Resilient Modulus Tests Research Articles

Application of lignin-based by-product stabilized silty soil in highway subgrade: A field investigation

Lignin is a by-product of paper and timber industry, and it has not been fully utilized in both developed and developing countries. Improper disposal or storage of lignin is not only a waste of natural resources, but also posing significant risk to public health and the environment. Sustainable reuse options for lignin in civil engineering infrastructures, such as road embankments and dam foundations, have been recently evaluated by laboratory testing. However, up to now studies on the actual filed performance of lignin in stabilizing silty soils in highway subgrade have been noticed to be quite limited. With this in view, a field trial was carried out to verify the viability of using lignin stabilized silty soil as a highway subgrade course material. Traditional soil stabilizer, quicklime, was selected as a control chemical mixture in the field trial for comparison purposes. The construction procedures of the subgrade silty soil stabilized by lignin and quicklime in field Sections were presented. A series of field tests, including California Bearing Ratio (CBR) test, resilient modulus (Ep) test, Benkelman beam deflection test, and dynamic cone penetrometer (DCP) test were carried out after the subgrade construction to investigate the effects of the curing time and additive content on the mechanical properties and bearing capacity of the stabilized silt. In addition, moisture content and compaction degree tests were conducted to evaluate the quality of the compacted subgrade soils. The test results indicate that at the bottom zone of the filled soil layers with 96% degree of compaction, the 12% lignin stabilized silt exhibits superior mechanical performances (i.e., higher value of CBR and Ep, and lower values of resilient deflection (Hr) and DCP Index) than the 8% quicklime stabilized silt after 15 days of curing. Under the same additive content (i.e., 8%), the bearing capacity of lignin stabilized silt is slightly lower relative to the quicklime stabilized one. The field trial results reveal that as a stabilizer of the subgrade soil, lignin has negligible environmental influences and induces low construction costs. The use of lignin as a stabilization chemical mixture for silty soil may be one of the viable answers to the reuse of biobased organic by-product in civil engineering. The outcome of this study is of great significance for the development of nontraditional, cost-effective, and environmentally friendly soil stabilizer in solidification/stabilization technology.

Performance evaluation of Hot Mix Asphalt (HMA) containing bitumen modified with Gilsonite

Iran-produced bitumen under the circumstances of severe temperature fluctuation, heavy traffic load and raining/freezing conditions show low efficiency; therefore, it is necessary to improve its properties accordingly. Existence of weakness in produced bitumen result in failure occurrence in asphalt pavements during service life of asphalt roads. Given the existence of considerable reserves of Gilsonite in Iran, its low costs compared with other additives and its remarkable properties, we can study asphalts modified by Gilsonite. At the present time, little research has been conducted on this modifier in the world and Iran (which its properties are still not quite evident for researchers). The most important failure in flexible pavements is permanent deformations which are known as rutting. Rutting is longitudinal depression in the wheel path in bituminous pavements. The rate and depth of rutting depend on the internal factors such as bitumen properties, aggregate, mixture properties and thickness of pavement layers. In this lab study, with regard to the technical and executive issues, common functional performance-based tests of bitumen were performed on specimens through addingGilsonite with 0, 2, 4, 6, 8, 10wt.% of made bitumen specimens. Then, the optimum percentage was calculated using the AHP. The specimens containing pure bitumen 60–70 and modified bitumen 60–70 with Gilsonite in two different aggregations (4 and 5) were made and the effects of adding Gilsonite in Marshall Stability and flow, indirect tensile strength and moisture sensitivity, as well as dynamic creep, and resilient modulus were evaluated by the UTM device. The research showed that adding Gilsonite to bitumen in hot asphalt mixtures considerably increases Marshall Stability and resilient modulus parameter in asphalt specimens. However, resilient modulus test indicated a significant reduction in flexibility property of asphalt mixtures made of modified bitumens. Moreover, increasing the flow number obtained from the dynamic creep test indicate the increase of rutting resistance.

Development of a Test Procedure for Freeze-Thaw Durability of Geomaterials Stabilized With Fly Ash

Abstract The objective of this research was to develop a freeze-thaw cycling test procedure and to investigate how the volume, moisture content, resilient modulus (Mr), and unconfined compressive strength (qu) of geomaterials, including soils and recycled materials, stabilized with fly ash change after freeze-thaw cycling. Three different types of materials (fine-grained and coarse-grained soils and recycled pavement materials) and five different fly ashes were used at different percentages (10, 12, 14, and 20 % by dry weight). Both one-dimensional and three-dimensional freezing of the specimens were considered. Freezing in three-dimensional was faster in terms of completing the freeze-thaw cycling and provided very similar results to the ones prepared in one-dimensional. Thus, three-dimensional freezing was adopted in this study without access to water (i.e., closed system). The results of this study indicated that the volume of all soil-fly ash mixtures tended to increase after freeze-thaw cycling; however, the volume change was not significant. Resilient modulus tests were conducted on all unstabilized materials, as well as on their mixtures with fly ash, while qu tests were conducted only on fine-grained soil and their fly ash mixtures. The Mr of all mixtures with one exception decreased by an average of 28.5 % when specimens were subjected to freeze-thaw cycling. The drop in the Mr of the specimens leveled off after 5 freeze-thaw cycles. A general trend of higher Mr of materials stabilized with fly ash (from 3 to 168 %), even after freeze-thaw cycles compared to unstabilized material was observed. In general, a reduction in unconfined compressive strength (qu) after freeze-thaw cycles up to 70 % was obtained. However, results showed that qu of stabilized soils that were subjected to freeze-thaw cycles were still higher (from 6 to 157 %) than the qu of unstabilized soils.

Rutting and Fatigue Performance Evaluation of Qingchuan Rock Modified Asphalt Mixture

To solve the problem of rutting and fatigue damage to asphalt pavement, rutting and fatigue performances of Qingchuan rock asphalt modified asphalt were studied, based on the dynamic shear rheometer test, the dynamic creep test, the rutting test, the indirect tensile fatigue test, the small-sized acceleration loading test, the compressive resilient modulus test, the BISAR3.0 Program and the rutting calculation method based on dynamic finite element method. The results indicate that Qingchuan rock asphalt modifier can obviously improve the anti-fatigue performance and anti-rutting performance of asphalt pavement. Taking the anti-rutting performance and the raw-material price of asphalt into consideration, a rock asphalt optimum content ranging from 5% to 8% is suggested. Qingchuan rock asphalt is a good modifier to solve the rutting and the fatigue damage of asphalt pavement.

Experimental investigation of the effect of using different aggregate types on WMA mixtures

In recent years, production of warm mix asphalt (WMA) mixtures with the help of chemical additives has been developed due to obvious advantages, such as reduction of pollution emissions, construction temperature and the possibility of carrying asphalt in long distances. Various additives can have positive or negative effects on the performance characteristics of WMA mixtures made from different types of aggregates. Although, effects of different types of aggregates have been more investigated on the performance of hot mix asphalt (HMA), the effects on WMA have been less studied. Therefore, in this study, three types of aggregates including: limestone (Li), siliceous (Si) and slag (Sl) from the metal production factories together with Sasobit and Zeolite additives were provided to be used for the WMA mixtures. After constructing the asphalt samples and determining the optimum binder, Marshall Stability, indirect tensile strength tests and resilient modulus test and the durability parameter determination were performed. Test results indicated that WMA-Sasobit mixtures have the greatest impact on reducing consumed percentage of binder in slag and siliceous aggregates compared to limestone aggregates. For both additives, WMA mixtures containing limestone aggregates showed higher resilient modulus and siliceous aggregates showed lower resilient modulus. Moreover, the results of indirect tensile strength of specimens containing limestone aggregates showed the highest value and siliceous aggregates showed the lowest one. TSR in the limestone and slag aggregates was improved using both additives, but Zeolite additives reduce TSR in the siliceous aggregates.

Mechanistic Estimation of Lightweight Deflectometer Target Field Modulus for Construction Quality Control

The lightweight deflectometer (LWD) is an emerging device for evaluating the quality of compacted layers. Establishing the proper field target modulus for the LWD is crucial for judging the quality of the compacted unbound layers. A rigorous numerical approach to determine the project-specific field target values for a LWD device during the pavement design process is presented in this study. The input parameters to the model include the thickness of the layers, as well as the nonlinear stiffness parameters of each layer estimated from the resilient modulus tests. Simple relationships are proposed to estimate the target modulus when the earthwork can be approximated as a single layer. A parametric study was performed to quantify the impact of the input parameters on the estimated target modulus. The applied load and the plate diameter of the LWD along with some of the nonlinear soil parameters significantly affect the target modulus. The processes of the development and validation of these models are presented in this paper. Furthermore, the impact of moisture variation on estimated target LWD modulus is discussed.

Investigating Stress Dependency of Unbound Layers Using Falling-Weight Deflectometer and Resilient Modulus Tests

Unbound layer materials, such as base and subgrade, exhibit stress-hardening and/or -softening, which can be determined from their resilient modulus values. However, unavailability of required amount of material and compaction variability between field and laboratory necessitate a need to predict stress dependency of the unbound layers by field tests. This study evaluates stress dependency of unbound layers using a falling-weight deflectometer (FWD) test. The FWD tests were conducted at multi-load levels on several pavement sections. The FWD back-calculated layer moduli are then used to determine bulk and octahedral shear stresses using the layered elastic analysis technique. Next, the regression analysis is performed to interpret the stress-dependent parameters, i.e., regression coefficients of pavement ME's resilient modulus model of nonlinear unbound material. It is observed that stress-hardening is dominant in the case of the base layer, whereas subgrade exhibits both stress-hardening and -softening. This was also confirmed by laboratory resilient modulus tests on both base and subgrade materials in this study. Therefore, it is recommended not to ignore either stress-hardening or -softening during nonlinear modeling of the unbound layers. In addition, in this study, empirical relationships are developed to perform inter-conversion of laboratory resilient and FWD back-calculated modulus incorporating the field state of stresses in base and subgrade.

Laboratory Evaluation of Ladle Furnace Slag in Unbound Pavement-Base/Subbase Applications

AbstractSteel is an inherently never-ending product, in terms of recycling and reuse. The steelmaking process creates an industrial by-product termed as slag. Ladle furnace slag (LFS) is produced at the final stages of the steelmaking process in ladle refining furnaces. The potential use of LFS as a base/subbase material requires a thorough knowledge of its engineering properties. In this research, an extensive suite of engineering characterization tests were carried out to evaluate the engineering properties of LFS. The effect of curing on the strength of unbound LFS was investigated using unconfined compression strength (UCS) and resilient modulus tests. The results showed that the UCS of unbound LFS increased by almost four times with 7 days of curing in a temperature-controlled and moisture-controlled chamber. The resilient modulus value of unbound LFS increased when increasing either confining pressure or deviator stress. The specimens with 7 and 28 days of curing had higher resilient modulus values ...

A statistical analysis on the mechanical properties of nanocomposite modified asphalt mixtures

ABSTRACTThis study aimed to characterize the rate of change that takes place in the mechanical properties of polymer-nanocomposite asphalt (PNMA) mixtures due to altering asphalt binder grade and styrene-butadiene-styrene (SBS) type. Laboratory testing program included Marshall stability, resilient modulus, and wheel-tracking tests. Test results were compared and analyzed statistically by means of two-way analysis of variance and Tukey test. Variance analysis indicated the significant effect of both binder type and SBS grade on mechanical properties of asphalt mixtures. Interaction between binder type and SBS grade is also meaningful in all the experiments. The results also show that the binder type is the primary affecting factor, followed by the SBS grade.

Rutting resistance and resilient modulus evaluation of polymer-modified SMA mixtures

ABSTRACTEthylene copolymer bitumen (ECB), namely Lucobit, as a thermoplastic polymer, SBS as a thermoplastic-elastomer polymer, and ethylene-vinyl-acetate (EVA) combined with Fischer-Tropsch wax and resin additives, namely Rheofalt WKR-2, as a modified thermoplastic polymer were used for stone matrix asphalt modification. Two types of asphalt modification processes including polymer-modified bitumen (PMB) and direct addition of polymer into mixture were employed and the effect of each one on resilient modulus and rutting resistance was evaluated by performing Indirect Tensile Resilient Modulus and Hamburg Wheel Tracking tests. PMB, SBS, and Rheofalt-modified mixtures resulted in lower rut depth and higher resilient modulus than did those modified by ECB. In direct addition of the polymer into mixture process, there is reduction in rutting resistance and resilient modulus of Rheofalt-modified mixtures in comparison with PMB. Furthermore, there was no improvement for ECB-modified mixtures by direct addition modification.

Laboratory investigation of the performances of cement and fly ash modified asphalt concrete mixtures

The influence of filler materials on volumetric and mechanical performances of asphalt concrete was investigated in this study. The AC60/70 asphalt binder incorporating with cement and fly ash as filler materials was mixed with limestone following the Marshall mix design method. The filler contents of cement and/or fly ash were varied. The non-filler asphalt concrete mixtures of the AC60/70 and the polymer modified asphalt were prepared for the purpose of comparison. The investigation programme includes the indirect tensile test, the resilient modulus test and the dynamic creep test. The tests are conducted under the humid temperate environments. All tests were then carried out under standard temperature (25°C) and high temperature (55°C) by using a controlled temperature chamber via the universal testing machine. The wet-conditioned samples were prepared to investigate the moisture susceptibility. Results show that cement and/or fly ash were beneficial in terms of improved strength, stiffness and stripping resistance of asphalt mixture. In addition, the combined use of cement and fly ash can enhance rutting resistance at wet and high temperature conditions. The results indicate that the strength, stiffness and moisture susceptibility performances of the asphalt concrete mixtures improved by filler are comparable to the performance of the polymer modified asphalt mixture.

Effects of mixture design variables on rubber–bitumen interaction: properties of dry mixed rubberized asphalt mixture

The utilization of crumb rubber in asphalt mixture has significantly evolved in the past few decades. However, the modification through dry process method has been a far less popular compared to the wet process due to a few drawbacks that affect its performance. One such concern that is often ignored by researcher relates to the rubber–bitumen interaction that causes swelling of the rubber particles within compacted asphalt mixture. Rubber–bitumen interaction refers to the absorption of bitumen particularly the maltenes fraction by rubber particles. This study investigated the effects of mixture design variables on the rubber–bitumen interaction and properties of rubberized asphalt mixtures fabricated through the dry method. The effects of rubber–bitumen interaction at different rubber sizes, bitumen contents, and curing periods were investigated using the “Basket Drainage Method”. While, the mechanical properties of rubberized asphalt mixtures were measured using resilient modulus and dynamic creep tests. Four types of gyratory compacted specimens of a dense grade mixture of asphaltic concrete were fabricated. The four specimen types comprised a control specimen without rubber and three other specimens with 2 % crumb rubber of varying sizes (1.18, 3.35 and 5.0 mm). Results showed that higher rubber–bitumen interaction can be obtained with the use of fine rubber size and high bitumen content, thus exhibiting greater rubber swelling particularly in the first 4 h of curing. Specimen with fine rubber can be easily compacted to achieve the target density which shows consistency in the volumetric properties. The addition of crumb rubber reduces the resilient and creep modulus of asphalt mixtures compared to the control mix. However, by initiating the rubber swelling extensively prior to compaction can possibly improve the compatibility and volumetric properties, thus enhancing better performance of the rubberized asphalt mixtures.

The Performance of Styrene Butadiene Rubber on the Engineering Properties of Asphaltic Concrete AC14

This study investigated the effects of adding various percentages of styrene–butadiene rubber (SBR) on the engineering properties and performance of asphaltic concrete. SBR was added into the mixture at 0%, 1%, 3%, and 5% on a mass-to-mass basis. Conventional bitumen used in this study was 80/100 PEN. The performances of SBR on the asphalt mixture properties were evaluated based on Marshall Stability, abrasion loss, resilient modulus, and dynamic creep test. Results indicated an improvement in the engineering properties and performance with the addition of SBR content. For instance, stability increased by 18.8% as the SBR content increased from 0% to 5%. Dynamic creep stiffness also increased by 46.2%. Similarly, the resilient modulus was also found to increase by approximately 84.6%.

Strength Development and Microfabric Structure of Construction and Demolition Aggregates Stabilized with Fly Ash–Based Geopolymers

The reuse of recycled construction and demolition (C&D) aggregates in civil engineering infrastructure applications has been considered a low-carbon solution to replace conventional pavement aggregates. Evaluating the strength development mechanism and interparticle flow of forces in geopolymer stabilized C&D aggregates will provide fundamental understanding of the behavior of stabilized C&D aggregates. The C&D aggregates studied are reclaimed asphalt pavement (RAP), recycled concrete aggregate (RCA), and crushed brick (CB). The performance of alkali-activated fly ash (geopolymer) on the stabilization of C&D aggregates, under different curing conditions and sample preparation methods were studied. Fly ash was used as the precursor for the alkali-activated binder that was used to stabilize the C&D aggregates. The effect of low and high content of fly ash–based geopolymers on strength development of recycled materials is investigated for the first time. Sodium silicate and sodium hydroxide were used, with different ratios, to intensify the alkaline environment for fly ash to accelerate the strength development of the mixture. The effect of static and dynamic compaction on the density and strength development was investigated for both low-content fly ash and high-content fly ash. Temperature treatment of geopolymer stabilized C&D aggregates up to 40°C and humidity curing in the moisture chamber for 7 days indicated improvement of the strength development of the mixture. The results of unconfined compressive strength (UCS) and resilient modulus testing of geopolymer-stabilized C&D aggregates indicate that alkali-activated fly ash is a viable binder for the stabilization of C&D aggregates.

Multivariate correlation among resilient modulus and cone penetration test parameters of cohesive subgrade soils

Extensive research has been conducted to establish empirical equations between the resilient modulus (Mr) and other testing parameters. Despite an increase in the correlation studies, less effort has been made in developing reliable correlations to predict the resilient modulus using cone penetration testing indices. In this research, an attempt has been made to propose new correlations between Mr and the piezocone penetration test (CPTU) indices of clayey soils by using a multivariate normal distribution approach. A database collected from 16 different sites in Jiangsu province, China, was presented to achieve this study. The database contains 124 sets of resilient modulus (Mr) values at the in-situ stress condition, cone tip resistance (qc), sleeve frictional resistance (fs), moisture (w) and dry density (γd). Four major procedures including the data transformation, correlation analysis, Bayesian updating, and back transformation were applied to derive the correlations among Mr and other indices in the framework of the multivariate normal distribution model. First, each individual parameter was converted to a standard normal variable using the Box-Cox transformation. Later, the correlation matrix of the multivariate normal distribution model was estimated using the product-moment (Pearson) correlation coefficients between all pairwise data. The uncertainties associated with the Box-Cox transformation parameters and the correlation coefficients were evaluated using a bootstrapping technique. Furthermore, the formulas for predicting the posterior mean, coefficient of variation (COV), median, and 95% confidence interval (CI) of Mr conditional on different indices were derived using Bayesian updating combined with back transformation. A new approach based on the Taylor-series expansion was proposed to approximate these statistics in this study. Comparisons between the correlations derived from the multivariate model, the database of Jiangsu clay, and the data collected from the literature demonstrated that the model should be capable of the correlations among the five indices, but it might be slightly biased when applied in the global dataset. This research highlighted a new method to establish the reliable correlations to update Mr using different testing indices.

Performance evaluation of recycled asphalt mixtures by construction and demolition waste materials

In recent years, Construction and Demolition waste materials (C&D waste materials) have become one of the main environmental and economical concerns to be managed. Using them as aggregate in pavement layers is considered a solution to reduce accumulated building debris in land-fills. In this research, after determining Optimal Binder Content (O.B.C.) of control mixture and those containing 10%, 20%, 30%, and 40% C&D materials, rutting performance of them were evaluated using indirect tensile resilient modulus test, Dynamic Creep test, and Wheel Tracking test. Furthermore, moisture susceptibility were investigated using wet/dry Indirect Tensile Strength (ITS). Using C&D waste materials increases O.B.C. and results of performance tests shows that recycled aggregates improve rutting resistance among which 30% is the most. Moisture damage resistance is also enhanced with C&D waste materials increase.

A model to predict changes in resilient modulus resulting from wetting and drying

The resilient modulus of a soil is an important parameter needed for pavement design. However, this parameter experiences post-compaction seasonal changes during the service life of the pavement as a result of wetting or drying of the soil during dry or rainy periods. Variations in the resilient modulus should be introduced into pavement design methodologies. Research literature shows resilient modulus results from other countries; however, the information is scarce for Mexican soils. In this paper, the authors show results of a research carried out in the laboratory to evaluate a model for the prediction of the effect of wetting and drying on the resilient modulus of soils classified as clays, silt, and sand. Several samples were prepared at optimum conditions using the Proctor standard test. Some specimens were then dried by allowing a loss of water through evaporation while others were allowed to gain water through capillarity (assumed to simulate post-compaction conditions). After the samples were conditioned to new water contents, resilient modulus tests were performed following the NCHRP 1-28A protocol. The results show that the resilient modulus can be predicted using a model which is a function of the deviator stress and confining pressure (i.e., (sd/s3) and the variation of water content from optimum water content conditions (i.e., the condition after field compaction). The R2 results when using the proposed resilient modulus model was 84.1%.

Effect of clay and lime nano-additives on the freeze–thaw durability of hot mix asphalt

Durability of hot mix asphalt (HMA) against freeze–thaw cycles is mostly related to bitumen-aggregate adhesion. Improving the bonding quality between aggregates and bitumen would reduce the HMA moisture susceptibility and increase its durability. This study focused on the effects of nano-additives, including nano-clay (NC) and nano-lime (NL) on the durability of HMA. Limestone and granite aggregates were used to prepare the HMA specimens. Nano-additives were blended with 60/70 penetration grade bitumen at different rates, including 3%, 6%, and 9% by weight of bitumen. The mechanical properties of HMAs were determined using indirect tensile strength (ITS) and resilient modulus tests before and after one, three, and five freeze–thaw conditioning cycles. Afterwards, the moisture damage of mixes were evaluated using the surface free energy (SFE) concept. The SFEs of unmodified and modified bitumens were measured using the Wilhelmy plate test. Likewise, the SFEs of aggregates were evaluated by a universal sorption device procedure. Based on the results obtained, the addition of proper NC and NL content will enhance the tensile strength and resilient modulus ratios. The optimum NC and NL contents were determined as equal to 3% and 6%, respectively. The difference between the bitumen-aggregate and water-aggregate SFEs showed peak points, which were obtained at the optimum additive content. These peak points were mostly in accordance with the peak of ITS and resilient modulus tests before and after conditioning cycles.

Mechanical Behavior of Basaltic Rocks from Serra Geral Formation Used as Road Material in Santa Catarina State, Brazil

This work presents physical, petrographic and mechanical characteristics of basalt aggregates from Serra Geral Formation in the State of Santa Catarina, Brazil, used as layers of simple graded crushed stone in pavement. The simple graded crushed stone chosen for the study was obtained from a quarry in the municipality of São José do Cerrito/SC, located in the mountainous region of Santa Catarina. The aggregates of this quarry were used to pave a segment of highway BR-282/SC from 2002 to 2006. This study presents the results of thin section analysis, which identifies the mineralogical composition of the material and clarifies aspects associated with the rock texture. In addition, resilient modulus tests are conducted, followed by numerical evaluation of the pavement’s structural behavior, field evaluation of elastic displacement with Benkelman beam testing, and comparison of the results. The entire highway segment was monitored throughout its implementation and was determined to be in good condition. The material used offers good performance as a pavement layer. Moreover, the methodology used for the design presents good correlation with the field tests.

Effects of nanoclay on hot mix asphalt performance

ABSTRACTThe purpose of this study was to evaluate of nanoclay effects as an additive on performance of asphalt mixtures. Two types of montmorillonite nanoclay, namely CA and CB, were used at concentrations of 2%, 4%, and 6%. Marshall, indirect tensile strength, resilient modulus, and dynamic creep tests were performed to investigate the effect of additives on moisture susceptibility, structural response, and rutting resistance. The results showed improvement of the asphalt mixture performance by adding nanoclay with respect to all tests. According to the results, samples containing nanoclay CA have better performance in comparison with the samples containing CB.