Ultrathin Whitetopping Research Articles

Strain-hardening cementitious composites ultra-thin whitetopping (SHCC-PUTW) for rapid asphalt pavement rehabilitation

Whitetopping is the concrete overlay used to upgrade distressed asphalt road surface, where the distressed asphalt is milled off and concrete is cast on top as the new wearing course. However, it requires road closure for multiple days, which is not accepted in many urban constructions. Precast concrete pavement (PCP) is the technology that shortens the construction period. However, it is associated with complicated construction procedures due to the brittleness of conventional concrete. In this paper, a brand-new PCP design, i.e., ultra-thin whitetopping (PUTW) is studied and applied in a demonstration project in Singapore. The PUTW is enabled by employing strain-hardening cementitious composites (SHCC) with significantly higher ductility than conventional concrete. The current work includes four parts. First, the desirable combinations of SHCC’s tensile and compressive uniaxial behaviors are identified in the analytical model and experimental study to enhance its flexural strength for pavement application. Second, the slab-to-slab joint efficiency in the PUTW, the critical mechanism in the structural design, is examined and validated with a full-scale cyclic wheel test. Third, the structural performance of the entire SHCC-PUTW is examined in a new finite element (FE) model validated against the wheel test. Based on the FE model, parametric studies on the SHCC material properties and PUTW slab dimensions are conducted to optimize the structural design. Fourth, a small-scale field project on the Jurong Island of Singapore, which involves the fabrication and installation of 11 SHCC-PUTW slabs, is reported to assess the feasibility of this new structural design.

Interface horizontal shear strength requirement in Ultra-thin whitetopping (UTW) pavement.

Ultra-thin whitetopping (UTW) is a thin (5-10 cm) layer of concrete overlaying over an existing asphalt pavement. This concrete layer is bonded on the asphalt surface. Although UTW has been successful in strengthening asphalt pavement, in some cases, the composite pavement may debond at the interface under the concrete slab due to high shear stress. This paper aims to determine the interface shear strength required for UTW pavement systems using theoretical methods and calibrated numerical models (FEMs). The study analysed 432 pavement scenarios with different slab sizes, thicknesses, and material properties. The results show that higher shear stress occurs when the asphalt modulus is stiffer. The size of the slab, the modulus of the supporting layer, and the asphalt thickness have only a minor effect on the shear stress value. However, the thickness of the concrete slab significantly affects the maximum shear stress in the UTW, with an increase of up to 36.6% when reducing the slab thickness from 100mm to 50 mm. The FEM calculations can be used to determine the required interface horizontal shear strength for UTW.

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.

Experimental Investigation of Cracking and Impact Resistance of Polymer- and Fiber-Enhanced Concrete for Ultra-Thin Whitetopping.

In order to investigate the effectiveness of polymer modification and fiber reinforcement on the cracking and impact resistance of concrete materials prepared for ultra-thin whitetopping (UTW), carboxyl butyl benzene latex and polyformaldehyde fibers were added to the conventional cement concrete mix. In addition, test methods that used an asphalt mixture performance tester (AMPT) and mechanical rammer were developed to evaluate concrete cracking and impact resistance, respectively. Results from the AMPT test revealed that the cracking resistance can be enhanced with polymer and fiber, especially the initial tensile load peak, which can be improved by more than 40% when fiber and polymer compound modification is applied. Meanwhile, the impact loading test revealed that the inclusion of both fiber and polymer results in a two-fold increase in the number of impacts before visible cracking occurs, and the number of blows to failure increased by 21.4%. Moreover, microstructures were investigated by scanning electron microscopy (SEM) to confirm the reinforcing mechanism of both polymer modification and fiber reinforcement.

Sustainable concrete pavements for low volume roads-Scientometric analysis of the literature

Developing countries like India invest huge amounts of money for the construction and maintenance of different roads which includes all types of roads. In this research paper a critical review of literature on sustainable pavements for low volume roads was made using sustainable materials for paving Ultra-thin white topping concrete overlays sustainable new pavements like Pervious concrete pavements, Roller compacted concrete pavements, Cell filled concrete pavements, Self-Compacting Concrete (SCC) Pavement and additional discussion on energy harvesting pavements done. Ultra-thin white topping concrete overlay has better-proven performance but interface bond strength is very critical to resist shear stresses which cause debonding of composite concrete layers. The porous cement or bituminous concrete helps to recharge the groundwater reducing the heat islands and makes nature eco-friendly but on the other hand clogging effect can retain the water in the pavement and causes failure of the pavement. Roller compacted concrete pavement, Self-Compacting Concrete (SCC) Pavement and cell-filled concrete pavements are good in terms of performance disadvantages are less. The Indian standard code should be developed to implement energy harvesting pavements that help to produce electrical energy which meets the need of society. Further Scientometric analysis of sustainable concrete pavements for low volume roads done using VOS viewer software and the database of research work from Dimensions software. From the research gap in keyword occurrences on this topic, it is observed that rice husk ash, recycled aggregate, aluminum dross and fatigue, modulus of elasticity has a wide gap indicating further research on the combination of these key words make sustainable concrete pavements further discussed regarding high impact research papers published, similarly countries were discussed in detail.

Analytical modelling of ultra-thin white topping cement concrete overlay on bituminous concrete pavement using ANSYS

PurposeThe ultra-thin white topping (UTW) is a cement concrete overlay of the thickness of 50–100 mm on bituminous concrete pavements with surface failures. This is a long-lasting solution without having short-term failures. This paper aims to design an ultra-thin cement concrete overlay using a developed critical stress model with sustainable concrete materials for low-volume roads.Design/methodology/approachIn this research paper, a parametric study was conducted using the ultra-thin concrete overlay finite element model developed with ANSYS software, considering the significant parameters affecting the performance and development. The non-linear regression equation was formed using a damped least-squares method to predict critical stress due to the corner load of 51 kN.FindingsThe parametric study results indicate that with a greater elastic modulus of bituminous concrete, granular layer along with 100 mm thickness of concrete layer reduces the critical corner stress, interface shear stress in a significant way responsible for debonding of concrete overlay, elastic strains in the pavement further the concrete overlay can bear infinite load repetitions. From validation, it is understood that the non-linear regression equation developed is acceptable with similar research work done.Originality/valueFrom the semi-scale experimental study, it is observed that the quaternary blended sustainable concrete overlay having a high modulus of rupture of 6.34 MPa is competent with conventional cement concrete overlay in terms of failure load. So, concrete overlay with sustainable materials of 100 mm thickness and higher elastic modulus of the layers can perform in a sustainable way meeting the environmental and long-term performance requirements.

A Study on the Influence of Interface Friction on Deflection and Stress of Ultrathin Whitetopping Using Finite Element Analysis

A Study on the Influence of Interface Friction on Deflection and Stress of Ultrathin Whitetopping Using Finite Element Analysis

Performance Studies on white topping layers over flexible pavement

The main focus of the present era is to construct a long-lasting and better performing pavement. 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 CC pavements have proved that they perform better and are long-lasting as new pavement as well as when used for rehabilitation of the existing pavement. And hence it is the era where the Thin and Ultra-Thin White Topping methods are gaining their popularity. Hence in this study, in order to arrive at the performance of the TWT and UTWT methods, various types of basic and the performance tests have been carried out with different combinations of concrete i). Plain Cement Concrete ii). Cement replaced by Ground Granulated Blast furnace Slag (GGBS) (50%) iii). With admixture (Conplast NC) iv) 50% Ground Granulated Blast Furnace Slag GGBS + Conplast NC. Later to understand the performance of these combinations, the composite beams with varying thickness are subjected to repeated wheel loads under Modified Immersion Wheel Tracking Equipment along with a bituminous layer of 50mm thick below the cement concrete layer. The performance results of 150mm thick admixture added CC beam and the 100mm thick GGBS & Admixture added CC beam has almost the same value. Hence, it can be concluded that the slab thickness can be reduced by 50mm by replacing 50% GGBS to the Admixture added CC beam.

Evaluation of Bonded Concrete Overlay of Asphalt under Accelerated Loading

Bonded concrete overlay of asphalt (BCOA), previously known as ultra-thin whitetopping (UTW), has been widely used to repair aged asphalt concrete (AC) pavements with moderate distresses. Because of the increasing costs of roadway maintenance, Louisiana has a great interest in determining whether thin BCOA (usually 2–6 in.) is a suitable and cost-effective alternative to the current practice of roadway maintenance. The objective of the study was to evaluate the performance of BCOA pavement and to identify the influence of in-situ interface bond strength on the performance of BCOA pavements. Three full-scale BCOA test sections with thicknesses of 6 in., 4 in., and 2 in. of Portland cement concrete (PCC) over an aged asphalt pavement were tested under accelerated pavement test (APT) loading under typical pavement conditions in southern Louisiana. Each section was trafficking-loaded to a failure (i.e., all the slabs in the loading path were cracked) under alternating load magnitudes of 9 kips and 16 kips of the ATLaS dual-tire wheel load. A falling weight deflectometer (FWD) backcalculated the effective thickness, a trench-cutting investigation was undertaken, and in-situ pull-off test revealed that a good bond was established initially between the PCC and AC layer. Several non-destructive test (NDT) methods indicated that the distresses of a BCOA slab could be coupled with a possible debonding at the PCC-asphalt interface. This paper mainly focuses on the APT results and the performance of BCOA test sections with different overlay thickness.

Evaluation of novel jointless engineered cementitious composite ultrathin whitetopping (ECC-UTW) overlay

The objective of this study was to evaluate the construction, material characterization, initial structural assessment, and cost of a novel jointless Engineered Cementitious Composite Ultra-Thin Whitetopping (ECC-UTW) overlay. After construction, early-age cracks (from less than 0.25 mm to up to 2.54 mm width) were observed in the 101.6-mm (4 in.) jointless ECC-UTW section; yet, the majority of the cracks coincided with areas where fiber clumps were observed during construction and places of heavy instrumentation. On the other hand, no cracks were observed in the 63.5-mm (2.5 in.) jointless ECC-UTW at early ages; yet, when winter arrived, micro-cracks (<0.25 mm in width) developed. These micro-cracks were attributed to the normal functioning of the ductile pseudo strain-hardening (PSH) mechanism of ECC materials. Falling Weight Deflectometer (FWD) evaluation conducted before and after the construction of the UTWs showed a significant reduction in pavement deflection after construction. This deflection reduction was much more substantial for thicker 101.6-mm UTWs; yet, no major difference in deflection reduction was found between the 101.6-mm ECC and the 101.6-mm regular concrete UTW sections. The 28-day compressive and flexural strength of ECC evaluated from field specimens underperformed that of previous studies by 9.6% and 14.8%, respectively; however, deflection capacity slightly outperformed that of previous studies by 4.1%. The flexural performance of the ECC material was vastly superior to that of regular concrete exceeding the flexural strength by 92%. All specimens evaluated in uniaxial tension exhibited a PSH behavior after first-cracking; however, the tensile strength and tensile ductility values obtained underperformed expected values for ECC M3-15% and exhibited substantial variability. Uniaxial tensile test results from field specimens were deemed unreliable. Cost analysis results showed that a cost reduction of 14.8% per lane kilometer is expected by implementing the proposed jointless ECC-UTW system compared to that of the regular jointed concrete UTW. The greatest construction cost savings for utilizing ECC originates from its potential jointless attribute and its reduced thickness.

A case study on maintenance of bituminous concrete pavement considering life cycle cost analysis and carbon footprint estimation

Transport infrastructure has a huge impact on the social and economic scenario of any nation across the world. The selection of pavement maintenance should be based on sustainable concept meeting the sustainability and Long-term performance requirements. Bituminous concrete pavement maintenance with a bituminous concrete overlay is not a better option whereas the concrete overlay is having better performance across the globe. In this paper, an case study was conducted on a bituminous concrete pavement including its design, life cycle cost analysis and greenhouse gas emissions using life cycle approach with maintenance options of bituminous concrete overlay and a Ultra-thin cement concrete overlay. It is observed when compared with bituminous concrete overlay, the Ultra-thin white topping concrete overlay with sustainable materials is the better option as the life cycle cost analysis using net present value method greenhouse gas emission are little bit higher when compared with the other using life cycle analysis. The study concludes maintenance of bituminous concrete pavement with Ultra-thin white topping concrete overlay the inclusion of sustainable materials is the better option since it improves long-term performance of the pavement and further considering the economic and environmental point of view.

Using post-cracking strength to determine flexural capacity of ultra-thin whitetopping (UTW) pavements

Utilizing fibrillated polypropylene fibers (FPP) in Ultra-thin whitetopping (UTW) has become increasingly popular to improve the flexural capacity of concrete slabs. The calculated flexural strength (i.e., modulus of rupture (MOR)) depends on the elastic formula of ASTM C78 does not illustrate the fiber’s benefits. Therefore, the concept of effective modulus of rupture (MOReff.) that is determined from the equivalent flexural strength ratio has been used to quantify the added flexural capacity of fibers on unreinforced concrete. The purpose of this study is to investigate the benefits of testing the FRC/asphalt composite beam on the flexural capacity of UTW. Three main parameters have been taken into consideration: FPP content, pavement thickness, and failure mode. Furthermore, comparison was made to verify the effectiveness of composite beams for flexural capacity. Six different cases of concrete beams and ten cases of FRC/asphalt composite beams were performed. The results of the composite beam showed that the flexural capacity was higher than the capacity of the concrete layer. In addition, using FPP in the composite beams improved the MOReff.. The results also revealed that testing UTW under noncommon failure modes did not reflect the real flexural capacity of UTW. The required UTW thickness depends on the proposed flexural capacity of the composite beam being less than the required thickness that is calculated depends on the concrete beam.

Research on Interlayer Bonding Treatment Technology of Ultra-Thin Whitetopping Material

Ultra-Thin Whitetopping has been studied and applied abroad as an emerging asphalt pavement overlay and pavement surface layer structure. UTW has the advantages of economy, durability and energy saving, and has broad prospects in urban road asphalt pavement maintenance, rural road surface, airport road surface and so on. For the UTW structure, the bonding condition between the board and the base layer has an important influence on the performance and life of the UW structure. The destruction of the interface between the layers is one of the important reasons for UTW damage. In this paper, the self-developed test piece forming mold was used to carry out the overlap test and the split test of the test piece to carry out the UTW interlayer adhesion performance test. The best interlaminar material and interlaminar treatment is obtained by drilling and engraving the interlayer polymer paste.

Three‐dimensional FEM loading stress analysis on a new airport concrete pavement ultra‐thin whitetopping overlay structure

In order to solve capability problems occurred in airport pavement slabs, a new airport concrete pavement ultra‐thin whitetopping (UTW) overlay structure was put forward on the basis of UTW theory. By modeling the structure in the FEM software ANSYS and applying loads on it, the structural critical loading position was determined, stress variation pattern at the bottom of the overlay slab was studied regarding the changes in overlay slabs' size and thickness as well as the bonding conditions between the asphalt overlay and UTW overlay. Meanwhile, the impact of the asphalt overlay on the tensile stress at bottom of the UTW overlay slab, which is strongly influenced by thickness and elastic modulus, was also explored. In order to minimize the tensile stress at the bottom of the overlay slab and prolong the lifespan of the pavement structure, the size and thickness of the UTW overlay should be strictly controlled—the size should not exceed 1.8 × 1.8 m while the thickness should be no less than 7 cm, and asphalt with elastic modulus over 1,500 MPa was recommended to be chosen as the raw material for the asphalt overlay.

Experimental investigation of interface treatment technique on interface shear bond fatigue behavior of Ultra-Thin Whitetopping

The bonded concrete overlays on existing asphalt pavements are classified into three subcategories namely whitetopping, thin-whitetopping and Ultra-Thin Whitetopping (UTW). The design service life of UTW overlays depends on several factors such as interface bond strength, slab thickness, slab size, material strength and underlying material condition. The quality of the interface bond depends on both surface preparation and the UTW placement procedure. The interface bond between two layers helps in the monolithic action of the pavement section by shifting the neutral axis from the middle of the UTW slab to the bottom of UTW slab. The composite action had a direct impact on the long-term performance of the UTW overlays. To assure good bonding, milling method is usually applied at the interfaces during UTW overlay construction. The interface bond strength due to milling technique can be measured with the help of several devices arranged by different laboratories. This paper investigates the interface shear bond strength and shear fatigue behavior of UTW pavement for different interface treatment techniques. For this experimental purpose, a laboratory direct shear testing method and procedure was used. Two interface treatment technique like groove and piercing method have been analyzed. Interface treatment with piercing technique had shown highest shear bond strength and k-modulus values. Incorporating groove interface technique with an inclination of 0–45 degrees and piercing interface treatment has been proposed. The interface shear bond fatigue behavior of piercing treatment technique with different debonding conditions are discussed. As expected the increase in debonding leads to decrease in interface shear stress and fatigue performance.

Interface Bond Strength of Ultra-Thin Whitetopping (UTW) and Hot Mix Asphalt (HMA) Composites by Direct Shear

Abstract Whitetopping is a portland cement concrete (PCC) overlay that is constructed on the top of existing bituminous or hot mix asphalt (HMA) pavement. The design and construction of UTW over HMA enables the composite to act as a monolithic layer. This article presents the findings of a laboratory study performed on interface shear strengths of UTW and HMA composites by direct shear approach. The objectives of the study were to evaluate the main effects of (i) different interface treatments, (ii) variation in the design binder content of HMA, and (iii) temperature conditioning and moisture conditioning on the interface shear strength. Based on the results of interface shear strength tests, the range of bond strength of UTW-HMA was found to be 0.22–1.29 MPa. Other factors like age of UTW, temperature conditioning, and moisture conditioning also had significant effects on the interface shear strengths of UTW-HMA composites.

Mechanical characterisation of concrete-asphalt interface in bonded concrete overlays of asphalt pavements

Bonded concrete overlay of an asphalt pavement (BCOA) is a rehabilitation technique consisting of 50–175 mm thickness concrete overlay on an existing asphalt pavement. This technique, known as thin (minimum 100 mm) or ultra-thin whitetopping (thinner than 100 mm) in the past, relies on the composite action of concrete and asphalt layers acting together with a third phase of the system being the interface between the two materials. For this study, the stiffness and strength/fatigue resistance of this interface have been characterised by means of a series of laboratory tests conducted on asphalt and composite cylindrical specimens under different loading and environmental conditions. Testing conditions included wet and dry, and temperatures between 5 and 40 °C, a range applicable to BCOA asphalt bases in California. Experimental results from this study indicate the mechanical nature of the concrete–asphalt interface is strongly related to that of the asphalt. The interface stiffness showed clear time dependency, and it significantly softened under wet conditions. Experimental results from this study are in line with common belief that water is one of the critical factors leading to failure of BCOA sections, but do not support the common belief that concrete does not bond well to new asphalt.

Ultra-thinwhite topping concrete mix with sustainable concrete materials – a literature review

ABSTRACTIndia is an agriculture-based country in which preserving the life of existing bituminous pavements connecting rural areas is very much important along with development of National highways and Expressways. Ultra-thin white topping is a thin concrete overlay of 50 mm–100 mm which can be constructed on bituminous pavement with surface failures, which provides long life and low life cycle cost. Incorporation of sustainable concrete materials in these pavements will improve flexural strength, abrasion resistance and solar reflectance and reduces carbon footprint. This paper discusses the key factors affecting the performance of ultra-thin white topping pavement, UTW Concrete mix blended with binary, ternary supplementary cementitious materials from the projects executed and recent research. The importance of research on quaternary blended SCM concrete in UTW overlays for bituminous roads makes pavement economic, enhances long-term performance and durability and increased sustainability were discussed. Further finite element modelling of ultra-thin white topping was done using the ANSYS software with the results obtained from the laboratory and it is observed that for concrete mix C3 UTW pavement with thickness 100 mm and 1000 mm, joint spacing as modulus of rupture is higher than critical Corner stress.

Low E Modulus Early Strength Engineered Cementitious Composites Material

For a reliable repair solution to be provided for the sinkage of concrete pavement slabs caused by the subsidence of subgrade, low E modulus early strength high ductility engineered cementitious composites (LMES-ECC) material was developed for ultrathin whitetopping overlay application. Low modulus of the topping material is advantageous for deformation compatibility with the existing substrate concrete without the experience of high stress. The high tensile ductility of LMES-ECC further increases the deformation compatibility and suppresses the reflective cracking, which is a major failure mechanism of pavement repair. Experimental studies were conducted on LMES-ECC with respect to its compressive strength, tensile properties, cracking behavior under restrained shrinkage, and flexural properties. The compressive strength and flexural strength of LMES-ECC at 3 days reached 31 MPa and 7 MPa, respectively, which satisfied both the requirement necessary to reopen traffic and the design strength of concrete pavement material. Unlike the brittle fracture of normal concrete, multiple microcracks (i.e., average crack width below 60 μm) developed in LMES-ECC before final fracture under tension and bending; this deformation resulted in a tensile strain capacity as high as 4% (about 400 times that of normal concrete) and large vertical deflection capacity. In addition, the E modulus of LMES-ECC was measured at 14 GPa, which was significantly lower than for normal concrete. The low modulus and high deformation capacity of LMES-ECC greatly improved the deformation compatibility of the topping overlay with the old concrete substrate, avoided brittle failure or large cracks of the overlay, and contributed to more effective pavement repair.

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.