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Investigation of tertiary Flow Behavior of bitumen stabilised materials with bitumen emulsion

Konieczna Katarzyna, Król Jan

Roads and Bridges - Drogi i Mosty

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2023

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Vol. 22, no. 4

491--502

EN

Cold recycling technology is gaining popularity as a sustainable way of rehabilitating existing asphalt pavements. Bitumen Stabilised Materials with bitumen emulsion (BSMs) are cold recycling mixtures (CRMs) that contain RAP, virgin aggregates, bitumen emulsion, water, and active filler and exhibit a combination of mechanical properties of both granular and viscoelastic materials. However, the BSMs’ mechanical performance in terms of viscoelasticity remains insufficiently explored. This study aimed to synthesize and adapt dynamic creep test methods, commonly used for HMA mixes, for characterizing tertiary flow behavior of BSMs. Tests were conducted on BSM mixtures with 50% and 70% RAP content, bitumen emulsion amount in the 4.5%–6.4% range, and 1% cement addition. The designed BSM series were also differentiated in terms of volumetric properties. Permanent deformation (PD) response of Bitumen Stabilised Materials was evaluated based on the analysis of the accumulated permanent strain curves obtained in repeated load tests. The experimental data were fitted to the Francken model, using an originally developed Python calculation script, to determine the Flow Number (FN) values for BSMs under specified loading stress and testing temperature conditions. The study showed that the specification of the Flow Number dynamic creep test parameters for testing BSMs requires an individual approach depending on the composition and volumetric properties of the mixture. With appropriately selected test conditions, the permanent deformation of BSMs can be evaluated by means of fitting the accumulated permanent strain curve to the Francken model and estimating Flow Number values.

PL

Recykling głęboki nawierzchni drogowych w technologii na zimno zyskuje coraz większą popularność, wpisując się w trendy zrównoważonego rozwoju w budownictwie. Mieszanki stabilizowane emulsją asfaltową (Bitumen Stabilised Materials — BSM), stosowane do wykonywania podbudów drogowych, zawierają destrukt asfaltowy, kruszywo doziarniające, wodę oraz środki wiążące: emulsję asfaltową lub asfalt spieniony oraz cement. W zakresie właściwości mechanicznych, mieszanki BSM wykazują właściwości charakteryzujące zarówno materiały ziarniste, jak i lepkosprężyste. Analiza źródeł literaturowych wskazuje, że aspekt lepkosprężystości mieszanek BSM nie został dotychczas wystarczająco zbadany. W artykule przedstawiono wyniki prac nad syntezą i adaptacją procedur badania pełzania dynamicznego, stosowanych do oceny odporności na deformacje trwałe mieszanek mineralno-asfaltowych, w celu przeprowadzenia oceny właściwości mieszanek BSM. Badania metodą Flow Number przeprowadzono na mieszankach BSM z 50% i 70% zawartością destruktu asfaltowego, ilością emulsji asfaltowej w zakresie 4,5%–6,4% oraz dodatkiem cementu na poziomie 1%. W celu wyznaczenia wartości parametru Flow Number analizowano przebieg krzywych skumulowanego odkształcenia trwałego przy zadanych warunkach obciążenia i temperatury. Dokonano oceny dopasowana modelu matematycznego Franckena do danych empirycznych. Przeprowadzone badania i analiza danych wykazały, że ustalenie parametrów badania dynamicznego pełzania Flow Number na potrzeby badań mieszanek BSM wymaga indywidualnego podejścia uwzględniającego skład i właściwości objętościowe tych mieszanek. Przy właściwie dobranych warunkach obciążenia i temperatury, możliwe jest przeprowadzenie oceny odporności na deformacje trwałe mieszanek BSM, stosując metody badawcze aplikowane do lepkosprężystych mieszanek mineralno-asfaltowych.

2

The use of gabbro dust in the cold recycling of asphalt paving mixes with foamed bitumen

Iwański M., Buczyński P., Mazurek G.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2016

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Vol. 64, nr 4

763--773

EN

Mineral fines are a waste product of aggregate production in quarries and asphalt mixing plants. The incorporation of mineral gabbro dust into foam bitumen causes developing of a mesh reinforcement in the recycled base mixture. This mesh reinforcement, observed in a recycled base structure, induces an increase in stiffness modulus, where its elastic part of complex modulus dominates over the imaginary part. Therefore, it is possible to create a recycled mixture with a lower susceptibility to loading time/temperature. In result, the presence of gabbro dust in recycled mixture limits the magnitude of strains induced by the traffic load. This paper presents the results of the tests carried out on the mineral dusts derived from gabbro rock. Structural and functional properties of the fines were determined to prepare their characteristics. Then, the cold recycled mixtures for the road base were designed with the 5–20% mineral fines content. The mixtures were prepared in cold recycling technology with foamed bitumen. Further tests involved determining mechanical and physical properties of the recycled mixes, including air voids content, Marshall stability, Marshall quotient (stiffness), indirect tensile strength and stiffness modulus at 20°C). The results indicated a positive influence of the gabbro dusts on the investigated parameters. With the use of ANOVA tests, the significance of the influence of the gabbro dust and foamed bitumen on these properties was evaluated. Harrington’s multicriteria method was employed to establish gabbro dust and foamed bitumen amounts, the addition of which would guarantee optimal properties of the recycled base mixture.

3

Resistance of the pavement to water and frost in the cold recycling technology

Iwański M., Chomicz-Kowalska A.

Structure and Environment

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2010

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Vol. 2, no. 1

9-17

EN

The road pavement structure (apart from having the required load capacity) should be water and frost resistant. This is important for pavements produced with the cold recycling technology. Foamed bitumen and, alternatively, bitumen emulsion were used for the resistance tests of the pavements. The bitumen binder content in the recycled material was 2.0%, 2.5% and 3.0%. The tests (stability against deformation, Marshall stiffness and indirect tensile strength (ITS)) showed that use of foamed bitumen is more advantageous than bitumen emulsion. That is in terms of mechanical properties of pavement. The measurements of resistance due to water and frost (according to AASHTO T283 method) and resistance to low temperature cracking (according to the PANK 4302 method) confirmed that pavement produced with the cold recycling technology is resistant to these climatic factors. The tests also showed that pavement produced with foamed bitumen is more resistant than pavement with bitumen emulsion. It is suggested, that general water resistance criterion (tensile strength retained (TRS)) of such pavement should be broadened to include e.g. the AASHTO T283 method.