Pothole Formation Research Articles

Bathymetric Monitoring of Alluvial River Bottom Changes for Purposes of Stability of Water Power Plant Structure with a New Methodology for River Bottom Hazard Mapping (Wloclawek, Poland).

The aim of this research was to produce a new methodology for a special river bottom hazard mapping for the stability purposes of the biggest Polish water power plant: Włocławek. During the operation period of the water power plant, an engineering-geological issue in the form of pothole formation on the Wisła River bed in the gravel-sand alluvium was observed. This was caused by increased fluvial erosion resulting from a reduced water level behind the power plant, along with frequent changes in the water flow rates and water levels caused by the varying technological and economic operation needs of the power plant. Data for the research were obtained by way of a 4-year geodetic/bathymetric monitoring of the river bed implemented using integrated GNSS (Global Navigation Satellite System), RTS (Robotized Total Station) and SBES (Single Beam Echo Sounder) methods. The result is a customized river bottom hazard map which takes into account a high, medium, and low risk levels of the potholes for the water power plant structure. This map was used to redevelop the river bed by filling. The findings show that high hazard is related to 5% of potholes (capacity of 4308 m3), medium with 38% of potholes (capacity of 36,455 m3), and low hazard with 57% of potholes (capacity of 54,396 m3). Since the construction of the dam, changes due to erosion identified by the monitoring have concerned approximately 405,252 m3 of the bottom, which corresponds to 130 Olympic-size pools. This implies enormous changes, while a possible solution could be the construction of additional cascades on the Wisła River.

Properties of Bituminous Binder Modified With Polyethylene

Bitumen is used as a binder in construction of flexible pavements since long. With the increase in population and number of vehicles, load on roads have been increased day by day. Thus roads which consist of unmodified bitumen suffer from serious drawbacks in the due course of time like rutting, thermal cracking, fatigue cracking, pothole formation etc. Hence, it is necessary to add a modifier in bitumen to enhance the binding property of later. Polyethylene, which is a non-degradable compound, become waste and creates pollution, owing to its high consumption. This polyethylene (melting point 120-180 °C; thermal degradation above 400 °C) in liquid state becomes sticky in nature and therefore can act as a binder. Also, major parts of both polyethylene and bitumen are hydrocarbon, hence polyethylene wastes (LDPE and HDPE) can be used to modify the bitumen and enhance the binder property of it. Like polyethenes, degradation of other polymeric wastes is also challenging and can be utilized for other purposes for minimizing the wastes and improvement in quality of available products.

Assessment of Evolutionary Trends in Mountain Grassland Soil Processes and Problems in Soil Protection and Their Rational Use

The objective of the survey was to assess evolutionary trends in the mountain-grassland soil processes and the environmental and anthropogenic impacts on soil degradation and land efficiency. Generalization of the previously studied materials in comparison with the data collected in route surveys carried out in the large river basins, including the Samur, Chirakhchai, Sulak, and other rivers, allowed for identifying the main factor affecting the evolutionary trends in the soil processes within the altitudinal zones in mountain regions in Dagestan. This is particularly the factor associated with both the climate and vegetation changes and the human economic activities. In addition, it has been proven that slope exposition and anthropogenic factors effect pedogenesis and soil degradation. Slopes of a southern exposition and the slopes of slightly different expositions from it are generally drier. Snow cover lasts for a long time, which is followed by rapid snowmelt. Therefore, the vegetation of such areas is poor, and, moreover, the occurred denudation processes are much stronger. According to the data collected on the basis of observations for the most recent 50 years, humus concentrations in the soils used in the economic circulation decreased by 0.5–1.2% and even by 1.5–2% in some of them. Annual soil washout comprises 12 million t on average. It involves approximately 50 thousand t of humus. Unregulated livestock grazing causes pothole formation, compaction by pathways, and sparse vegetation. Therefore, a 20–30% reduction in the projective vegetation land cover can induce a five- to sevenfold increase in the volume of eroded material in long-term erosion when compared to a 70–75% vegetation land cover. In addition, the current pedogenic processes are affected by global warming, differences in soil moisture and temperature regimes on slopes of different expositions in the altitudinal zonation system, and high erosion rates caused by natural and anthropogenic factors. Complex erosion-control measures, including amelioration by slitting once every 3–4 years, grazing regulation, and evenly distributed grazing with taking slope expositions into account, are required.

Common surface defects in asphalt road pavements and unexpected causes

Correct interpretation of the cause or causes of defects and deterioration of road pavements is important for the selection of the most appropriate maintenance or repair strategies and for the design of new pavements. However, identifying the cause of pavement defects is not as simple as merely looking for aspects of specifications that have not been fully met. The cause of failures is often attributed to a number of factors, one of which, if absent, would not necessarily result in any defects. This paper describes and analyses three case studies where three different mechanisms have caused the deterioration of both asphalt concrete and double chip sealed surfacings. The first mechanism is the peculiar formation of potholes below certain structures and trees, which can result in large-scale ravelling and potholing on certain road categories. The second mechanism is an unusual cause of the flushing of bitumen on both types of surfacing. The third mechanism results in the formation of potholes at roundabouts in tropical countries. The paper concludes by recommending the appropriate maintenance measures for the cause of each defect and appropriate designs to minimise the likelihood of their occurrence.

Formation of Potholes Associated with Bedrock Gorges on Mesozoic Sandstone of Khari River, Kachchh Mainland, Western India

The potholes are perceptible erosional features associated with bedrock channels. They play an essential role in bedrock incision studies, but little work has been published on the development of potholes, especially in Bedrock Rivers in India. The present site-specific study aims to analyze the role of physical properties of bedrock and associated structures in the process of development of potholes and to classify the potholes based on their dimensions. The Khari River gorge formed over Mesozoic Sandstone with six bedrock terraces exposed along a confined segment of the river. The site is manifested by strath terraces, grooves, potholes, and knick points. Three stretches of Khari Gorge have been studied in detail for this purpose. The pothole dimensions, joint orientations, rock mass strength, physical properties of rock, and placing of potholes to present active channels were measured. The analysis shows the inverse relationship between the size of pothole and rock properties. The distance of potholes and active channels govern the essential factor and manifest the role of flow hydraulics. The high density of matured potholes near active channels over immature potholes supports primary control of hydraulics of flow over rock properties.

Elephant Tracks: A Biogenic Cause of Potholes in Pleistocene South African Coastal Rocks

Helm, C.W.; Cawthra, H.C.; De Vynck, J.C.; Dixon, M., and Stear, W., 2021. Elephant tracks: A biogenic cause of potholes in Pleistocene South African coastal rocks. Journal of Coastal Research, 37(1), 59–74. Coconut Creek (Florida), ISSN 0749-0208.The Cape south coast of South Africa contains extensive outcrops of Pleistocene aeolianite and cemented foreshore deposits. More than 250 vertebrate tracksites have been identified in these deposits, including 35 elephant tracksites. In places, where large palaeosurfaces are occasionally exposed, numerous potholes are evident on the remains of what is most likely a palaeo-coastline. Features suggestive of elephant tracks are apparent on such surfaces and in overlying layers. In order to develop, potholes require a disturbance or depression in the surface to act as a “pothole-precursor” on which erosive forces can act. While elephant tracks or similar biogenic origins for potholes have not previously been described, such an explanation appears plausible for at least some pothole features in areas known to have harboured elephants or other large vertebrate trackmakers when these surfaces were composed of unconsolidated sand. Four sites on the Cape south coast are examined and described. Evidence for use of beaches as travel corridors for elephants is described, and candidate Pleistocene trackmaker species are considered. The age of these palaeo-surfaces is considered to range from Marine Isotope Stage 11 to Marine Isotope Stage 5. It is concluded that depressions formed by elephant tracks should be considered as a precursor for the formation of potholes on suitable Pleistocene surfaces in littoral zones.

Evaluation of UAV–CRP Data for Monitoring Transportation Infrastructure Constructed over Expansive Soils

Application of unmanned aerial vehicles (UAVs) for civil infrastructure monitoring has gained impetus owing to the advancement of aerial platforms paralleled with the development of sophisticated sensors. Photogrammetry is the science of measuring distances from two or more images, and close-range photogrammetry (CRP) is a part of photogrammetry that involves calculating measurements of an object within a maximum distance of 305 m away from the inspecting sensors. Geotechnical problems including differential heaving and related cracking of expansive soils cause extensive damage to pavement infrastructure. Feasibility of using UAV–CRP technology in health monitoring of pavement infrastructure constructed over problematic soils has been comprehensively studied, and this paper presents an overview of these results. Pavement performance data including longitudinal and transverse slopes, as well as distress conditions such as pavement surface cracking, pothole formation, and rutting or excessive deformation, are monitored via UAV–CRP technology, and these data sets are comprehensively analysed. UAV–CRP-interpreted performance indicators showed a very good agreement with those obtained from traditional methods surveys and profiler studies. With the further research, the UAV–CRP technology will play an important engineering role in safe, inexpensive and comprehensive health monitoring of infrastructure built over problematic soil conditions.

Investigation of Pothole Severity and Maintenance Methods in Canada through Questionnaire Survey

This paper investigates the severity of pothole problems, conducts a critical assessment of current maintenance practices, and identifies resources available for pothole repair based on the results from a questionnaire survey of six provincial transportation agencies in Canada. The survey outcomes indicated a greater percentage of moderate to highly severe potholes in the study area. Freeze-thaw cycles were identified as the most influential factor in pothole formation. A large portion of pothole repair operations are conducted in the summer period. The frequently used patching materials were conventional cold mix, hot-mixed asphalt, Quality Pavement Repair, and Innovative Asphalt Repair. The throw-and-go method is commonly used for pothole repair operations in all seasons. The durability of a winter-repaired patch is significantly less than that of summer. Raveling, edge disintegration, and cracking are the most concerning distresses of patch failure, which could be a result of inadequate stability, adhesion, cohesion, and stripping potential of patching materials.

MCA on mechanism of river bed potholes growth: a study of middle Subarnarekha River basin, South East Asia

Pothole is an exceptional dynamic micro-fluvial erosional landform of the river bed. Subarnarekha River is a rejuvenated antecedent river and occupies a significant part of the Chotanagpur Plateau. The river bed of the Subarnarekha River and the confluence zones of Subarnarekha-Lokjoriya and Subarnarekha-Kharsoti have favourable conditions for the development of potholes. Geological (joint and fracture on river bed) and hydrological (stream power, water discharge, flow velocity) parameters are taken into consideration to understand the mechanism of pothole growth. Multi-criteria analysis (MCA) has been done to understand the governing factor influencing the mechanism of pothole development. The results are analysed in a quantitative way, and the micro-scale field observations have been represented using ArcGIS10.2.2 and IBM SPSS 22. Using the MCA it has been inferred that ‘joint length’ is the prime contributing factor responsible for pothole formation in the middle Subarnarekha River basin, Ghatsila. The main significance of this research work is the study of micro-geomorphic landforms mechanism near confluence and other places of the river bed.

An intrusive origin of some UG-1 chromitite layers in the Bushveld Igneous Complex, South Africa: Insights from field relationships

The UG-1 chromitite in the Bushveld Complex is a 1m thick massive layer overlain by orthopyroxenite (4–9m thick) and underlain by anorthosite (1.5–2.0m thick), which is strongly interleaved with numerous thin layers of UG-1 chromitite (mm to 10s of cm thick). The chromitite-bearing anorthosite is further underlain by mottled anorthosite, which is devoid of chromitites. Sometimes, the massive UG-1 chromitite may be hosted entirely within orthopyroxenite; in this study, however, the orthopyroxenite occurs intermediate to the massive UG-1 layer and the footwall interleaved anorthosite unit, which has a 10cm thick chromitite layer at the contact. Though the UG-1 chromitites display complex features in the field outcrops (e.g., presence of numerous anorthosite autoliths, bifurcations, and dimpled contacts with anorthosite), the ones discussed in this study are distinctive and diagnostic of the emplacement mechanism for this chromitite layer. In this study of the UG-1 chromitite at the Impala Platinum mine, the chromitite is seen to form a small pothole (≈1.5m deep; 3.6m wide) that cuts down into the underlying orthopyroxenite (exposed only on the right side of the pothole) and anorthosite layers. A 15cm thick UG-1 chromitite layer (85 modal% chromites) is observed to protrude or branch out of the pothole margin and laterally extend into the anorthosite, with which it shows several crosscutting features. Examples include truncation of layering defined by interstitial pyroxene mottles within the footwall anorthosite against the protruding UG-1 layer, and truncation of several thinner UG-1 layers in the hanging wall anorthosite against erosive outlines of this chromitite layer. These observations strongly attest to the emplacement of the protruding UG-1 chromitite layer as a sill into the anorthosite. The presence of thin anorthosite lenses with high aspect ratios within this UG-1 layer, along with lateral variations in thickness of the layer, its irregular contact with the host anorthosite, and disturbances observed for the UG-1 layers in the footwall anorthosite adjacent to the erosive contact, implies that the superheated melt, parental to the chromitite, chemically dissolved the anorthosite and made space for it to flow as a sill within the latter. The probable mode of emplacement of the laterally protruding UG-1 layer would be through the opening of fractures related to the event of pothole formation where there is ponding of hot, thick and dense melt above the anorthosite. The melt subsequently filled the fractures and flowed laterally into the anorthosite thereby eroding it. An open magmatic system ensured continuous addition of melts in the pothole and their supply into the sill. This study thus emphasizes that some of the UG-1 chromitite layers within anorthosite can be emplaced as sills, and not all need to form from discrete cyclical pulses of chromite-saturated and plagioclase-saturated melts being brought into the chamber.

Geo-hydrological response to pothole formation: a quantitative study of Kharsoti River, India

This work includes the mechanism of pothole morphology, development, growth and dynac changes in meso and micro level. The study highlights some inter linkages of certain specific parameters like geological and hydrological concerns in pothole mechanism of Kharsoti River. Reviewing our geomorphological knowledge, potholes are mainly found to be concentrated in upper most part of the river where the stream energy is maximum but here our study area is included in the middle part and lower part of the Kharsoti River which is a typical example of rejuvenated antecedent tributary river of Subarnarekha River in Chhotanagpur plateau and exist like a bedrock river. Both shearing (geological) and huge discharge (hydrological) response are the concerned mechanisms in the development of potholes as micro fluvial landforms. One the basis of the analysis it is necessary to give a new threshold of quantitative methods in landforms study under a systematic scientific geographical background. Regarding the hydrological parameters like discharge, suspended load, stream power, velocity have been considered and some normal attributes like slope, bedrock character, rocky exposed on the riverbed etc. This type of work will help to open a new window for studying the micro landform mechanism in a contemporary method.

How does anisotropy in bedrock river granitic outcrops influence pothole genesis and development?

AbstractPothole formation and development may be influenced by joint sets and other heterogeneities within bedrock, as well as by hydraulics. Previous research indicates that most potholes found in rivers of the mountainous Spanish Central System exhibit preferred orientations associated with dominant joints and correlate more strongly with variations in substrate resistance than with hydraulics. Weathering and erosion weaken rock surfaces, which leads to decreased mechanical resistance. We start from the hypothesis that different mechanisms of pothole formation may create around the pothole a distinctive signature in terms of ultrasound pulse velocity and surface hardness. We develop a conceptual model and test it using potholes for which we know the mechanism of formation, demonstrating that the spatial and statistical distributions of dynamical mechanical properties and surface hardness of a pothole may provide insight into its genesis. Copyright © 2016 John Wiley & Sons, Ltd.

Delineation of Pothole-Dominated Wetlands and Modeling of Their Threshold Behaviors

AbstractTime-invariant contributing area and full hydrologic connectivity are commonly assumed in traditional watershed delineation and modeling. In reality, however, contributing area of a depression-dominated prairie basin varies and undergoes a progressive evolution process that is characterized by unique threshold behaviors associated with the depression filling–spilling–merging–splitting–depleting dynamics. The research reported in this paper aims to precisely delineate prairie potholes and the associated wetlands, effectively characterize their dynamic hydrotopographic properties, and further quantify the resultant threshold behaviors and spatiotemporal variability in hydrologic connectivity. Delineation and modeling for a wetland site in the Prairie Pothole Region (PPR) highlighted the crucial role of topographic characteristics in the formation, evolution, and connectivity of prairie potholes. Particularly, the modeling tests for real rainfall demonstrated the significant impacts of complex rainfa...

Differential control in the formation of river potholes on basalts of the Paraná Volcanic Province

Variations in rock properties control geomorphic processes and thus landscape evolution. Potholes developed on basaltic riverbeds are generally associated with vesicular-amygdaloidal zones, although they also occur in massive basalts. Until now, this relationship has not been quantified, nor have the parameters controlling the development of these features in basalts been evaluated. Based on field data collected from 71 sites distributed in three rivers in the Paraná Volcanic Province (PVP), southern Brazil, we investigated the relationship between the occurrence of potholes and features of basalt flows. Reaches were analyzed both in areas with potholes and in areas without these features. The data collected refer to the joint density, the intact rock strength measured with a Schmidt hammer and the typology of basaltic units in terms of vesicularity. It was found that potholes preferentially occur in vesicular-amygdaloidal units (86%). This predominance is not associated with the joint density, which is the same in massive basalts (≈5 m/m2); moreover, potholes occur in basalts with very different joint densities. The intact rock strength is lower in vesicular-amygdaloidal basalts (58) than in massive basalts (61) and does not explain fully the preferential abrasion in vesicular-amygdaloidal units because potholes occur with varying resistances. The basalt strength is a secondary variable. The controlling parameter seems to be vesicularity, which by producing irregularities in the bed and flow triggers the formation of potholes. In the massive basalts, irregularities are produced primarily by joints. In massive basalts there seems to be an upper threshold of stream power beyond which the formation of potholes is restricted (drainage area ≈700 km2; slope ≈0.06). A lower threshold in stream power could also exist to massive basalts of the study area and it is suggested by the inexistence of potholes in sites with drainage area less than 100 km2.

Pothole Formation and Occurrence in Black Vertisols of Central and Western India

Soil cracks are a unique feature of black vertisols. Evaporation loss is inevitable from lateral exposure of surface and sub-surface cracks. On the other hand, these cracks provide increased opportunity for soils to recharge during the rainy season. In this process, water that drains into larger size cracks moves down the soil profile and eventually results in pothole formation due to the existence of a network of sub-surface cracks. An investigation was done to evaluate pothole characteristics under different land use systems in black vertisols of central and western regions of India. In both the regions, the potholes had smaller volume in arable land than in non-arable uncultivated land. The size and volume of potholes in central India were greater compared to that in western India, where the highest volume of potholes was registered under perennial vegetation followed by agriculture–horticulture system, uncultivated fallow fields and arable lands. However, cultivated fields had less a incidence/occurrence of potholes than uncultivated fields. Similarly, the marginal land in western India registered the highest volume of potholes than other land use systems. The study gives insight to some of the researchable issues and strategies to minimize soil slumping in black vertisols, characterization of soil properties within and adjacent to potholes as well as soil and nutrient loss through potholes.

Pavement Raveling Detection and Measurement from Synchronized Intensity and Range Images

Raveling on asphalt surfaces is a loss of fine and coarse aggregates from the asphalt matrix. The severity of raveling can be an indicator of the state of pavements, as excessive raveling not only reduces the ride quality but eventually leads to pothole formation or cracking. Hence, raveling must be detected and quantified. In this study and for the first time, raveling was quantified from a combination of two- and three-dimensional images. First, a texture descriptor method called Laws’ texture energy measure was used in conjunction with Gabor filters and other morphological operations to distinguish road areas. Then, digital signal processing techniques were used to detect and to quantify raveling. Hundreds of images captured by an automated pavement surveying system were used to test and to show the promise of the proposed algorithm.

A technique to dispose waste plastics in an ecofriendly way – Application in construction of flexible pavements

Waste plastics, littered both by domestic and industrial sectors was found to be a source of raw material for the flexible pavement. Waste plastics, mainly used for packing are made up of PE, PP and PS, their softening point varies between 110 °C and 140 °C and they do not produce any toxic gases during softening. But the softened plastics have a tendency to form a film like structure over the aggregate, when it is sprayed over the hot aggregate at 160 °C. The formed PCA is a better raw material for the construction of flexible pavement. PCA was then mixed with hot bitumen of different types and the mixes were used for road construction. PCA + bitumen mix showed improved binding property and poor wetting property. The sample showed higher Marshall Stability value in the range of 18–20 kN and the load bearing capacity of the road is increased by 100% and there is no pothole formation. The roads laid since 2002 using PCA + bitumen mixes are performing well. A detailed studies on the performances of these roads shows that the PCA bitumen mix roads are performing well. This is an eco friendly and economic process too.

The Environmental Impact of not Having Paved Roads in Arid Regions: An Example from Mongolia

There is a generally held perception that roads have neg-ative environmental impacts (Clevenger et al. 2003;For-man 2003; Roedenbeck et al. 2007). Ironically, thisparadigm stems from regions where fences and regulationsrestrict vehicles to paved roads. The situation is different insparsely populated rural areas in the developing world,where the scarcity of paved roads forces drivers to createtheir own tracks, often with considerable environmentaldegradation as a result. Arid and semi-arid regions, espe-cially those with communal land ownership and easilymotorable terrain, are particularly prone to this practice andthe consequent degradation is widespread—plaguingregions in Central Asia, the Middle East (Batanouny 1985),South America (Pe´rez 1991), and Africa (Rickard et al.1994). In such circumstances, the paradigm contradicts itsown purpose—paved roads here would in fact have apositive environmental impact, as they reduce the need for‘‘off-road driving’’.The land degradation that could have been avoided bythe construction of paved roads can be seen clearly insatellite imagery. We illustrate the destructive potentialthat this practice is having in Mongolia.Mongolia is a sparsely populated, landlocked countrywhich has seen an economic growth spurt since the 1990s.This growth has given rise to an increased need for trans-port by road, not just internally, but also internationally, toand from Russia and China. Yet, almost all vehicularmobility in this vast country relies on dirt-tracks—in 2008only about 2,600 km of the 49,500 km of the nationalintercity roads were paved (National Statistical Office ofMongolia 2008).The land degradation typically begins when repeatedusage renders an original track unsuitable for driving due tothe formation of washboard, ruts, potholes, and corruga-tions in the soil—a process facilitated by snowmelt, rain-fall, and sub-soil permafrost-thawing. Consequently, asystem of quasi-parallel trails is generated, denuding largeswathes of land (Fig. 1a). The communal land tenure tra-dition in Mongolia (a predominantly nomadic pastoralistcountry) and usage of rugged 4-wheel drive vehicles fur-ther compounds the problem, as there is practically norestriction to either vehicular movement or vehicle speeds.In addition to generating dust, which affects drivingsafety, the compulsory use of dirt-tracks considerablyincreases the costs of goods and public transport due toincreased fuel consumption and vehicle maintenancerequirements. However, for the low traffic densities foundon many routes here, these costs are small in comparison tothe environmental costs. The passing of vehicle-tires deci-mates native flora and fauna, and also degrades habitat(Brown and Schoknecht 2001). Moreover, vehicles compactthe ground, damaging its ability to absorb and retainmoisture and nutrients (Belnap 2002). In doing so, surfacewater flows are concentrated and speeded up, thus leadingto soil erosion, increased sediment loads in water coursesand consequently, damage to aquatic habitats and waterquality as well (Misak et al. 2002). Full re-vegetation ofdamaged swaths takes between 10 and 15 years after thetrack has ceased to be in use. However, the pioneeringplants are mostly invasive weed species, such as Tumble-weed (Salsola collina), Fringed sagebrush (Artemisia frig-ida), and Chinese wild-ryegrass (Leymus chinensis), and notthe native grasses such as Needle-leaf sedge (Carex duri-uscula) and Feather-grass (Stipa krylovii), that are socio-economically important to the indigenous pastoralists,

Management of black Vertisols characterized by pot‐holes in the Chambal region, India

AbstractCrop yields in rainfed areas are primarily dependent on the rainfall pattern and stored soil moisture. High smectite clay causes the formation of cracks, which are a striking feature of black Vertisols which are also distinguished by the presence of pot‐holes. Soil water is recharged during the rainy season via these cracks, which also results in pot‐hole formation. This study was undertaken to evaluate the effect of different conservation measures on pot‐holes. Length, width and depth were measured during dry spells after the onset of the monsoon under various field treatments. The results indicate that uncultivated fields have a greater volume of pot‐holes (573 m3/ha) than cultivated ones due to unbroken gentle slopes, which would have caused silt‐laden runoff to travel longer distances to form pot‐holes. The results show that among the cultivated fields, a control plot had the maximum volume of pot‐holes (450 m3/ha), followed by a conservation bench terrace (CBT) (231 m3/ha), residue incorporated (RI) fields (142 m3/ha) and contour furrow areas (CF) (119 m3/ha). The CBT field treatment had a higher volume of pot‐holes despite a high percentage of micro‐aggregates and high total porosity.

Investigation of the Use of Limestone Screenings in Roadway Construction

Disposal of limestone screenings, or limestone fines, creates problems for many quarry operations. Much of the fines is either stockpiled or deposited back into the quarry pit. A laboratory study and pilot project were conducted to determine if limestone screenings could be stabilized and used as a structural layer in road construction and, if so, to evaluate their effectiveness through performance monitoring. Compaction, unconfined compression, freezing and thawing durability, and wet–dry durability tests were performed. Falling weight deflectometer tests were used to compare stiffness differences, and temperature data were used to determine the number of freezing and thawing cycles that each test section underwent. Laboratory compaction and unconfined compression test results confirmed that limestone screenings can be stabilized for use as a structural layer. Freezing and thawing and wet–dry durability test results showed that cement kiln dust (CKD) is not an acceptable stabilizer because of its poor durability performance. Class C fly ash (FA) and CKD mixtures were determined to be acceptable. Test Section 1 (30% CKD) most likely failed due to freeze–thaw action. Visual observations showed good performance of Test Section 2 (15% FA and 15% CKD), and the two control sections showed no rutting or pothole formation.