Nano-scale evaluation of moisture damage in asphalt

Moisture damage is one of the major problems of asphalt pavements in United States. The moisture damage problem in asphalt has been studied for decades; still it remains an unsolved problem. Traditional macro-scale tests and methods failed to describe how and what factors affect moisture damage because moisture damage in asphalt is related to asphalt chemistry and adhesion characteristics, which are below micron scale phenomena. To this end, asphalt chemistry and adhesion values are studied at nano-scale to understand moisture damage in this study. Nano-scale measurements are conducted using an Atomic Force Microscope (AFM) in the laboratory. In an AFM test, adhesion forces of dry and wet asphalt samples are measured by probing the sample surface with AFM tips. Nano-scale pull-off force or adhesion between sample molecules and tip molecules are measured. To facilitate the study of asphalt chemistry, AFM tips are modified using chemical functional groups such as carboxyl (-COOH), hydroxyl (-OH), ammin (-NH3) and methyl (-CH3), representing the chemistry of asphalt binder. Thus functionalized tips facilitate the measurement of adhesion within the asphalt binder. In addition, silicon nitride (Si3N4) tips are used. Silicon nitride resembles aggregate molecules (e.g. silica aggregate) that are used to produce asphalt concrete or pavements. Thus adhesion value measured using a silicon nitride tip can be considered as the adhesion value of asphalt-aggregate interface. It is shown in this study that the adhesion within the asphalt binder varies depending on the chemistry of asphalt. AFM testing on asphalt is non-trivial and very challenging as AFM tips stick to the asphalt surface due to the viscous and soft nature of asphalt binder. AFM testing also requires smooth surface of a test sample. This study has developed a methodology for asphalt sample preparation for AFM testing. Simply, pouring asphalt binder on a glass substrate and melting to free flow and then cooling it generates an AFM asphalt sample with a root mean square surface roughness below 10 nm. Such sample surface is smooth enough for AFM testing. Through trial and error, this study has calibrated a set of AFM testing parameters that are suitable for successful adhesion measurement in asphalt binder. In all cases, a set of AFM samples are tested under dry condition, and a set of identical samples are tested after wet conditioning. Polymer is almost an essential component of asphalt binders now-a-days. However it is not known whether polymer modification helps reduce moisture damage potential of asphalt. Therefore, both base binder and polymer modified asphalt binder are characterized herein using AFM. Two common polymers Styrene-Butadyne (SB) and Styrene-Butadyne-Styrene (SBS) are used to modify the base asphalt. The goal is to examine whether polymer modification helps reduce moisture damage at nano-scale. In addition to polymer, a chemical modifier known as Elvaloy is included in this study to examine whether Elvaloy is more effective than polymer in regards to moisture damage. It is shown that both base and modified asphalt binders are vulnerable to moisture damage to some degree. However, base binder is the most susceptible to moisture damage among all the binders. It is evident that the SB polymer modification of asphalt is good for interface adhesion, whereas the SBS polymer modification is good for achieving higher adhesion within the asphalt binder. Antistripping agents are commonly used to reduce moisture damage potential of an asphalt binder. A number of antistripping agents are available in the market. However, it is not know which antistripping works better than others. To examine, five common antistripping agents such as lime, klingbeta, wetfix, morlife and unichem are considered for AFM testing in this study. It is evident from this study that moisture damage occurs in asphalt binder having an antistripping agent. Hydrated lime provides higher moisture damage resistance to asphalt binders that the liquid antistripping agents such as morlife, unichem, klingbeta, and wetfix. Statistical analysis of the adhesion test results is performed. Based on Pearsons p-value (significance test), it is concluded that the adhesion value measure by an AFM varies with the type and amount of antistripping agent present in an asphalt sample. Finally, an attempt is made to correlate nano-scale adhesion value of an asphalt binder to macro-scale strength value representing moisture damage. Only polymer modified binders are considered for examining such correlations. Macro-scale indirect tension tests are conducted on wet and dry asphalt concrete samples. A good correlation exists between the macro-scale indirect tensile strength ratio, and nano-scale adhesion ratio of wet and dry samples.\u2

Use of a New Transportation Algorithm for Profit Maximization

A transportation calculation is advanced, and it makes it possible to be able to effectively plan the assets with the end goal of augmenting the benefit of an assembling organization. The distribution indicators (DI) have been resolved from the distinction of the bigger unit profit and the average value of total unit profit of each row and column. Also, the area of the fundamental cells has been resolved as the biggest entrance of the transportation table (TT) along the biggest DI. The most extreme benefit given by this calculation is closer to the other benefit. The strategy, however, is represented with numerical examples to legitimize its proficiency

Urban-Biased SME Finance in Bangladesh: Way to Solve the Puzzle

Small and Medium Enterprises (SMEs) play a vital role in the economic progress of developing countries such as Bangladesh. SMEs have earned special significance for their role in poverty reduction programs and potential contribution to general economic and industrial growth. SMEs are considered one of the motivating forces of Inclusive Growth, which has become the national policy of Bangladesh Bank in the past few years. Nevertheless, it can be questioned whether SMEs in Bangladesh are making any contribution to the inclusive growth. There is evidence which indicates that SME credits are concentrated in the urban regions than in rural areas by a notable margin, although Bangladesh Bank has achieved its targeted SME credit disbursement in recent years. Therefore the study aims to discover the reason for this urban concentration of financial institutions in Bangladesh. We have collected data from Bangladesh Bank's own data bank. In addition, the study looks at the potential role of Bangladesh Bank, as well as examining what policy measures can be undertaken to improve access to SME credit by rural entrepreneurs, in order to achieve inclusive growth in Bangladesh. Keywords: SME, Inclusive Growth, Bangladesh, Credit, Bangladesh bank

Particle-scale numerical study on screening processes

The present study aimed to increase the understanding of the industrial screening process by using the discrete element method simulation (DEM) and machine learning modelling. Thus, the study focused on understanding the fundamentals of the complicated screening processes by investigating the process model with different controlling factors through particle-scale analysis. The particle-scale analysis was also linked to several macroscopic models and screening processes such as percolation of particles under vibration, the local passing of particles from the screen, choking of screening, non-spherical shaped particles contact detection and packing and machine learning modelling. The computational and theoretical analyses as well as machine leaning helped to clarify the use of particle-scale analysis and screening processes in several areas. The outcomes of this thesis include: (i) the percolation of particles under vibration and the machine learning modelling of percolation velocity to predict the size ratio threshold; (ii) a better understanding of screening process based on local passing of inclined and multi-deck screen and physics informed machine learning modelling to predict the particles passing; (iii) a logical model to predict the choking judgement of screen while combining the numerical results and machine learning and (iv) a novel contact force model for non-spherical particles by Fourier transformation and packing. The research in this thesis is useful for the fundamental understanding of the effect of particles’ contact force, operational conditions, particle properties, percolation and sieving on the screening process. Moreover, the novel process models based on artificial intelligence modelling, DEM simulation, and physics laws can help the design, control and optimisation of screening processes

Evaluation of Foundation Difficulties over Soft Organic Soil

Over the past 50 years, Dhaka, the Capital of Bangladesh, has experienced a rapid growth of urban population. This high population increase demands rapid expansion of the city. Unfortunately, most parts of Dhaka having competent subsoil for building construction are already exhausted. As such, new areas are being reclaimed by both government and private agencies using dredged fill from nearby river sources. A very soft organic layer exists below the filling layer that is highly plastic and highly compressible. SPT Nvalues of filling layer and organic layer vary from 2 to 11 and 1 to 2, respectively. It is observed that settlement of the organic layer varied from about 242 mm to 637 mm in between 1.8 to 12.7 years, respectively, due to overburden pressure of 100 kPa. Moreover, the existing organic layer may cause negative skin friction to the pile foundation and make foundation difficulties

Compressive behavior of perlite/sodium silicate composite foam modified by boric acid

In this work lightweight expanded perlite/sodium silicate composite foams were manufactured with varying quantities of boric acid (BA) 0-2.88 wt.%. The composites were characterized for density, compressive strength (CS), compressive modulus (CM), and energy absorption (EA) up to 50% strain. The compression tests were also conducted at various crosshead speeds to evaluate the strain rate dependency of the foams. The hygroscopic tests were done to evaluate water absorption properties and investigate the effects of water absorption on the compressive properties of the foams. The CS, CM, and EA of the foams increased for a boric acid content of 0.74 wt.%, but further addition of BA caused a gradual decrease in these characteristics. The range of sp. CS (3.80-5.93 MPa/(g/cm3)) achieved were found to be well compatible with the values of building materials in the literature. The foams appeared to be sensitive to the strain rate in compression, causing variations in the compressive properties as well as the trends of stress-strain curves. Furthermore, the addition of BA in the composite reduced water absorption up to a BA content of 1.46 wt.%. The compressive properties were also highly influenced by the hygrometric test