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Xie J.,Wuhan University of Technology | Chen J.,Wuhan University of Technology | Wu S.,Wuhan University of Technology | Lin J.,Wuhan University of Technology | Wei W.,Hubei Construction Science Research and Design Institute
Construction and Building Materials | Year: 2013

Lack of superior natural crushed stone and negative dumping effects on environment promote the recycling of basic oxygen furnace slag (BOF). Since BOF based asphalt pavements have been utilized for a certain history, their in-service performances necessitate comprehensive investigation imperatively, with respect to moisture sensitivity and permanent deformation behavior in particular. In this study the surface of BOF was firstly characterized by electron probe micro-analysis (EPMA) coupled with X-ray wavelength Energy Disperse Spectroscopy (EDS). Then the surface energies of asphalt and BOF were measured by determination of contact angles and they are further used to determine the work of adhesion. The asphalt mixtures incorporating BOF as coarse aggregate were prepared and subsequently subjected to modified Lottman test, immersion rutting test and fatigue life test to determine the moisture resistance. Also dynamic creep test was carried out to characterize the permanent deformation behavior at different high temperatures and various stress levels. Results show that the CaO-FeO-MnO-MgO solid solution and inert CaO are the major compositions on the surface of BOF. Large contents of Al and Ca elements may be beneficial for the bond energy between BOF and asphalt. The results of contact angle demonstrate that BOF possesses superior wettability with asphalt to basalt. The results combined with modified Lottman test show the superior moisture sensitivity of BOF based asphalt mixture to basalt based mixtures. And at higher temperature (above 45 °C), mastic performs a prominent role in the resistance of BOF based mixture to permanent deformation. Additionally the permanent deformation behavior of BOF based asphalt mixture can be perfectly modeled and the results provide possibility to the establishment of predicting model for the permanent deformation of asphalt pavement with BOF. © 2012 Elsevier Ltd. All rights reserved.

Xie J.,Wuhan University of Technology | Wu S.,Wuhan University of Technology | Lin J.,Wuhan University of Technology | Cai J.,Wuhan University of Technology | And 2 more authors.
Construction and Building Materials | Year: 2012

Basic oxygen furnace (BOF) slag need full characterization in laboratory to eliminate potential issues such as volume expansion, moisture damage when it is used in asphalt mixture. In this paper, BOF was detected by XRD, XRF and SEM to determine mineralogical properties, chemical compositions and microtopography. As a major factor directly exacerbating moisture damage, the precipitates generated from the reaction of BOF and water were also analyzed. The BOF prepared asphalt mixtures were further characterized by resilient modulus and indirect tensile strength tests. Subsequently dissipated creep strain energy limits (DCSE f) were calculated to assess their moisture sensitivity. Results show that the mineralogical compositions are significantly different for BOFs with vesicular texture and dense texture while there is relatively higher content of β-C 2S in the former. The DCSE f result indicates that the BOF prepared mixture is superior to basalt mixture after several freeze-thaw, with respect to moisture sensitivity. The precipitates mainly consists of calcium hydroxide (Ca(OH) 2), calcium silicate hydrogen (C-S-H), calcium silicate and gypsum. Therefore the failure mechanism in BOF dense-graded asphalt mixtures in moist environment is determined as the formation of Ca(OH) 2, C-S-H and calcium silicate, which leads to partial structural failure and facilitates water infiltration. © 2012 Elsevier Ltd. All rights reserved.

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