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Sustainability opportunities for concrete pavements
Jim Grove, Suneel Vanikar and Leif Wathne
There is an increasing awareness about sustainability in our societies. Even in the highway construction sector, there is an understanding that construction activities should focus on ways to preserve or enhance economic, environmental and social well being. Sustainability approaches can be incorporated during the design, construction, and maintenance phases of highway projects. Concrete paving traditionally incorporates many environmentally responsible practices into routine practice and has done so for decades. Building on these current practices will aid in advancing sustainable technology to further raise the bar. This paper outlines the opportunities that are available before construction, during construction, and after construction of concrete pavements. A look into the future is also included, providing a glimpse of new materials and paving innovations. Opportunities before construction must focus on longevity. They include optimizing the pavement design, the selection of by-product materials for the concrete mixture, and minimizing the amount of cement in the mixture. The use of supplementary cementitious material both utilizes by-product material at the same time enhancing the performance of concrete. Other responsible uses of by-products are discussed. Opportunities during construction focus on the use of locally available materials, and means to complete projects sooner. Through the use of two lift paving, local materials may be used that normally do not meet durability requirements. In-place recycling can save time, money, and reduce the environmental impact. Methods to complete projects sooner positively impact sustainability by minimizing work zone durations and minimizing the impact to the travelling public. Opportunities after construction focus on maintenance practices which extend the pavement life thereby increasing safety and delaying the need for future construction. Concrete pavement restoration and concrete overlays provide a long term solution to many pavement rehabilitation needs. By taking advantage of all these sustainable strategies before, during, and after construction, highway administrators and engineers can ensure that highway infrastructure is part of the solution to sustainability challenges, enhancing their overall societal footprint in the process.
Fly ash blended cement for concrete pavements
D.G. Kadkade and P.K. Mishra
Concrete pavements have long been considered the sustainable alternative because they last longer than bituminous ones. The example of about seven-decade-old Marine-drive road in Mumbai is a living testimony to this fact. However, recent focus on sustainable constructions has encouraged the concept of green constructions for roads and highways. Green highways are therefore expected to be environmentally responsible and sustainable in all aspects including design, construction and maintenance. Concrete pavement can meet this requirement with its many benefits. For example, concrete pavements have great rigidity and consequently a good distribution of the load on the foundation and excellent fatigue behaviour. Oil, organic substances and other chemicals do not affect such surfaces. The lighter colour of concrete pavement reduces the power needed to adequately illuminate roads and can help counteract the urban heat-island phenomenon. Finally, the durability and wear resistance of concrete pavements ensure surface characteristics for quiet, fuel-efficient and safe roadways. However, what is remarkable about concrete pavements is that they can be designed by incorporating supplementary cements materials such as fly ash, making them more sustainable than ordinary Portland cement pavements.
Edge stresses and deflections of unbonded conventional whitetopping overlay
D.R. Jundhare, K.C. Khare and R.K. Jain
This paper reports the edge stresses and deflections of an unbonded conventional whitetopping overlay computed using Finite Element Method (FEM) with 3-dimensional (3D) brick elements SOLID45. The model offers eight nodes with three degrees of freedom per node- translations in the nodal x, y and z directions to represent the plain cement concrete overlay and Hot Mix Asphalt (HMA). The subgrade was modeled as the Winkler foundation that consists of a bed of closely spaced, independent, linear springs. Axle loading was applied on the edge of the overlay to carryout the nonlinear static analysis using ‘ANSYS’ (Version 10) software. The stresses and deflections obtained were compared and validated with three sets of data; one data obtained from Falling Weight Deflectometer (FWD) test conducted in the field, second from theoretical values from Westergaard’s analysis and finally using ALIZE Model.
Use of polypropylene fibre reinforced concrete as a construction material for rigid pavements
Rahul Jain, Rishi Gupta, Makrand G. Khare and Ashish A. Dharmadhikari
Quantitatively concrete occupies the largest volume in any modern construction activity and it is expected that there will be no substitute for concrete in the near future. Since such high volumes of concrete are being used for new construction, it is imperative to produce good quality concrete that will be durable with enhanced mechanical properties to maximize the service life of a structure. Though good concrete can be produced using automation and controlled environment, it is not possible to alter its inherent brittle nature and the lack of any tensile strength. In this context, fibre reinforced concrete (FRC) seems to be a viable alternative. The present study focuses on feasibility of using polypropylene fibres as secondary reinforcement to concrete to change its brittle nature. Accordingly, various percentages of polypropylene fibres were added to concrete and a series of laboratory experiments were conducted to investigate the use of polypropylene FRC in rigid pavements. Mechanical properties of concrete such as compressive strength, modulus of elasticity, flexural strength and toughness, abrasion and impact were determined. Except for abrasion, polypropylene fibres improved the mechanical properties of control concrete and 0.6% by volume was found to be the ideal fibre dosage.
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