Print Email Facebook Twitter Investigation of transversal cracking in cement bound reclaimed asphalt road base courses Title Investigation of transversal cracking in cement bound reclaimed asphalt road base courses Author Baggio, Gianpaolo (TU Delft Civil Engineering and Geosciences; TU Delft Engineering Structures) Contributor Erkens, S. (mentor) Houben, Lambert (mentor) Braam, Rene (graduation committee) Stigter, J (graduation committee) van der Ven, D (graduation committee) van Gurp, C.A.P.M. (graduation committee) Degree granting institution Delft University of Technology Date 2017-12-14 Abstract This thesis is a study on the cracking behaviour of road bases constructed with cement bound reclaimed asphalt (also known in the Netherlands as AGRAC). It is decided to focus on this material because of the few researches available on the topic although the material being widely applied, at least in the Netherlands. Thegoal of adding cement to the recycled asphalt aggregate is primarily to increase the resistance to permanent deformation (rutting). But, as in all cement-bound materials, in the AGRAC base layer shrinkage cracks might occur which could reflect through the overlying asphalt layers. Because of this, during the last decades the cement content was reduced from the initial 4-5% down to 2-2.5% (by mass). In order to study the cracking behaviour of AGRAC, in this research one grading and two cement contents (2% and 4% m/m) are considered. A series of tests is performed to evaluate the properties of the two AGRAC mixes at different values of curing time (up to 130 days) and 3 different temperatures (0, 15 and 30°C). The dependence on the curing time and temperature are considered because of the presence in the mix of cement and bitumen respectively. In particular the tests performed are: indirect tensile strength, modulus of elasticity, shrinkage, thermal deformation, Poisson’s ratio and relaxation. The mechanical properties retrieved from these tests are used as input in a model which predicts the occurrence of cracks in an AGRAC base. If cracks occur, the model characterizes the crack pattern in terms of time of occurrence of the cracks, crack spacing and crack width. The calculations are done in two cases: non-weakened (plain) and weakened (with joints) base.From the laboratory tests performed a dependence of the mechanical properties of AGRAC on the material temperature is clearly visible. Interesting results are also derived from the model, which shows the influence of the time of construction of the base (the worst scenario is observed for construction in August) and the difference in the cracking behaviour between the two AGRAC mixes (2 and 4% cement m/m). It is observed that the AGRAC mix with 4% cement leads to a higher risk of cracking compared to AGRAC 2%. In the worst scenario of base with AGRAC 4% constructed in August many crack series occur with a very close final crack spacing. The model shows how in this case even applying saw-cuts in the base is inefficient in terms of controlling the crack formation process. Subject cement bound reclaimed asphaltAGRACcement contenttemperaturerelaxation ITT testcrack patternmodel To reference this document use: http://resolver.tudelft.nl/uuid:9ed87f5b-e2f7-46d6-8952-ba239f945eaf Part of collection Student theses Document type master thesis Rights © 2017 Gianpaolo Baggio Files PDF G_Baggio_Masters_thesis.pdf 34.81 MB Close viewer /islandora/object/uuid:9ed87f5b-e2f7-46d6-8952-ba239f945eaf/datastream/OBJ/view