Roller Compaction Research Articles

A PSO-ANN Intelligent Hybrid Model to Predict the Compressive Strength of Limestone Fillers Roller Compacted Concrete (RCC) to Build Dams

The compressive strength of the roller-compacted concrete (RCC) is an essential indicator of quality when designing dams. RCC is optimized in most cases through experimental studies conducted vigorously. This study aims at developing a smart system to predict the compressive strength of the limestone fillers RCC that is used to build dams. The prediction is made base on the following parameters: the maximum diameter of the aggregates, the compactness of the granular mixture, the rates of both cement and limestone fillers, water/cement ratio and the RCC age. The cement strength is taken in to consideration using a corrective equation. Two metaheuristic systems are developed: artificial neural networks (ANN), and a hybrid system consisting of an ANN optimized by a particle swarm optimization (PSO) algorithm. An experimental database is built containing 500 vectors taken from RCC formulations given by lab activity reports about 04 dam projects. The best results were achieved through the PSO-ANN hybrid system. This prediction system is validated by an experimental study conducted on 20 RCC formulations, and a comparison was made with the Laboratoire Central des Ponts et Chaussees (LCPC) method. The prediction resulting from the PSO-ANN system is of a good accuracy level with a correlation factor R2 = 0.85 and a low root mean squared error of 1.45. Finally, a user interface based on the model developed is created.

Strength and Durability of Hybrid Fiber-Reinforced Latex-Modified Rapid-Set Cement Preplaced Concrete for Emergency Concrete Pavement Repair

The benefits of using reinforcing fibers in latex-modified rapid-set cement preplaced concrete for emergency pavement repairs were examined in terms of strength, permeability, and durability as functions of the type of fiber. Single-type fibers, including jute, poly (vinyl alcohol) (PVA), and nylon fibers, as well as hybrid fiber mixtures prepared with two of the aforementioned fibers at a 1:1 weight ratio, were evaluated. Fibers were incorporated into the concrete mixture at 1.2 kg/m3. A vibratory press compactor that simulates roller compaction was used to increase compaction and densification of the resulting pavement repair material. The hybrid fiber-reinforced latex-modified rapid-set cement preplaced concrete (HFLMC) was manufactured to satisfy the criteria for opening traffic, i.e., compressive strength of 21 MPa or higher, and flexural strength of 3.5 MPa or higher after 4 h. Pavement requiring repair was removed and replaced with coarse aggregate. The rapid-set binder, fibers, and latex were then mixed and placed onto the coarse aggregate layer. The repair was considered complete after compaction. The resulting HFLMC satisfied all of the test criteria. Furthermore, concretes made with hybrid fibers were more mechanically sound than those made with a single fiber variety. Hybrid fiber concretes made with PVA and nylon fibers exhibited the best properties for emergency pavement repair. These results indicate that HFLMC is suitable for emergency pavement repair.

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.

Assessing the Influence of Aggregates and Cement Types on Fresh Roller Compacted Concrete Mixture

Roller compacted concrete mixture RCC is considered as a sustainable pavement construction material, it is a heavy-duty concrete mixture with zero slump. An attempt has been made in the present investigation to design the fresh RCC mixture using two types of coarse aggregates (crushed and rounded), two types of fine aggregates (silica and river sand) and two types of cement (ordinary Portland and sulphate resistance). Concrete mixtures with dense gradation were prepared and compacted according to modified proctor design procedure. A moisture-density test was used to determine the maximum density and optimum moisture content and of RCC mixtures for each mix. Five different percentages of cement (10-18) % are implemented and six different percentages of moisture (4 – 8) %) % are used to determine the dry density-moisture content relationships. It was observed that the maximum dry density of rounded aggregates mixture is higher than that of crushed aggregate mixture by (4.2, 8.3, 4.2, 4.2, and 5.1) % and (4.1, 1.4, 4.1, 2.0, and 2.7) % for (18, 16, 14, 12, and 10) % cement content respectively for mixtures constructed with silica and river sands respectively with ordinary Portland cement. However, the maximum dry density of rounded aggregate mixture is higher than that of crushed aggregate mixture by (3.5, 4, 7.1, 5.5, and 4.4) % and (2.7, 4.8, 2.3, 4.4, and 4.2) % for (18, 16, 14, 12, and 10) % cement content respectively for mixtures constructed with silica and river sands respectively with sulphate resistance cement. It was concluded that 12 % of Portland cement and (6 to 7) % of moisture are proper combination when silica or river sand were implemented, while (12 and 14) % of sulphate resistance cement and (6 to 7) % of moisture are proper combination when silica or river sand were implemented. abstract must be a precise and reflection of what is in your article.

UV–VIS spectra as potential process analytical technology (PAT) for measuring the density of compressed materials: Evaluation of the CIELAB color space

Measurement methods for determining the density of compressed materials, being a critical quality attribute, provide an important parameter for successful processing. In this study, a novel approach was developed for determining the density of compacts using ultraviolet–visible spectrophotometry. The assumption within this context was that a change in density affects the corresponding color information of the compact. From the obtained spectra of the visible range, the color information of the compact was calculated which turned out to be directly proportional to the density of the compact. In comparison, the obtained spectra were analyzed using partial least square regression. The results of this study showed that both methods could be used predicting the density of a compact from the corresponding visible spectrum at identical accuracy. In contrast to the partial least square regression, the correlation of the color information as a direct output parameter of the spectrophotometer with the density required no excessive data pre-processing. Subsequently, the easier and faster data processing of the color information over the partial least square regression, conceives using this novel approach as potential process analytical technology tool for implementation into a compression process e.g., tableting or roller compaction.

Discrete element modelling of ribbon milling: A comparison of approaches

Roller compaction followed by milling of the generated ribbons is a typical dry granulation route. It is desirable to be able to predict the size distribution of the granules exiting the mill based on the ribbon properties and mill operational conditions. Two DEM-PBM approaches for predicting this size distribution are compared; a direct approach where the size distribution is experimentally determined, and an indirect approach where the successive change in size distribution due to each stressing event is determined mathematically by the PBM. The experimental component of the direct approach assumes shear deformation to be the dominant breakage mechanism. This approach provides a reasonable agreement to experimental data, though the influence of mill parameters is not experimentally tested. When considering breakage to be driven by impact, the indirect approach predicts the correct magnitude of fines generation, though incorrectly predicts the fine fraction to increase with impeller speed. When abrasion is assumed to be the dominant breakage mechanism, the indirect approach suggests the same trend, though with a less pronounced effect of impeller speed and a closer agreement to experimental data. Prediction accuracy is expected to improve by considering distributions of stressing conditions and material strength, the latter being explicitly captured in the experimental component of the direct approach. Furthermore, the direct approach accounts for the variable loading conditions of the fragments in the mill.

Simplifying Johanson’s roller compaction model to build a “Virtual Roller Compactor” as a predictive tool – Theory and practical application

The purpose of the study is to build a “virtual roller compactor” as a predictive tool to assess the roll force (RF)-maximum pressure (Pmax) and RF-ribbon density relationship for pharmaceutical roller compaction. We provided a theoretical basis to demonstrate that, there exists a critical nip angle for a pharmaceutical powder, beyond which the RF-Pmax relationship is insensitive to wall friction angle or effective angle of internal friction. We showed that for most pharmaceutical roller compaction, the critical nip angle is lower than 17 degree, and can be exceeded via wall friction elevation, using rolls with non-smooth surface. Under this condition, the original Johanson model can be substantially simplified to a single equation requiring only one material property (compressibility). By performing manufacturing-scale roller compaction using materials with diverse compressibility, we showed that the simplified, friction angle-free model performed similar to the original Johanson model. It can predict the RF-Pmax and RF-ribbon density relationship well after applying a correction factor. The predictive tool, in the form of a user-friendly graphical user interface, was created based on the simplified model. The tool was adopted for in-house, bench-scale formulation development and scale-up because of its ease-of-use, good predicting capability, and very low material demand.

Binder jetting additive manufacturing: observations of compaction-induced powder bed surface defects

This paper, for the first time, reports observations of a type of powder bed surface defects (i.e., surface ridges) induced by forward-rotating roller compaction. Three compaction thicknesses, 0, 30, and 180 µm, were tested at a layer thickness of 120 µm. Surface ridges occurred on the powder bed surface when compaction thickness was 180 µm, but not when compaction thickness was 0 or 30 µm. The formation of surface ridges was a cumulative process where the number and height of surface ridges first increased and then reached a plateau as the number of spread and compacted layers increased.

Superpave Gyratory Compactor as an Alternative Design Method for Roller Compacted Concrete in the Laboratory

AbstractThe introduction of the Superpave gyratory compactor (SGC) to pavement laboratories was a large step for the design process of hot mix asphalt (HMA). Considering the similarities between HM...

A Multi-variate Mathematical Model for Simulating the Granule Size Distribution in Roller Compaction-Milling Process

Granule size distribution (GSD) is one of the critical quality attributes in the roller compaction (RC) process. Determination of GSD for newly developed pharmaceutical compounds with unknown ribbon breakage behaviors at the RC milling step requires a quantitative insight into process parameters and ribbon attributes. Despite its pivotal role in mapping the process operating conditions to achieve desired granule size, limited work has been presented in literature with a focus on RC-milling modeling. In this study, a multi-variate mathematical model is presented to simulate the full size-distribution of granulated ribbons as a function of ribbon mechanical properties. Experimental data with a lab-scale oscillating milling apparatus were generated using ribbons made of various powder compositions. Model parameters were determined by fitting it to experimental data sets. Parameters obtained from the first step were correlated to ribbon Young's modulus. The model was validated by predicting GSD of data that were excluded in model development step. Predictive capabilities of the developed model were further explored by simulating GSD profiles of a granulated pharmaceutical excipient obtained at three different conditions of a real-scale Gerteis RC system. While maintaining the milling operating conditions similar to the lab-scale apparatus (i.e., screen size and spacing, and low rotor speed), the proposed modeling approach successfully predicted the GSD of roller compacted MCC powder as the model compound. This model can be alternatively utilized in conjunction with an RC model in order to facilitate the process understanding to obtain granule attributes as part of Quality-by-Design paradigm.

Discrete Simulation of Vibratory Roller Compaction of Field Rockfills

Vibratory roller compaction is a well-known method in improving the mechanical properties of field rockfills. However, the meso mechanism of rockfill densification under vibratory roller compaction has not been understood clearly. This paper presents a discrete numerical method to simulate the vibratory roller compaction of field rockfills. Firstly, rockfill particles were modeled by irregular and stochastic clusters, which can be breakable. In addition, the segregation of field rockfills was replicated in a practical manner. Then, a new model of the vibratory roller was presented, in which the frame inertia was considered. Finally, the developed method was applied to simulate the vibratory roller compaction of field rockfills in the Shui Buya Project. Results show that (1) the numerical simulations of vibratory roller compaction of field rockfills agree well with the field experiments; thus, the feasibility and rationality of the developed simulation method are verified; (2) the dynamic response of field rockfills under vibratory roller compaction can be predicted by the presented numerical method with calibrated model and parameters; (3) the new roller model with frame inertia considered is much more accurate than the roller models in early studies. Thus, the developed discrete numerical method can be further adopted to explore the meso mechanism of rockfill densification under vibratory roller compaction in the future.

Experimental and Analytical Investigation on the Interlayer of Roller Compacted Concrete

AbstractRoller compacted concrete (RCC) is a dry concrete with zero slump and is constructed in layers. RCC dams are generally weak in interlayers. The bond strength and the permeability of the int...

A study on the pelletizing condition for roll compaction of powdered radioactive wastes

Dried powder of radioactive wastes cannot be disposed of as such unless it is solidified by an appropriate solidification agent. However, the volume of the solidified waste form increases to a large extent due to certain limitations (incorporation ratio) while mixing the wastes with a solidification agent. As a result, the cost of waste disposal increases and filling up the disposal facility's capacity occurs fast. To address this problem, roll compaction technology can be used to reduce the physical volume of the powdered wastes. Powdered wastes (contaminated soil and bio-shield concrete) were converted to rigid pellets of certain shape and size (H 6.5 x W 9.4 mm) by a special roll compactor. The operating parameters (hydraulic pressure, roll speed, feeding rate, roll gap) of the roll compactor were evaluated, and the volume reduction factor of each waste powder and the strength of the pellet were estimated.

Prediction model of compaction process parameters for pavement of cement emulsified asphalt mixture based on effective compaction work

Cement emulsified asphalt mixture (CEAM) is a semi-flexible pavement material, which is formed by the organic combination of aggregate, cement, emulsified asphalt and water. The compaction process of CEAM includes demulsification of emulsified asphalt, hydration of cement, evaporation of water, and formation of a three-dimensional interwoven network of aggregate, cement and asphalt. Therefore, it has different compaction deformation characteristics from the hot asphalt mixture. In order to explore the theoretical model of compaction process parameters for pavement (PCPP), which are based on compaction deformation characteristics and strain energy theory, effective compaction work (ECW) was defined as the compaction work consumed by viscoplastic compression displacement of the material. The mechanical response is studied by compressive testing and a calculation model for lab-scale effective compaction work (LECW) is established for CEAM. Furthermore, a calculation model for effective compaction work in pavement (PECW) is established based on the work-energy equivalence principle and roller compaction datas. In addition, a prediction model of PCPP for target dense degree (TDD) is obtained by the equivalence of LECW and PECW, and the introduction of energy absorption efficiency (EAE). Moreover, the PCPP combination modes during three stages, i.e., initial compaction, re-compaction and final compaction, of the roller are determined according to the compaction deformation characteristics of CEAM material. Based on the compaction combinations modes, the compaction process parameters combinations (CPPC) during the three compaction stages for the TDD are derived from the prediction model. The reliability of the proposed model is verified by a road compaction test. The CPPC results reveal the reliability of established LECW and PECW models. However, the EAE of vibration compaction in the prediction model is revised to be 76.05% after the road compaction test. The prediction model and introduction of EAE provide a theoretical baseline for the parametric design of compaction and construction process of CEAM and other pavement materials.

The Feasibility of Using Micro Silica Sand Powder as Partial Replacement of Cement in Production of Roller Compacted Concrete

Roller compacted concrete (RCC) is a special type of concrete with zero or even negative slump consistency. In this work, it had aimed to produce an RCC mix suitable for roads paving with minimum cost and better engineering properties so, different RCC mixes had prepared i.e. (M1, M2, M3, and M4) using specified percentages of micro natural silica sand powder (SSP) as partial replacement of (0%, 5%, 10%, and 20%) by weight of sulfate resistant Portland cement. Additionally, M-sand, crushed stone, filler, and water had been used. The results had obtained after 28 days of water curing. The control mix (M1) had satisfied the requiredf ‘cwith accepted results for the other tests. M2 mix with SSP of 5% had achieved the highest results. Thef ’cfor sawed cubes of (10*10*10) cm had increased by 2.26% and 3.16% when tested in directions (ꓕ and //) to the direction of loading respectively.Rresults for sawed prisms of (38*10*10) cm had increased by 8.78% and 8.43% when tested on top and bottom faces respectively. The density had increased by 1.04% while the absorption and volume of permeable voids had decreased by 8.11% and 7.83% respectively. The UPV results had also increased by 2.44% and 0.81% for cubes and prisms respectively when compared to the control mix. M3 mix with SSP of 10% had also achieved satisfactory results when compared to the control mix.

Retraction Note: Exposure Assessment for Roller Compacted Concrete Dam Construction Integrated Real-Time Location Information

Roller compacted concrete (RCC) dam projects are generally initiated in dynamic environment, where space conflicts occur frequently. Construction workers are often exposed to dangers posed by activities performed by teams other than their own. Therefore, it’s critical for construction security to conduct fairly precise exposure assessment. Several research studies have been proposed to address this site safety issue. Despite their valuable contributions, few of them have noticed that, for some construction processes, their hazard scope may exceed the work space. Another limitation is that most traditional methods expound space factor and time factor separately rather than comprehensively. Accordingly, the present paper proposes a novel method to quantify exposure frequency integrated with the real-time location information of three-dimensional cross activities. Combined with the construction process cycle and the operation time characteristics, conflicts between impact space and work space are determined in real time, which is more accurate as the interaction between construction activities is certain at each moment. With a reliable assessment of hazard exposure levels, construction managers will be able to provide solutions to reduce hazards to acceptable levels.

WITHDRAWN: Strength and behaviour of roller compacted concrete using crushed dust

Roller compacted concrete is one of the recently developed materials in pavement construction. It is the concrete with zero-slump, highly compacted concrete which is a reliable, economical and durable material for low speed and heavy-duty pavements. The present study highlights identification of materials for roller compacted concrete. It intends to analyse the use of Roller Compacted Concrete Pavement (RCCP) as an alternative of traditional Bituminous Concrete pavements that suffer from rutting and cracking due to heavy loading and hot weather conditions. The study is done using zone II crusher dust, crushed stone and 43 grade cement as constituent materials of Roller Compacted Concrete (RCC). The mechanical strength characteristics of various mixes of roller compacted concrete (RCC) using zone II crusher dust is presented in this work. In this study various mixes were prepared using materials (cement, crusher dust, aggregate). The mixes were proportioned using soil-compaction tests. The Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) of the mixes were determined using Modified Proctor’s Test. Mechanical properties of the mixes have been obtained and the effect of cement content and water/cement (W/C) ratio on mechanical properties has been studied. From the results it is observed that there is a remarkable increase in the compressive strength as well as split tensile strength of roller compacted concrete on increase of cement content. The study concludes that the roller compacted concrete can be used for both base and surface course as well as in other geotechnical applications.

Loss-in-weight feeding, powder flow and electrostatic evaluation for direct compression hydroxypropyl methylcellulose (HPMC) to support continuous manufacturing

Minimizing variability in the feeding process is important for continuous manufacturing since materials are fed individually and can impact the final product. This study demonstrates the importance of measuring powder properties and highlights the need to characterize the feeding performance both offline with multiple refills and in the intended configuration for the continuous manufacturing equipment. The standard grade hydroxypropyl methylcellulose (HPMC) had material buildup on the loss-in-weight feeder barrel from triboelectric charging and resulted in more mass flow excursions and failed refills which were not observed with the direct compression grades. The location of the electrostatic buildup changed when the feeder was connected to a hopper instead of feeding offline into a collection bucket. Overall, the direct compression HPMC exhibited better flow which resulted in more accurate loss-in-weight feeding with less excursions from the target mass flow and all refills were completed in the first attempt. The improvements with the direct compression HPMC would be beneficial when running any continuous process (wet granulation, roller compaction, or direct compression) or other processes where loss-in-weight feeding is utilized, such as melt extrusion or twin screw granulation.

Control Strategy for Process Development of High-Shear Wet Granulation and Roller Compaction to Prepare a Combination Drug Using Integrated Quality by Design.

In this study, we developed a control strategy for a drug product prepared by high-shear wet granulation and roller compaction using integrated quality by design (QbD). During the first and second stages, we optimized the process parameters through the design of experiments and identified the intermediate quality attributes (IQAs) and critical quality attributes (CQAs) relationship, respectively. In the first stage, we conducted an initial risk assessment by selecting critical process parameters with high impact on IQAs and CQAs and confirmed the correlation between control and response factors. Additionally, we performed Monte Carlo simulations by optimizing the process parameters to deriving and building a robust design space. In the second stage, we identified the IQAs and CQAs relationship for the control strategy, using multivariate analysis (MVA). Based on MVA, in the metformin layer, dissolution at 1 h was significantly correlated with intrinsic dissolution rate and granule size, and dissolution at 3 h was significantly correlated with bulk density and granule size. In dapagliflozin layer, dissolution at 10 min and 15 min was significantly correlated with granule size. Our results suggest that the desired drug quality may result through IQAs monitoring during the process and that the integrated QbD approach utilizing MVA can be used to develop a control strategy for producing high-quality drug products.

Improved Manufacturability and In Vivo Comparative Pharmacokinetics of Dapagliflozin Cocrystals in Beagle Dogs and Human Volunteers

Dapagliflozin (DAP), which improves glycemic control in patients with type 2 diabetes mellitus, has poor physical properties against heat and moisture, thus hindering its manufacturing potential. The superior physicochemical properties of a recently developed cocrystal of DAP and citric acid (DAP cocrystal) in comparison with those of DAP and Forxiga®, a patented solvate form with propandiol monohydrate, were identified via structural analysis and moisture sorption isotherm. For the first time, the formulation, manufacturability, and in vivo bioavailability of DAP cocrystals were successfully investigated to develop oral dosage forms that substitute Forxiga®. The intrinsic dissolution rate of DAP cocrystal was controlled by varying particle size distribution. Unlike the direct compression (DC), roller compaction (RC) was more preferable to obtain good flowability of dry granules for a continuous manufacturing system. The cocrystal structure was maintained throughout the stability assessment period. In Vitro dissolution pattern differences of the optimized DAP cocrystal tablet with RC and the reference tablet, Forxiga® 10 mg, were pharmaceutically equivalent within 5% in four different media. Furthermore, comparative pharmacokinetic analysis confirmed that a 10 mg DAP cocrystal tablet with RC was bioequivalent to a 10 mg Forxiga® tablet, as assessed in beagle dogs and human volunteers.