Premature Pavement Failure Research Articles

Use of antioxidants to retard aging of bitumen: A review.

Oxidative aging of bitumen is an inevitable and irreversible phenomenon. Exposure to detrimental factors such as sunlight, oxygen, and UV radiations accelerates the aging of bitumen and bituminous pavement. The aging process induces hardening and embrittlement in bitumen, leading to premature pavement failure. Therefore, for constructing sustainable long-lasting pavements anti-aging additives are used. Among the available additives, the use of antioxidants has emerged as a promising solution to mitigate the aging of bitumen. The current review aims to summarise the existing literature for a comprehensive understanding of the effectiveness of these additives as aging inhibitors. It provides an overview of the chemical pathway involved during bitumen oxidation and various quantification techniques to measure the effect of aging. This review also highlights the potential use of antioxidants in bitumen and elaborates on the working mechanism of different types of antioxidants to prevent bitumen aging. Further, the effect of modification in bitumen at micro, macro, and mixture levels are discussed. Additionally, cost analysis and future prospects on the use of antioxidants for bitumen are presented.

Recycling flue gas desulfurization ash in enhancing the comprehensive moisture susceptibility of asphalt mixtures

Moisture susceptibility of asphalt mixtures is a major concern in areas with heavy rainfall or humid climates, as it can lead to premature pavement failures. As a typical industrial by-product during the flue gas desulfurization process of coal-fired, flue gas desulfurization ash (FGDA) with alkali mineral can facilitate the water damage resistance of asphalt mixtures. However, low density and high hydrophilic coefficient of FGDA limit its improvement effect. Hence, the comprehensive moisture susceptibility of asphalt mixtures with FGDA deserves systematic investigation. In this study, the properties indexes of FGDA and FGDA-limestone filler (LF) composite fillers were characterized. And the moisture susceptibility of asphalt mixtures containing six dosages of FGDA-LF fillers under hydrostatic damage and moisture induced sensitivity tester (MIST) hydrodynamic damage conditions were determined. The comprehensive assessment index of FLAM was explored based on radar chart assessment mean. The results indicate that FGDA with high alkali minerals and flocculent sphere morphology promotes the improvement of dispersivity and compatibility and the generation of homogeneous integral structure. Incorporating FGDA in FGDA-LF composite filler degrades its apparent density and elevates fineness and hydrophilic coefficient. Under MIST hydrodynamic damage, FLAM demonstrates the larger RMS and TSR than asphalt mixture with LF, accompanied by smaller attenuation compared to hydrostatic treatment. FLAM with F3 reveals the lowest rutting depth of 8.65 mm and creep slope of 1.92 × 10−4 and the largest comprehensive assessment index of 0.9998, indicating its optimal comprehensive moisture susceptibility. It is suggested that 30% FGDA might be an appropriate substitution amount for LF in FLAM.

Relative Compatibility Analysis of Aggregate-Binder Systems in Arkansas against Stripping

Compatibility holds great importance because it can predict the overall performance of asphalt mixtures. Incompatible aggregate-binder duos can result in a weak and friable mix as well as increase mixtures’ stripping potential. Being unaware, local agencies and contractors often struggle with premature pavement failure, which consequently places unexpected strain on the budget. Thus, this study assessed the compatibility among 18 asphalt binders with a performance grade (PG) of PG 64-22, PG 70-22, and PG 76-22, each collected from six different refineries; and eight different types of aggregates (sandstone, novaculite, limestone, and dolomite, each collected from two different quarries). Viscosity, penetration, pH, and work of cohesion values of binders were used to develop a binder ranking system. Similarly, the aggregates were ranked based on physical (specific gravity and absorption), durability (abrasion resistance and soundness), and chemical (pH and surface free energy) properties. Overall relative rankings of aggregates and binders were also provided by assigning weight factors to different tested parameters. A total of 144 aggregate-binder mixture systems were ranked based on their dry and wet work of adhesion values as well as Texas boiling test results. The compatibility ratio (CR) was also computed, and each of the systems was designated A, B, C, or D based on their relative CR values. Upon analysis, three binders (S2B2, S3B1, and S4B1) and three aggregates (DM2, LS2, and DM1) were designated as the most preferable construction materials. CR values predicted LS2, DM1, and DM2 mixtures as the most compatible mixtures. SS2, LS1, and DM2 mixtures showed the highest stripping resistance in the Texas boiling test. These databases are expected to help the agency and asphalt producers to select compatible binders and aggregates for producing durable asphalt concrete.Practical ApplicationsThis study covered a wide variety of aggregates and asphalt binders prevalent in but not limited to Arkansas. A database developed under this project was based on observed individual aggregates’ and binders’ performances as well as their combined performances. The information provided in this study will help contractors and agencies to choose the most appropriate aggregate-binder system within their reach for producing quality asphalt mixtures. By knowing the rankings, state agencies can adjust project budgets and assign timely rehabilitation due to the usage of less compatible aggregate-binder systems. Contractors can tweak the existing mix design if they must use local but inferior materials. This ranking will also help them to select project-specific materials depending on the project’s significance. The refineries as well will have the opportunity to improve their products to be more compatible with local materials.

Review: Shear Properties and Various Mechanical Tests in the Interface Zone of Asphalt Layers

Over four decades, researchers have extensively focused on bonding flexible pavement layers. Scholars have concentrated on the partial or complete lack of interlayer bonding between asphalt layers, which is the primary cause of premature pavement failures, such as cracking, rutting, slippage of wearing courses, and decline in pavement life. These defects are observed within the high horizontal force areas owing to increased speed, braking, and sharp angles when entering or exiting highways and the variations in paving materials, traffic load, and climatic factors. Various studies have investigated the debonding of flexible pavements, and test methods have been developed to find effective solutions. This review is aimed at summarising and discussing certain factors influencing shear strength performance, such as tack coat material, surface characteristics of multi-layer construction of flexible pavements, and different mechanical shear tests. First, bonding in the interface zone area and its Effect on the shear strength performance is reviewed. Subsequently, the types of materials and construction methods and their effects on the bonding quality of the interface zone area are clarified. Finally, the linear relationships between certain effects and the Ability of nanofibers to improve the emulsion properties are discussed. However, no agreement on the optimum tack coat could be obtained owing to the variety of surfaces. Hence, a milling surface is recommended for higher shear strength. The shear test is the most used method for verifying the interlayer bonding strengths, and continuous research endeavours are recommended to analyse debonding in multi-layer asphalt pavements.

Evaluation of Performance of Pavement Founded on the Reinforced Earth Sections along Outer Ring Road, Nairobi

There are no existing local design manuals and construction guidelines for reinforced earth structures in Kenya. The objective of this study was to evaluate the performance of the pavement found on reinforced earth sections along Outer Ring Road. The structural evaluation was determined from deflection measurements using Falling Weight Deflectometer (FWD), while the functional evaluation was by visual condition survey, roughness, and rut depth measurements. Classified traffic counts and axle load surveys were undertaken. It was established that the design traffic would be exceeded in year 10 after opening the road. The surface condition survey indicated that the pavement surface for the entire road was generally in good condition. The roughness rating for the entire road was rated "Good", while ten sections of reinforced earth embankment were rated "Fair". The characteristic rut depths on the reinforced earth sections were higher than the lane characteristic rut depth for the entire road. Three sections of the reinforced earth showed low severity, while the rest had no rutting. The PCI for the pavement on reinforced earth sections were lower than pavement on other sections of the road due to a higher International Roughness Index (IRI). The FWD deflections were higher on reinforced earth sections. It was found that the mean pavement moduli for surfacing and base, crack relief and subbase layers at reinforced earth sections were lower than for the pavement in other sections hence requiring thicker overlays. The overall residual life of the road was 17 years, while for the reinforced earth sections was 15 years. Based on the findings, monitoring of the traffic and performance of pavement on the reinforced earth embankments is vital for interventions to prevent premature pavement failure. There is a necessity to develop a design manual and construction guidelines for reinforced earth structures based on the local conditions in Kenya.

A critical review of the fatigue life prediction of asphalt mixtures and pavements

New pavement construction techniques and the increased use of recycled materials have led to unexpected and premature pavement failure in recent years. The pavement's exposure to daily and seasonal extreme temperature and repeated vehicular loads accumulate damage. Pavement cracking occurs once the cumulative damage surpasses the material's cracking threshold. Fatigue crack is the most common pavement cracking type. Over the past four decades, researchers have carried out numerous experiments and analyses to understand pavement cracking. This paper aims to provide an overview of fatigue cracking and discuss various fatigue test methods for characterizing asphalt concrete mixtures. The article also discusses the most common phenomenological and mechanistic models for predicting the fatigue life of asphalt concrete pavements based on different fatigue test results. The paper details the implementation of the commonly used numerical models found in numerical simulation software and their prediction ability for the fatigue life of a pavement structure. Two major flaws in current evaluation methods are the sensitivity of experimental results and the lack of reliability of some predictive models. Multiscale asphalt material characterization is the ongoing practice for determining the most appropriate performance evaluation tool. However, proceeding with future research objectives is unrealistic until the accuracy of the tests and reliability of the predictions can be verified against actual field results. This critical review of the fatigue life predictions of asphalt mixtures and pavements should help to refine or redefine the right course of action for future research. • Summarize the fatigue cracking, fatigue test methods, constitutive models, and numerical simulation software programs. • Study the theory, application, advantages, and disadvantages of mechanistic and phenomenological models. • Comparing the three prediction approaches reveal that mechanistic models accurately rank pavement mixture performance according to actual pavement conditions.

Behaviour of High-Modulus Asphalt Concrete from the Perspective of Deformation Characteristics - Stiffness

High-modulus asphalt concrete is a specific type of asphalt mixture which is used for several decades in pavement engineering. It was originally invented as a solution which should help to minimize the effects of permanent deformation caused mainly by heavy traffic and mainly during the periods with elevated temperatures. These mixtures are used either in binder or base courses, whereas for base courses, it is important to combine reasonably the high stiffness with good fatigue life to avoid premature pavement failures not caused by rutting but by fatigue cracking. In this respect, various types of HMAC used and designed in the Czech Republic were tested first and foremost to determine stiffness. The stiffness modules were tested according to EN 12607-26, test method IT-CY, at selected temperatures representing cold, moderate and high service temperatures. The susceptibility to temperature change can be shown by thermal susceptibility for each mixture. In the parallel test, specimens were laboratory age to identify the changes in stiffness caused by thermo-oxidative ageing. This allows calculating a simple measure of the ageing index. Not presented in this paper but performed as a very last test was resistance to crack propagation.

Non-destructive ultrasonic evaluation of construction variability effect on concrete pavement performance

It is commonly recognized that non-uniformity of as-constructed Portland Cement Concrete (PCC) pavement may negatively affect long-term pavement performance. Conventional wisdom states that PCC thickness deficiency is the most important factor causing premature pavement failures. To address it, transportation agencies often impose strict penalties for not meeting the designed slab thickness requirements, thus contractors build slightly thicker slabs to avoid fines. However, other aspects of construction variability on pavement performance are mostly ignored by studies because conventional methods for construction uniformity assessment fail to provide sufficient information to quantify their effect. This study utilized a non-destructive ultrasonic test to evaluate in-situ pavement construction variability. To investigate the correlation between construction variability and surface distresses, a combination of non-destructive ultrasonic thickness measurements and visual distress surveys were performed in highways prior to rehabilitation. PCC slab thicknesses and shear wave velocities were computed from recorded ultrasound signals. An in-depth statistical analysis was performed to investigate possible relations between thickness or shear wave velocity and distresses using various pavement performance parameters. The main results of this analysis illustrate the importance of material quality and uniformity control during construction, since alterations in material properties significantly influence the presence of distresses. Shear wave velocity variations significantly correlate to cracked and broken slab panels in two sections, and, more importantly, to any type of distress in all tested pavement sections.

A Framework for Introducing Climate-Change Adaptation in Pavement Management

Greenhouse gas emissions have caused global temperatures to rise since the mid-20th century accompanied by sea-level rise (SLR). Temperature increases and SLR-induced groundwater rise have been shown to cause premature pavement failure in many roadway structures. Hybrid bottom-up/top-down (hybrid) adaptation approaches have shown promise by initially investigating an asset’s response to incremental environmental change and then identifying the timing of critical effects for budgetary planning. This improves practitioners’ understanding of the asset’s climate resiliency and informs adaptation-plan development to minimize both cost and risk. In this study, a hybrid approach to pavement adaptation with climate-change-induced temperature and groundwater rise is demonstrated at a case-study site in coastal New Hampshire. The hot-mix-asphalt (HMA) thickness that achieves a minimum of 85% reliability is calculated for 70 combinations of incremental temperature and groundwater rise. Increasing the base-layer thickness improves resiliency against rising temperatures, but rising groundwater diminishes this improvement demonstrating that both HMA and base-layer thickness increases are needed. Thirteen adaptation pathways are evaluated for pavement performance, life-cycle costs, and road-surface inundation over a 60-year pavement management period. A stepwise and flexible adaptation plan is developed that includes HMA overlays with prescribed thickness and application timing, base-layer rehabilitation options, and re-evaluation opportunities.

Moisture susceptibility of hydrated lime modified mastics using adhesion test methods and surface free energy techniques

ABSTRACT Moisture damage is one of the major factors that has been reported to affect the performance of asphalt pavements which depends mainly on the bond strength between bitumen, aggregates and mineral filler. In the presence of moisture, this bond weakens and results in premature pavement failure. One of the many ways of mitigating moisture damage effects is the use of anti-stripping agents. Hydrated lime has been found to be one of the most efficient anti-stripping agents among the common additives used with asphalt mixtures. This study attempts to quantify the bond strength of hydrated lime modified mastics with different aggregates (granite and limestone) under moisture conditions using a combination of surface free energy techniques and conventional adhesion test methods. From the surface free energy technique, the moisture susceptibility was studied in the form of dry work of adhesion, work of debonding and various energy parameters. Two conventional techniques, the PATTI test and the rolling bottle test were used to assess bond strength under wet conditions. The results of all three techniques lead to the same conclusion that hydrated lime is an active filler that improves moisture damage resistance compared to the other natural fillers but that the improvement is highly dependent on aggregate mineralogy.

Ettringite induced heaving in stabilized high sulfate soils

Stabilization of expansive soils using lime and cement additives have been used by practitioners over the years. However, recent heaving and premature pavement failures in lime and cement-treated subgrades containing sulfates led to questioning the use of calcium-based stabilization methods for these soils. Annually, millions of dollars are spent to repair pavements distressed by this Ettringite induced heaving. Based on the past studies, researchers and practitioners have proposed various methods to treat sulfate soils. Applicability of these methods is mostly limited to soils with sulfate levels below 8000 ppm. Soils with sulfate content above 8000 ppm are termed as “high sulfate” soils, and chemical treatment of such soils is currently not considered. A research study was designed to aid in understanding the heaving phenomenon in soils with sulfate contents above 8000 ppm and to develop practical techniques to stabilize such soils. High sulfate soils were sampled and treated with lime at varying mellowing periods and treated soils were then subjected to the engineering and chemical tests. Tests results were analyzed to understand the effectiveness of mellowing period on the heaving phenomenon of these soils. Treated soils at higher mellowing periods showed reduced sulfate-induced heaving when sulfate levels are lower than 30,000 ppm. Sulfate levels in excess of 30,000 ppm did not result in effective treatment of soils. It was also observed that compaction void ratios and soil clay mineralogy have a significant impact on the swell behavior of chemically treated high sulfate soils. An innovative method comprising of aerial technologies is used to monitor the pavement heaving. This keynote paper provides a comprehensive review of stabilization of high sulfate soils and methods studied to mitigate sulfate heaving.

Review of soil compaction: History and recent developments

Abstract Compaction of soils is a major construction activity in civil engineering, and particularly in the transport industry. This paper presents a brief historical account of soil compaction development with special emphasis on transport geotechnics. Proctor’s curves and California Bearing Ratio (CBR) are reviewed and the associated state-of-the-art field specifications are discussed. The properties of compacted soil and the typical behaviours of compacted fill under in-service conditions are discussed. Intelligent compaction is being increasingly adopted with a view to increased uniformity in compaction, lack of which is a major cause of premature pavement failure. However, it needs further advancement to make it more intelligent. The current state of the ability to predict compacted soil behaviour is reviewed and the limitations are identified. Of more recent developments, interpretation of compacted soil behaviour with a three-dimensional state boundary surface is highlighted, and simplified behaviour can be interpreted and used in routine practice. Areas that need further advancements in theory and practice are highlighted.

Adaptation Planning to Mitigate Coastal-Road Pavement Damage from Groundwater Rise Caused by Sea-Level Rise

Sea level in coastal New England is projected to rise 3.9–6.6 ft (1.2–2.0 m) by the year 2100. Many climate-change vulnerability and adaptation studies have investigated surface-water flooding from sea-level rise (SLR) on coastal-road infrastructure, but few have focused on rising groundwater. Groundwater modeling in New Hampshire’s Seacoast Region has shown that SLR-induced groundwater rise will occur three to four times farther inland than surface-water flooding, potentially impacting 23% of the region’s roads. Pavement service-life has been shown to decrease when the unbound layers become saturated. In areas where groundwater is projected to rise with SLR, pavements with groundwater 5.0 ft (1.5 m) deep or less are at risk of premature failure as groundwater moves into the pavement’s underlying unbound layers. In this study, groundwater hydrology and multi-layer elastic pavement analysis were used to identify two case-study sites in coastal New Hampshire that are predicted to experience pavement service-life reduction caused by SLR-induced groundwater rise. Various pavement structures were evaluated to determine adaptation feasibility and costs to maintain the designed service-life in the face of rising groundwater. This investigation shows that relatively simple pavement structural modifications to the base and asphalt concrete (AC) layers of a regional corridor can eliminate the 80% to 90% service-life reduction projected with 1.0 ft SLR (year 2030) and will delay pavement inundation by 20 years. Pavements with adequate base-layer materials and thickness require only AC thickness modification to avoid premature pavement failure from SLR-induced groundwater rise.

Study of ravelling failure on dense graded asphalt pavement

Ravelling is the loss of bond between aggregates and asphalt binder. This distress is more common in porous asphalt concrete when the voids content is 20% or more. However, premature pavement failure in terms of ravelling on a dense graded asphalt concrete pavement in China occurred within 3 years after the pavement was opened to traffic. The objective of this paper is to determine the cause of this distress. A preliminary investigation did not find evidence of either inadequate design- or construction-related issues. Detailed investigations were undertaken to identify the possible cause of failures. Cores and material samples were also tested in the laboratory. The results indicated that the asphalt mixture at this section fully met the specified requirements of a conventional mixture. The adhesions between binder and aggregate also met the specified requirements and the air void content of the mixture was 5·3%. X-ray diffraction indicated that some aggregates contained illite and kaolinite, which are expansive clays. It was found that this was the primary reason for the distress. Although selection of proper aggregate materials and quantities is standard practice, there is a need to include requirements for contamination by weathered products in the crushed stone.

Flexible Pavement Interface Bonding: Theoretical Analysis and Shear-Strength Measurement

Abstract It has been proven that the interface bonding between asphalt layers is critical to flexible pavement performance, especially for pavement overlays. However, the requirement on interface bonding strength has not been specified to prevent premature pavement failure, such as slippage cracking or early fatigue cracking. In this paper, pavement structural analysis was conducted to predict the interface shear stress between the surface and intermediate asphalt layers under the combination of vertical and horizontal loading at different temperatures. The effect of interface debonding on pavement life was quantified using the state-of-art mechanistic–empirical pavement-analysis software (AASHTO Pavement-ME) with local parameters. Field cores were taken to measure the interface bonding strength; using the direct shear device theoretical analysis, results show that the minimum-bond-strength requirement should be around 70 psi to prevent premature pavement failure, such as slippage cracking or fatigue cracking. This requirement can be easily achieved in field projects based on the testing results of bond strength from field cores.

Geosynthetics with enhanced lateral drainage capabilities in roadway systems

Abstract While moisture-induced distress is one of the major causes of premature pavement failure, geosynthetics are only seldom used to provide internal drainage within the structure of roadway systems. This is likely because conventional geosynthetic drains are only suitable to manage flow under saturated soil conditions, whereas unsaturated conditions prevail in pavement systems. Recent insight into the interaction between geosynthetics and unsaturated soils has led to new advances in geosynthetic manufacturing, including the development of geotextiles with enhanced lateral drainage (ELD), which allow drainage even under unsaturated conditions. This paper highlights the benefits of ELD in a number of roadway situations, including: (1) enhanced lateral drainage of moisture migrating upward from a high water table, (2) enhanced lateral drainage of moisture infiltrating downward from the surface, (3) control of frost heave-induced pavement damage, (4) control of pavement damage caused by expansive clay subgrades, and (5) enhanced lateral drainage in projects involving soil improvement. The mechanisms of moisture migration, as well as the impact of ELD are evaluated in each of these situations. Additionally, case histories involving recently constructed pavements involving the use of ELD geosynthetics are presented for each specific drainage application. The selected case histories involve post-construction evaluation of the ELD geosynthetic’s performance either through assessment of lateral drainage, condition surveys of pavement sections with and without ELD geosynthetics, or in-situ monitoring of moisture content. Assessment of the data collected illustrates the beneficial impact of ELD used in the various pavement scenarios. Overall, this paper illustrates that incorporation of enhanced lateral drainage in roadway systems results in a range of improvements for pavement performance.

Effects of moisture on warm mix asphalt containing Sasobit

The asphalt industry has been at the forefront of sustainable development. Warm Mix Asphalt (WMA) has been developed to cope with issues such as high energy prices and air pollution. These mixes require less energy and generate fewer pollutants during production in comparison with conventional Hot Mix Asphalt (HMA). Although a promising technology, the durability of WMA is not clear because long-term WMA fieldperformance data is limited. This study investigated the susceptibility of Sasobit-modi ed WMA to moisture, since moisture damage is a major cause of premature pavement failure in asphalt concrete. To this end, WMA samples were made using di fferent concentrations of Sasobit and the results were compared with those from HMA mixtures. The e ffect of hydrated lime as an anti-stripping agent was also investigated. The tensile strength ratios indicate that the introduction of hydrated lime and Sasobit increased the resistance ofasphalt mixtures to moisture. Fracture energy and toughness were used to evaluate the crack resistance of specimens under dry and wet conditions. In comparison with Sasobit, hydrated lime increased crack resistance of mixtures. The results indicate that hydrated lime can be used as a compatible and eff ective anti-stripping agent for WMAs containing Sasobit.

The identification and treatment of poor durability Karoo dolerite base course aggregate - evidence from case studies

The Karoo Supergroup covers approximately 57% of South Africa's surface area and the sedimentary rocks therein generally do not yield acceptable pavement aggregates. The Karoo Dolerite Suite (intrusions) present in these sedimentary units have successfully been used as pavement aggregate sources, but numerous cases of premature pavement failure due to alleged rapid degradation of the dolerite have been reported. Durability tests are included in basic or mafic igneous rock aggregate specifications, but rapid pavement failures continue to occur. A study was recently undertaken to identify cases where degradation of Karoo dolerite was the cause of pavement failure. A secondary objective of the study was to determine if any observed degradation could have been identified using currently specified or alternative testing methods. Three such case study sites are presented in this article and the properties of their materials compared to those from five non-problematic dolerite materials. It is shown that the poor performance of the case study materials was likely due to the poor durability of the materials, manifesting as a reduction in resistance to abrasion and attrition. The identification of the observed poor durability could not have been performed accurately using only the currently specified test specifications. Alternative tests that allow an accurate differentiation to be made were, however, identified and, based on the results, tentative limits set. Additionally it was shown that modification of problematic Karoo dolerite base course materials, by applying lime at a rate less than the initial consumption of lime, can be successful in preventing further rapid pavement failures.

Performance of Sand-Treated Clay Subgrade Supporting a Low-Volume Flexible Pavement

Low-volume roads constitute a major portion of the world's transportation infrastructure and hence require an economical and effective pavement design. When constructed on unstable and soft subgrades, these roads are susceptible to premature pavement failures and require subgrade stabilization. The presented research focuses on mechanical stabilization of soft clay with graded sand that has been adopted as a base course for pavements. For this study, a local soft clayey soil from Dallas was mixed with various fractions of a graded sandy soil, and the stiffness behavior of the compounded material was studied. The soil mixtures were then studied for their basic soil characterization, including standard Proctor compaction studies. Statically compressed soil specimens were prepared and then evaluated for their unconfined compressive strength and resilient moduli. Resilient moduli results were used in the design of low-volume roads, both with aggregate base and with no aggregate base. Results show that the variation of sand content in soft soil considerably affects the strength and stiffness properties of the subgrade. The effects of improved subgrade performance on the aggregate base and surface layers of the low-volume pavement are highlighted.

Stabilization of High-Sulfate Soils by Extended Mellowing

The use of lime to stabilize expansive soils has been the preferred technique for many years. However, heaving and premature pavement failures in lime-treated expansive subgrades containing sulfates led to the search for alternative stabilization techniques. Of the several techniques developed, precompaction mellowing has the potential to be effective in stabilizing sulfate-bearing soils. Yet this method needs experimental evaluation. In the current study, an attempt was made to assess the stabilization effectiveness of precompaction mellowing on high-sulfate soils. For this task, six natural expansive soils from Texas, with sulfate contents varying from 200 to 44,000 ppm, were collected. Soils with low-sulfate contents were spiked with additional sulfates to make them high-sulfate soils. Basic classification and chemical tests were performed to establish the clay mineralogy of the soils. Three mellowing periods (0, 3, and 7 days) were studied. The test soils were treated with lime and allowed to mellow for the specified periods. Following the mellowing, the samples were subjected to three-dimensional tests for volumetric swell, shrinkage, and unconfined compressive strength (UCS). To study the consumptions of alumina and silica during sulfate–soil–lime reactions, reactive alumina and silica measurements were also attempted. The authors observed that shrinkage was of no concern in treated soils because the shrinkage invariably reduced with lime treatment. In four of the six soils, precompaction mellowing reduced sulfate-induced swell to a level below the natural expansive swelling. The UCS strengths of treated soils decreased slightly with mellowing. Reasons for the anomaly in UCS strengths and ineffectiveness of precompaction mellowing in two soils were explained.