Thin Whitetopping Research Articles

Comprehensive Review of Thin White Topping for Asphalt Road Enhancement

Comprehensive Review of Thin White Topping for Asphalt Road Enhancement

Optimizing durability of the thin white topping applying Taguchi method using desirability function

White topping is a relatively new rehabilitation technology for giving strength to Asphalt pavement. Time to time resurfacing is necessary for bituminous pavement in hot climate region of India where heavy vehicles, operating under frequent start/stop conditions. So, we can apply white topping where recurring problem arises due to rutting of bituminous pavement. In India, endeavors to develop both traditional and ultra-thin white toppings as well as thin white toppings were built on an experimental basis, but their outcomes have not been specifically tracked. The performance and existence of pavement is affected by a range of things such as the load imposed by means of the site visitors plying on it, the weather, indigenous materials used and renovation standards. To examine their overall performance below Indian site visitors and climatic conditions road roughness test, compressive power by way of taking concrete cores and visible inspection survey has been executed.Moreover, the necessity for the new sorts of concrete with higher durability and higher overall performance for precise purposes, as compared to the available sorts, is sensed greater than ever. The concrete durability, laid low with one kind of variables consisting of compressive strength, resistance and permeability, has already attracted the attention of many researchers. In this research the effects of adding white topping concrete, changes in the humidity and temperature of the rehabilitated surrounding atmosphere are investigated to observe whether they will cause any growth in compressive strength and resistance of concrete and/or any decay in its permeability. For this, the Taguchi method is carried out as a method of design of experiment to get the most excellent level for every variable, accompanied by applying the regression approach to model the variables. finally, the final most desirable degrees for the sturdiness are offered primarily based on the desirability function.

Study on Comparision of Life Cycle Cost Between White Topping and Btiuminuos Overlays

Abstract: The focus of the present study is on construction of long-lasting and better performing pavements. Usually, with respect to the rehabilitation of the pavement, the construction agencies go with the bituminous overlays as their first priority without considering the condition of the existing pavement structure. But the advantages of cement concrete (CC) pavements that have proved to perform better and are considered to be long-lasting must be explored. The use of Thin White Topping (TWT), and Ultra-Thin White Topping (UTWT) pavements is currently gaining popularity in the area of pavement construction.. And hence it is the era where the Thin and Ultra-Thin White Topping methods are gaining their popularity. The present study provides details on the approaches adopted in measuring the performance of TWT and UTWT pavement surfaces built of plain cement concrete, cement in cement concrete replaced by 50% ground granulated blast furnace slag, cement in cement concrete replaced by an admixture called Conplast NC, and 50% of cement in cement concrete replaced by GGBS and Conplast NC. The study also includes comparison of strength of composite beams of various thicknesses when subjected to repeated wheel loads under Modified Immersion Wheel Tracking Equipment when supported by a 50mm thick bituminous layer below. The performance results on the tests on the specimens of 150mm thick admixture-added CC beam and the 100mm thick GGBS-cumAdmixture-added CC beam were almost the same. This indicated that the thickness of cement concrete slabs could be reduced by 50mm by replacing 50% of cement in cement concrete with GGBS-cum Admixture-added CC beam. Based on the study on cement concrete, and composite beams, and the study of life cycle costs, it was observed that a road surface with cement concrete overlay would be more appropriate when compared to a bituminous concrete (BC) overlay. Together, these findings suggest that the concrete overlay acts as the most economic method.

Performance of Rubberized Concrete and the Effect of Temperature and Stainless Steel Fibers

Rubberized concrete is widely used in construction by utilizing the advantages of partially replacing fine or coarse aggregate with rubber to enhance several properties of concrete and provide an environmentally friendly solution. This paper experimentally explores the influence of utilizing crumb rubber (CR) as an alternate coarse aggregate in concrete. Concrete specimens were prepared with different percentages of rubber (0%, 5%, 10%, 15%, and 20%). Additionally, other parameters, such as freezing–thawing cycles, temperature, and stainless steel fibers (SSFs), were investigated. The workability of fresh concrete and the compression properties of hardened concrete were examined. Reductions in the mechanical properties of rubberized concrete were obtained. The compressive strength reductions ranged between 13% and 50%, based on the percentage of CR in the concrete mix. However, a lesser unit weight and higher toughness were obtained relative to conventional concrete. The average unit weight decreased by 1.3%, 2.5%, 3.4%, and 5.7% of the control mixture when 5%, 10%, 15%, and 20% of the CR were incorporated into the concrete mixtures, respectively. Regression models to predict the compressive strength and unit weight of concrete with CR were developed. In addition, a life cycle cost analysis (LCCA) to identify and quantify the possible benefits of using CR in concrete mixes was carried out. Using rubberized concrete mixtures for thin whitetopping offered a slightly lower net present value compared to the ordinary concrete mix.

Design and development of methodology for construction of thin white topping for rural roads in India

A large proportion of villages in India have been connected with water bound macadam (WBM) or bituminous roads. Rural roads usually have a low volume of traffic, consisting mostly of light transport vehicles with less frequency of heavy traffic. Maintenance of these roads is neglected because of the paucity of funds and the created road asset is in deteriorated condition. The non-availability of suitable soil and aggregates has made projects unviable and cost prohibitive. This aggregate scarcity will increase further as a result of environmental conservation and restriction on mining. There is a need to develop alternative pavement designs to construct sustainable and durable rural roads. The stabilization of soil/aggregate is being used worldwide towards optimal usage of scarce resources. The concepts of soil/aggregate stabilization and Cold In Place Recycling technique provide a comprehensive solution for rehabilitation of existing road and greenfield road construction. Cold In Place Recycling process allows usage of locally available marginal materials. The stabilization process can use a wide range of stabilization agents such as soil-aggregate mix, lime, cement, fly ash, foamed bitumen, emulsion, polymers, and other proprietary chemical stabilizers. Two rural roads are identified under Mukhya Mantri Gram Sadak Yojana Research and Development Scheme. Pavements are designed considering cement treated base. These roads are constructed using the Cold In Place Recycling technique. The existing water bound macadam (WBM)/deteriorated bituminous surface is stabilized with cement. Bituminous concrete and Thin White Topping are provided as wearing course. The performance of pavement is evaluated after 2 years of construction. Also, the balance life of the pavement is checked and the results are satisfactory. The stabilized pavements offer superior strength and longevity, even in extreme climatic conditions, and provide better performance. The design charts for Thin White Topping for rural roads are not available, hence the design charts for Thin White Topping of M30/M35/M40 grade concrete on Cement Treated Base of varying thickness and different subgrade CBR are prepared based on IRC 62-2014 for traffic less than 50 CVPD, 51 to 150 CVPD, and less than 450 CVPD. These charts are ready to use and act as a guide to the Field Engineers. The optimum thickness of Thin White Topping can be selected from the chart for known subgrade CBR and Traffic. The effect of variation of CTB thickness on Thin White Topping thickness can be determined from the chart.

Influence of axle load on the fatigue life of thin whitetopping with fibre-reinforced concrete

Influence of axle load on the fatigue life of thin whitetopping with fibre-reinforced concrete

REHABILITACIÓN DEL FIRME DE CUATRO GLORIETAS MEDIANTE UN REFUERZO DELGADO DE HORMIGÓN (“THIN WHITETOPPING”)

This article describes the design and construction of the structural rehabilitation of the bituminous pavement of four roundabouts by means of the arrangement of a 12 cm layer of vibrated concrete with fibres with very close joints (technique known as "thin whitetopping"). The roundabouts, which belong to the N-II National Road as it passes through La Jonquera (Spain), are subject to high levels of heavy vehicle traffic (IMDp > 4,000 heavy vehicles/day). In the project phase, the causes of deterioration of the original road surface were studied, its remaining bearing capacity was characterised and the thickness of concrete to be used was calculated. In the most damaged areas, the bituminous mixture was completely replaced by a lower quality concrete which was adhered to the concrete of the reinforcement by means of metal connectors. In addition, a detailed design of the transitions between the rehabilitated and the existing pavement and the arrangement of the joints was also carried out. Throughout the document, the different tasks carried out for the design and construction of the adopted solution are described in detail and, finally, design and construction recommendations are provided based on the results obtained. Keywords: Concrete, concrete bonding, Concrete with fibres, Reinforcement of pavements with concrete, Fuel resistance, Whitetopping.

A critical review of the PCA and IRC methods of thin white topping pavement design

The concept of Thin White Toppings (TWT) is gaining momentum across the nations as an economical and durable rehabilitation technique for the bituminous roads in distress compared to repairs or rehabilitations done with bituminous mixes. On the other hand, constructing a completely new cement concrete (CC) pavement in these stretches by removing the existing pavement structure is a very costly alternative. So, Portland Cement Association (PCA) constructed some test sections of TWT and developed the performance equations based on the performance of the test sections. Indian Roads Congress (IRC) adopted these equations and simplified them with minor changes for calculating the stresses. These changes lead to overestimation of stresses and subsequent reduction in cost saving for TWT compared to constructing a new concrete pavement. The present study examines the differences between IRC and PCA design methods for TWT by considering various parameters. Both methods consider 8 T single axle load and 16 T tandem axle load for estimating the stresses in CC layer. The stresses estimated with IRC equations are higher compared to the stresses estimated with PCA equations of the order of 40 to 50 percent for 8 T single axle load and of the order of 0 to 22 percent for 16 T tandem axle load.

English

English

A Cost Effective Solution for Repair and Resurfacing of Distressed Asphalt Pavement by Coating of Ultra-ThinWhitetopping

Fly ash, a waste derived from coal burning in thermal power plants is bounteous in India causing severe health, environment and dumping problems. Now days, it is estimated that about 150 million tons of fly ash are being produced from various thermal power plants in India. Utilization of fly ash in bulk quantities, ways and means is being discovered all over the world to use it for the construction of embankments and pavements. This way the fly ash concrete are made a 'greener' building material and the discarded natural wastes can be re-utilized, avoiding otherwise wasteful landfill and harmful open incineration. To make value added concrete for development of sustainable infrastructure there is a great need to study the technical details concerned with various industrial wastes in concrete and to reduce environmental hazards. The significant increase in the number of automobiles observed in the recent years has created a need not only for the construction of new highways but also for the maintenance and rehabilitation of existing highway networks. Pavements are prone to damage due to the repeated wheel loads as well as temperature and other environmental effects. Ultra-thin white topping (UTWT) / thin white topping (TWT) is a technique which involves placement of a thinner (than normal) thickness ranging from 2 to 4 /4 to8 inches with closely spaced joints and bonded to an existing asphalt pavement. The application of UTWT/TWT has been targeted to rehabilitate deteriorated asphalt pavements with fatigue and/or rutting distress. However the actual depth of UTWT/TWT depends on the grade of concrete used, intensity of traffic, thickness of existing asphalt pavement after milling etc. So our study is concerned with eco-efficient utilization of Fly Ash (F-class) as partial replacement of cement in concrete. The aim of the present study is to investigate the low cost UTWT/TWT made of fly ash (F-class). The fly ash (F-class) was replaced within the range of 10-40% by weight of cement. In the present study, 5 different mixes of fly ash concretes are tested for parameters like: compressive strength, flexural strength, modulus of elasticity and cost.

REHABILITATION OF LOW VOLUME FLEXIBLE PAVEMENTS BY WHITE TOPPING-A CASE STUDY

In India the nature of overlay treatment in the name of maintenance on flexible pavements is generally Hot Mix Asphalt (HMA) as this technology is in for many years. Lack of interest in selecting different resurfacing alternative is seen in road contractors because of ease in construction of HMA overlay and experience gained by them in construction of HMA overlay. Whitetopping can be a very interesting resurfacing technique for existing asphalt pavements when rutting is the major distress on pavement surface. In the present work an attempt is made to evaluate the structural and functional condition of existing flexible pavements and provide a cost effective rehabilitation solution. A network of six urban roads coming under Tumkur Municipality is selected an extensive field, laboratory investigation, pavement analysis and design of rehabilitation alternative has been carried out. The field work consists of road inventory, traffic studies, MERLIN and BBD studies. PCI is computed based on selected distress parameters (Rut, Patch, Pothole, Cracks). In addition, IRI, BI and characteristics pavement deflections are computed from MERLIN and BBD surveys. Based on PCI, IRI, BI and deflection values pavement rehabilitation measures are considered. The summary of overall condition assessment on functional and structural evaluation in majority of the cases has resulted in ‘resurfacing’. In the present study an attempt has been made to design whitetopping section and asphalt overlay as a minor rehabilitation alternative for the in-service flexible pavements. The whitetopping design has resulted in 5 thin whitetopping sections and 1 ultra-thin whitetopping section. Strengthening by asphalt overlay has resulted in different overlay thicknesses for selected roads. Finally cost comparison between whitetopping and asphalt overlay reveals that for majority of selected roads whitetopping proves to be a cost effective rehabilitation solution than the asphalt overlay.

Fatigue-Life Prediction of Full-Scale Concrete Pavement Overlay over Flexible Pavement: Super-Accelerated Pavement Testing Application

Thin concrete pavement overlay placed on the top of flexible pavements is referred to as a thin whitetopping (TWT) pavement, which is one of the rehabilitation treatments for deteriorated flexible pavements. The primary goal of this study is to evaluate the fatigue performance of full-scale TWT pavement due to repeated traffic loading. Super-accelerated pavement (SAP) tests on full-scale TWT concrete slabs were performed under static and constant cyclic loading. The stationary dynamic deflectometer (SDD) (a truck-mounted SAP testing device) was used to statically and dynamically load the TWT slabs. In order to monitor the response of the TWT slabs, accelerometers and linear variable differential transformers (LVDTs) were installed and the dynamic displacements of slabs were recorded during the entire testing period. The test results show that the tested slabs have dynamic displacement peaks around the number of load repetitions corresponding to the first visible cracks. The dynamic displacement increased at a higher rate after the occurrences of the first visible crack. In addition, the tested slabs showed a stress redistribution phenomenon during the crack propagation. The concepts of the stress level and equivalent fatigue life were used to eliminate, in part, influences of other factors (that is, the water-cement ratio [w/c] and aggregate type and gradation) and correct the effect of different stress ratios, respectively. The S-N curve developed from this study was very close to Thompson and Barenburg’s S-N curve after the application of the equivalent fatigue-life concept.

Revised Design Procedure for Thin and Ultrathin Bonded Whitetopping

Development of design procedures for bonded whitetopping overlays has been based on the assumption that failure mechanisms are a function of overlay thickness; namely, thin whitetopping results in longitudinal cracking and ultrathin whitetopping results in corner cracking. However, field data from whitetopping sections indicate that failure modes are dictated by slab size rather than overlay thickness. The revised procedure presented here for thin whitetopping and ultrathin whitetopping offers four primary enhancements to the Portland Cement Association and Colorado Department of Transportation procedures that traditionally have been used: (a) the failure mode is dictated by the joint spacing and not the overlay thickness, (b) the stress adjustments factors have been calibrated with an extensive data set, (c) the equivalent gradients to be used as the design input are defined according to the pavement structure and geographical location of the project and, (d) the effect of temperature change on hot-mix asphalt stiffness is considered. Comparisons of the predicted performance for the revised procedure with the actual performance for four separate projects showed that the predicted thicknesses are reasonable. It was also found that the predicted thickness obtained with the revised procedure was sensitive to the thickness of hot-mix asphalt, the level of traffic, and the modulus of rupture of the portland cement concrete, as expected.

Redefining the Failure Mode for Thin and Ultrathin Whitetopping with 1.8- × 1.8-m Joint Spacing

Bonded whitetopping is a thin concrete overlay on a distressed asphalt pavement. The existing design procedures for bonded whitetopping assume the failure mode is a function of the overlay thickness. It has been traditionally assumed that the failure mode for thin whitetopping [overlay thickness greater than 102 mm (4 in.) but less than 152 mm (6 in.)] is transverse cracking, and the failure mode for ultrathin white-topping [overlay thickness between 51 mm (2 in.) and 102 mm (4 in.)] is corner cracking. However, the performance of in-service whitetopping overlays indicates that the actual failure mode is dictated more by slab size than by overlay thickness. For both thin and ultrathin whitetopping with 1.8-m (6-ft) joint spacing, cracks initiate at the bottom of the overlay at the intersection of the transverse joint and the wheelpath and propagate longitudinally. At times, these cracks will continue to propagate in the longitudinal direction and intersect the adjacent transverse joint; at other times, they will turn on a diagonal and propagate toward the lane–shoulder joint. To verify this failure mechanism observed in the field further, a three-dimensional finite element model subjected to environmental and wheel loads was developed. The results support the proposed failure mode, showing that the critical tensile stress is indeed in the wheelpath and at the bottom of the portland cement concrete overlay. This type of failure results in a longitudinal crack.

Use of Benkelman Beams for Measuring LTE in Whitetopping: An Alternative Tool to FWD Test

Whitetopping is a rehabilitation or structural strengthening alternative on hot mix asphalt (HMA) pavement. It is constructed on the top of existing HMA pavement. Generally, falling weight deflectometer (FWD) deflection measurements are used to obtain the load transfer efficiency (LTE) of the transverse joints. However, the use of FWD in India has been very limited so far because of its high cost and difficulties encountered in maintaining the equipment. Therefore, a need has been aroused to identify an alternative to FWD test, which can be cost effective and easily available. In this work, Benkelman beam deflection test has been conducted using two Benkelman beams simultaneously placed on two adjacent slabs near transverse joint for measuring LTE of 150 mm thick in-service thin whitetopping constructed at Dahanukar Colony, Kothrud, Pune city. An alternative tool has been developed for measuring LTE in whitetopping.

Effect of Different Dosages of Polypropylene Fibers in Thin Whitetopping Concrete Pavements

This article describes how an experimental laboratory study was undertaken to evaluate the engineering properties for four different concrete mixtures: a control mixture with no fibers and mixtures with polypropylene fibers using the following dosages: 3, 5, and 8 lb/yd³ (1.78, 2.97, and 4.75 kg/m³). Various samples were collected during construction and tested for compressive strength, flexural strength, and toughness using cylindrical, prismatic, and round panel specimens. Because the toughness results cannot be taken into account using common concrete pavement design methodologies, which is especially true for the round panel test, an analysis was performed that took into account the additional benefit of the polypropylene fibers using a residual strength approach. It was concluded that the effect of the addition of fibers was best captured using the round panel test. It was also concluded that the use of 5 lb/yd³ (2.97 kg/m³) fiber dosage had the best value-added benefit to the mixture.

UTW Behavior on Asphalt Pavements Tested with HWLS

The objective of this research is to evaluate how the physical properties and thickness of asphalt pavements influence behaviors of ultra thin whitetopping (UTW). The results of the three-dimensional finite-element method reveal that properties of asphalt and concrete layers, bonding between the two layers, and temperature strongly affect the distress of UTW. Based on results of FEM analysis, a wheel tracking device called the “heart wheel load simulator (HWLS)” was developed and used to perform an experiment to observe behavior variation in accordance with asphalt and concrete layer thicknesses as well as temperature. The results of HWLS simulation show that the effect of temperature is not significant and the increase of the tensile strain with the increase of a load is relatively small for a 100mm concrete layer, as compared to a 50mm concrete layer. In addition, for a 50mm concrete layer with a less than 150mm asphalt layer, the increased ratio of the tensile strain at the bottom of the concrete slab is significantly higher. Therefore, this research recommends that an at least 150mm asphalt layer after milling be required in order to apply UTW safely.

DYNAMIC BEHAVIORS OF ULTRA THIN WHITE TOPPING STRUCTURE UNDER TRAFFIC LOADS

ホワイトトッピング工法は, 既存のアスファルト舗装の上に薄いコンクリート版を施工する修繕工法の一種である. その力学的な特性は, コンクリート版とアスファルト層が一体となって挙動することにある. ホワイトトッピング工法では, アスファルト層の力学的寄与分が大きいため, その挙動が舗装全体の挙動に大きく影響する. 構造設計においては, このようなアスファルト層の効果を考慮した構造モデルが必要となる. 本研究では, 3次元有限要素法に基づいた構造モデルを開発した. このモデルは, 材料モデルとして一般化 Voigt モデルを用い, アスファルト層の粘弾性効果を考慮する. 載荷試験の結果から本構造モデルの検証を行うとともに, 交通荷重に対するホワイトトッピング構造の力学的挙動について考察した.

Performance, Analysis, and Repair of Ultrathin and Thin Whitetopping at Minnesota Road Research Facility

Thin and ultrathin whitetopping overlays are becoming a more common method of pavement rehabilitation. It is important to gain information on the types of distresses that occur in the overlays and effective repair techniques. In 1997 the Minnesota Department of Transportation constructed several thin and ultrathin whitetopping test cells at the Minnesota Road Research (Mn/ROAD) facility. Typical distresses included corner breaks, transverse cracks, and reflective cracks. The finite element program ISLAB2000 was used to investigate stress patterns and their relation to the distresses. Different techniques for repairing ultrathin whitetopping were investigated. Various techniques were also used to deter reflective cracking, including various bond-breaking materials and full-depth sawing at strategic locations along the longitudinal joint to prevent cracks from propagating into adjacent panels at misaligned transverse joints. Four of the six sections had present serviceability indexes (PSIs) greater than 3.5 before the repairs, showing that a good level of performance has been maintained after 4.7 million equivalent single-axle loads. The two sections that exhibited the largest drop in PSI were the overlays with 1.2- × 1.2-m (4- × 4-ft) panels. The repairs made in sections containing these panels have brought the PSI back up to an acceptable level (PSI > 3). The thin and ultrathin whitetopping test sections at Mn/ROAD have shown that whitetopping is a viable rehabilitation alternative for asphalt pavements. The importance of choosing an optimum panel size was exhibited. It has also been shown that when necessary, it is easy to repair ultrathin whitetopping sections. Various techniques for repairing each type of distress have been summarized.

Mechanistic Design of Thin Whitetopping Pavements in Colorado

A mechanistic design procedure was developed for the state of Colorado to determine the required concrete thickness of thin [12.7 cm to 17.8 cm (5 in. to 7 in.)] whitetopping overlays on asphalt pavements. Field testing was conducted to evaluate critical load locations for whitetopping with joint spacing up to 3.66 m (12 ft). The load-induced flexural strains were used to calibrate fully bonded stresses computed by applying finite element analysis techniques to partially bonded stresses measured in the field. For each test section, load testing was conducted throughout the course of a day to develop a temperature correction for the critical stresses derived for zero temperature gradient (zero slab temperature curling). Equations predicting the critical concrete flexural stresses and asphalt concrete strains for use in whitetopping were developed. A mechanistic design procedure is described that allows the evaluation of trial whitetopping thicknesses and joint spacings. The procedure computes the concrete and asphalt fatigue life for specific material properties. Iterations are required to determine the appropriate parameters that provide the required design life for both concrete and asphalt layers. In addition to the design procedure, the effect of surface preparation during construction was studied by comparing identical slabs constructed on milled and unmilled asphalt. It was concluded that existing asphalt pavement should be milled and cleaned before concrete placement for an overall reduction of 25 percent in the critical load-induced stresses. However, new asphalt, such as that placed in repair patches, should not be milled before concrete placement to avoid a 50 percent increase in critical load-induced stresses.