Joint faulting behaviour of innovative short concrete slabs

Pavements are one of the largest assets of a city and their functional condition (ride quality) is priority for their clients. In jointed plain concrete pavements (JPCPs), the presence of joint faulting (JF) reduces the ride quality. Today, short slabs are available as a cost-effective JPCP innovation. The objective of this paper is to analyse the JF behaviour of JPCPs with short slabs. For this, a deterioration model to predict it and trends of JF observed in short slabs of Chile and the United States are considered. The HDM-4 model always yields lower JF per joint in short slabs than in traditional ones. However, real-world short slabs show not only lower JF per joint (that the modelled JF), but also that more joints do not necessarily mean more JF per length of pavement that affect the ride quality. One of the relevant explanatory factors for it is the radical reduction of crack width at joints, which produces a fundamental increase of the load transfer efficiency. To maintain favourable behaviour observed in the field it is recommended to assure joint activation and to provide adequate stiffness of the layers below the short slabs.Pavement Engineerin

Modelling the effect of plastic sheet curing on early age temperature development in concrete pavement

Prediction of the temperature development at an early age is a good starting point to assess the development of the restrained thermal stress and thermal cracking in rigid pavements. This paper presents a numerical early age concrete pavement temperature prediction model. It enables to evaluate the effect of various paving conditions, such as paving time, curing method, air temperature, wind speed, and the concrete placement temperature, on the early age concrete pavement performance. A critical review of current heat flux models at the pavement surface covered with a plastic sheet is presented. An extension of existing models to quantify the effect of the plastic sheet curing method is introduced, based on the energy balance method. The numerical implementation procedure for the proposed temperature prediction model is solved by the finite difference method. The temperature prediction model was verified with field measured data of two test sections. The predicted temperature shows a satisfying match with field measured data. Lastly, the effect of plastic sheet curing and its duration on the development of the pavement temperature was analysed by the proposed theoretical model.Pavement Engineerin

Innovations in concrete pavements for a sustainable infrastructure

Concrete pavements (CPs) are durable and they do not need periodic invasive maintenance interventions. Nevertheless, CPs are hardly chosen when only initial costs, instead of life-cycle costs, are considered in the evaluation. Nowadays, there are innovations in Jointed Plain Concrete Pavements (JPCPs) that reduce initial costs about 25% with respect to alternatives with equivalent structural capacity. This paper addresses the question if the innovations early-entry saw-cutting of joints, joints without seals and shorter joint spacing (without dowels bars) are able to maintain the traditional life-cycle performance of CPs. All these innovations affect the joints of the JPCP, and these ones the JPCP performance. Accordingly, the objective of the present paper is to analyse the effects of the joints behaviour on the performance of the JPCPs innovations. The joint behaviour is characterized by the joint activation and opening, the joint capacity to transfer traffic loads and the joint deterioration. The calculations of the joints activation and opening are made with a model developed by the authors. For the estimation of the joint transfer capacity; the results of finite-element software are used. The analysis is completed with field data of the JPCPs innovations. The innovations analysed contribute to a sustainable infrastructure as they can maintain, and even improve, the traditional life-cycle performance of CPs with lower initial costs. Nevertheless, for the design hypotheses to be valid, it is necessary to assure the joints activation and to limit the joints opening to 1.2 mm. With this purpose, for the analysed conditions, it is recommended to cut the joints at least at 30% of the JPCP thickness.Structural EngineeringCivil Engineering and Geoscience

Determination of fracture energy of early age concrete through a uniaxial tensile test on an un-notched specimen

Unlike the notched specimens for conventional concrete fracture tests, this paper introduces a deformation-controlled uniaxial tensile test on an un-notched specimen. The surface of the dog bone-shaped specimen is a second order parabolic curve, and the gradual change in the specimen shape does not lead to extreme stress concentrations. Another significant feature of the tension test set-up is that it is built with three hinges, to accommodate the alignment of the specimens. The specimen preparation, test conditions, and the tension test set-up are explained in detail. The fracture energy of the concrete is determined by the obtained complete softening curves. The fracture energy is found to increase with age, going towards a horizontal asymptote as concrete hardened in a tested age range of 1 day to 90 days. Moreover, the rate of development of the fracture energy was found to be higher when compared to tensile strength and stiffness.Pavement Engineerin

Uncracked joints in plain concrete pavements: causes, effects and possibilities of improvements

During the construction of Jointed Plain Concrete Pavements (JPCPs) in Chile, it was observed that joints remained uncracked. The objectives of this paper are to evaluate the effects of uncracked joints (UnCrJ) in JPCPs and to propose possible solutions or improvements to avoid or minimize this phenomenon. Considering low thermal amplitude as cause of UnCrJ, a rational-based, detailed and empirically validated model is used to predict UnCrJ and crack width. The modelled results are not only due to material changes but also to the location of the series of cracks in time in the JPCP system. The paper contributes with this rational approach, instead of an empirical-simplified one, to achieve the objectives. For the modelled conditions, the “as-built” slab length range is 8 m to 56 m instead of the 4 m designed one. Then, more curling, joint faulting, water infiltration in sealed joints and load transfer efficiency ≤ 70% are expected.The alternative solutions proposed are associated to innovations as short joints spacing, unsealed joints and saw-cuts up to 50% thickness made with thin blade (≤ 3mm), which was verified with new field evidence provided in the article.Pavement Engineerin

Experimental evaluation of load transfer efficiency of non-dowelled concrete pavements

Generally, joint performance in concrete pavements is evaluated in laboratory by applying dynamic loads that require large scale experimental setups. In order to propose a simplified laboratory test, a comprehensive literary review of the fundamentals of load transfer at joints is made, and the load transfer efficiency obtained via a reduced scale test is compared under static and dynamic conditions. The results confirm feasibility of static analysis via a reduced scale test for evaluating load transfer efficiency of non-dowelled concrete pavements.Pavement Engineerin

Application of aging methods to estimate long term performance of secondary materials for road construction

Long term performance of secondary materials is becoming a challenging aspect in road construction since due to their benefits they are being used on a large scale, but on the other hand their future behaviors are difficult to estimate. In this study, aging is proposed as a means of exploring the long-term mechanical and physical performance of secondary materials. A Blast Furnace Slag (BFS) mixture which is routinely used in the Netherlands in road (sub-) base construction was selected as a reference material. The A32 motorway in the Netherlands was used as a source of field aged granulated BFS materials. The base layer of this motorway, suddenly experienced serious failure. Different failure mechanisms have been hypothesized. In order to estimate future behavior of secondary materials and to prevent similar problems to occur an aging protocol was suggested to detect at an early stage potential poor material performance. Two types of aging approaches were chosen and applied to the field aged and fresh materials being steam aging and cyclic freezing and thawing. Both aging treatments have affected mechanical and chemical characteristics. The study of response variables showed there is a linkage between compressive strength, expansion, micro cracking and amount and type of binder.Structural EngineeringCivil Engineering and Geoscience

Laboratory characterization of the load transfer-crack width relation for innovative short concrete slabs pavements

Aggregate interlock is the dominant load transfer mechanism in non-dowelled Jointed Plain Concrete Pavements, as the innovative short concrete slabs. Although the Load Transfer Efficiency of this pavement innovation is based on that mechanism, the structural design methods do not relate the Load Transfer Efficiency by aggregate interlock with its direct cause, which is the Crack Width under the joints. The objective of the present article is to characterise in the laboratory the Load Transfer Efficiency−Crack Width relation for innovative short slabs Jointed Plain Concrete Pavements. Additionally, as an alternative to large-scale laboratory tests to study the Load Transfer Efficiency, a practical test on a reduced scale is proposed. The results confirmed that short slabs Jointed Plain Concrete Pavements with high-quality aggregates are able to provide adequate Load Transfer Efficiency (above 70%) without dowels bars. Based on the laboratory results, complemented with previous field data, a Load Transfer Efficiency−Crack Width curve is proposed and made available for structural design methods of short slabs Jointed Plain Concrete Pavements. Finally, the laboratory test on a reduced scale is useful to develop specific Load Transfer Efficiency−Crack Width relations using standard equipment available in traditional concrete laboratories.Pavement Engineerin

Fracture analysis of cement treated demolition waste using a lattice model

Fracture properties of cement treated demolition waste were investigated using a lattice model. In practice the investigated material is applied as a cement treated road base/subbase course. The granular aggregates used in this material were crushed recycled concrete and masonry. This results in six different types of phases in the mixture: recycled concrete, recycled masonry, mortar, interface between recycled concrete and mortar, interface between recycled masonry and mortar and interface between recycled concrete and masonry. In order to numerically analyze the fracture behavior of cement treated demolition waste, a cross section image of a cylindrical specimen (?150mm) for monotonic indirect tensile test (ITT) was digitized and processed to obtain a multiphase lattice image showing every individual phase. The mesh area used for the lattice model was 1 mm2. Simulation results show that when the simulated ITT loading direction varies on the image, the simulated indirect tensile strengths (ITS) have a larger scatter compared to the variation of experimental results of ITS in the laboratory. This indicates that the numerical simulation of cemented granular demolition waste using a 2D lattice model is strongly influenced by the loading direction on the simulated image. This should be because of high heterogeneity of the mixture, especially the arrangement of aggregates along the loading direction. With a model correlation factor 2, the average simulated ITS that is obtained under different loading directions on one image is comparable to the experimental ITS.Structural EngineeringCivil Engineering and Geoscience

Investigation of the resilient behavior of granular base materials with simple test apparatus

In many developing countries, where resources are at premium, thin asphalt layers or chip seals are widely used to provide a durable all weather pavement surfacing. In such pavements the role of granular layers is very important in the general performance of the structure. Pavement designs in these countries are empirical in nature and rely on simple input parameters like California Bearing Ratio (CBR) values. Although widely applicable the traditional CBR test does not provide the mechanical properties such as resilient and permanent deformation characteristics of granular road materials. This paper documents the characterization technique developed to determine the mechanical behavior of granular (sub-) base materials based on CBR test using repeated load cycles. The confining pressure developed in the complex CBR stress state is estimated using strain gauges. Finite Element analysis has been attempted to model the repeated load CBR (RL-CBR) and derive an equivalent resilient modulus. Furthermore, a large scale cyclic load triaxial test was carried out on coarse unbound granular materials (UGMs) to validate the result of the RL-CBR. The RL-CBR test reasonably estimates the resilient modulus of UGMs which can be used as an input in mechanistic pavement design analysis in the absence of triaxial testing facilitiesStructural EngineeringCivil Engineering and Geoscience