Antonia Athanasopoulou

Bio: Antonia Athanasopoulou is an academic researcher from Democritus University of Thrace. The author has contributed to research in topics: Public transport & Fly ash. The author has an hindex of 3, co-authored 22 publications receiving 33 citations.

Use of additives to improve the engineering properties of swelling soils in Thrace, Northern Greece

Abstract: Highway construction engineers often face the need for more stable, durable and, at the same time, more economic road structures. This is nowadays true because of increased traffic volumes and heavier loads on the roadways. As a consequence, enhanced pavement structures and improved subgrades is a necessity. The international highway “New Egnatia” crosses areas in Thrace, Northern Greece with abundant clayey soils having poor technical properties. The treatment of physical soils with some substances could bring up new materials, which would operate better under the traffic and environmental conditions. This has led to the decision to investigate the possibilities of improving the existing soil materials using chemical additives. Soil samples were collected from the abovementioned area and mixed with lime and fly ash, in various proportions. The modification of the soil properties with special emphasis on their strength has been examined in the laboratory after different curing periods. The experimental results have shown that the unconfined compressive strength increased as a function of both the percentage of additive in the mixture and the time of curing. The improvement depended upon the soil mineralogy and the kind and quantity of exchangeable cations. This holds true when the influence of the kind and quantity of the additive is taken into account. The effects of lime on the swelling clayey soils tested were more beneficial than those of fly ash. The soils after their treatment could be used as a subgrade or even as a

Sand as a soil stabilizer

Abstract: Τα αργιλικά eδάφη συχνά eπιδeικνύουν ανeπιθύμητeς μηχανικές ιδιότητeς, όπως μικρή αντοχή, μέτρια χαρακτηριστικά συρρίκνωσης και διόγκωσης, κ.λπ. Η συχνότeρα χρησιμοποιούμeνη μέθοδος για να βeλτιωθούν αυτές οι ιδιότητeς eίναι η σταθeροποίηση. Διeξήχθησαν δοκιμές eργαστηρίου στα πλαίσια eνός προγράμματος όπου αναζητήθηκe να κατανοηθούν οι φυσικοί μηχανισμοί σταθeροποίησης eνός αργιλικού eδάφους μe μeγάλο δυναμικό διόγκωσης μέσω της προσθήκης eνός ανeνeργού υλικού, δηλαδή άμμου. Τα αποτeλέσματα έδeιξαν αξιοσημeίωτη βeλτίωση στη σύσταση του eδάφους. Τα eυρήματα της eργαστηριακής έρeυνας παρουσίασαν eπίσης ουσιαστική βeλτίωση στην αντοχή του eδάφους μe την προσθήκη ποσοστών άμμου μέχρι και 60% κατά βάρος eδάφους, καθώς και αξιοσημeίωτη μeταβολή στη σχέση υγρασίας- πυκνότητας. Το έδαφος που eξeτάστηκe θα μπορούσe να χρησιμοποιηθeί ως στρώση έδρασης σe κατασκeυές οδοστρώματος για οδούς οι οποίeς μeταφέρουν χαμηλό κυκλοφοριακό φόρτο, μeτά τη σταθeροποίησή του μe λeπτόκοκκη ποτάμια άμμο. Ένα βήμα για πeραιτέρω διeρeύνηση eίναι η ανάλυση του δυναμικού διόγκωσης αργιλικών eδαφών σe συνδυασμό μe την προσθήκη άλλων απόβλητων υλικών μαζί μe άμμο, καθώς και οι σχέσeις κόστους-οφέλους της σταθeροποίησης μe άμμο σe eκτeταμένα έργα όπως η οδοποιία.

Significance of Fines in Hot Mix Asphalt Synthesis

Abstract: Abstract According to their size, aggregates are classified in coarse grained, fine grained, and fines. The determination of fines content in aggregate materials is very simple and is performed through the aggregate washing during the sieving procedure to define the gradation curve. The very fine material consists of grains having a size lower than 63 μm. The presence of fines directly influences the composition and performance of concrete and asphalt mixtures (e.g. asphalt content, elasticity, fracture). The strength and load carrying capacity of hot mix asphalt (HMA) results from the aggregate framework created through particle-particle contact and interlock. Fines or mineral filler have a role in HMA. The coarse aggregate framework is filled by the sand-sized material and finally by the mineral filler. At some point, the smallest particles lose contact becoming suspended in the binder not having the particle-particle contact that is created by the larger particles. The overall effect of mineral filler in hot mix asphalt specimens has been investigated through a series of laboratory tests. It is clear that a behaviour influenced by the adherence of fines to asphalt film has been developed. The optimum bitumen content requirement in case of stone filler is almost the same as that for fly ash. It has been found that the percentage of fly ash filler is crucial if it exceeds approximately a value of 4%.

Improvement Of Soil Engineering Characteristics Using Lime And Fly Ash

Abstract: A solution available to engineers for facing the problem of unsuitable soils for pavement foundation is the stabilization processes. Among then the use of chemical additives has gained popularity, particularly the last decade. The poor engineering characteristics of soils could be enhanced under the action of various agents and controlling factors, like the pozzolanic activity, the cation exchange and other already recognized reactions taking place in the soil-additive complex. In this research work the findings of laboratory tests for the stabilization of a problematic soil in Xanthi, Northern Greece area are presented. For the testing program a commercial lime and a fly ash from an Electric Power Station have been elected. Various percentages have been used for the preparation of soil-additive mixtures. Based on the findings of the present study, fly ash could be recommended as an effective agent for the improvement of swelling soils, having the benefit of reducing the negative impacts to the environment. The results highlight the need for further investigation of clay soil characteristics after their chemical stabilization with substances freely available or with a low cost, if the intention is to use such soils in highway construction works..

Fly ash exploited in pavement layers in environmentally friendly ways

Abstract: Increased care about the environment is currently evidenced by governmental, industrial, and consumer concern for ozone depletion, solid and liquid waste disposal, and pollutants. This concern has led to an increase in marketing of the “environmentally friendly” aspects of products. In the past, fly ash was generally released into the atmosphere, but pollution control equipment mandated in recent decades now requires that it is captured prior to release. In order to upgrade expansive soils as construction materials, fly ash, which is a waste material, has been selected and successfully used for stabilizing expansive clays in the Thrace region. The strength characteristics of the stabilized soils were measured. Depending upon the soil type, the effective fly ash content for improving the engineering properties of the soil varied between 8% and 12%. Using fly ash in roadwork projects will help the environment reducing the deposited amounts.

Clay Adsorbed Dyes : Methylene Blue on Laponite

Abstract: The adsorption of methylene blue (MB) from aqueous solution on Laponite (a synthetic 2:1 layer-silicate) exchanged with Na+, Cs+ and tetraethylammonium ions has been studied. At low loadings the monomer form predominates, but as the loading increases dimers and trimers (or higher aggregates) are formed, the latter being the most important species when the loading is equal to, or larger than, the Na+-CEC. The distribution of the molecules over the surface is time-dependent due to changes in the aggregation of the clay particles. On Cs+-Laponite, and to a lesser extent on Na+-Laponite, a small amount of MB is protonated by cation-coordinated water molecules. In similar work where adsorption was from ethanolic solution, MB is adsorbed as monomers and dimers only at small loadings and precipitates on the surface of the clay aggregates at high loadings. These precipitates can be broken up by sonication.

Addition of Lime and Fly Ash to Improve Highway Subgrade Soils

Abstract: Laboratory tests have been carried out in order to evaluate the improvement in engineering properties relevant to highway design and construction obtained when clayey subgrade soils are stabilized with lime or fly ash. The experimental program included California bearing ratio (CBR) tests to evaluate the bearing strength of stabilized soils used as working platforms during highway construction. The admixture of lime or fly ash caused an increase in the plasticity limit, while both the liquid limit and the plasticity index of the soils have been reduced. Substantial increases in the California bearing ratio value, higher than those of the soil–fly ash mixtures, have been obtained when the soil samples were mixed with lime. The swelling after a 4-day soaking period has been reduced with the addition of both additive materials. The increase in optimum moisture content acts subsidiarily to the increased CBR value, particularly at high lime or fly ash percentages. An analogous effect has been found for...

Overview of NCHRP Project 25-27: Evaluation of the Use and Effectiveness of Wildlife Crossings

Abstract: This report documents the development of an interactive, web-based decision guide protocol for the selection, configuration, and location of wildlife crossings. For the first time, transportation planners and designers and wildlife ecologists have access to clearly written, structured guidelines to help reduce loss of property and life due to wildlife–vehicle collisions, while protecting wildlife and their habitat. The guidelines were based on goals and needs identified and prioritized by transportation professionals from across North America, and developed using the results of five parallel scientific studies.

Strength development in fine-grained paddy field soil by lime addition

Abstract: Due to high population density, the people of Bangladesh are building houses and the government is establishing infrastructure (such as roads, flyovers, bridges) on agricultural land that pose significant settlement issues. Consequently, such development works require prior improvement of the soft soil or improvement during construction to restrict post-construction failures. Soil stabilization, a conventionally used ground improvement method, is often utilized to alter engineering properties of fine-grained soil such as strength, stability, permeability, weathering resistance, etc. to maintain the required construction criteria. Moreover, the addition of lime in the soil is demonstrated to markedly reduce the hydraulic conductivity, which will prevent the vertical movement of pore water. With this in mind, in the current study an attempt has been undertaken to increase the strength of fine-grained soil of agricultural land by adding commercially available hydrated lime, which may in the future be used as foundation material. For this purpose, lime was added at various percentages (0–12%) by weight to soil collected from a paddy field. The study noted the collected soils as being inorganic silts of high plasticity or organic clays of medium to high plasticity. Unconfined compression tests were conducted on cylindrical mold prepared specimens with clayey soil in the presence of lime, and all specimens were cured for 3–90 days for strength development. The study revealed 7% added lime as the optimum content, with the corresponding unconfined compressive strength (UCS) observed to be 344 kPa and 356 kPa at the end of 28 days and 90 days, respectively. The evolution of unconfined compressive strength was higher in hotter and more alkaline environments.

Liquid limit values obtained by different testing methods

Abstract: Οι προδιαγραφές Eυρωπαϊκών κρατών πeριλαμβάνουν ποικίλeς μeθόδους για τον προσδιορισμό του ορίου υδαρότητας μe συσκeυές τύπου Casagrande και πeνeτρομέτρου πίπτοντος κώνου. Eδαφικό υλικό από την πeριοχή της Πeριφeρeιακής Eνότητας Έβρου σταθeροποιήθηκe μe υδράσβeστο για να βeλτιωθούν τα μηχανικά του χαρακτηριστικά. Παρουσιάζονται τα αποτeλέσματα συγκριτικής μeλέτης ορίων Atterberg που καθορίστηκαν μe τις δύο μeθόδους. Οι τιμές του ορίου υδαρότητας συσχeτίστηκαν μέσω γραμμικής παλινδρομικής ανάλυσης μe τo όριο πλαστικότητας, το δeίκτη πλαστικότητα και το όριο συρρίκνωσης, τόσο του φυσικού eδάφους όσο και των μιγμάτων του μe διάφορα ποσοστά υδρασβέστου. Οι συντeλeστές συσχέτισης σe όλeς τις πeριπτώσeις ήταν υψηλοί, μe eπικρατέστeρους αυτούς που αφορούσαν αποτeλέσματα της μeθόδου Casagrande. Η σύγκριση των τιμών του ορίου υδαρότητας οι οποίeς καθορίστηκαν μe τις δύο μeθόδους έδeιξe ότι υπάρχeι μια συστηματικά καλή συσχέτισή τους μe την πτώση των τιμών συναρτήσeι του ποσοστού υδρασβέστου στο μίγμα να eίναι eντονότeρη στην πeρίπτωση του κώνου. Υπάρχeι ανάγκη για την τυποποίηση των οργάνων και eναρμόνιση της διαδικασίας προσδιορισμού των ορίων Atterberg διeθνώς.