Deformation Behavior of Clay-Water Suspensions

http://www.goingtomeet.com/1097

Deformation Behavior of Clay-Water Suspensions

http://www.goingtomeet.com/1097

Fatigue Characterization of Bituminous Binders Containing Crumb Rubber from End-of-Life Tires

This paper presents the outcomes of an experimental investigation which focused on the fatigue behavior of bituminous binder for paving applications prepared by combining a single reference neat bitumen with different types of crumb rubber products derived from the processing of end-of-life tires. In the laboratory preparation of the blends, crumb rubber dosage was conveniently limited in order to obtain binders characterized by viscosity values compatible with standard operating conditions normally adopted in the production and compaction of bituminous mixtures. Results obtained from time sweep tests carried out in equi-stiffness conditions showed that fatigue performance is enhanced by the use of the considered crumb rubber modifiers with a dosage-dependent improvement of both fatigue life and crack propagation amplitude. Given that the considered crumb rubber products were quite similar, no significant effects were associated to changes of crumb rubber type

Performance-Related Characterization of Bituminous Binders and Mixtures Containing Natural Asphalt

Natural asphalt as an additive in bituminous mixtures was subjected to evaluation by means of performance-related laboratory tests carried out on materials sampled from a production plant and a test section. Compaction issues were discussed by referring to binder viscosity and by considering the volumetrics of laboratory-compacted specimens. Mixture stiffness was assessed by means of repeated load indirect tensile tests carried out on field cores and by constructing pseudo master curves. Models were employed for the quantification of effects associated to enhanced compaction and binder ageing. Fatigue was also investigated by means of indirect tensile test

Rutting Behaviour of Wearing Course Mixtures in Severe Temperature and Loading Conditions

Following the construction of a major motorway pavement in Northern Africa, relevant rutting phenomena were observed after opening to traffic. Preliminary investigations showed that permanent deformations were limited to the upper wearing course layer which was designed according to set requirements. In order to define the most appropriate rehabilitation strategy, investigations were carried out by focusing on the volumetric and mechanical properties of the employed wearing course mixture. Compaction properties were assessed by making use of a gyratory shear compactor and of a rubber-wheeled roller. Moreover, simulative wheel-tracking tests were carried out in severe temperature and loading conditions. Additional tests were performed on an alternative bituminous mixture containing polymer granules. Based on the obtained results the possible causes of the above described distress phenomena were identified and the use of the alternative bituminous mixture as a technical solution to adopt for rehabilitation was considere

Experimental Investigation for the Analysis of Cold-Recycled Bituminous Mixtures

The Authors present the results obtained in a experimental investigation carried out to provide technical support to the construction of a cold-recycled bituminous sub-base layer of a major Italian motorway. Compliance of the employed materials and of the resulting recycled mixture to requirements set in Technical Specifications and to the adopted job-mix formula were verified by means of laboratory tests. Field observations focused on the evaluation of the void content of the compacted sub-base layer and on its stiffness evolution in the short term curing phase. Finally, mix design was carried out by following a procedure based on the use of the gyratory shear compactor and on the optimization of the composition of the fluid phase. The procedure was validated by performing volumetric and mechanical tests both on the optimized mixture and on a mixture prepared according to the job-mix formul

Mix design and mechanical characterization of self-compacting cement-bound mixtures for paving applications

This paper presents the results of an experimental investigation which focused on self-compacting cement-bound mixtures to be employed for paving applications, especially for pavement foundations in road tunnels. Recipes of the investigated mixtures, which contain reclaimed asphalt pavement material and mineral sludge, were defined by optimizing the packing of the aggregate skeleton and by checking the flowability characteristics of cement pastes and composite mixtures. Long-term stiffness and strength properties were evaluated by means of triaxial and quick shear tests. Based on the obtained results and on their interpretation, a mix design procedure was proposed. General conclusions were drawn with respect to the behaviour of self-compacting cement-bound mixtures and to the possible developments of future research

Self-compacting cement-bound pavement foundations for road tunnels: performance assessment in field trials

This paper presents the results of an experimental investigation which was carried out with the purpose of assessing the performance-related properties of self-compacting cement-bound mixtures to be employed in pavement foundations in road tunnels. The mixtures contained a significant quantity of recycled components and function-specific additives. Characteristics of the mixtures, which were produced in a concrete batch plant, were studied by means of laboratory and field tests. Investigated properties included flowability, compressive strength, resilient modulus and bearing capacity. It was found that mixtures prepared with a cement dosage of up to 100 kg/m3 possess the required properties of flowability, strength and stiffness. On the contrary, mixtures with higher cement dosages (150 and 200 kg/m3) fail to meet all the performance-related requirements as a result of their high long-term strength which jeopardises excavatability. Obtained results also highlighted the effects of the different components on the properties of the mixtures and led to the definition of acceptance criteria which can be adopted in actual construction works

Investigating cohesive healing of asphalt binders by means of a dissipated energy approach

The paper reports the results of an experimental investigation in which the cohesive healing properties of different types of asphalt binder were evaluated by means of the dissipated energy ratio approach. A specifically designed testing methodology was proposed which involves comparing the response of binders subjected to continuous oscillatory shear loading carried out without rest periods and with single rest periods introduced at predefined levels of damage A rheological parameter (Healing Ratio) was introduced to quantify the magnitude of healing occurring during rest time and to rank the consequent healing potential of binders. Obtained results indicate that the investigated binders did not completely recover their original fatigue resistance after rest time, confirming the existence of some intrinsic irreversible damage, the amount of which depends on the total damage experienced before load removal. Experimental results also indicate that healing performance of binders can be significantly enhanced by polymer modification. Keywords: Healing, Fatigue, Dissipated energy ratio, Asphalt binder, Polymer modificatio