Accelerated Laboratory Testing for Reflective Cracking

One of the most used methods of rehabilitation of road structures is the laying of a protective asphalt layer over a degraded concrete. The main problem of this solution is the reflective cracking, more precisely the transmission of the existing cracks in the lower layer in the asphalt pavement. The method presented in this article involves an accelerated laboratory test on specimens composed of a pre-cracked concrete slab over which an asphalt slab is glued, subjected to equivalent traffic loads. This test allows the observation of the crack propagation from the lower layer to the upper layer, until it yields, through parameters such as deformed specimen, opening and length of the crack in asphalt, but also the opening of the existing crack in concrete, relative to the number of cycles. By relating these parameters, important conclusions can be drawn about the behavior of the composite structure at reflective cracking, being able to choose the optimal recipe of the protective asphalt layer.

Investigation of the Effect of the Deck Material on the Cost in Cable-Stayed Bridges with Different Spans

Recent developments in the social sphere also cause an increase in transportation activities. Increased transport activities lead to the construction of new roads and bridges. Different bridge construction systems are available to overcome large span obstacles. Cable-stayed bridges are more advantageous construction systems than other bridge type building carrier systems in overcoming large spans through suspension cables. Therefore, it is also widely preferred by designers. The biggest factor in the development of cable-stayed bridges is undoubtedly steel cables. Cable-stayed bridges are bridge structures that become lighter with the increase of the span, which has a more expanded flexibility, and that includes a cable system with the effect of nonlinear factors. Costs of cable-stayed bridges vary according to different spans. The span as well as the deck material used in the bridge system have a great effect on the cost. In cable-stayed bridge systems, decks are constructed of reinforced concrete and steel. The costs of cable-stayed bridges are widely discussed around the world; therefore, the effect of the span and deck material on the cost of cable-stayed bridges is being investigated. The main bearing elements of such bridges are cables, decks, and towers, and among these elements, the tower bridge carries all the weight of the bridge, even other external loads such as vehicle, wind, etc. In this study, the three-dimensional model of the cable, deck and tower elements that make up the cable-stayed bridge system was created and analysed using the CSI Bridge Program. The AASHTO LRFD Standards, which are widely used in the analysis of bridge systems with the CSI Bridge program and the design of bridge systems in the world, were used. In the study, the analysis and designs of cable-stayed bridges with reinforced concrete and steel deck at 250, 500, 750, 1000, 1500, 2000 meters span were carried out. The amount of materials and costs used in the analysis and design of the cable-stayed bridge systems were obtained and the results were interpreted.

Static and Dynamic Structural Health Monitoring System for Bridges

This document describes a system for static and dynamic monitoring of the structural health of bridges, but not only. The need to develop the system resulted from the difficulties encountered by the authors in installing and operating complex monitoring systems, composed of elements from different manufacturers, with different measurement technologies, power supplies, communication modes and software applications. The described system facilitates the integration of different measurements, sensors, power supplies and communication technologies, in a unitary system that allows both static and dynamic measurements, simultaneously.

Effects of Coarse Aggregate Shape and Texture on Engineering Properties of Roller Compacted Concrete Prepared for High Traffic Routes

Use of roller-compacted concrete in pavement construction is increasing. Roller compacted concrete is a zero-slump, highly compacted concrete that is placed by equipment similar to that used in asphalt pavement construction. This investigation was conducted to collect the state-of-the-art information on effects of coarse aggregate size and texture on the strength and workability of roller-compacted concrete (RCC) for pavement construction and maintenance. Concrete specimens containing cubical and rough coarse aggregate, irregular and rough coarse aggregate, angular and rough coarse aggregate, rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate were prepared at 1:3:3 concrete mix ratio and 0.4 water cement ratio. Laboratory testing of specimens derived from the concrete specimens showed excellent results for cubical and rough coarse aggregate, irregular and rough coarse aggregate, and angular and rough coarse aggregate. Specimens from the rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate performed poorly in laboratory. The study therefore recommends the use of cubical and rough coarse aggregate, and irregular and rough coarse aggregate in the production of roller-compacted concrete for pavement construction and maintenance.

Carbonation Resistance Classes of Concretes

Concrete carbonation is a phenomenon that occurs by the penetration into the cement stone of CO2 present in the atmosphere. The phenomenon occurs in the presence of water in which CO2 dissolves, forming carbonate ions, which in turn react with calcium ions in the pores of the concrete, resulting in calcium carbonate (calcite). The diffusion of CO2 occurs through pores and surface defects, it thus penetrates deeper into the concrete and the carbonation reaction can occur at a greater depth, eventually exceeding the thickness of the cover, causing corrosion of the reinforcement. [1] In the case of reinforced concrete bridges, corrosion induced by carbonation of concrete is one of the main causes of degradation. Thus, in the design stage of the reinforced concrete bridge structures, the inevitable process of carbonation of the concrete must be taken into account, in the design of the durability, by calculating the thickness of the concrete cover layer. This article aims to present the concept of carbonation resistance class, which will be a major change in the standard based on which the thickness of the concrete cover for reinforcement will be determined. This presentation is made in the context of the European performance approach to durability. In this sense, an analysis of the experimental results obtained in research on concrete prepared with different types of cements, carried out in collaboration with the laboratory of the Reinforced Concrete Structures Department, within the Technical University of Civil Engineering Bucharest. Proposals for classification in the carbonation resistance classes for concretes prepared with two types of cements are also presented.

Research on the Parameters Influencing the Numerical Analysis of the Fatigue Behaviour of a Forklift-ARM

Estimating the remaining service life of a forklift for an objective reference is not only a requirement of the applicable legislation but also represents a challenge for specialized technical staff. It is well known that the first fatigue failure element of a forklift is its fork. A simulation using the SolidWorks suite and its result is presented in this article. It allows the identification of critical areas of fatigue failure. Based on the design of the subassembly and the loading scheme of the original product, the model under analysis with finite element was made on a 1: 1 scale. The filet areas also required a comparative analysis of the results obtained depending on the choice of mesh and discretization element. Starting from the mechanical properties of the material as well as the association with the characteristic fatigue yield curves (Wohler), a method for estimating the remaining service life of the structure is proposed. The aspect related to obtaining exact results without an excessive consumption of computing resources was also taken into account.

Characterization of Coconut Shell Ash and Eggshell Powder as Supplementary Cementitious Materials in Roller Compacted Concrete Industrial Access Pavements and Parking Facilities

The cost of cement used in concrete works is on the increase and unaffordable, yet the need for hydraulic cement concrete and other cement concrete based infrastructures keeps growing with increasing population, thus the need to find alternative binding materials that can be used solely or in partial replacement of cement. The use of waste materials with pozzolanic properties in concrete production is a becoming a worldwide practice. The assessment of the pozzolanic activity of cement replacement materials is becoming increasingly important because of the need for more sustainable cementing products. In this study, a mixture of coconut shell ash and eggshell powder is used as partial replacement of hydraulic cement in ranges of 0%, 5%, 10%, 15%, and 20%. The concrete specimens were prepared at 1: 3: 2.5 mix ratio of cementitious material, fine aggregate and coarse aggregate. The mix ratio satisfied the minimum cement content of 148.32kg/m3 (250Ib/yd3) and the minimum cementitious material content of 267 kg/m3 (450Ib/yd3) for roller compacted concrete pavement. The compressive strength, splitting tensile strength and flexural strength tests were carried out to assess the strength characteristics of ternary concrete mixture containing coconut shell ash and eggshell powder and the feasibility of using coconut shell ash and eggshell powder as partial replacement of cement in industrial plant access concrete roads and parking lots. The results indicate that a mixture of coconut shell ash and eggshell powder can be used up to 20% by weight for replacement of cement in roller compacted industrial plant access concrete roads and parking lots.

Residents’ Willingness to Adopt Cycling as Intra-City Transport in Calabar, Nigeria

This study investigated the willingness of residents to use bicycles for intra-city transportation in Calabar, South-South Nigeria. Administered questionnaires were successfully retrieved (82%) from residents of all income and employment groups in the 22 political wards of the study area. Stratified sampling technique was used to select survey participants. Initial socioeconomic characteristics of respondents in intercept only model was used to predict the willingness of respondents to ride in the city. Twelve problems of bicycle transportation were further presented to participants who rated them using a six-point scale (1-6), highly unwilling to highly willing to ride, respectively. Logistic Regression Analysis was employed to predict the probability that a respondent would be willing to ride. The predictor variables were respondents’ gender, age, education, occupational status, 12 bicycle infrastructure characteristics and dummy variables coding each socioeconomic scenario. A test of the full model versus a model with intercept only was statistically significant, χ2 (24, N = 315) = 50.5, p < .001 and χ2 (19, N = 315) = 36.5, p < .001. The model was able to correctly classify 86% of those willing to ride and 29.1% of those unwilling to ride, for an overall success rate of 66.2%. The study revealed that there is no gender sensitivity in the willingness of residents to ride in the city. In model 2, the odd ratio of some bicycle infrastructure characteristics such as bicycle lanes (1.181), conflicts with motorist (1.338), lack of respect for cycling (1.078), culture/stigma (1.046), weather (1.013), potholes (1.222), safety issues (1.280), and illumination (1.241) are more significant in predicting the probability of respondents to ride bicycles. The study recommended designated bicycle paths/trails to motivate residents to ride bicycles in the city.

Sustainable Urban Transport on Three Wheels

Many of our global warming problems come from transport. The majority of people who need transport the most in the developing world are too poor to pay for the highest-technology vehicles which are not polluting. In the past 10 years, 3-6-passenger, battery-powered, Small Electric Passenger Vehicles (as this article is calling them, SEPVs) have appeared in major cities in the developing world. These slow, relatively safe, easily maneuverable, non-polluting and low-cost vehicles, on their three little wheels, are cutting the size of the world’s transport carbon footprint. Recognize that this paper is only focused on carbon footprint: carbon emissions. It is not about “pollution in general” or “emissions in general”. No other published article has explicitly considered the potential of the SEPV to contribute in reducing a nation's contribution to carbon footprint and thus to global warming. This article makes the case for building urban transport strategy and policy around such vehicles, in developing countries, in order to lower the countries' carbon footprint: that is its original contribution. The data showed that the SEPVs made a significant contribution to reducing the potential carbon footprint of transport in the small city of Cox’s Bazar, in Bangladesh, proportionate to its population. The inference is that SEPVs could reduce the carbon footprint of the nation if they become a major, integrated part of urban transport in the megacities, which creates most of the country's carbon footprint. Other developing countries should study Cox's Bazar's example. India is already ahead of the game.

Special-Purpose River-Port Sediment Valorization as Road Construction Material Emphasising Environmental Aspects

Special-purpose river port sediment was investigated for its potential use as a road construction material. Sediment samples were extracted from three locations in three small river ports, and detailed laboratory research was conducted to determine its basic mechanical properties and characteristics that can potentially have an adverse influence in a roadside environment. The results of the research conducted indicate that there is a need for systematic monitoring of the quality and quantity of sediment in special-purpose river ports of the Danube River Basin to maintain its mobility and prevent flooding. The basic engineering characteristics (Proctor elements, Atterberg limits, California bearing ratio, and unconfined compressive strength) determined represent the good potential of the sediment samples tested herein for use in road construction. In addition, the chemical characteristics tested indicate the need for detailed analyses of the potential environmental risk before application in civil engineering structures