Laboratory Compaction Methods Research Articles

Assessing cracking resistance and threshold limits of bituminous mixtures with IDEAL-CT and predictive modeling techniques

This paper presents a comprehensive study to establish the threshold limit of CTIndex for the Marshall mixes. The study also aims to assess the impact of different design factors on the cracking resistance of bituminous mixtures using the Indirect Tensile Asphalt Cracking Test (IDEAL-CT) test. This study considers 2 different aggregate sources, 2 different gradations, 5 different types of Design Aggregate Gradation (DAG), 3 binder types, and 5 levels of compactive effort. The test results show that higher cracking resistance can be achieved using a smaller nominal maximum size of the aggregate (NMAS), finer gradation, modified binder, and decreased compactive effort with aggregates having low abrasion and absorptive characteristics. This study also comprehends the influence of volumetric parameters of the bituminous mixes on fracture resistance. It was found that at a particular Optimum Binder Content (OBC), higher bulk specific gravity of the compacted specimen (Gmb) and voids filled with asphalt (VFA) result in reduced CTIndex, specifying poor cracking performance. While higher air voids (AV) and voids in mineral aggregate (VMA) lead to increased CTIndex, indicating better-cracking resistance. Statistical analysis tools were used to evaluate the significance of the influential factors that are affecting the cracking potential of the mix. Different Machine learning models were also developed to predict CTIndex based on the design factors considered in the study. The random forest (RFR) model showed strong accuracy, reflected by low Mean Absolute Error (MAE=3.16), Mean Absolute Percentage Error (MAPE=9.57), Root Mean Square Error (RMSE=4.23), and a high coefficient of determination (R²=0.95) value, notifying a precise fit and reliable predictions. Additionally, a GUI has been also developed to enhance the practical usability of the model for wider usage. Further, the present study proposes the threshold value of CTIndex for the selection of crack-resistant bituminous mixtures. Moreover, the study investigated the correlation between laboratory and field compaction methods and validated the initial threshold specification of CTIndex for the Marshall mixes. Despite of the variations in different compaction methodologies and specimen thickness, a strong positive correlation (R² > 0.76) between laboratory and field cores of BC-1 and DBM-2 indicates that the performance criteria are adequate and justified.

Effect of Production and Curing Methods on the Properties of Roller-Compacted Concrete: A Review

Roller Compacted Concrete (RCC) exhibits many characteristics of both asphalt and rigid pavements, but their use is restricted. Many reasons led to this decision, including the fact that RCC is a type of concrete mixture that requires a specific consistency. It should be firm enough to be compacted by a roller compactor but also have enough moisture to ensure even distribution. The lab-field performance difference of RCC is another reason for decreasing its use. The laboratory RCC mixes are prepared using the modified Proctor compaction method. Subsequently, specimens are fabricated utilizing a vibratory hammer (VH) to evaluate their strength properties. Nevertheless, in the construction industry, pavement is built utilizing static, pneumatic, and vibratory rollers. Consequently, quality control is carried out by acquiring pavement samples and comparing them to laboratory samples. Each of these procedures employs different processes and energies, resulting in variations in field and laboratory behavior. In this investigation, some studies will be discussed about the RCC behavior under field and lab conditions using various design methods, such as the vibrating table (VH), vibratory table (VT), gyratory compactor (GC), and modified proctor (MP). These studies showed a difference in RCC mechanical and macroscale properties between laboratory compaction methods. For instance, VH specimens led to a higher evaluation, while GY specimens produced a less favorable estimation of the hardened properties observed in the field. While the MP and VT compacted specimens had a comparable structural arrangement to the field, they exhibited notable differences in terms of porosity and strength. Other studies revealed the essence of the curing stage in terms of RCC mechanical properties and indicated that some curing processes, like compound curing, may improve RCC performance.

Macro-meso multiscale analysis of asphalt concrete in different laboratory compaction methods and field compaction

The difference between asphalt concrete (AC) compacted in the laboratory and the field significantly influences its gradation design and performance evaluation accuracy. In this research, the effect of the laboratory compaction and field compaction on AC characteristics were compared using the characteristic indexes of surface texture, internal structure, asphalt binder distribution, aggregate distribution, compressive resilience modulus, and the crack resistance index (CRI). Six different compaction methods for AC specimens were studied, and five different types of laboratory compaction equipment were used, namely the Marshall compactor, Steel segmented roller compactor (SSRC), Superpave gyratory compactor (SGC), shear box compactor (SBC), and roller. The results showed that a uniform texture of AC surface was created with vibration and kneading. The aggregate contact distribution of specimens compacted by SGC, SBC, and roller was similar to field compaction as an inverse “bathtub” shape. The aggregate rotation angle of AC compacted by SGC, SBC, and roller showed higher randomness. The coarse aggregate of specimens degraded after Marshall compaction. The fine aggregate coated with more asphalt binder being moved towards the middle height of the specimen, resulting in higher asphalt binder content in the middle layer during the compaction of SGC and SBC. The specimens compacted with SGC and SBC had better mechanical properties, especially in the middle layer of the specimen. The increase of aggregate contact points improved the mechanical properties of the mixture. The free movement of aggregates was helpful for slippage of aggregates and promoted the filling of voids with asphalt mastic to make the skeleton structure more compact. Correlation analysis showed that SGC and the roller could better reproduce the field compaction state.

A Laboratory Compaction Method for Dry-Consistency Concretes

A Laboratory Compaction Method for Dry-Consistency Concretes

Effect of laboratory compaction mode, density and suction on the tensile strength of a lime-treated silty soil

Facing the need to adopt a laboratory compaction method of natural or lime-treated soils which is repeatable and representative of real in-situ compaction conditions for dike or road constructions, the effects of compaction mode, dry density and suction on the tensile strength of natural and lime-treated silty soil compacted in laboratory have been investigated in a systematic way. Soil specimens were prepared from three different modes of compaction: the static kneading compaction, the standard Proctor compaction and a dynamic in-mold compaction. For kneading and Proctor compaction, small cylindrical samples were extracted at different locations in larger compacted specimen with a milling machine controlled by computer. On the contrary, the so-called “in-mold compaction” consists in compacting the soil in a mold with the final required dimensions. The small cylindrical samples were then submitted to various suctions from 0 to 2000 kPa during seven days. At the end, dry density of samples was measured with a 3-dimensionnal scanner and tensile strength was determined from indirect (Brazilian) tensile tests. The same investigation was also performed, with similar number of specimens, on untreated soil. In-mold compaction provides the best repeatability of obtained tensile strength (essentially because of the controlled and uniformly distributed dry density though the specimen) but is not representative of real compaction condition. Also, it is observed that the tensile strength of untreated soils is strongly affected by suction level and slightly by dry density. At the opposite, for lime-treated soil, little variations of dry density may have a significant impact on the tensile strength while suction plays a secondary role. This study reveals that, when compacted lime-treated soils are used as a bearing element (like in road subgrades or subbases), a particular attention must be paid on the quality of compaction process to avoid under-compacted zones that could lead to material weakness.

A Experimental Study of Laboratory Compaction and Sand Cone on Foundation Tub Soil

Soil is a very important material so that it must be able to support the loads above it, so the soil must have a sufficiently good soil bearing capacity. In this study, the soil compaction was compared with the laboratory compaction method with the sandcone method. The objectives of the study were knowing the characteristics of the soil and knowing the laboratory compaction compares with the sandcone compaction in the foundation tub. Soil is drawn from the same point for the Proctor Test and Sand cone Test. The results of this test are used in the foundation model test. Characteristics testing in the laboratory: moisture content, density, consistency limits (LL, PL), sieve analysis, hydrometer, laboratory compaction and sandcone. Research result It was found that the soil type was based on the AASHTO classification was A-7-5 and the soil classification based on the Unifield Soil Classification System (USCS) was MH. Laboratory compaction (Proctor Test) average moisture content of 32.26%, γd maximum 1.33 g/cm³, and the sandcone compaction of model foundation test of soil without foundation ɣd was 1.36 g/cm³ , Vertically arranged tire foundation ɣd was 1.36 g /cm³ , horizontally arranged tire foundation ɣd was 1.36 g /cm³

Influence of Laboratory Compaction Method on Compaction and Strength Characteristics of Unbound and Cement-Bound Mixtures

During road construction, granular materials for the unbound base course (UBC) and cement-bound base course (CBC) are mostly compacted by vibratory rollers. A widespread laboratory test for determining the optimal moisture content (OMC) and maximum dry density (MDD) of the mixture for installation in UBC and CBC is the Proctor test. Considering that the Proctor test does not produce any vibrations during compaction, this paper compares the Proctor test and the vibrating hammer test. The examination was conducted on UBC and CBC with varying cement content and aggregate types. All mixtures were compacted by both methods with the aim of determining the compaction and strength characteristics. The results indicated the high comparability of the two test methods for mixtures with natural aggregate in terms of MDD, OMC, density and strength characteristics (California bearing ratio (CBR) for UBC and 28-day compressive strength for CBC). For mixtures with higher cement content, the OMC difference depending on the laboratory compaction method used can be significant, so the laboratory compaction method should be chosen carefully, particularly for moisture-susceptible materials. This paper also reveals that by increasing the proportion of rubber in the mixture, the compaction and strength characteristics differ significantly due to the compaction method. Therefore, when using alternative and insufficiently researched materials, the compaction method should also be chosen carefully.

A new approach to laboratory roller compaction method and its influence on surface texture and permanent deformation of asphalt mixtures

ABSTRACT Pavement structures must guarantee safety, trafficability and comfort to highways users during its service life. The quality of these parameters is related to distresses that may occur as surface distortions, that might be caused by mechanical behaviour problems and to surface texture, which also affect highway safety. The surface texture is evaluated by parameters such as microtexture and macrotexture, related to aggregate rugosity and mixture characteristics, respectively. Both mechanical behaviour and surface texture can be affected by the compaction method of the mixture, as it affects the internal structure and the internal friction between aggregate particles, resulting in alterations in the permanent deformation resistance and surface aspects of the mixture. Hence, this paper proposed a new laboratory compaction method, using roller compaction with vibration, considering three aggregate gradations. This study evaluated the effect of the laboratory compaction method in the permanent deformation resistance and the surface texture of samples, comparing to field mixtures. The proposed compaction method presented efficiency for dense-graded mixture. The mixture's performance regarding mechanical behaviour and surface texture according to the compaction method variation was also dependent on the aggregate gradation. Mixtures with a discontinuity on the gradation presented a negative impact due to the vibration process.

Meso-Scale Kinematic Responses of Asphalt Mixture in Both Field and Laboratory Compaction

Compaction is one of the most critical steps in asphalt pavement construction. Traditional compaction relies heavily on engineering experience and post-construction quality control and can lead to under/over compaction problems. The emerging intelligent compaction technology has improved compaction quality but is still not successful in obtaining mixture properties of a single pavement layer. Besides, very few studies have discussed the internal material responses during field and laboratory compaction to explain the meso-scale (i.e., particle scale) compaction mechanism. Knowledge in those areas may greatly promote the development of smart compaction. Therefore, this study aims to investigate the kinematic behavior of the asphalt mixture particles (translation and rotation) under six types of field and laboratory compaction methods and establish the relationship between the field and the laboratory compaction by using a real-time particle motion sensor, SmartRock. It was found that particle movement pattern was mainly affected by the compaction mode. At the meso-scale where particle behavior is the focus, the kneading effects of a pneumatic-tire roller can be simulated by laboratory gyratory and rolling wheel compaction, and the vibrating effects of a vibratory roller can be simulated by Marshall compaction. However, none of those laboratory compaction methods can completely simulate the field compaction. Under vibratory rolling, particle acceleration decreased fast in the breakdown rolling stage. Under pneumatic-tire rolling, particle angular position change was related to aggregate skeleton, and particle relative rotation showed a decreasing trend that was consistent with the laboratory gyratory compaction results. Those kinematic responses can potentially be used to monitor density change in field compaction.

Characteristics of void distribution and aggregate degradation of asphalt mixture specimens compacted using field and laboratory methods

Asphalt mixtures compacted in the field and in a laboratory show obvious differences in their internal structures, and this affects the evaluation of pavement performance. Hence, in this study, to find a laboratory compaction method most similar to the field method, the effect of the field method and multiple laboratory compaction methods on the internal structure of asphalt mixture specimens was investigated. First, based on the principle of keeping the same compaction degree, specimens cored from field specimens were prepared with six laboratory methods. Then X-ray computed tomography (X-ray CT) and digital image processing (DIP) technologies were used to analyze the internal structure of the specimens, including the spatial distribution and particle size of the voids, as well as the aggregate degradation. Finally, the similarity of the laboratory specimens to the field specimens was evaluated. The results indicated that the spatial distribution of the voids was affected by the compaction methods. The edge effect was different in specimens with different heights. The symmetry of the distribution curve of the air voids was affected by the distribution of the compaction effort. The void particles in a certain size range occupied most of the volume, and the size distribution of the void particles inside the specimens was affected by the compaction methods. In the compaction process of the static load method, the aggregates were constrained and seriously broken, while the dynamic load and the kneading action could protect aggregates from being broken. In general, the partial specimens compacted using a Superpave gyratory compactor (SGC) and a shear box compactor (SBC) were more similar to the field specimens than other laboratory specimens. This study offers a reliable basis for studying the internal structure of asphalt mixture specimens compacted using different methods and for guiding laboratory compaction based on the field method.

Visualization and quantification of lab vibratory compacting process for aggregate base materials using accelerometer

Although being widely used as the quality control for field compaction, neither the standard nor modified Proctor tests match the compaction effort of existing field compaction machineries commonly used today. More importantly, these methods are incapable of identifying the compactability of soil materials other than maximum dry density and optimum moisture content. With the widespread application of intelligent compaction (IC), there is a need to develop a new laboratory compaction method for soil and aggregate materials in which a detailed compaction process could be visualized or quantified. In this study, a lab scale vibratory compactor, asphalt vibratory compactor (AVC), was adopted to compact an aggregate base material with a mounted accelerometer. Based on dry density-moisture content curves, the AVC compaction was more effective in compacting cohesionless soils than the standard Proctor test, and there existed an optimum AVC parameter setting to acquire the highest dry density of aggregates as well as more stable frequency spectrums. In addition, by using the discrete-time Fourier transform the lab compaction process could be visualized through the frequency-domain spectrums. Two IC parameters, Compaction Meter Value (CMV) and the Compaction Control Values (CCV), were calculated for specimens at different water content. The CCV value had a more stable pattern and two distinct compaction stages could be identified for the lab compaction, which could be used to construct the lab compaction curve. Based on the lab compaction curves, AVC has the potential to identify the moisture content and compactability of soil materials and to guide the field compaction.

Influence of laboratory aggregate compaction method on the particle packing of stone mastic asphalt

The type of aggregates and their packing characteristics under compaction are key factors for the design of asphalt mixtures with improved performance, namely, with respect to resistance to permanent deformation. A good example is Stone Mastic Asphalt (SMA), known by its stone–on–stone structure. In the U.S.A., the aggregate particles packing characteristics in a SMA, specially the stone–on–stone effect, are normally assessed using the “manually dry–rodded” method. However, this method may not be representative of field aggregate particle packing conditions, which may compromise the SMA performance. This article presents new findings regarding aggregate laboratory compaction methods to optimise the coarse aggregate structure in a SMA. Particle breakage, bulk density, air voids (compacted & uncompacted skeleton) in the aggregate / coarse aggregate were assessed for existing methods as well as for new methods using existing compactors, but with different procedures and/or specific devices, e.g. Proctor hammer. The assessed methods were: (1) “non–compaction”; (2) “manually dry–rodded” method; (3) established Proctor compaction; (4) modified Proctor compaction (light and heavy compaction) and (5) steel roller compaction. The 2 latter “new methods” aimed at mechanically simulating the dry-rodded method and the effect of field compactors, respectively. The results highlight that the new laboratory compaction methods developed with Proctor and steel roller compactor, provide a particle packing that is more representative of the field conditions, comparatively to other aggregate compaction methods.

Laboratory Compaction Method of Soft Clay and Natural Plant Fiber/Shell Mixtures

One method of soil stabilization is to mix the soil with natural materials such as fibers or shells from plants. Generally, the samples are compacted in a laboratory by mean of Standard and Modified Proctor Compaction tests. The results of compaction are the relationship between water content and density, as indicated by the dry unit weight of the samples. In principle, this compaction process reduces the pore space filled with air in the soil. In this condition, soil is not saturated with water. The method cannot be used to compact soils that are in water-saturated conditions such as soft clay soils which are commonly found in wetland areas. This paper focuses on describing methods for compacting soft clay mixed with additional materials such as fibers and shells from plants. Two steps must be taken to compact samples of mixed soil and natural material. Firstly, determining the percentage of the mixture at which the sample can be compacted, and secondly, determining the optimum fiber/shell content to produce maximum density. The equipment and energy used are the same as the Proctor standard compaction test. Examples of calculations and results obtained for each material (i.e., empty fruit bunches and oil palm shells) are presented and discussed in the paper. Compaction procedures in the laboratory for the mixture of soft clay and other materials are also suggested in the paper.

The effects of compaction methods and mix parameters on the properties of roller compacted concrete mixtures

Despite the wide use of RCC, there is no specific compaction methodology developed to simulate the site conditions in the laboratory. Yet, there are few compaction methods that are generally used to produce RCC specimens in the laboratory environment. The most common methods are the vibrating table and the vibrating hammer found in ASTM, and the modified proctor and Superpave gyratory compactor (SGC), which are suggested to be standardized. However, it is not well known how these different compaction techniques can reflect the properties of RCC in situ. In this study, RCC mixtures which consist of two different cement dosages and two types of aggregate gradations were compacted by the four laboratory compaction methods mentioned above, to investigate the effect of laboratory compaction methodology on the physical properties and mechanical performance of RCC. The first three methods are the ones commonly used in the literature, while the fourth method (SGC) is thought to best represent the field compaction conditions with the kneading action. Moreover, regressions models were derived for each of the compressive and splitting tensile strengths based on the mix parameters. The statistical analysis showed that the compressive and splitting tensile strengths were highly affected by the compaction ratio, then by the cement content. The water content seemed to be dependent on the compaction ratio and had a small effect on the strengths. The ideal laboratory compaction methods in terms of strengths and compaction ratio within the acceptable Vebe consistency time were determined as the SGC first and the vibrating hammer second.

Laboratory Compaction Study and Mechanical Performance Assessment of Half-Warm Mix Recycled Asphalt Mixtures Containing 100% RAP.

The use of low-carbon and energy-efficient paving technologies is gaining worldwide acceptance in recent years as a means to encourage commitment towards more sustainable pavement management practices. However, there still remain some technical gaps regarding mix design procedures for the half-warm mix asphalt (HWMA) mixtures’ preparation and characterization in the laboratory. To this end, three different laboratory compaction methods (e.g., static load, Marshall impactor, and gyratory compactor) were selected and put into assessment to define the most suitable compaction test method for half-warm mix recycled asphalt (HWMRA) mixtures with 100% reclaimed asphalt pavement (RAP). Posteriorly, the effect of four-accelerated curing treatments (0, 24, 48, and 72 h) on the mixtures’ mechanical performance was investigated. Then, advanced mechanical characterization of the mixture performance was conducted to quantify the indirect tensile strength (ITS), stiffness modulus, rutting, and four-point bending (4PB) fatigue test. Thus, based on the authors’ findings, the HWMRA mixtures with 100% RAP and emulsified bitumen exhibited proper volumetric (e.g., air voids and density) and mechanical behavior in terms of moisture damage, ITS, stiffness modulus, rutting, and fatigue cracking. These findings encourage greater confidence in promoting the use of these sustainable asphalt mixes for their use in road pavements or urban streets.

Towards smart compaction: Particle movement characteristics from laboratory to the field

Compaction is one of the most critical steps in asphalt pavement construction that controls pavement density and ultimately impacts pavement performance. Because of the complexity of asphalt mixture property and the lack of fundamental understanding about compaction mechanisms, field compaction control is mostly experience-based in practice which brings out many problems such as under/over compaction. Very few studies have given insight into particle interaction characteristics under different rollers especially at meso-scale. On the other hand, Superpave gyratory compaction (SGC) is widely used as the laboratory compaction method to simulate field compaction. However, the relationship between SGC and different types of rollers has not been clearly stated. Therefore, this study aims to employ a real-time particle motion sensor, SmartRock, to investigate how particle reacted to different rollers during the field compaction and its relationship with SGC. Findings from this study could contribute to the understanding of the compaction mechanism and initiate a new path toward smart compaction through real time compaction quality control. It was found that particles mainly translated vertically under static and vibrating roller. The kneading action of the pneumatic-tyred roller produced the horizontal translation and three dimensional rotation of the particles. Laboratory study showed that SGC can well simulate the kneading process by pneumatic-tyred roller. Some preliminary results indicated that the SmartRock can reasonably report the real time internal temperature of asphalt mixture during compaction, which could be beneficial to compaction quality control.

Comparative Evaluation of Compacting Process for Base Materials using Lab Compaction Methods

Precise characterization of the compactability of aggregates and soils in the laboratory has always been a challenge to pavement technologists. The present study investigated compactability of aggregates and soils through the comparison of three laboratory compaction methods, the Superpave Gyratory Compactor, the Marshall impacting hammer, and a vibratory compacting machine. Accelerometers were attached to the Marshall impacting hammer and a laboratory scale vibratory compactor to capture the dynamic response of soils and aggregates during compaction. The results from this comparative experiment indicated that there was a consistent relationship between the stiffness of soils and aggregates and the dynamic responses from impaction and vibration, which can be used to better characterize the compactability of different paving materials through laboratory testing.

The effect of laboratory compaction method on the resilient behaviour and fabric of aggregate base course materials

Aggregate base course (ABC) layer is a key structural component of most pavements. The compaction of ABC is a crucial procedure affecting its mechanical performance. There are two different methods commonly used in the lab to compact ABC specimens: impact and vibratory. Past studies have demonstrated that the compaction method can affect the resilient deformation behaviour of ABC. However, the reasons for these differences in terms of the constituent ABC particle properties and the resultant compacted aggregate fabric remains unclear. This study evaluates the influence of the laboratory compaction method on the resilient behaviour and fabric of two ABC materials with differing mineralogies. Resilient modulus tests performed on the specimens compacted with the two methods result in different behaviours. A series of subsequent laboratory tests were performed to explain the observed resilient behaviour by assessing changes in aggregate morphology and fabric. The study presented herein incorporates digital imaging analyses using a novel specimen preparation technique. The results demonstrate that impact compaction can degrade ABC materials that are susceptible to crushing. This, in turn, increases the resilient modulus of the ABC by increasing the number of contact points between particles. It is recommended that the compaction method used in the laboratory match the compaction processes in the field as best as possible to obtain the most representative resilient modulus test results.

Comparison between Static and Dynamic Laboratory Compaction Methods

In engineering practice, earth construction requires suitable soil compaction, usually relating to the California Bearing Ratio which called (CBR) is a used sidelong way to estimate the shear strength and stiffness modulus of subgrade in pavement design works. For these types of soils, California Bearing Ratio could be used as a method of compaction assessment being an indicator of soil bearing capacity. Thus, a new method has been created to determine the CBR values based on the MDD and OMC values by using static CBR tests to close the gap between laboratory and field data regarding developing further to improve engineering parameter, especially for pavement design. During the last years, few comparisons had been proposed by various researchers. This study was carried out to find the comparisons CBR values between dynamic and static methods for four different types of soils that locate in Selangor, Malaysia. This study has been calculated the dynamic and static Maximum Dry Density (MDD) and Optimum Moisture content (OMC) values to use these values to determine the CBR values. Based on the results, a static CBR test shows more available results than the dynamic CBR test regarding the CBR values to get an accurate and economical design for the subgrade and pavements layers.

Comparison on properties of cement-stabilised gravel prepared by different laboratory compaction methods

This paper presents a comparison of the properties of cement-stabilised gravel (CSG) prepared in laboratory by the static pressuring compaction method (SPCM) and the vibration compaction method (VCM). The compaction characteristics, gradation variation, unconfined compressive strength (UCS), splitting strength (SPS), and resilient modulus (RM) of the laboratory-prepared CSG by SPCM and VCM are measured and compared. The effects of compaction method, gradation structure, cement content, and curing time on the compaction characteristic, gradation variation, and mechanical properties of CSG are investigated. Field measurements are subsequently conducted to validate the laboratory investigations. The results show that the CSG prepared by VCM has optimum water content and smaller gradation variation and larger density than those of CSG prepared by SPCM. The UCS, SPS, and RM of CSG prepared by VCM are 1.87–2.37, 1.54–2.74, and 1.53–1.96 times those of the CSG prepared by SPCM, respectively. Moreover, the results show that the mechanical properties of CSG prepared by VCM have a correlation of 91.7% with the field drilled CSG, which is better than the SPCM.