SCB fatigue test. The fatigue cracks in the asphalt mixture were observed in three stages, i.e., crack initiation, crack propagation, and failure. It was found that the crack propagation stage consumes a significant portion of the fatigue life since the tensile contact forces mainly increase in this stage.