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Rigid airport pavements are a critical part of the Australian airport pavement inventory. The thickness design of rigid airport pavements in Australia was previously based on Australian developed charts and a conservative characteristic concrete strength, but in recent years this has changed to reliance on the software FAARFIELD provided by the US. Australian designers have used FAARFIELD in combination with the historical and conservative definition of concrete strength. That conflicts with the intended use of a less conservative Australian concrete strength value for inputting into FAARFIELD. The unintended consequence of this change in Australian practice is an additional 44 to 74 mm of concrete slab thickness, depending on the aircraft type, subgrade support, and concrete strength used. This additional thickness costs an additional AUD 185,000 to AUD 429,000 and 154,000 to 333,000 kg.eCO2 for a modest 100×100-m rigid airport pavement development. This additional financial and environmental burden is not justified, and Australian airport pavement designers should adjust their thickness design calculations to avoid this unintended overdesign in the future. This example also serves as a lesson regarding the potential consequence of mixing elements from different systems for pavement thickness design. [ABSTRACT FROM AUTHOR]

This paper presents research about a mixture design method of pavement concrete coblending rubber and fiber into ordinary concrete. Mechanical-based tests regarding the compressive strength, elastic modulus, splitting tensile strength, flexural strength, and four-point bending stiffness were conducted to evaluate the flexural toughness of concrete, and a slab-based three-point bending test was designed to evaluate the bending toughness improvement of the road pavement concrete slab. The results indicated that with the increase in single rubber content, the compressive strength and elastic modulus of concrete decreased continuously. The rubber concrete specimen remained relatively complete in appearance during destruction, showing the satisfied ductile failure characteristics to pavement usage with the optimal rubber content of 10%. After adding basalt fiber (BF) or polypropylene fiber (PPF), with the increase of fiber content, the bending stiffness of concrete decreased, the corresponding deflection of peak load increased continuously, and the bending deformation capacity of concrete could be significantly enhanced. Compared with the reference group, when the rubber content is 10%, and basalt fiber content is 0.5%–2%, the equivalent initial bending strength of fiber-reinforced rubber concrete is increased by 105.4%–164.4%. In general, BF is better than PPF in improving the toughness of rubber concrete, and the optimal dosage of BF is 1% of concrete volume in this test. When loaded to the limit load, the deflection of the basalt fiber–reinforced rubber concrete slab in the middle of the bottom span was about four times higher than that of the benchmark concrete slab, the bending deformation capacity and toughness of the basalt fiber–reinforced rubber cement concrete slab have been greatly improved. From the test results, the mixture design method of flexible pavement cement concrete based on rubber and fiber coblending was proposed, which contributes to the development of flexible materials for concrete pavement. [ABSTRACT FROM AUTHOR]

Over the years, thicknesses of continuously reinforced concrete pavement (CRCP) increased to accommodate rising truck traffic. With a fixed percentage of longitudinal reinforcement relative to the concrete cross-sectional area, thicker slabs necessitate more reinforcement and reduced bar spacing, potentially hindering consolidation. To address this issue, two-mat steel design was implemented in Texas for pavements with thickness of 330 mm (13 in.) or larger. Performance evaluations of thick CRCPs revealed that horizontal cracking developed at the depth of reinforcement where one-mat steel was placed, while no horizontal cracking was observed where two-mat steel was used. Pavement responses with one-mat and two-mat reinforcements with different depths were analysed by three-dimensional modelling with a finite element analysis (FEA) programme for the wide range of environmental loadings. Maximum concrete vertical tensile stresses around longitudinal reinforcement at transverse crack area are a good indicator of horizontal cracking potential; those stresses were evaluated, along with concrete stresses at top of the slab, which are responsible for top-down transverse cracking. The results show that the two-mat design causes higher concrete stresses at the top of the concrete slab and lower concrete stresses around the longitudinal reinforcement, leading to increased transverse cracks and a reduction in horizontal cracking potential. [ABSTRACT FROM AUTHOR]

This study investigates the early-age behaviour of continuously reinforced concrete pavement (CRCP) on the semi-rigid base, including structural behaviour during transverse crack propagation and curling behaviour both in the longitudinal and transverse direction. Field experiments are operated on a CRCP section in Wuhan, China. Vibrating wire strain gauges were installed at mid-slab and slab edge in the longitudinal and transverse direction for concrete strain and temperature measurement. Testing results showed the complexity of early-age behaviour of CRCP on semi-rigid base and curing with wet burlap sheets. An early-age transverse crack may originate from the bottom of the concrete slab due to the water absorption of the dry semi-rigid base. The development of a transverse crack took several cooling cycles. Curling behaviour in the longitudinal direction did not correspond to the temperature gradient after transverse crack occurrence. Typical curling motion in the transverse direction was found in the mid-slab rather than the slab edge. The findings of this study would lead to a better understanding of the early-age structure behaviour of CRCP on semi-rigid base and its impact on later road performance. [ABSTRACT FROM AUTHOR]

Structural fibers contribute to the overall performance of concrete pavements by mitigating various distresses. To understand the influence of structural fibers on the pavement structural responses and distresses, the Minnesota Department of Transportation (MnDOT) constructed two ultra-thin (3 and 4 in. thick) and three thin (5 and 6 in. thick) fiber reinforced concrete cells along with one plan concrete control test cell at the Minnesota Road Research (MnROAD) facility in 2017. These test cells have 6 ft x 6 ft concrete slabs and were constructed on the granular base layer. While the structural designs of these cells were intended for roads with low to moderate traffic volume, the cells were subjected to accelerated loading to complete the study in a short period of time. This paper summarizes the design and construction of the six test cells and provides a comprehensive discussion on the joint performance behavior and transverse joint faulting trends, emphasizing the influence of the fibers on the abovementioned. It was found that fibers can improve joint performance and decrease faulting in thin concrete pavements. Regarding the ultra-thin pavements, no conclusion was possible to be drawn on the contribution of the fibers. [ABSTRACT FROM AUTHOR]

Thermally induced stresses of a concrete slab are quantified based on in situ temperature measurements. PT100A sensors recorded the temperature at four specific depths during 23 days in autumn. Best-fit quadratic polynomials are used to extrapolate the measured temperatures to the top and the bottom of the slab. The obtained surface temperature histories are used as boundary conditions for the solution of the transient heat conduction problem in thickness direction. Postprocessing the thermal eigenstrains provides access to the eigencurvatures of the plate and to the eigendistortions of the plate-generators. Stresses resulting from the constrained eigencurvatures of the plate are computed numerically, for values of the modulus of subgrade reaction amounting to 50, 100, 200, and 300 MPa/m. Self-equilibrated eigenstresses resulting from the prevented eigendistortions of the plate-generators are quantified analytically. Daily maxima of tensile stresses in corner regions at the top of the slab, and in the central region at its bottom, are found in the early morning and in the early afternoon, respectively. Disregarding the eigenstresses leads to an underestimation of tensile stresses in corner regions by at least $33\, \percnt$ 33 % and an overestimation in the central region by at least $26\, \percnt$ 26 %. The misestimations increase with decreasing modulus of subgrade reaction. [ABSTRACT FROM AUTHOR]

Incorporating Phase Change Materials (PCM) through encapsulation is an effective method to regulate the pavement surface temperature. The present study investigates the effect of the thermal properties of concrete and encapsulating material on the cooling potential of PCM incorporated concrete pavements. An enthalpy-porosity based pore-scale heat transfer model was developed that simulates the melting of PCM in concrete pavements subjected to solar radiation. Two types of PCMs, i.e. Organic Mixture 35 (OM 35) and Organic Mixture 42 (OM 42) were incorporated into concrete slabs with the help of expanded clay aggregates (ECA) as PCM carrier. In the top 0.1 m layer of concrete, a total of 98 numbers of ECA-PCM balls of 1 cm diameter were distributed uniformly. The cooling potential of pavements with OM 35 and OM 42 improved by 82.67 % and 81.70 %, respectively with increase in the porosity of ECA from 0.1 to 0.9. Further, as the thermal conductivity of concrete increased from 1.2 to 2.4 W/mK, the cooling potential of OM 35 and OM 42 incorporated pavements increased by 36.48 % and 38.29 %, respectively. However, the thermal conductivity of the encapsulating material showed marginal influence on the cooling potential and therefore may be neglected. [ABSTRACT FROM AUTHOR]

Predicting faulting failure is useful in the optimal concrete pavement design. In this study, artificial neural networks and the random forest method have been used to predict the amount of this failure. The general prediction model was created by inserting 32 available input variables into artificial neural networks. An integer two objectives optimisation problem was designed to select features that significantly affect the faulting. After applying this method, 19 important variables were identified and used to develop two simplified models based on artificial neural networks and the random forest method. It is shown that the simplified model developed by artificial neural networks is the best model to accurately predict the faulting considering the number of input variables. The cumulative number of days when the precipitation is more than 12.7 mm, the elastic modulus of concrete slab, the number of days passed since the pavement was built, base thickness, the cumulative ESALs in the traffic lane, and the annual average number of days when the temperature is more than 32°C were identified as the most important parameters in predicting faulting using the random forest method. A Sensitivity analysis has been then performed on these variables and optimal values were determined. [ABSTRACT FROM AUTHOR]

Meteorological and subsurface factors influence pavement's response to cold fronts. Prediction of pavement temperature, particularly icing, is important to winter pavement maintenance which relies on an estimated time for the formation of ice. However, the prediction development is limited by test data on pavement icing. A model column consisting of soil samples and a concrete pavement slab retrieved from the Dallas Fort Worth airport was used to replicate the airport pavement structure, including subgrade. The soil was classified using USCS, tested for optimum moisture content and compacted in lifts in the column. Thermistors and moisture sensors were placed at different depths. The pavement slab was fitted with temperature sensors throughout. The system was installed in a freezer box,wrapped in insulation and plastic. Three cold front scenarios were selected from observed airport weather data and simulated in the freezer box using varying rates of temperature decrease and precipitation. The formation of ice on a pavement surface was observed at 10–20 min after the start of precipitation. This time frame is not affected by the freezer box cooling rate. The icing time found from this study is useful for the development of prediction models for icing onpavements. [ABSTRACT FROM AUTHOR]

The unavoidable transverse non-uniformity of settlement and moduli for part-fill and part-cut subgrade may have some critical impact on concrete pavement structures, hence, some structural optimisations of pavement based on the working conditions of subgrade are essential. In this study, on account of the practical working conditions of part-fill and part-cut subgrade, a finite element model of concrete pavement structure on part-fill and part-cut subgrade developed previously was conducted to analyse the effects of slab thickness, slab concrete modulus of rupture, tie bar diameter and tie bar spacing. Furthermore, improvement methods and strategies were analysed and proposed for the four parameters respectively with fatigue cracking design life under loading as the target and maximum stress at the bottom of slab as the criterion. The results verified the feasibility of incorporating non-uniformity of modulus and settlement into the design phase of concrete pavements on part-fill and part-cut subgrade. Additionally, concrete pavement parameter optimisation priority should be given to concrete modulus of rupture, slab thickness, followed by tie bar diameter and spacing. It can provide a useful reference for designing concrete pavement structures on part-fill and part-cut subgrade. [ABSTRACT FROM AUTHOR]

Lamb and Rayleigh waves-based dispersion analysis has been carried out for non-destructive surface wave testing of different slab-like structures involving a concrete roof slab, a concrete floor, a concrete pavement, and an asphaltic pavement. An impact was generated by gently striking the slab's free surface with a hammer. A method has also been given to generate the governing (predominant) dispersion mode in the case of Rayleigh wave propagation considering the complex nature of the dispersion function $\vert {{ D}\lpar {c\comma \; \kappa } \rpar } \vert$ | D (c , κ) | ; $c$ c and $\kappa$ κ refer to phase velocity and wavenumber, respectively. The theoretical dispersion plots generated from the inversion analysis by varying the values of different input parameters were subsequently closely matched with the corresponding obtained field dispersion images for different cases in order to back compute the elastic profile of the slab/pavement. For developing the dispersion images, the Park's wavefield transformation method was employed. For checking the thicknesses of the different layers, cylindrical cores were also extracted. The study is expected to be useful for evaluating different slab-like structures, including pavements, by using surface wave-based non-destructive tests. [ABSTRACT FROM AUTHOR]

The surface layer of military airfield pavements is prone to damage, including cracking, abrasion, and spalling. It is proposed to strengthen the pavement mortar layer by laying fiber mesh to solve these issues. In this study, three meshes of carbon fiber, aramid fiber, and basalt fiber were selected for surface reinforcement across six pavement slabs of 1.5m (length) × 1.5m (width) × 0.25m (height). The drop hammer impact test was carried out on the six pavement slabs. The test data were analyzed using impact times, crack development characteristics, and development models on the surface deflection as evaluation indices. The results show that the fiber mesh can effectively improve the impact resistance of concrete pavement slabs. Aramid fiber mesh best strengthened the pavement surface, whereas the basalt fiber mesh had the least strengthening effect. However, the mesh size has a negligible influence on the impact resistance of concrete pavement slabs. The effect of fiber mesh on improving the impact resistance of the concrete pavement slab corner was greater than that of the concrete pavement slab edge midpoint. Considering the performance and cost indicators, within the scope of the study, aramid fiber mesh is the most suitable for surface strengthening of airfield concrete pavement. [ABSTRACT FROM AUTHOR]

The unavoidable transverse non-uniformity of settlement and moduli for part-fill and part-cut subgrade may have some critical impact on concrete pavement structures, hence, some structural optimisations of pavement based on the working conditions of subgrade are essential. In this study, on account of the practical working conditions of part-fill and part-cut subgrade, a finite element model of concrete pavement structure on part-fill and part-cut subgrade developed previously was conducted to analyse the effects of slab thickness, slab concrete modulus of rupture, tie bar diameter and tie bar spacing. Furthermore, improvement methods and strategies were analysed and proposed for the four parameters respectively with fatigue cracking design life under loading as the target and maximum stress at the bottom of slab as the criterion. The results verified the feasibility of incorporating non-uniformity of modulus and settlement into the design phase of concrete pavements on part-fill and part-cut subgrade. Additionally, concrete pavement parameter optimisation priority should be given to concrete modulus of rupture, slab thickness, followed by tie bar diameter and spacing. It can provide a useful reference for designing concrete pavement structures on part-fill and part-cut subgrade. [ABSTRACT FROM AUTHOR]

Lamb and Rayleigh waves-based dispersion analysis has been carried out for non-destructive surface wave testing of different slab-like structures involving a concrete roof slab, a concrete floor, a concrete pavement, and an asphaltic pavement. An impact was generated by gently striking the slab's free surface with a hammer. A method has also been given to generate the governing (predominant) dispersion mode in the case of Rayleigh wave propagation considering the complex nature of the dispersion function $\vert {{ D}\lpar {c\comma \; \kappa } \rpar } \vert$ | D (c , κ) | ; $c$ c and $\kappa$ κ refer to phase velocity and wavenumber, respectively. The theoretical dispersion plots generated from the inversion analysis by varying the values of different input parameters were subsequently closely matched with the corresponding obtained field dispersion images for different cases in order to back compute the elastic profile of the slab/pavement. For developing the dispersion images, the Park's wavefield transformation method was employed. For checking the thicknesses of the different layers, cylindrical cores were also extracted. The study is expected to be useful for evaluating different slab-like structures, including pavements, by using surface wave-based non-destructive tests. [ABSTRACT FROM AUTHOR]

The surface layer of military airfield pavements is prone to damage, including cracking, abrasion, and spalling. It is proposed to strengthen the pavement mortar layer by laying fiber mesh to solve these issues. In this study, three meshes of carbon fiber, aramid fiber, and basalt fiber were selected for surface reinforcement across six pavement slabs of 1.5m (length) × 1.5m (width) × 0.25m (height). The drop hammer impact test was carried out on the six pavement slabs. The test data were analyzed using impact times, crack development characteristics, and development models on the surface deflection as evaluation indices. The results show that the fiber mesh can effectively improve the impact resistance of concrete pavement slabs. Aramid fiber mesh best strengthened the pavement surface, whereas the basalt fiber mesh had the least strengthening effect. However, the mesh size has a negligible influence on the impact resistance of concrete pavement slabs. The effect of fiber mesh on improving the impact resistance of the concrete pavement slab corner was greater than that of the concrete pavement slab edge midpoint. Considering the performance and cost indicators, within the scope of the study, aramid fiber mesh is the most suitable for surface strengthening of airfield concrete pavement. [ABSTRACT FROM AUTHOR]

The study investigates the hygrothermal behavior of pavements used in sidewalks with pervious concrete paving (PCP) and traditional concrete paving (TCP) slabs tested in an experimental site located in a tropical region. Meteorological variables (incoming and outgoing radiation) were monitored alongside pavement-related variables (solar reflectivity, surface temperatures, stored heat fluxes, and soil moisture under the concrete slabs) during dry, transition, and wet seasons. The lower solar reflectance index of the PCP slabs, due to their medium gray color, was responsible for increased solar energy absorption and higher surface temperatures when compared to the TCP slabs, in light gray color. Voids and pores within the PCP microstructure helped to store less energy during the daytime, releasing less energy to the adjacent thermal environment during nighttime. In turn, because of the high levels of incident solar radiation in the tropics, the cooling effect provided by the evaporation of the water retained inside the cementitious matrix lasted on average 12 h after precipitation. [ABSTRACT FROM AUTHOR]

The falling weight deflectometer (FWD) test is a common non-destructive testing method for evaluating the structural capacity of pavements. At present, data processing of the FWD test mainly focuses on the deflection data, while paying less attention to the deflection-time history. Because a FWD is equipped with impulse loads and geophones, which allow for the generation and capture of surface wave signal propagation, it is hypothesized that Rayleigh wave dispersion theory can be applied to calculate the modulus profile along the pavement depth by analysing the dispersive properties of the deflection signal measured during FWD tests. To test this hypothesis, we develop a new methodology for the FWD test and data analysis, referred to as the FWD dispersion curve method. We first introduce the concept of the new method, followed by an illustration of the procedure and the experimental set-up. Case studies on three concrete pavement segments are then presented to evaluate the effectiveness of the FWD dispersion curve method. Modifications to the existing FWD device are further recommended for the impact loading sources and signal collection process so that the modulus of a much shallower layer, such as the concrete slab and upper asphalt layers, can be obtained. This article is part of the theme issue 'Artificial intelligence in failure analysis of transportation infrastructure and materials'. [ABSTRACT FROM AUTHOR]

Falling weight deflectometer (FWD) tests are performed worldwide for assessing the health of pavement structures. Interpretation of FWD-measured surface deflections turns out to be challenging because the behavior of pavement structures is temperature-dependent. In order to investigate the influence of temperature on the overall pavement performance and on the stiffness of individual layers, temperature sensors, asphalt strain gauges, and accelerometers were installed into one rigid (concrete) and two flexible (asphalt) pavement structures, mostly at layer interfaces. Three different methods for installation of the strain gauges are compared. From correspondingly gained experience, it is recommended to install a steel dummy as a place-holder into the surface of hot asphalt layers, immediately after their construction and right before their compaction, and to replace the dummy with the actual sensor right before the installation of the next layer. Concerning the first data obtained from dynamic testing at the field-testing sites, FWD tests performed at different temperatures deliver, as expected, different surface deflections. As for the rigid pavement, sledgehammer strokes onto a metal plate, transmitted to the pavement via a rubber pad, yield accelerometer readings that allow for detection of curling (=temperature-gradient-induced partial loss of contact of the concrete slab from lower layers). In the absence of curling, the here-proposed sledgehammer tests yield accelerometer readings that allow for quantification of the runtime of longitudinal waves through asphalt, cement-stabilized, and unbound layers, such that their stiffness can be quantified using the theory of elastic wave propagation through isotropic media. [ABSTRACT FROM AUTHOR]

Airport pavements are prone to early defects during the construction phase, and their early performance during the construction phase is significantly affected by the external temperature field. This article takes the concrete pavement of Xiamen Xiang'an New Airport as an example and uses a three-dimensional (3D) humidity simulation program for cement concrete pavement to study the evolution behavior of the early stage humidity field of the pavement in a humid and hot climate environment. The results indicate that the evolution law of the humidity field of the concrete pavement slab was consistent with the environmental field, presenting a 24 h periodic variation. The environmental field had a significant impact on the humidity of the surface layer of the pavement slab, and the humidity decreased rapidly with time. There was a humidity gradient on both the horizontal plane and the cutting plane of the slab, the horizontal humidity was concentrated from the boundary into the middle of the slab, and the sectional humidity was concentrated from the top to the bottom of the slab. Environmental parameters, construction parameters, and material and structural parameters all influenced humidity through humidity exchange or by changing the saturated vapor pressure inside the slab. The humidity field was most sensitive to environmental humidity and maintenance methods, but less sensitive to material parameters and structural parameters. Through analysis, it is advisable to avoid hot seasons, choose periods of increased environmental humidity, adopt appropriate maintenance methods during construction to reduce humidity stress on the slab, and therefore decrease early stage deterioration and improve service life. [ABSTRACT FROM AUTHOR]

Solar pavements are a new type of pavement structure that harvest energy from the sun and have been widely investigated in recent years. A critical step toward the acceptance and development of solar pavement structures is investigating their mechanical response, which is conducted in this study. Here, a typical pavement structure with functional photovoltaic, cement concrete, base, subbase, and subgrade layers was selected. This is one of the most acceptable forms of the solar pavement structure. A numerical simulation of the solar pavement was conducted by establishing a 3D model using the finite element software ABAQUS. The effects of the vehicle critical load position, elastic modulus, geometric size, linear expansion coefficient of the photovoltaic panel (PVP), and cement concrete slab (CCS) thickness on the mechanical response of the solar pavement under vehicle and temperature loadings were investigated. The results indicated that the critical load position of the solar pavement in the middle of the long side of the concrete slab was the same as that of the traditional concrete pavement. The PVP parameters influenced the mechanical response in the following order: elastic modulus, linear expansion coefficient, and geometric size. By increasing the CCS thickness from 0.20 to 0.28 m, the CCS load stress decreased by 15%; however, the curling stress increased significantly from 0.85 to 1.97 MPa. An increase in the PVP linear expansion coefficient caused the curling stress of the solar pavement to first decrease and then increase. A linear expansion coefficient of 1 × 10–5 resulted in minimum curling stresses of 0.42 and 1.70 MPa for PVP and CCS, respectively. [ABSTRACT FROM AUTHOR]

The general solution of the axial symmetry elastic space problem in cement concrete pavement is an elementary question. Combining the Love method and the Southwell method, the Southwell operator was used in the variable selection process, the displacement function was introduced to express the displacement component by the Love method, the expression of stress indicated by the displacement function was obtained by combining the displacement components, geometric equations, and physical equations, then the stress was substituted into the equilibrium equation, the biharmonic equation of displacement function was obtained by mathematical operation, and finally, a new general solution of the axisymmetric elastic space problem in cement concrete pavement was obtained. According to the proposed general solution, mechanical calculation for a cement concrete pavement slab on Winkler foundation was carried out, the displacement curve at the top surface of the slab and the stress curve at the top, middle, and bottom surface of the slab were derived, and the results showed that the method is feasible in the calculation of cement concrete pavement. The general solution provided a new method for solving the axisymmetric elastic space problem of cement concrete pavement. [ABSTRACT FROM AUTHOR]

Improved criteria for the material properties and mix proportions of concrete slabs to enhance the performance of concrete pavements at Incheon international airport (IA) in the Republic of Korea are suggested. Gimpo IA and Gimhae IA were selected for comparison with Incheon IA based on their facility status and annual flight processing capability. After Incheon IA, Gimpo IA and Gimhae IA have the second and third largest annual numbers of flights per unit area of runway, respectively. Criteria for aggregate and mix proportions were chosen for improvement because of durability cracks (the major form of pavement distress at Incheon IA) due to the poor quality of aggregates used and repeated freeze–thaw cycles. Compared with the other airports, the mix specifications of the concrete slab at Incheon IA showed lower contents of cement and liquid admixture, a higher abrasion rate of coarse aggregate and a larger content of fines in the aggregate. Improved criteria were established based on a comparison of results. Concrete specimens were fabricated using the improved criteria and the performance of the concrete pavement was evaluated by testing the air content and freeze–thaw resistance of 12 mixes with different contents of cement, liquid admixture and fines in the aggregate. [ABSTRACT FROM AUTHOR]

Temperature gradient through the thickness of the concrete pavement slab results in slab curling and induces longitudinal bending stresses in the slab. Historically, temperature distribution or gradient has been considered linear, though it can be nonlinear in many cases. In this study, numerical modeling is conducted to compare the bending stresses due to nonlinear temperature with those due to the linear temperature distribution. It became evident from the results that the nonlinear temperature results in higher stress levels. In addition, this study also evaluates the effects of aged coefficient of thermal expansion (CTE) on the magnitude of bending stresses. Numerical modeling is conducted and it is found that aged CTE results in increased stresses up to 12.5% in the top and bottom fibers of the pavement slab. These increased stress levels may result in higher pavement distresses during the design service life and the pavement may not perform through its designed life. [ABSTRACT FROM AUTHOR]

Transverse cracking of concrete pavement in Ohio has been a major issue in interstate routes that reduces its service life to approximately ten to fifteen years, costing Ohio department of transportation great deal of maintenance funds. Major factors that aggravate slab failure are slab length, axle spacing and permanent built-in curl which are not directly incorporated in the AASHTO 1993 design procedure. The procedure implies an increasing thickness of concrete will be needed as traffic increases. However, fatigue testing of concrete beams has shown concrete can endure an unlimited number of loads if the stress ratio (SR) is kept below a critical value. Therefore, field and experimental data from Ohio concrete pavements were employed to validate a 3D finite element (FE) model with which critical slab stresses were calculated for several slab geometries. Results from stresses and fatigue damage analyses showed slab thickness of 12 in (305 mm) and slab length of 13 ft (3.9 m) were optimum for concrete pavement in Ohio. Long term pavement performance analysis showed the 12 in (305 mm) thick by 13 ft (3.9 m) long slab exhibited superior performance in terms of IRI, faulting, cracking, and cost over a 50-year design life. [ABSTRACT FROM AUTHOR]

Microwave deicing technology, as a new environmentally friendly deicing technology, can effectively solve the problem of the frequent icing of road surfaces in the winter, which affects the safety of traffic. To improve the efficiency of microwave deicing on cement concrete pavement, this study proposed the use of magnetite, iron sulfide slag, steel slag, lead–zinc slag, and graphite as microwave-absorbing materials, and conducted microwave deicing tests under the influence of five factors, namely the form of the pavement surface structure, the content of the microwave-absorbing material, microwave power, the shielding state, and dry and wet conditions. Layer by layer, we selected the combination of pavement surface structure, microwave-absorbing material content, microwave power, shielding state, and dry and wet conditions on the bottom surface of the concrete slab with the optimal deicing effect. The results showed that the 2 cm scattered microwave-absorbing surface concrete structure has the fastest heating rate; the higher the magnetite content and microwave power, the higher the deicing efficiency; the maximum heating rate can be increased by 17.6% when the shielding layer is set at the bottom of the cement concrete slab; and the heating rate of the microwave-absorbing concrete slab in the wet state is increased by 20.8% relative to the dry state. In summary, 7000 W of power, a magnetite content of 60 vol % in the scattered microwave-absorbing surface, a shielding layer set at the bottom surface, and wet conditions can greatly improve the efficiency of microwave deicing compared with the microwave ice melting effects of plain cement concrete and other microwave-absorbing materials mixed into the concrete. In addition, the temperature uniformity of the microwave-absorbing materials is essential to improve the deicing efficiency of microwave-absorbing concrete, so it is essential to explore it further. [ABSTRACT FROM AUTHOR]

Observation of fatigue cracking in concrete pavement slabs can be an indication that the life of the pavement is coming to an end. Alternatively, cracked slabs can be due to uneven foundation support and just an isolated occurrence. The resulting action and cost for these two conditions are vastly different. What if there was a way to predict when a pavement's life could be extended using concrete pavement restoration compared to when it was necessary to reconstruct? This paper provides a novel way, using a 3D Slab Based Methodology to characterise cracking in jointed plain concrete slabs and combines this with Remaining Service Life and hazard rate based on Weibull reliability theory to provide that answer for conventional concrete pavements. Using examples of several different pavements a comparison of this method to the traditional percent cracking is made. The results show that the new method, incorporating the impending failure concept, enables researchers and transportation agencies to identify the end of a concrete pavement's life better than percent cracking by taking full advantage of 3D pavement surface data. [ABSTRACT FROM AUTHOR]

With the day–night temperature and moisture levels changing every day, expansion and shrinkage of concrete slabs is always occurring; therefore, joints provide extra room for concrete slab deformation. The joint spacing in jointed plain concrete pavement (JPCP) is continuously affecting long-term pavement behaviors. In this study, data from the Long-Term Pavement Performance (LTPP) program were analyzed, and the behaviors of JPCP with different joint spacings were compared to discover the joint spacing effects. Since LTPP has an enormous database, three representative sections located in different states were selected for analysis, where the variable factors such as temperature, moisture, and average annual daily truck traffic (AADTT) were almost the same between the three sections. Three different joint spacings, including 15 ft (4.5 m), 20 ft (6 m), and 25 ft (7.5 m), were compared based on the collected LTPP data. The involved long-term pavement performances, such as average transverse cracking (count), average JPCP faulting, international roughness index (IRI), and falling weight deflectometer (FWD) deflections were compared between JPCP with different joint spacings. Based on the comparative analysis, the JPCP constructed with a 15 ft joint spacing demonstrated the best long-term performance. It showed no transverse cracking, the lowest average JPCP faulting, the best IRI value, and the smallest FWD deflection during the entire in-service period. With proper joint spacing, the cost of road maintenance throughout the life cycle could be significantly reduced due to there being less distress. Therefore, it is recommended to optimize the joint spacing to about 15 ft in JPCP in future applications. [ABSTRACT FROM AUTHOR]

Jointed plain concrete pavements are designed on the basis of edge stresses developed at the bottom of the slab, under environmental and vehicular loads. Various parameters related to material, traffic, environment and surrounding conditions of the pavement slab influence these stresses. This paper presents the effect of tie bars, aggregate interlocking, interface friction and lateral placement of wheel load on edge load stresses. An instrumented concrete pavement section with a dry lean concrete base layer was constructed and load tests were conducted. The test results indicated a significant reduction in edge load strains due to tie bars and aggregate interlocking at saw-cut longitudinal joints. An average load transfer efficiency of 60% was achieved at tied saw cut joints. The friction at the interface of concrete slab and underlying dry lean concrete base layer also considerably reduced the bottom tensile strains. Extra-widening of the slab by a minimum of 250 mm or providing a tied concrete shoulder showed an equivalent effect in reducing the bottom edge strains. [ABSTRACT FROM AUTHOR]

As a commonly used surface structure for airport runways, concrete slabs are subjected to various complex and random loads for a long time, and it is necessary to investigate their fracture performance at different strain rates. In this study, three-point bending fracture tests were conducted using ordinary performance concrete (OPC) and basalt fiber-reinforced airport pavement concrete (BFAPC) with fiber volume contents of 0.2, 0.4, and 0.6%, at five strain rates (10−6 s−1, 10−5 s−1, 10−4 s−1, 10−3 s−1, and 10−2 s−1). Considering parameters such as the peak load, initial cracking load, double K fracture toughness, fracture energy, and critical crack expansion rate, the effects of the fiber volume content and strain rate on the fracture performance of concrete were systematically studied. The results indicate that these fracture parameters of OPC and BFAPC have an obvious strain rate dependence; in particular, the strain rate has a positive linear relationship with peak load and fracture energy, and a positive exponential relationship with the critical crack growth rate. Compared with OPC, the addition of basalt fiber (BF) can improve the fracture performance of airport pavement concrete, to a certain extent, where 0.4% and 0.6% fiber content were the most effective in enhancing the fracture properties of concrete under strain rates of 10−6–10−5 s−1 and 10−4–10−2 s−1, respectively. From the point of view of the critical crack growth rate, it is shown that the addition of BF can inhibit the crack growth of concrete. In this study, the fracture properties of BFAPC were evaluated at different strain rates, providing an important basis for the application of BFAPC in airport pavement. [ABSTRACT FROM AUTHOR]

To explore the fatigue characteristics of self-compacting rubberized concrete (SCRC) pavement, notched slabs with a 10% rubber content were fabricated. Monotonic and fatigue tests were carried out, including incremental amplitude tests controlled by crack mouth opening displacement (CMOD), load, and alternative constant and incremental amplitude loads. Meanwhile, the fracture process was dynamically monitored with acoustic emission (AE), and the failure characteristics were analyzed based on AE parameters. Under monotonic loads, cracks mainly develop along with the interface between aggregates or rubber particles and cement. The cumulative ring counts and damage evolution show a three-stage distribution. The b-value fluctuates dramatically initially and less in the middle and later stages under monotonic tests. Under fatigue loads, brittle fractures are significant and fatigue life increases. Only one inflection point appears in the cumulative ringing counts curve and damage evolution curve, the critical damage is lower. The fluctuation range of the b-value are higher. The cumulative ringing counts, AE signal intensity, damage parameter based on AE energy, and b-value can dynamically reflect the crack growth and damage evolution of SCRC slabs. The fracture mode analysis based on AF-RA manifests cracks are mainly tensile, and the fracture mode is the type I. [ABSTRACT FROM AUTHOR]

The excessive use of cement has caused incremental production of greenhouse gases, one of the consequences of which is the overheating of the planet. These detrimental effects have highlighted the importance of pozzolanic materials and accordingly using alkali-activated concrete pavement instead of cement as a solution. Moreover, using fiber concrete surfaces is a predominant method to repair the concrete pavement due to the high speed of performance and the reduction of thickness. For this purpose, various amounts of sinusoidal steel fibers, kortta embass and kortta twist were added to alkali-activated concrete pavement. The results showed that with an increase in the fiber percentage, compressive strength, flexural strength, energy absorption, splitting tensile strength, impact resistance, skid resistance, resistance against freezing and thawing cycles are enhanced. On the other hand, the thickness of the concrete slab and water penetration into the concrete decreased. However, these cases are somewhat efficient for the sinusoidal steel fibers and then, the process begins to decrease. [ABSTRACT FROM AUTHOR]

Cracking is a common fault in asphalt and concrete pavements, which causes water damage and further defects if not repaired in timely fashion. Conventional pavement crack sealing methods based on machines and manual operations are generally subjective, labour-intensive, risky, and inefficient. A laboratory prototype of an automatic pavement crack sealing platform is proposed in this paper, which uses a modified three-dimensional (3D) printer and computer vision. A modified 3D printer based on fused deposition modelling (FDM) was combined with an image capturing platform, an image processing algorithm and a path planning method to form the automated pavement crack sealing platform, which can automatically detect pavement cracks and seal them with bitumen emulsion sealant. Specimens of concrete pavement slabs with cracks were produced in the laboratory to test the proposed method, and the cracks were then detected and sealed by the proposed platform. The results show that 3D printing is an effective method for automated pavement crack sealing, which is recommended in the field of automatic road maintenance and repair. [ABSTRACT FROM AUTHOR]

Crack width is a critical factor influencing the behaviour and performance of a roller-compacted concrete pavement (RCCP) because wide cracks can result in water infiltration and poor load transfer, leading to faulting, excessive deflection and further cracking. The crack width may be affected by temperature changes, concrete drying shrinkage and creep, crack spacing and the base material. An empirical equation to predict the crack width has been proposed by the American Association of State Highway and Transportation Officials (Aashto). However, this equation is quite simplified because a uniform strain distribution is assumed along the slab length. In this work, a mechanistic approach to predict the crack width in RCCP was developed using a three-dimensional finite-element model considering a non-linear friction model between the slab and the base. Moreover, the effect of concrete creep on the crack width was incorporated using the effective modulus method. The mechanistic model was validated with crack width data from two full-scale RCCP test sections in South Korea. The mechanistic model showed good agreement with the field data, whereas the Aashto equation tended to over-predict the crack widths. The proposed model is thus helpful to predict the crack width in a concrete pavement slab for given environmental conditions, slab geometry, material properties and base material. [ABSTRACT FROM AUTHOR]

Based on the design of a prefabricated pervious composite cement concrete pavement slab, the interface properties and bending deformation properties of basalt pervious concrete (BPC) and PVA fiber base impervious concrete (PFBIC) composite specimens were studied. The effects of the different interfacial agents on the interfacial bonding performance were compared using a splitting tensile strength test and interfacial shear test. The deformation capacity of the composite specimens under bending load was tested using a three-point bending test, with the symmetry of the model considered and compared with the deformation capacity of the BPC specimen and PFBIC specimen. The results showed that the compressive strength of the BPC prepared using an orthogonal test reached 40.30 MPa, while the permeability coefficient was 2.41 mm/s. Different interface treatment processes determine the interface bonding properties. The best interface treatment method can induce the interface bonding strength to be higher than the strength of the BPC matrix itself, while the interface transition zone matrix will be denser without obvious microscopic defects. Under the bending tensile load, the ultimate bending stress reached 6.58 MPa and the maximum deflection in the midspan was 0.81 mm. As a protective layer, the PFBIC can alleviate the disadvantage of the insufficient strength of the BPC and can improve the bending ultimate bearing capacity of the BPC-PFBIC through its own stiffness. [ABSTRACT FROM AUTHOR]

Composite pavements made from a hot-mix asphalt layer over a Portland cement concrete slab typically suffer from reflective cracking. Due to repetitive slab joint movements, concentrated stresses occur under the asphalt layer and propagate towards the surface. Recently, top-down reflective cracking has been observed in the field on pavements with no traffic. Previous studies have indicated that asphalt ageing may be the main cause of this problem. However, top-down reflection cracks may occur when upward curling of the concrete slab base creates a concentrated stress on top of the asphalt. Other design parameters such as thickness, stiffness or joint spacing may also influence this cracking behaviour. In the study reported in this paper, reflective crack propagation under thermal loading was investigated to identify potential factors that cause top-down reflection cracks. The results showed that top-down reflection cracks appeared only in composite pavements where the slab base had a low elastic modulus. [ABSTRACT FROM AUTHOR]

Concrete airfield pavements can frequently suffer from initially small and relatively shallow delamination of the subsurface concrete layer. It may be due to natural and forced temperature impact on the pavement. As a result of these impacts, thermal stresses and other phenomena are formed in the concrete slab. The significant phenomena are those related to the movement of water vapour in the slab cross-section and the associated processes leading to defects of the concrete structure. They are due to the complex interaction of various phenomena: thermal, humidity and strength that were considered damage stimulants. [ABSTRACT FROM AUTHOR]

Accurate monitoring of concrete pavement support condition is critical for pavement maintenance. This paper proposed a novel support condition monitoring method using distributed optical fiber sensing (DOFS) technology. The DOFS-based method can precisely monitor the support condition on a larger scale. Single-mode optical fiber with a particular rubber encapsulation was applied as a compression sensor, measuring the interfacial compression status between the concrete pavement slab and the pavement base through a compression-to-strain transfer mechanism. Finite element analysis (FEA) and laboratory experiments were conducted to compression-to-strain transfer mechanism. It was revealed that the average compression-to-strain transfer efficiency reached over 1900 μϵ/mm. The design parameters of the compression sensor were also provided based on the FEA and experiment results. A quasi-distributed sensing system was developed to capture the two-dimensional support condition by connecting the sensors in a particular path. The sensing system's effectiveness was demonstrated by conducting full-scale tests and using the pressure-sensitive film (PSF) as a comparison. The test results showed a great deal of applicability for support condition monitoring under concrete pavement. [ABSTRACT FROM AUTHOR]

Accurate estimation of the in situ strength of concrete at early age is very important as it provides the necessary information required to start subsequent construction operations. Overestimation of the strength may cause serious safety hazards and underestimation may lead to unnecessary costly delays. This study investigates the performance of the maturity method in estimating the strength of in situ concrete subjected to cold weather at early age. Instrumented concrete slabs were subjected to cold weather conditions at early ages and their strengths were measured using drilled core samples from the slab. Sensors embedded in the slabs measured the temperature in the concrete which was used to estimate the strength using the maturity method. The measured core strengths at 24 and 72 h after casting are then compared with the estimated strengths using the maturity method and its performance is evaluated. The core strengths are also compared with the strength of standard cylinders cured at the same condition as the slabs. More than 250 cylinders from two slab thicknesses and four batches of concrete were used in the experiments to obtain statistically significant experimental data. The results show that the maturity method performed much better than the standard cylinder strength. On average the standard cylinder strength underestimated the core strength by more than 40% while the maturity method overestimated the strength by less than 10% with a lower variation. [ABSTRACT FROM AUTHOR]

The void beneath cement concrete pavement slab (CCPS) is one of the common defects, which can cause the pavement cracking when heavy vehicle load is exerted on the pavement. The void expands when the water trapped inside erodes the inner surfaces of void circularly, bringing more cracks easily. Due to the close relationship with the erosion of the void, the hydrodynamic pressure distribution in saturated void beneath CCPS is investigated in this paper. Firstly, a theoretical expression of the hydrodynamic pressure in saturated void is proposed taking in account the law of mass conservation and the theorem of momentum. Secondly, the deformation patterns of the CCPS and the fluid-structure interaction (FSI) are discussed based on the proposed method. The results show that the hydrodynamic pressure and the water flow velocity in the void are overvalued while the rigid deformation pattern of CCPS is employed and the FSI is ignored. Finally, some influence factors are discussed. It is obtained that, both the maximum hydrodynamic pressure and the average velocity of water increase with the increase of the load amplitude, the vehicle speed and the void dimension. The conclusions are helpful for the prevention and maintenance of void beneath the CCPS. [ABSTRACT FROM AUTHOR]

The void at the bottom of a cement concrete slab is a common problem of composite pavements. It is of great significance to evaluate the spring stiffness, void size, and soil base elastic modulus at the bottom of cement concrete slab timely and accurately for the maintenance and guarantee of the pavement performance. In this paper, the composite pavement at a joint is modeled and the load transfer mechanism is realized by using spring groups for simulating the dowels that connect the two slabs of the joint. A database is established based on a large number of simulation results of joint load transfer efficiency and voids and the changing law of load transfer efficiency of cement concrete slab reveals their relationship. Taking into consideration the spring stiffness, void size, and soil base elastic modulus, the void evalua\tion method of composite pavement cement concrete slab is established by using back propagation neural network algorithm. The results show that the void evaluation method can provide the void determination map with two parameters. The values of the two parameters can be determined by the deflection basin. After querying the Atlas, the void determination can be more accurate. The research results provide scientific guidance for the void identification of the composite pavement and can effectively extend the service life of the pavement. [ABSTRACT FROM AUTHOR]

A rapid and reliable method to detect the activation of contraction joint cracks is needed to assess the effectiveness of sawcut depth and timing on new concrete pavements and for forensic investigation. A one-sided ultrasonic measurement technique is presented that detects the existence of a contraction joint crack, which is not visible from the concrete slab surface. A multi-sensor ultrasonic array device is used to generate and receive ultrasonic shear waves (S-wave) across the inspected joint. The acquired time-domain signals are used to calculate a newly defined feature, called normalised transmission energy (NTE), across the joint. A laboratory experiment investigated the proposed technique on three 500 × 500 × 150 mm3 concrete specimens with 38 mm notch depth, the first without a propagated crack, the second with a narrow width crack, and the third specimen with a full-depth open crack. The laboratory results demonstrate that the NTE technique can identify the existence or not of a crack beneath the notch. Finally, the NTE technique coupled with a 2D decision boundary equation was field validated on 152 concrete pavement contraction joints with various slab thickness (e.g. 102 to 152 mm) and notch depths (less than 38 mm) from multiple projects in Illinois and Iowa (USA). [ABSTRACT FROM AUTHOR]

Curling stresses in rigid pavements are the result of temperature gradient through the thickness of the concrete slab. These stresses have a periodic nature, and the induced cyclic flexural curling stresses lead to the cracking of the concrete slab. In a previous research by the authors, a phase change material (PCM)-rich concrete overlay was proposed as an effective method to control this failure mechanism. A PCM-rich concrete overlay is a concrete surface layer that contains a relatively high percentage of PCM. In the previous study, a phenomenological approach was employed, and it was demonstrated that the incorporation of PCM improves the curling fatigue performance of the concrete slab. Using fracture mechanics, this paper builds upon the findings of the previous study, and it serves as a mechanistic verification of the conclusions of the previous work. A modified Paris' Law was adopted to calculate the cumulative fatigue-fracture damage of the concrete slab due to cyclic thermally-induced curling stresses. The findings of this research demonstrated that the PCM-modified concrete slab undergoes a curling-induced fracture process that is less severe than the slab without the PCM. The impact of this reduction was quantified in terms of an improved fatigue-fracture performance of the pavement. [ABSTRACT FROM AUTHOR]

Under the repeated action of traffic and thermal loads, a cement concrete pavement slab may partially lose contact with its base course, and voids may develop underneath the slab. Such distress will greatly impact the pavement performance. To fill the voids and restore the base support to the slab, the technology of polymer grouting has been increasingly adopted in recent years due to its advantages of quick application and high efficiency. There is, however, a lack of research on the mechanistic responses and performance of such a repaired rigid pavement under coupled influences of thermal and traffic loads. Existing literature has mainly focused on normal cement concrete pavement structures (i.e., without polymer grouted voids). This study intends to fill the research gap by investigating the time-domain characteristics of thermal stress response of a cement concrete pavement with underlying voids filled with polymer grout, along with design traffic loads. The finite element method was adopted with a 3-dimensional nonlinear temperature field within the pavement. A program module was developed in the Abaqus FEA software environment for temperature effect analysis. It was found that under the coupling action of thermal and traffic loads, thermal stress had a greater influence on the critical slab stress at the slab corner than those at other slab locations. Through the comparative analysis before and after polymer grouting repair, the critical tensile stress at the slab corner under the vehicle and thermal loads can be effectively reduced. The polymer performance is stable after three years. [ABSTRACT FROM AUTHOR]

Steel-concrete composite box girders with corrugated steel webs (CSWs) are broadly used in bridge engineering, in which the joints between top RC slabs and steel girders with CSWs are usually subjected to transverse bending moments caused by off-center vehicle loads. Stud connectors arranged in the joints usually bear repeated pull-out forces in this case and are prone to fatigue failure. Therefore, two reduced scale joints between top slabs and weathering steel girders with CSWs were designed and tested, on which variable amplitude fatigue loads were applied to investigate the fatigue performance of studs incorporated in the joints. The two joints presented similar fatigue behavior, i.e., cracks of not more than 0.26 mm in width appeared on the surface of the top slab during the fatigue loading, and the separation of the top RC slabs and the top girder flanges was observed; meanwhile, minute cracks developed along the welds connecting the CSW with the bottom girder flange, and the stiffness of the joints gradually decreased due to the accumulation of fatigue damage. The two joints underwent 2,650,000 and 2,103,600 load cycles respectively before fatigue failure occurred. After partially demolishing the RC slabs, several welded head studs in the joints were observed fractured at the roots and detached from the top girder flange. Whereafter, finite element (FE) models referring to the test joints were developed and analyzed, and the effect of the wave height (WH) of the CSW and the transverse row spacing (TRS) of studs on the distribution of pull-out forces among studs was investigated. It showed that the pull-out force bore by each stud in the joint was distributed unevenly even in the same row. Then, a modification factor α was introduced to revise the pull-out forces of studs calculated in the theoretical method. An equation to determine the factor was fitted, considering the effect of the WH of the CSW and the TRS of studs. Finally, the detail category for studs bearing pull-out forces in the joints was discussed based on the experimental results and the collected test data, and it was preliminarily recommended studs subjected to pull-out forces can be classified into detail category 45 specified by Eurocode 3 in fatigue design. • Fatigue tests on the joint between the top slab and the steel girder with corrugated steel web (CSW). • Numerical analyses on the stress distribution of group studs in the joints between top slabs and steel girders with CSWs. • Fatigue detail category of studs subjected to pull-out forces caused by transverse bending moments. [ABSTRACT FROM AUTHOR]

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. • Precast SHCC slabs used to upgrade asphalt pavement with shallow damage (70 mm thick). • SHCC mix proportions optimized to enhance flexural strength for the PUTW application. • Full-scale cyclic wheel tests verify inter-slab load transfer by underlying asphalt. • Finite element model verifies and optimizes the overall structural performance. • Monitored full-scale field trial with 13 SHCC slabs at a bus stop in Singapore. [ABSTRACT FROM AUTHOR]

Beech dowels for shear force transfer in composite ceilings with board stacks and concrete Generally, timber‐concrete‐composite ceilings are built with notches and/or metal fasteners as connection. A new and steel‐free composite solution uses beech dowels for the transfer of shear forces. For this purpose, the timber profiles are milled to trapezoidal profiles on the upper side. Beech dowels, which are implemented transversely to the span direction in the profiles, ensure a fitting connection with the concrete layer. Experimental studies regarding the load‐bearing behaviour of the composite action were carried out. Due to the occurring shear forces, the timber profiles have to withstand local bearing stress in the dowel holes. The dowels sustain shear and compressive stress perpendicular to the grain, which substantially defines the compound stiffness. However, the adhesive bond and friction between timber and concrete affect the composite action significantly. The load‐bearing capacity of the connection is bounded by the shearing and splitting behaviour of the unreinforced concrete slab, since the dowel forces lead to intermittent stress. [ABSTRACT FROM AUTHOR]