Concrete Pavement Rehabilitation Research Articles

A Numerical Study on the Crack Propagation of Homogenized Micro-Crack Crushing for Concrete Pavement

Homogenized micro-crack crushing is a new method of concrete pavement rehabilitation that makes full use of the bearing capacity of the original concrete pavement, whereby the treated pavement can be directly overlaid with hot mixed asphalt concrete. In order to solve the problem of longitudinal crack extension of a cracked core in the weak position of local pavement, the crack propagation mode of concrete slabs under low-velocity impact from different numbers and distributions of impact heads was studied using numerical simulation. Moreover, field tests were also carried out to determine the optimal layout of drop hammer impact heads, and the numerical simulation results were compared with the experimental data. The results show that, when a concrete slab is impacted by a single impact head, the bottom of the slab first cracks and then the crack develops upward until the main crack runs through the concrete slab. However, when the concrete slab is impacted by multiple-impact heads, including three or four impact heads, the concrete slab forms a triangular or quadrilateral fracture core, respectively. The numerical simulation results are in good agreement with the laboratory experiments. Through the optimized arrangement of the hammer’s impact heads, the problem of longitudinal crack extension of a cracked core can be effectively solved, and the probability of reflection cracks can be reduced.

Evaluation of the Strength Properties of Asphalt Concrete using Natural Fibres as Reinforcing Additives

The period of maintenance and rehabilitation of asphalt concrete pavement can be increased by using fibres as reinforcement in a bituminous mix. Shredded Sisal fibre (Agave sisalana) and Sponge gourd (Luffa cylindrical) were used as reinforcements in bituminous mix. The fibres were added to hot mix asphalt in varying proportion of 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight. The strength of fibre reinforced asphalt concrete was determined by conducting Marshall stability test. The tensile strength on 40 strands of fibre gave 167.43 N/mm2 and 24.58 N/mm2 for Sisal fibre and sponge gourd fibre respectively. Marshall Stability test results indicated that Sisal fibre gave minimum and maximum values of 4.46 kN and 5.54 kN, respectively, which exceeded the 3.5 kN minimum stability value for wearing course in the Nigerian General Specification for Roads and Bridges. The flow values obtained showed that the flow values are more than the 4 mm minimum value except for 0.1 sisal fibre dosage which has a value of 3.99 mm. The high flow values obtained was an indication of the reinforcing effects of the fibres which made the asphalt concrete stronger and hence have great resistance to plastic deformation.

Life Cycle Assessment of Concrete Pavement Rehabilitation: A Romanian Case Study

The most well-known and used evaluation system to determine the life cycle of a product, is the life cycle assessment (LCA). In Europe, the use of the life cycle assessment (LCA) to assess the environmental performance of products is becoming commonplace, which is why substantial efforts have been made in the last two decades to develop new life cycle assessment (LCA) methodologies and software. This paper evaluates the life cycle assessment (LCA) for the rehabilitation of a national road sector in Romania. The biggest ecological problem facing mankind is the effect of global warming and climate change associated with this phenomenon, due to the increase of the concentration of pollutants to the atmosphere, and this paper presents the results of the life cycle assessment (LCA) based on a cradle-to-gate approach. For this case study, were used three rehabilitation alternatives. These alternatives and the existing pavement structure were analysed using the GaBi software, Ganzheitlichen Bilanzierung (German for holistic balancing), to assess the environmental impact of global warming, the stratospheric impact of ozone, and the impact on human health. The results obtained in this study illustrate the importance of a life cycle assessment approach for evaluating the sustainability for different designs and for the construction of road rehabilitation options.

Roughness Modeling for Composite Pavements using Machine Learning

A large number of paved highway surfaces comprises composite pavements as a result of concrete pavement rehabilitation that uses an asphalt overlay on top of the concrete surface. Annually, billions of dollars are spent on the maintenance and rehabilitation of road networks. Roughness is one of the several indicators of road conditions used to make objective decisions related to road network management. The irregularities in the pavement surface affecting the ride quality of road users can be described by a standard roughness index defined as the International Roughness Index (IRI). Roughness prediction models can identify rehabilitation needs, analyze rehabilitation effects, and estimate future pavement conditions to implement different Maintenance and Rehabilitation (M&R) activities to extend the pavement life cycle and provide a smooth surface for road users. This study intended to develop pavement performance models to predict roughness for asphalt overlay on concrete pavement sections using the Long-Term Performance Pavement (LTPP) program database. Artificial Neural Networks (ANNs) approach was used to develop roughness prediction models. A total of 52 pavement sections with 592 data points were analyzed. Five models were developed, and the best performing model, Model 5 was found with an average square error (ASE) of 0.0023, mean absolute relative error (MARE) of 12.936, and coefficient of determination (R2) of 0.88. Model 5 utilized one output variable (IRIMean) and 14 input variables (i.e., Initial IRIMean, Age, Wet-Freeze, Wet Non-Freeze, Dry-Freeze, Dry Non-Freeze, Asphalt Thickness, Concrete Thickness, CN Code, ESAL, Annual Air Temperature, Freeze Index, Freeze-Thaw, and Precipitation). The ANN model structure utilized for Model 5 was 14-9-1 (14 inputs, 9 hidden nodes, and 1 output). Environmental impacts and traffic repetitions can cause severe damage to the pavement if timely maintenance and rehabilitation are not performed. By considering the effects of the M&R history of the pavement, it is possible to obtain realistic prediction models for future planning. Therefore, the developed ANN roughness performance models in this paper can be used as a prediction tool for IRI values and guide decision-makers to develop a better M&R plan. Local and state agencies can use available historical traffic and climatological data in the developed models to estimate the change in IRI values. Utilizing these prediction models eliminates time-consuming data collection and post-processing, and consequently, a cost reduction. This low-cost tool will improve the condition assessment and effective M&R scheduling.

Exploratory analysis of LTPP faulting data using statistical techniques

Long-Term Pavement Performance (LTPP) database that stores considerable and free-to-access pavement information provides beneficial resources to researchers to develop transverse joint faulting prediction models that are very useful for joint concrete pavement design, rehabilitation and management. To develop accurate and robust faulting prediction models, the investigation of the LTPP faulting data is a prerequisite. This study conducted an Exploratory Data Analysis (EDA) of LTPP data by performing statistical analysis and graphically displaying the relevant factors and their correlation with faulting. This analysis was conducted based on two parts of the LTPP historical data, i.e., the pre-repair and post-repair faulting. For the pre-repair data, the relevant factors in faulting are classified into four categories, namely, traffic repetition, pavement information, local climate and material properties. To better examine the effect of the relevant factors in faulting, the descriptive statistics of factors were calculated and the grey relational analysis and the simple linear regression with one variable at a time were performed. In the regression testing, the P-value shows the significance of the individual relevant factors but it is likely to contradict the realistic relationships when the spurious correlation occurs. Through a thorough investigation, the study illustrated the rationale of the occurrence of the spurious correlation. For the post-repair data, the LTPP maintenance data were examined to evaluate the effectiveness of the individual maintenance treatment by calculating the faulting reduction after applying the treatment.

Surface rehabilitation of Portland cement concrete (PCC) pavements using single or double surface dressings with soft bitumen, conventional or modified emulsions

Surface dressings are a sustainable maintenance alternative for pavements with surface distresses, due to the low amount of resources involved. This paper aims to analyze the viability of using twelve different surface dressing solutions, including three binders (conventional and modified emulsions, and a soft 160/220 bitumen) and a covering with diluted emulsion, for surface treatment of Portland cement concrete (PCC) pavements. Several test methods were used to evaluate the macrotexture, skid resistance, adhesion, and resistance to wearing on a large scale prototype. In general, single surface dressings increased further the macrotexture of the concrete pavement surface. The skid resistance of single and double surface dressings was similar. The best surface dressing in the pull-off test was that with the 160/220 bitumen. The conventional and modified emulsions presented similar mechanical adhesion in the Vialit plate test. Concerning the prototype wearing test, the best result was obtained for the double surface dressing with bitumen covered with diluted emulsion. Based on this work’s results, the surface dressings are a potential surface rehabilitation alternative for concrete pavements.

The Chemical-Mineralogical Characterization of Recycled Concrete Aggregates from Different Sources and Their Potential Reactions in Asphalt Mixtures.

The incorporation of a recycled concrete aggregate (RCA) as a replacement of natural aggregates (NA) in road construction has been the subject of recent research. This tendency promotes sustainability, but its use depends mainly on the final product’s properties, such as chemical stability. This study evaluates the physical and chemical properties of RCAs from two different sources in comparison with the performance of NA. One RCA was obtained from the demolition of a building (recycled concrete aggregate of a building—RCAB) and another RCA from the rehabilitation of a Portland cement concrete pavement (recycled concrete aggregate from a pavement—RCAP). Characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), UV spectroscopy, and atomic absorption spectrometry were used to evaluate the RCAs’ coarse fractions for chemical potential effects on asphalt mixtures. NA was replaced with RCA at 15%, 30%, and 45% for each size of the coarse fractions (retained 19.0, 12.5, 9.5, and 4.75 sieves in mm). The mineralogical characterization results indicated the presence of quartz (SiO2) and calcite (CaCO3) as the most significant constituents of the aggregates. XFR showed that RCAs have lower levels of CaO and Al2O3 concerning NA. Potential reactions in asphalt mixtures by nitration, sulfonation, amination of organic compounds, and reactions by alkaline activation in the aggregates were discarded due to the minimum concentration of components such as NO2, (–SO3H), (–SO2Cl), and (Na) in the aggregates. Finally, this research concludes that studied RCAs might be used as replacements of coarse aggregate in asphalt mixtures since chemical properties do not affect the overall chemical stability of the asphalt mixture.

Influence of recycled concrete aggregates from different sources in hot mix asphalt design

The waste generated by the construction industry generally has an undesired negative impact on both human and animal life as well as the environment. Among these wastes, recycled concrete aggregate (RCA), due to its good residual physical, mechanical, mineralogical, and chemical properties, has attracted promising potential for re-use and incorporation in the construction of new infrastructural elements. These infrastructure applications include construction of sidewalks, curb and gutters, subbase/base layers, and/or as a partial replacement of natural aggregates (NA) in the production of hot mix asphalt (HMA) mixtures. In this laboratory study, experimental research work was conducted to evaluate the influence of RCA on the mechanical properties and performance of RCA modified HMA mixtures against a control HMA mixture without any RCA. RCAs were obtained from two different concrete sources, namely: (a) one from the demolition of a building (RCAB), and (b) another one from the rehabilitation of a Portland cement concrete pavement (RCAP). Both NA and RCA were characterized taking into account physical and mechanical properties. HMA mixtures were produced using the Marshall mix-design method by replacing 0.0% (control), 15%, 30%, and 45%, respectively, of the coarse NA fraction with RCA. Thereafter, laboratory testing (i.e., Scanning Electron Microscopy [SEM], resilient modulus, indirect tensile strength, etc.) including material property characterization and performance evaluation were conducted on HMA samples. Overall, the laboratory test results showed that the RCA modified mixtures exhibited a similar behavior to conventional HMA mixtures, but with greater environmental benefits and potential cost savings through the recycling and reuse of waste concrete aggregates. However, it was observed that the laboratory performance of RCA modified mixtures is strongly dependent on the RCA source and dosage, with RCAP exhibiting superior performance over RCAB. HMA mixtures produced with RCA provided higher optimum asphalt-binder content (OAC) than that of mixes with NA.

Numerical analysis of rehabilitated concrete pavement using crack-and-seating technique

ABSTRACT Crack-and-seating is a Portland cement concrete (PCC) pavement rehabilitation technique that has been practically used to mitigate reflective cracking, however, the mechanism is not well understood. This study applied the coupling discrete-continuum modelling method to a field project, which is aimed to evaluating the effect of hammer-introduced crack on the stress at the tip of joint and at the tip of crack that control the reflective cracking of a rehabilitated PCC pavement with asphalt concrete (AC) layer. Particle Flow Code (PFC) was used for modelling asphalt overlay and the fractured PCC pavement while Fast Lagrangian Analysis of Continuum (FLAC) was used for modelling base and subgrade soil. The numerical simulation and analysis has validated that crack-and-seating can effectively reduce the shear stress at the tip of joint. Reducing the distance from the location where the hammer-introduced crack is introduced to the joint can effectively reduce the shear stress, and such distance is recommended to be 0.1–0.2 m. When the hammer-introduced crack’s length is 0.225 m, that is, the tip of crack is 1/10 of the thickness of PCC slab distant from the PCC slab surface, reflective cracking that would ultimately occur in the AC overlay can be effectively mitigated.

Investigation on the fracture mechanism of homogenized micro-crack crushing technology for portland cement concrete pavement rehabilitation

The homogenized micro-crack crushing technology for concrete pavement maintenance has received increased attention in China. To study the fracture mechanism of the homogenized micro-crack crushing technology, a low-velocity impact test system is developed and experiments using concrete slabs of different thicknesses are conducted with different drop heights and hammer weights. Furthermore, the fracture of concrete slabs under impact loading is simulated using the continuous-discontinuous element method. Finally, the fracture mechanism is investigated in a case study. It is concluded that a cylindrical compression–shear fracture surface appears under the impact head while the fractured blocks are still interlocked with each other. The main cracks in the concrete slabs are initiated and propagate parallel to the longer side of the impact head, whereas branch cracks develop perpendicular to the main cracks. These cracks radiate from the center of the impact head. The cracks inside the concrete develop upward from the bottom of the slabs. Because fractured blocks divided by micro-cracks can interlock with themselves and the crack distributions tend to be uniform, it is beneficial for portland cement concrete pavement rehabilitation to be overlaid by a hot-mix asphalt mixture.

EXPERIENCE ON IMPLEMENTATION OF HOT IN-PLACE RECYCLING OF ASPHALT CONCRETE IN UKRAINE

Rehabilitation of asphalt concrete layers of road pavements using HIR technologies enables effective elimination of surface defects (rutting, cracking, raveling, bleeding (flushing)) including defects caused by the non-conformity of asphalt concrete to the standard specifications. Due to the economical and ecological advantages, HIR technologies belong to the present-day effective alternative methods of rehabilitation of asphalt concrete pavements. In Ukraine, HIR technologies were first applied on intermediate repair works on an area of the international road I-01 “Kyiv-Chernihiv-Novyye Yarylovichi” in the 2013. Now, HIR technologies have been applied on repair works on numerical objects including areas on such state motor roads as I-01, I-06, N-09, R-10, R-67. The presented paper analyzes the results of monitoring of materials and technologies which was aimed on HIR performance investigation supported by State Road Agency of Ukraine (Ukravtodor) throughout 2014-2018. The results of monitoring of HIR technologies including laboratory evaluation of materials and also field testing of the rehabilitated pavements led to the conclusions fitted by the world-wide experience on implementation of HIR technologies. 1. Being applied to the structurally sound pavements, HIR provides effective elimination of surface defects of flexible pavement to a depth of (50-60) mm including defects caused by the non-conformity of asphalt concrete to the standard specifications. However, HIR is not suitable for existing asphalt pavements which have too much variation in asphalt concrete composition and thickness within the project limits. 2. The efficiency of asphalt pavement rehabilitation using HIR technologies largely depends on precise engineering consideration which determines the efficiency of preparatory (repair) works including some special works such as: – correction of cracks in case of cracking that extends below the depth of hot recycling; – re-compaction of an unbound base layer(s) in case of the insufficient compaction causing “alligatored” network-like cracking of asphalt pavement. 3. Proper technical and working conditions of the rehabilitated pavement during the nominal life cycle could be maintained by overlaying the surface treatment using bituminous emulsion materials or by single-pass overlaying a new hot-mixed asphalt concrete layer. Investigations accomplished during the implementation of HIR technologies allow enhance quality of recycled materials and also promote the entire adaptation of HIR technologies to the Ukrainian standards. Keywords: asphalt pavement rehabilitation, hot in-place recycling, recycled asphalt concrete, field testing, road pavement strength measurement, rutting measurement.

REABILITAÇÃO DE PAVIMENTOS RÍGIDOSINCORPORADOS AO TABULEIRO DE OBRAS DE ARTES ESPECIAIS

The rigid concrete floor incorporated in the slab of the board is a Portland concrete pavement executed separately from the slab, but later incorporating to this slab by means of staples. In the process of recovery of this type of pavement, it is necessary to perform structural evaluations of the pavement, to be defined which services are to be executed, the execution sites, the approximate times of work and the degree of necessity of these services. The objective of this work was to describe the whole process of rehabilitation of concrete pavements in Portland cement, taking as an example a bridge of intense traffic and without possibility of total interruption of traffic.

인산마그네슘 세라믹의 염소 이온 투과 저항성 및 길이변화 특성에 관한 성능 평가

콘크리트 포장도로는 동절기 제설제에 의한 내구성 저하가 심각한 위협으로 거론되고 있고 그 보수에도 많은 비용이 소요되고 있다. 따라서 이러한 콘크리트 포장재에 대한 적절한 보수 대책의 마련과 이에 활용될 우수한 성능의 보수 재료가 요구되고 있는 상황인데, 본 연구에서는 국내에서 개발된 인산마그네슘 세라믹(Magnesium phosphate ceramics)을 대상으로 압축강도 특성 및 염소이온 침투 저항성, 길이변화 특성을 평가하여 국내 콘크리트 포장 도로의 보수 재료로 적용 가능성을 검토하였다. 평가 결과 모르타르의 유동성은 190mm의 평범한 수준을 나타내었으나 다소 점성이 높고 재료 자체의 흐름성은 크지 않았다. 응결 시간은 12분으로 매우 빠른 경화가 이루어졌으며 이에 따라 신속한 작업이 요구되었다. 모르타르의 압축강도 성능은 2시간에 38.4MPa, 24시간에 73.8MPa, 28일에 111.0MPa로 재령 초기부터 높은 수준을 나타내었다. 염소이온 침투 저항성 시험 결과 모르타르의 경우 143 Coulombs, 콘크리트의 경우 173 Coulombs으로 매우 우수한 수준을 나타내었다. 콘크리트의 길이변화 시험 결과는 재령 40일까지 <TEX>$60{\times}10^{-6}$</TEX> 이하로 완만하게 감소하였으며, 보통의 시멘트 콘크리트의 길이변화 수준과 비교할 때 1/10 이하의 수준으로 우수한 체적안정성을 확보하고 있었다. 이상과 같이 인산마그네슘 세라믹은 우수한 강도 성능과 염소이온 침투 저항성, 체적 안정성을 보유하고 있음을 확인하였고, 향후 작업 시간이나 작업성에 대한 개선이 요구되며, 현장 적용시에는 이러한 부분에 대한 주의가 필요하다. The performance degradation of concrete pavement by winter deicer is very serious in Korea, and its maintenance and rehabilitation brings a high expense. Therefore, a suitable method for rehabilitation of such concrete pavement and repair material of proper performance are required. In this study, the properties of compressive strength, ability to resist chloride ion penetration, and properties of dry shrinkage of magnesium phosphate ceramics were assessed to evaluate its applicability as a repair material for concrete pavement in Korea. As a result, the mortar flow showed a normal level of 190 mm, but the viscosity was high and the self-flow ability was poor. The setting time was 12 minutes, leading very rapid-hardening, and thus a prompt work was required. The compressive strength of mortar was 38.4MPa in 2 hours, 73.8MPa in 24 hours, and 111.0MPa in 28 days, showing a significant level. As a result of the test to chloride ion penetration resistance, mortar showed 143 Coulombs, and concrete showed 172.6 Coulombs, which fell under very low level. The drying shrinkage of MPC concrete in 40 days was below <TEX>$60{\times}10-6$</TEX>, and comparing with normal cement concrete, it showed the level below 1/10 of other concrete to secure an excellent volume stability. As above, magnesium phosphate ceramics has excellent strength performance, chloride ion penetration resistance, and volume stability, and this in the future shall be used in construction under the consideration of working time or workability, requiring further improvement for such performance.

Research and application of a black rapid repair concrete for municipal pavement rehabilitation around manholes

Cracks and potholes around manholes on carriageways have long been a problem for municipal asphalt concrete roads. The traditional repairing method not only requires a long period of traffic interruption, but also does not meet the requirements of durability and aesthetic appearance. A black rapid repair fibre concrete (BRRFC) was developed for asphalt concrete pavement rehabilitation around manholes, based on a series of optimisation and scaled tests. As a super high-early-strength concrete, BRRFC has capacity to carry normal traffic loads after pavement manholes repairs for 8h. Meanwhile, it offers other advantages such as uniform and stable black colour, good performance in dry-shrinkage and wear resistance, low-cost, and easy construction. Applications of BRRFC in numerous municipal maintenance works showed that rehabilitated manhole areas were still intact and no obvious colour difference between the new and old pavement concrete after several years of service, achieving significant social and economic benefits for sustainability.

Application of the Texas Department of Transportation Continuous Deflection Device to Select Rehabilitation Strategies for Concrete Pavements

In 2013, the Texas Department of Transportation completed development of its total pavements acceptance device (TPAD), which contains the next generation of rolling deflectometer integrated with ground penetrating radar and video logging. TPAD collects data at 2 mph and provides deflections measurement at 2-in. intervals from three rolling geophones. In this paper, the development of TPAD is described with typical outputs from the data processing software. How TPAD deflections can be used to determine the load transfer efficiencies of joints and cracks is described, along with the correlation with falling weight deflectometer measurements. Four case studies are presented illustrating typical TPAD data on a range of problem concrete pavements in Texas. These case studies include pavements with a debonded concrete overlay, pavements with voids beneath the slab, and a section that has full-depth patching. The TPAD data collected on US-75, which is a jointed concrete pavement in very poor condition, are presented. TPAD provides highly useful data for planning the rehabilitation of concrete pavements in Texas. Since its development, TPAD has been used on 15 major rehabilitation projects. A popular application is to determine if an upcoming project is a good candidate for an engineered thin asphalt overlay or if more major structural improvements are required.

Evaluating the performance of sustainable perpetual pavements using recycled asphalt pavement in China

Abstract The vast highways network in China is moving from the phase of construction to the phase of maintenance, and with the introduction of new technique of perpetual pavement in last decade, it is necessary to consider recycling as one of the promising solutions for rehabilitation of old asphalt concrete pavement and ultimately to convert them into perpetual pavements. The aim is to reuse the existing pavement materials for several reasons, mainly to preserve natural resources such as aggregates, and to satisfy economic requirements by reducing the cost of highway construction and rehabilitation. A detailed testing program has been carried out on recycled asphalt pavements materials (RAP) to evaluate their mechanical and structural characteristics to be used for the construction and rehabilitation of road pavements. Different types of RAP mixes have been stabilized by Portland cement to find the most suitable one from the point of view of design, construction, economy and environment. The analysis of life cycle costs has been carried out using system analysis and management of pavement program (SAMP5). The analysis of life cycle costs showed that the use of Portland cements with small percentages improves the structural characteristics of recycled asphalt materials to be used as stabilized base pavement layers for new or rehabilitated old road pavements and also for the construction and rehabilitation of perpetual pavements. A large amount of savings in construction and rehabilitation cost has been achieved by the use of stabilized RAP materials in addition to important contributions to the environment and preserving of natural resources.

Flexural strengths and fibre efficiency of steel-fibre-reinforced, roller-compacted, polymer modified concrete

A new material suitable for the structural repair of concrete pavements has been developed at Coventry University exhibiting high flexural, shear and bond strengths and high resistance to reflection cracking, demonstrating also unique placeability and compactability properties.This article deals with the standard equivalent flexural strengths evaluated using the identical fibre bridging concept and the size effect. Correlation of flexural strengths for beams of different sizes was achieved and the efficiency of fibre in the mix was scrutinised. It was concluded that the efficiency was much higher in the new steel-fibre reinforced, roller compacted, polymer modified concrete (SFR–RC–PMC) mix than in conventional concrete. The high efficiency revealed by the fibre bridging law is mainly attributed to a lower water to cement ratio. It was also found that the fibre aspect ratio influences significantly the flexural performance of the new material. The very high flexural strength extracted from the SFR–RC–PMC, compared to conventional steel-fibre reinforced concrete is very favourable to worn concrete pavement rehabilitation.

접착식 콘크리트 덧씌우기를 위한 초속경화 첨가재 현장 혼합 폴리머 개질 콘크리트의 적용성 연구

PURPOSES : Recently, bonded concrete overlay has been used as an alternative solution in concrete pavement rehabilitation since its material properties are similar to those of the existing concrete pavements. Deteriorated concrete pavements need rapid rehabilitation in order to prevent traffic jams on Korean expressways. Moreover, speedy and effective repair methods are required. Therefore, the use of bonded concrete overlay with ultra-rapid hardening cement has increased in an effort to reopen promptly the expressways in Korea. However, mobile mixer is required for ultra-rapid hardening cement concrete mixing in the construction site. The use of mobile mixer causes various disadvantages aforementioned such as limitation of the construction supply, open-air storage of mixing materials, increase in construction cost, and etc. In this study, therefore, hydration accelerator in-situ mixing on polymer modified concrete produced in concrete plant is attempted in order to avoid the disadvantages of existing bonded concrete overlay method using ultra-rapid hardening cement. METHODS : Bonded concrete overlay materials using ultra-rapid hardening cement should be meet all the requirements including structural characteristics, compatibility, durability for field application. Therefore, This study aimed to evaluate the application of hydration accelerator in-situ mixing on polymer modified concrete by evaluating structural characteristics, compatibility, durability and economic efficiency for bonded concrete overlay. RESULTS : Test results of structural characteristics showed that the compressive, flexural strength and bond strength were exceed 21MPa, 3.15MPa and 1.4MPa, respectively, which are the target strengths of four hours age for the purpose of prompt traffic reopening. In addition, tests of compatibility, such as drying shrinkage, coefficient of thermal expansion and modulus of elasticity, and durability (chloride ions penetration resistance, freezing-thawing resistance, scaling resistance, abrasion resistance and crack resistance), showed that the hydration accelerator in-situ mixing on polymer modified concrete were satisfied the required criteria. CONCLUSIONS : It was known that the hydration accelerator in-situ mixing on polymer modified concrete overlay method was applicable for bonded concrete overlay and was a good alternative method to substitute the existing bonded concrete overlay method since structural characteristics, compatibility, durability were satisfied the criteria and its economic efficiency was excellent compare to the existing bonded concrete overlay methods.

Accelerated Slab Replacement Using Self-Consolidating Concrete

A self-consolidating concrete (SCC) mix was developed to accelerate the construction of replacement slabs in concrete pavement rehabilitation projects. This work was part of a larger research project to develop an innovative process involving the use of temporary and reusable precast slabs and an SCC mix for construction of replacement slabs to reduce construction time and increase contractor production in concrete pavement rehabilitation projects. Two requirements were set for the SCC mix, high workability and flow rate without segregation, and a minimum 6-h compressive strength of 2,200 pounds per square inch [psi (15 MPa)] required by the Florida Department of Transportation (DOT). The SCC mix incorporated Grade 57 aggregate as well as a combination of admixtures, including a high range water reducer, workability retainer, water reducer and set retarder, and accelerator. Laboratory trial batches were prepared for the proposed mix and tested for workability and strength. On the basis of test results of the trial batches, the refined SCC mix was developed to achieve the high workability needed for faster concrete discharge and finish and to attain the Florida DOT's 6-h strength requirement of 2,200 psi (15 MPa) for slab replacements.

Concrete pavement rehabilitation procedure using resonant rubblization technology and mechanical–empirical based overlay design

Reflective cracking distresses frequently occur on the hot mix asphalt (HMA) overlay due to the movements of the underlying Portland cement concrete (PCC). Rubblization was proven in North America to be an effective approach among slab fracturing technologies for solving the premature reflective cracking problem. This paper presents the procedure of applying the rubblization technology in HMA overlay design in a research effort in China to develop the Chinese standard. In the study, the validity of rubblization was analyzed by a trench survey and sieve tests; the layer moduli of the composite subgrade and rubblized concrete slab were determined using FWD and plate bearing tests and a conversion chart; the thickness design for the HMA overlay over the rubblized PCC pavement was conducted using a Chinese version mechanistic–empirical design process; and finally the in-service monitoring over the pavements built using the developed procedure was conducted to test the validity of the procedure.