Transport Research International Documentation (TRID)

Sustainable valorization of tailings and crushed stone wastes for novel high early-strength road-building material (HERM): Performance optimization, micro-mechanism, and field implementation

Thu, 24 Jul 2025 11:29:30 GMT

The efficient reuse of gold mine tailings and crushed stone waste is a critical step toward sustainable mining practices. In this study, a novel high early-strength road-building material (HERM), comprising gold mine tailings, crushed stone, and cementitious materials derived from solid waste, is formulated for mine roadway pavements. A systematic investigation is conducted into the effects of varying compositions on the uniaxial compressive and flexural strengths (UCS and UFS) of the HERM, with the formulation optimization carried out using response surface methodology (RSM). The optimal mix design is determined with a water–binder ratio (W:B) of 0.288, a binder–aggregate ratio (B:A) of 1:1.290, and a tailings–crushed stone ratio (T:C) of 0.596. At just one day of curing, the optimized HERM achieves a UCS of 46.196 MPa and a UFS of 13.800 MPa, which confirm its excellent early strength performance. The strength mechanism is further elucidated by XRD, SEM-EDS, FTIR, and TG-DTG analyses, which reveals that early strength development is primarily attributed to the formation of AFt gels, along with C–S–H and Ca(OH)₂. An in-situ road construction trial is successfully executed at the Sizhuang Branch Mine, where the material enables the restoration of full pedestrian and vehicle traffic within 24 h of placement. These results highlight the practical viability of the proposed HERM and its value in promoting low-carbon, resource-efficient mining infrastructure.

Performance Properties and Carbon Emissions of Cold Mix Cold Laid Asphalt Rubber Mixture

Tue, 08 Jul 2025 09:57:33 GMT

Based on the indoor experiments and a test section constructed in the G5 national expressway project, a comprehensive study was implemented regarding the performance properties and environmental characteristics of cold mix cold laid asphalt rubber mixture. Results showed that the Marshall stability and dynamic stability of the mixture were greater than those of the hot mix dense graded asphalt crushed stone. However, its residual stability was slightly lower than the latter. Both the high-temperature stability and water stability could meet technical requirements for pavement middle-layer and lower-layer asphalt mixtures. Additionally, the total in-construction carbon emissions of cold mix asphalt rubber mixture were 2,970.77 kg per 1,000 m² surface layer, mainly caused during the mixture transportation, paving, and rolling stages. This part accounted for 47.1% and 51.9% of the total emissions. The in-construction emissions of hot mix dense graded asphalt-treated permeable base was 6,151.80 kg per 1,000 m² surface layer, which mainly resulted from the heating of aggregates and asphalt as well as the fuel consumption of transportation, paving, and rolling machinery. The carbon emissions of hot mix asphalt mixture were about twice that of cold mix asphalt rubber mixture. It suggests cold mix asphalt rubber mixture greatly reduced carbon dioxide and harmful gas emissions and lowered personnel labor intensity, showing outstanding environmental advantages.

Development of Crushed Quarry Aggregate Surfacing Specifications

Tue, 01 Apr 2025 08:39:01 GMT

South Dakota’s transportation system includes over 83,000 miles of roads of which about ten percent are state-controlled, and three percent are federal routes. The remaining 72,000 miles are mostly low-volume roads (LVR). A LVR is defined as a road that carries less than 400 vehicles per day. Typically, these roads fall under the jurisdiction of counties, townships, and municipalities. LVRs play an important role in the State’s economy by providing essential links not only between rural areas but also between rural and urban areas. A significant portion of LVRs in South Dakota are gravel. While South Dakota local governments are not bound by the State’s gravel surfacing specification, survey results from the SD2009-08 study entitled Gravel Surfacing Guidelines for South Dakota, revealed the majority of local government respondents use the State Gravel Surfacing specification. For some areas of the state, there is a shortage of “natural” gravel that will meet the Gravel Surfacing specification as per the 2015 SDDOT Standard Specifications for Roads and Bridges. This is due to the drying up of the state's “natural” gravel pits, which will only get worse over time. In addition to gravel supply concerns, rising costs and tightening budgets have encouraged local governments to consider and construct roads with alternate aggregate materials under a range of specifications. These include SDDOT Base Course specifications, local specifications, or no specifications at all. Local governments, in areas having nearby quarries, have installed aggregate surfacing using crushed quarry aggregate, which is defined as crushed limestone, quartzite, or granite. According to the local owners and SD Local Transportation Assistance Program (LTAP) personnel, several of these surfaces perform similarly to “natural” gravel surfacing. The fines in the material appear to have a binding quality that creates a firm roadway surface. Unfortunately, the criteria for defining a well-performing crushed quarry aggregate surfacing and the specifications associated with that performance have never been established. Currently, the only way to duplicate a well-performing crushed quarry aggregate surfacing is through trial and error. Through the development of criteria defining a well-performing aggregate surface and the establishment of the associated specific requirements for crushed quarry material, owners would be provided an alternative option to “natural” gravel surfacing that is readily duplicated and available.

Analysis of Static Plate Load Test Results According to Czech, French, and German Methodologies

Fri, 21 Mar 2025 09:03:39 GMT

Many countries have a specific way of performing and evaluating the static plate load test for assessing the railway substructure deformation resistance, so its values cannot be easily compared for different countries. This paper describes an experimental study that compares the evaluated results of performed static plate load tests according to Czech, French, and German methodologies. To obtain comparable results, several measurement campaigns were carried out on test layers of crushed aggregates in experimental conditions and on a subgrade surface of soil stabilized by hydraulic binders or on sub-ballast layers of crushed aggregates on real railway track structures. The results were further statistically evaluated by arranging them in graphs, and the mutual correlations between individual methods were found. The dependence of the results turned out to be polynomial. For the comparison regarding the tested subsoil material, the correlation appeared to be better for aggregates than for stabilized soils. The performed experimental study aimed to compare the results of the static plate load test according to the mentioned methodologies and to establish mutual correlations between them. Its results can be used for adapting the requirements for the deformation resistance of the railway substructure defined in foreign standards to the Czech environment.

Spatial and temporal changes in small-strain shear modulus of geogrid-stabilized crushed aggregate materials

Thu, 06 Mar 2025 09:23:21 GMT

Geogrid stabilization can be used by transportation agencies to build durable roadways over soft subgrade soil. The performance of geogrid stabilization is highly dependent on the properties of the geogrid material, the aggregate material, and the interaction between the two materials when combined. Therefore, transportation agencies need to perform their own studies to assess the performance of geogrid stabilization for their local materials. Additionally, the current knowledge base needs to be continually expanded to a variety of aggregate-geosynthetic composites to develop performance-based design methods for geosynthetic-stabilization. This study evaluates the long-term performance of two geogrids used to stabilize a crushed aggregate material. A full-scale traffic loading system was built to simulate a full half-axle (40kN) traffic load for thousands of load cycles. Two trials were completed using the same crushed aggregate material. For each trial, two geogrid-stabilized sections, and one control section were evaluated. The performance of the test sections was monitored for 4000 load cycles by measuring surface rutting and completing multichannel analysis of surface waves (MASW) to measure aggregate stiffness. Results showed that the geogrid-stabilized sections had better long-term performance than the control sections with lower degradation of the as-built aggregate stiffness. There was good agreement amongst the MASW results, rutting measurements, and Shakedown analysis. It has been concluded that MASW is an effective method for evaluating the long-term performance of geogrid stabilization in aggregate layers with a customized instrumentation plan according to the targeted measurements.

Suitability of Using Crushed Concrete Adjacent to Geotextiles in Underdrain Systems Second Phase: Field Trial Before Implementation

Mon, 03 Mar 2025 17:01:43 GMT

Due to the increasing interest in the use of recycled concrete as a base course aggregate, the Virginia Department of Transportation (VDOT) identified the need for an in-depth research investigate the clogging potential of the geotextile used in highway edgedrains if crushed hydraulic cement concrete (CHCC) is placed adjacent to the drainage fabric geotextile. To answer the research needs of the VDOT and address the discrepancies in the existing literature, George Mason University conducted a laboratory-based study and published their findings (VTRC 21-R12). The study identified two major mechanisms through which CHCC reduces the flowability of the geotextile used in underdrains: physical (fine particles migrating onto the voids in between the filaments of the geotextile) and chemical (precipitation of chemicals within geotextile filaments) phenomena. The findings showed that although the drainage fabric geotextile experienced some level of reduction in its flow capacity, as was expected, the reduction was not significant enough to impact and impede the overall flow of the geotextile/CHCC system. However, the laboratory study had some limitations, e.g., while simulating the physical and chemical phenomena simultaneously, temperature, rain, and humidity variations during seasonal changes were not accounted for, the potential effects of the pavement over the top of CHCC were not included, and drainage pipes were not considered. The research reported herein is the second phase of the laboratory study and involved constructing a full-scale field test site within VDOT’s Harrisonburg facility. The test site consisted of seven sections, each side of which was constructed to include a 4-inch drainage pipe covered by No. 57 stone wrapped with drainage fabric, per VDOT’s UD-4 edgedrain standards. In all seven sections, an unbound base course was placed in direct contact with drainage fabric. Sections with CHCC content included an unbound base course with (i) 100% CHCC, (ii) 40% CHCC + 60% virgin aggregate (V.A.; Blend 1), and (iii) 20% CHCC + 80% V.A. (Blend 2). Replicates of these sections were constructed as paved (to simulate actual roadway conditions) and unpaved (to provide data comparable with those of the previously completed laboratory study). Additionally, the seventh section was constructed as unpaved with a 100% V.A. section, which served as the control section. The constructed site was evaluated for about 3 years, and performance evaluations were conducted approximately every 6 months by analyzing the exhumed drainage fabric geotextiles and borescope surveying the drainage pipes. The findings confirmed the observations of the previous study by capturing the physical phenomenon. However, the data from the unpaved CHCC section showed approximately 2.5 times less tufa precipitation (chemical phenomenon) on the drainage fabric geotextile than what was previously noted in the one-year laboratory study. For the paved sections, data observed over 3 years were used to predict possible tufa growth on the drainage fabric’s surface in 30 years. This prediction showed that even after 30 years, the surface area of the geotextile that is covered with tufa precipitation could be less than what was observed in the one-year laboratory study. If this prediction holds true, then the drainage fabric geotextile used in this study would continue to function hydraulically in 30 years. Borescope inspections of the drainage pipes showed signs of precipitation in the sections with 100% CHCC and 40% CHCC (Blend 1) but not in those with 20% CHCC (Blend 2) and 100% V.A. Although all the drainage pipes constructed continued to function hydraulically within the duration of this study, the chemical precipitation within the 100% CHCC and 40% CHCC sections of the drainage pipes needs further monitoring. This is because the quantitative estimation of continuing chemical precipitation within the pipes requires more data than what was available within the duration of this study.

Quantifying the relative contributions of particle crushing and ITZ damage to the strength of cement-stabilized pervious recycled aggregate base materials: Laboratory testing and refined DEM simulation

Mon, 24 Feb 2025 13:45:31 GMT

Driven by the sponge city initiative and zero net carbon emission strategy, recycled brick and mortar aggregates from building demolition wastes (BDWs) have emerged as partial or full substitutes for increasingly depleted natural aggregates to construct cement-stabilized pervious recycled aggregate base materials (CPRABMs). These recycled aggregates feature lower particle crush strength, greater variability, and lower durability, thus jeopardizing the long-term stability of CPRABMs. This study aimed to reveal the micromechanical mechanisms that influence the macroscopic compressive strength of CPRABMs by focusing on damage to the interfacial transition zone (ITZ) and the behavior of particle crushing. First, single-particle crushing experiments were conducted on various types of aggregates in the laboratory, along with unconfined compression tests on CPRABM specimens, to ascertain the statistical distribution characteristics of the single-particle strength and modulus, as well as the crack propagation patterns throughout the experiments. A refined discrete element method (DEM) model was subsequently constructed to simultaneously account for particle crushing and ITZ damage, quantifying the contribution rate of each component within the material to the overall strength of the specimens. The results show that the single-particle crush strength and modulus exhibit significant size effects, with their magnitudes decreasing in the order of natural gravel, recycled mortar, and recycled brick aggregates. The macroscopic compressive strength of CPRABMs is strongly controlled by the ITZ strength, but the controlling role is weakened by the increasing degree of crushing of recycled aggregates. The aggregates within the grain size range of 4.75-9.50 mm experienced the most profound particle crushing, thus necessitating a reduction in their proportion and/or replacement by natural aggregates. The maximum content of recycled aggregates is recommended to not exceed 50 %. The findings could provide theoretical basis and technical guidance for the design optimization of CPRABMs.

Using Reclaimed Asphalt Pavement in Backfilling Works Beneath the Structures

Mon, 27 Jan 2025 08:55:18 GMT

Reclaimed asphalt pavement (RAP) is produced in significant amounts. Nevertheless, the use of RAP is limited due to the absence of laboratory and field performance data. This research addresses laboratory and field tests to evaluate the use of RAP and various adapted mixtures in constructions such as road-bed layers and substitution layers. Modified proctor compaction, California bearing ratio, unconfined compression test, and static plate loading tests have been conducted on RAP, a mixture of RAP and crushed stone aggregates (CSA), and RAP stabilized with cement to satisfy the objective. Results have shown that 100% RAP material is suitable for use as a sub-base material. The ability of RAP material to be utilized as a cement-treated base layer is more pronounced when it is stabilized with cement (100% RAP + 8% and 10% cement). Utilization of 100% RAP stabilized with cement has been demonstrated to be economical in comparison with 100% CSA without cement. Finally, RAP material has shown good performance as a substitution layer.

Flexural Fatigue Performance of Hemp Fiber–Reinforced Concrete Using Recycled Concrete Aggregates as a Sustainable Rigid Pavement

Fri, 27 Sep 2024 13:48:25 GMT

This research delved into the mechanical and fatigue attributes of hemp fiber–reinforced concrete (HFRC) using both natural crushed aggregates (NCA) and recycled concrete aggregates (RCA) for sustainable rigid pavements. The additional hemp fiber ratios were 0%, 0.5%, 0.75%, and 1.0% by volume of concrete. The accelerated setting times were found due to hemp fibers facilitating rapid cement hydration. The compressive strengths were found to typically decrease with increasing hemp content. Mixes with 0.5% hemp (NCA-0.5H-FRC and RCA-0.5H-FRC) met the local road authority’s rigid pavement standards, with enhanced energy absorption and ductility. Flexural strength was optimal at 0.5% hemp, with all mixes meeting the standard 4.2 MPa. The flexural fatigue test indicated that higher hemp content significantly improved the fatigue life of HFRC under repetitive loading. Scanning electron microscopy (SEM) analysis demonstrated hemp fibers’ role in enhancing bond strength and interactions with cement matrix, thereby improving the concrete performance. While NCA mixes outperformed RCA ones, hemp fiber’s reinforcing effect was consistent across both types of aggregates. The study indicated hemp fiber’s potential in applications like pavements, highlighting 0.5% as the optimal hemp content for balancing enhanced mechanical properties while mitigating potential drawbacks. This research paves the way for the broader adoption of hemp fiber–reinforced concretes in sustainable construction endeavors.

Implementation of Recycled Crushed Concrete Aggregate in Class P Concrete

Thu, 22 Aug 2024 16:00:17 GMT

The successful use of recycled concrete aggregate (RCA) in continuously reinforced concrete pavement (CRCP) in a field trial near Sealy, Texas, under Texas Department of Transportation (TxDOT) Project 0-7074 demonstrated the potential for increasing the sustainability of concrete paving while still achieving target performance. Based on the progress made under TxDOT 0-7074 and in line with ongoing TxDOT and Federal Highway Administration (FHWA) initiatives to reduce the carbon footprint of new concrete construction, this implementation project aims to build upon the previous trial near Sealy, while expanding the depth and breadth of the implementation to include significantly longer trial sections with a wider range of RCA replacement levels. The research team will facilitate implementation of the project findings by documenting the results of laboratory and field studies in the Research Report of the TxDOT Research Project "Increase the Allowable Content of Recycled Crushed Concrete Fine Aggregate in Class P Concrete." The Research Report will include specific recommendations on the use of recycled crushed concrete fine and coarse aggregate into Class P concrete.

Function Design of Cement Stabilized Crushed Stone Drainage Base

Mon, 29 Jul 2024 16:27:06 GMT

Based on analysis of the influence degrees of structure types at early damages of cement pavements in large-grade highways, combined structure type of cement stabilized crushed stone drainage base and semi-rigid base is proposed. Base on function analysis of drainage base, design principles and indices of the cement stabilized crashed stone mixture are determined. And then, the type of coarse framework, distributing of cement slurry, and the component of grading are determined according to new characters of material design method which including the optimum vibrating compaction techniques and the dynamic stress press-in test having confined pressure and the volume design method in grading components. Finally, the method for determining the reasonable consistency of cement stabilized crushed stone mixture is presented, which adopts porosity diversity and strength as evaluation criterion. The void-framework cement stabilized crushed stone mixture demanding drainage base function will be consequently designed.

Physico-Mechanical and Petrographic Appraisal of Carbonate Rocks as Construction Aggregate: A Case Study from Lesser Himalaya, Pakistan

Thu, 25 Jul 2024 10:24:41 GMT

Owing to the exceptional role of crushed rock aggregates in construction, their prospective reserves fulfilling qualitative and economic parameters should be identified to meet their ever-increasing demand. This research aims to unlock new sources of high-quality construction materials, thereby optimizing concrete performance and meeting the requirement for sustainable building materials. The study investigated the physicomechanical and petrographic properties of Jurassic, Cretaceous, and Eocene limestones of the Kawagarh Formation (KF), Samana Suk Formation (SSF), and Margalla Hill Limestone (MHL) along the Abbottabad–Nathiagali roadside section, as per the American Society for Testing and Materials (ASTM) and British Standards Institute (BSI). The results of geotechnical investigations are flakiness and elongation index (19.6–34.85% and 17.53–31.2%), specific gravity (2.64 to 2.67), water absorption (0.34–0.63%), unconfined compressive strength (41.72–80.65 MPa), loss angeles abrasion value (15.63–19.08%), impact value (15.38–19.36%), and the soundness (0.9–1.97%). These results showed values within the acceptable range according to ASTM and BSI standards. Petrographically, the KF is classified as mud and wackestone, the SSF was mainly classified as wacke-packstone and grainstone, while the MHL was classified as bioclastic wacke and packstone. The dominancy of micrite matrix favors the strength of aggregate, whereas porosity, microfractures, stylolites, and allochems adversely affect the mechanical properties of rock aggregates. Based on reserve estimation, the studied sections possess significant exploitable reserves and are feasible for quarry operations. The studied rocks can be utilized to produce high-strength concrete, optimizing its performance and quality.

Strong interlocking skeleton gradation design and performance evaluation of cement-stabilised crushed gravel via vertical vibration test method

Tue, 23 Apr 2024 16:02:01 GMT

To control the cement-stabilised crushed gravel (CSCG) shrinkage crack and improve the road performance, analysing the composition of CSCG structure on performance influence law and cut-off of coarse and fine aggregate, the strong interlocking skeleton gradation (SISG) of CSCG based on vertical vibration test method (VVTM) was proposed and its performance was verified. The mechanical strength prediction equation of CSCG was established. The results demonstrate that 4.75 mm was the demarcation point of coarse and fine aggregates. When the coarse aggregate forms a stable framework and cement stone is completely filled in the framework, it can form SISG and reduce the shrinkage deformation. In particular, SISG includes coarse aggregates having sizes of 19–31.5, 9.5–19, and 4.75–9.5 mm in a mass ratio of 50:30:20, a fine aggregate grading I value of 0.65, and a coarse-to-fine-aggregate ratio of 65:35. The maximum dry density, CBR value, unconfined compressive strength, and splitting strength of SISG increased by ~1.3%, 9%–17%, 4%–12%, and 4%–8%, respectively, compared with the gradation median values obtained based on the Chinese standard. Furthermore, the error between the simulated CBR values and the measured values was <7%. The proposed mechanical strength prediction equations exhibit high reliability.

Research on Reasonable Cement Slurry Consistency of Cement Stabilized Crushed Stone Permeable Base

Fri, 19 Apr 2024 09:38:54 GMT

The former researches have shown that the permeable base materials should have sufficient void and high strength. But they are always controversial. Only when the cement slurry consistency is reasonable, equal void and high strength is possible. However, in the material design, slurry design is not paid enough attention to comparing with gradation. There is not an effective experimental method to determine the reasonable slurry consistency either. A new experiment with drainage weight as evaluation index is designed to evaluate reasonable cement slurry consistency. After studying the relation between drainage weight and time, standard drainage time is determined as 60s. By building the relations among drainage weight, 7d strength, and void diversity between up and down part, the criterion of drainage weight is less than 150g. Finally, following the method, 4 gradations are chosen to verify the strength, the cleavage strength, resilient modulus, and shrinkage. The results present that the materials designed by this method have good mechanic performance.

Study on Performances of Cement Stabilized Aggregate with Different Aggregate Gradation

Fri, 19 Apr 2024 09:38:54 GMT

The ratio of coarse aggregate and fine aggregate has great influence on the performance of cement stabilized crush stone. This paper presents the results of a laboratory evaluation of cement stabilized crush stone with three kinds of aggregate gradation. Samples were prepared using 4, 5, 6 or 6,8, 10% cement which depend on different aggregate gradation and were cured for 7, 28, and 90 days at room temperature. All the samples were made using vibration compactor. Result shows: at the same level of cement contents and maintenance conditions, dense mixture with few coarse aggregate and more fine aggregate has better compressive strength and compression resistant resilience modulus, but its anti-cracking and anti-erosion performance is worse; dense mixture with more coarse aggregate which can form "framework structure" in the mix has slightly bigger compressive strength and compression resistant resilience modulus than the former, at the same time its anti-cracking and anti-erosion performance is improved; porous mixture which has more coarse aggregate and few fine aggregate has minimum compressive strength and compression resistant resilience modulus, but its anti-cracking and anti-erosion performance is best.