![]() ![]() ![]() Hydraulic cement sets and hardens in the presence of water and remains durable and tough after hardening. Cement can be categorized into two main types depending on how it reacts with water. The model shows how in this case even applying saw-cuts in the base is inefficient in terms of controlling the crack formation process. Cement is made out of pulverized and crush stones mixed with chemicals such as lime and calcium silicate. In the worst scenario of base with AGRAC 4% constructed in August many crack series occur with a very close final crack spacing. The base is a layer that also consists of crushed stone but slightly smaller stones than the sub-base In some cases, stone dust or stone fines will be mixed with the aggregate to reduce voids and will hold the layer in place better. It is observed that the AGRAC mix with 4% cement leads to a higher risk of cracking compared to AGRAC 2%. 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). From the laboratory tests performed a dependence of the mechanical properties of AGRAC on the material temperature is clearly visible. The calculations are done in two cases: non-weakened (plain) and weakened (with joints) 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 mechanical properties retrieved from these tests are used as input in a model which predicts the occurrence of cracks in an AGRAC base. In particular the tests performed are: indirect tensile strength, modulus of elasticity, shrinkage, thermal deformation, Poisson’s ratio and relaxation. The dependence on the curing time and temperature are considered because of the presence in the mix of cement and bitumen respectively. 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☌). 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. Because of this, during the last decades the cement content was reduced from the initial 4-5% down to 2-2.5% (by mass). concrete mix and hot asphalt mix ovals to calculate the. But, as in all cement-bound materials, in the AGRAC base layer shrinkage cracks might occur which could reflect through the overlying asphalt layers. cement concrete, bituminous concrete pavement, road base, construction fill, railroad. The goal of adding cement to the recycled asphalt aggregate is primarily to increase the resistance to permanent deformation (rutting). 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. 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). Investigation of transversal cracking in cement bound reclaimed asphalt road base coursesīaggio, Gianpaolo (TU Delft Civil Engineering and Geosciences TU Delft Engineering Structures) ![]()
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