Question

Select an actual project of your civil engineering field. Provide an overview and brief of the project. Apply theory of production and supply and demand concepts on various features of the project.

Answer 1

Advance pavement design :

The objective of this research project is to develop an analytical model for rigid pavement joints that can be implemented into advanced pavement design models. This report documents a background investigation including a comprehensive review of rigid pavement joint models with a particular emphasis on their joint and foundation modeling capabilities. The major historical developments in airport rigid pavement design are discussed. Closed form solutions akin to those by Westergaard were derived in this study for the maximum responses on the unloaded side of a rigid pavement slab edge capable of a degree of load transfer. When used together with Westergaard's own closed form equations for the free edge problem, the formulae derived from this study constitute a complete solution of the edge load transfer problem, recognized over the years as a critical consideration in rigid pavement design.

Many road managers and stakeholders are looking for more and better options for the construction and maintenance of flexible and rigid pavements. Well-designed strategies for pavement construction and maintenance have attracted the interests of researchers since a large number of existing pavements are facing deterioration all over the world. The selection and engineering properties of paving materials are crucial factors affecting the durability and therefore demanding standards of sustainability of the constructed pavement. Researchers worldwide are putting extensive efforts to develop and promote advanced pavement materials and structures for constructing and maintaining sustainable pavements. Pavement materials that can improve durability, cut costs, reduce depletion of raw materials, and lower environmental impacts are desirable for such purposes. Meanwhile, some new design ideas that differ from traditional pavement structures have shown noticeable benefits in terms of pavement durability or cost. In this regard, exploring the benefits of using advanced materials in flexible and rigid pavements is continuously investigated and has currently gained increasing attention. The articles of this issue cover original research papers that will contribute to the development and implementation of advanced pavement materials for sustainable transportation infrastructure.

The current Hungarian pavement overlay design method is outdated in respect of considering techniques that are already commonly used. In this paper we present the summary of a mechanical approach of overlay design currently under development at the Budapest University of Technology and Economics, Department of Highway and Railway Engineering. The scope of the method is to take into consideration the actual bearing capacity and fatigue performance of the pavement structure which is divided into homogenous sections determined based on bearing capacity. The method uses the area parameter of the deflection bowl to identify the representatively weak sections of the road. Based on actual pavement thickness and deflection data, back-calculation is used to determine the moduli of the layers. By using the Odemark transformation, strains are computed for various overlay thicknesses using MET. Finally, given the design traffic of the road sections in ESALs the required overlay thickness is determined as a function of the allowed strain at the bottom of the asphalt layers. The method is demonstrated in a case study, the results, as expected, provided a more refined and fit for purpose solution, compared to the current conservative methods.A pavement structure, understandably, is interposed between the wheel and ground (soil), in order to support and sustain the repeated applications of wheel loads without undergoing undue deformation. The roadway structure is, thus, expected to be stable and non yielding so as to generate only least possible rolling resistance for the heavy wheel loads. The pavement is made of higher quality materials, though, the strength of materials of different layers differ with a more specific functional attribute. Based on the composition, pavement structure is categorised as either flexible or rigid or composite.Need for Advanced /High-Performance Materials and Technologies

With natural materials getting depleted, efforts were on to find succor in other methods and materials, but till recently, the development of improved materials was mainly focused at improving specific properties of locally available materials by using additives (admixtures, extenders, modifiers). There had been no strong impetus to seriously consider replacing conventional construction materials with new materials. However, by realising that the age of natural construction materials and the use of conventional materials in their present form is coming to an end at a faster pace. The new technologies need to be developed fast to continue to support the construction activities including rehabilitation and reconstruction of pavements along the road network. Thus, concerns about limited availability and sustainability are driving the search for new and advanced materials for roadway construction.

The currently used materials for pavement construction can be classified as follows:

1. Natural (Raw) Materials: Stone or brick aggregates, bitumen and natural resins.
2. Manufactured (Processed) Materials. Metallic materials (steel, aluminum, zinc), ceramic-based materials (portland cement, natural pozzolans), industrial by-product materials (fly ash, slag, silica fume), other waste products (crumb rubber), polymers, fibers and fiber-reinforced polymers, synthetic aggregates—typically, lightweight and slag aggregates.
3. Composite Manufactured Materials like. PCC and clad steels.

Further, there is an array of identified materials under the above classes of materials that show potential applications and these advanced materials identified include the following:

1. Aggregate Materials: Synthetic Aggregates, Manufactured Aggregate Using Captured CO2
2. Bituminous Binder Materials: Sulfur-Extended Bitumen/Asphalt, Bio-Derived Bituminous/Asphalt Binders, High Modified Asphalt Binders (HIMA)
3. Bituminous Mixes: Warm Asphalt Mixtures, Perpetual Asphalt Pavement Systems, Porous Asphalt Pavement, Recycled Asphalt Pavements (RAP).
4. Cementitious Materials: Performance-Specified Cements, Next-Generation Sustainable Cements, Eco-Friendly Cements, Energetically Modified Cement.
5. Concrete Materials: Engineered Cement Composites (ECCs), Titanium Dioxide–Modified Concrete, Pervious Concrete, Self-Consolidating Concrete, Sulphur Concrete, Autoclaved Aerated Concrete, Geopolymer Concrete, Hydrophobic Concrete, Ductile Concrete.
6. Metallic and Polymer Materials: Vitreous Ceramic Coatings for Reinforcing Steel, Fiber-Reinforced Polymer Bars for CRCPs and Dowel Bars, Zinc-Clad Dowel Bars, Microcomposite Steel for Dowels/Tie Bars.

However, the article is focused on the emerging and potential materials and techniques that are more relevant to flexible pavement only.

Factors Responsible for The Paradigm Shift

There is a strong need worldwide to optimise the use of materials currently used for pavement construction and to seek advanced materials that are cheaper, better performing, and less damaging to the environment. The factors seeking advanced highway construction materials include:

• Conservation of resources—support national efforts to create sustainable solutions to minimise the impact of construction on the environment
• Reduced ecological footprint
• Reduced costs—get more lane-kilometers constructed or rehabilitated for a given constrained budget
• Extended service life
• Optimised use of locally available materials
• Achieving environmental benefits—reduced carbon footprint, reduced congestion-related emissions
• Reduced work zone–related traffic delays and safety concerns—use materials that reduce the potential for early failures

Emerging Technology Specifications for Flexible Pavements

Presently, there is a necessity of extending our road network to all terrains and environment and flexible pavement being preferred pavement type, there is an immediate need of switching over to high performance/new/alternate materials and technologies that are applicable to flexible pavements and are able to provide sustainable solutions. To exemplify, bitumen bound layers are normally used in wearing, surfacing, base and binder courses. They may be thick or thin, hot or cold, plant-mixed or site-mixed and so on, but the binding constituent, bitumen has many variants at this time and may include neat or straight run bitumen, cutback bitumen, fluxed bitumen, bitumen emulsion, to name. Likewise, there are other options with different materials to be used in different layers of flexible pavements. The promising new technologies are:

• High performance materials (modified bitumen & multi-grade bitumen)
• Stone matrix asphalt (SMA)
• Warm mix technology
• Cold bituminous mix and half-warm mix technologies
• Waste plastic in road construction
• Self repairing roads
• Micro surfacing
• Recycling (RAP in bituminous and granular layers)
• Sulphur extended bituminous base courses
• Geo-cells and geo-textiles in pavement construction
• New generation additives for soil stabilisation
• Waste materials including industrial slags and fly ash