Laboratory study of grouted macadams impregnated with mine waste geopolymeric binder

A new type of pavement has been gaining popularity over the last few years in Europe. It comprises a surface course with a semi-flexible material that provides significant advantages in comparison to both concrete and conventional asphalt, having both rut resistance and a degree of flexibility. It also provides good protection against the ingress of water to the foundation, since it has an impermeable surface. The semi-flexible material, generally known as grouted macadam, comprises an open-graded asphalt skeleton with 25% to 35% voids into which a cementitious slurry is grouted. This hybrid mixture provides good rut resistance and a surface highly resistant to fuel and oil spillage. Such properties allow it to be used in industrial areas, airports and harbours, where those situations are frequently associated with heavy and slow traffic. Grouted Macadams constitute a poorly understood branch of pavement technology and have generally been relegated to a role in certain specialist pavements whose performance is predicted on purely empirical evidence. Therefore, the main objectives of this project were related to better understanding the properties of this type of material, in order to predict its performance more realistically and to design pavements incorporating grouted macadam more accurately. Based on a standard mix design, several variables were studied during this project in order to characterise the behaviour of Grouted Macadams in general, and the influence of those variables on the fundamental properties of the final mixture. In this research project, one approach was used to the design of pavements incorporating Grouted Macadams: a traditional design method, based on laboratory determined of the stiffness modulus and the compressive strength.

Heavily obscured AGN: an ideal laboratory to study the early co-evolution of galaxies and black holes

Obscured AGN are a crucial ingredient to understand the full growth history of super massive black holes and the coevolution with their host galaxies, since they constitute the bulk of the BH accretion. In the distant Universe, many of them are hosted by submillimeter galaxies (SMGs), characterized by a high production of stars and a very fast consumption of gas. Therefore, the analysis of this class of objects is fundamental to investigate the role of the ISM in the early coevolution of galaxies and black holes. We present a multiwavelength study of a sample of six obscured X-ray selected AGN at z>2.5 in the CDF-S, detected in the far-IR/submm bands. We performed the X-ray spectral analysis based on the 7Ms Chandra dataset, which provides the best X-ray spectral information currently available for distant AGN. We were able to place constraints on the obscuring column densities and the intrinsic luminosities of our targets. Moreover, we built up the UV to FIR spectral energy distributions (SEDs) by combining the broad-band photometry from CANDELS and the Herschel catalogs, and analyzed them by means of an SED decomposition technique. Therefore, we derived important physical parameters of both the host galaxy and the AGN. In addition, we obtained, through an empirical calibration, the gas mass in the host galaxy and assessed the galaxy sizes in order to estimate the column density associated with the host ISM. The comparison of the ISM column densities with the values measured from the X-ray spectral analysis pointed out that the contribution of the host ISM to the obscuration of the AGN emission can be substantial, ranging from ~10% up to ~100% of the value derived from the X-ray spectra. The absorption may occur at different physical scales in these sources and, in particular, the medium in the host galaxy is an ingredient that should be taken into account, since it may have a relevant role in driving the early co-evolution of galaxies with their black holes.

Experimental Study on Friction between Saline Ice and Steel

Understanding the interaction of sea ice with offshore structures is of primary importance for the development of technology in cold climate regions. The rheological properties of sea ice (strength, creep, viscosity) as well as the roughness of the contact surface are the main factors influencing the type of interaction with a structure. A device was developed and designed and small scale laboratory experiments were carried out to study sea ice frictional interaction with steel material by means of a uniaxial compression rig. Sea-ice was artificially grown between a stainless steel piston (of circular cross section) and a hollow cylinder of the same material, coaxial to the former and of the same surface roughness. Three different values for the roughness were tested: 1.2, 10 and 30 μm Ry (maximum asperities height), chosen as representative values for typical surface conditions, from smooth to normally corroded steel. Creep tests (0.2, 0.3, 0.4 and 0.6 kN) were conducted at T = -10 ºC. By pushing the piston head towards the cylinder base, three different types of relative movement were observed: 1) the piston slid through the ice, 2) the piston slid through the ice and the ice slid on the surface of the outer cylinder, 3) the ice slid only on the cylinder surface. A cyclic stick-slip motion of the piston was detected with a representative frequency of 0.1 Hz. The ratio of the mean rate of axial displacement to the frequency of the stick-slip oscillations was found to be comparable to the roughness length (Sm). The roughness is the most influential parameter affecting the amplitude of the oscillations, while the load has a relevant influence on the their frequency. Guidelines for further investigations were recommended. Marco Nanetti - seloselo@virgilio.it

Laboratory verification of predicted permanent deformation in asphalt materials following climate change.

In the past a change in temperature of 5°C most often occurred over intervals of thousands of years. According to estimates by the IPCC, in the XXI century is expected an increase in average temperatures in Europe between 1.8 and 4.0°C in the best case caused by emissions of carbon dioxide and other GHG from human activities. As well as on the environment and economic context, global warming will have effects even on road safety. Several studies have already shown how increasing temperature may cause a worsening of some types of road surface damages, especially rutting, a permanent deformation of the road structures consisting in the formation of a longitudinal depression in the wheelpath, mostly due to the rheological behavior of bitumen. This deformation evolves during the hot season because of the heating capacity of the asphalt layers, in fact, the road surface temperature is up to 24°C higher than air. In this thesis, through the use of Wheeltrack test, it was studied the behavior of some types of asphalt concrete mixtures subjected to fatigue testing at different temperatures. The objectives of this study are: to determine the strain variation of different bituminous mixture subjected to fatigue testing at different temperature conditions; to investigate the effect of aggregates, bitumen and mixtures’ characteristics on rutting. Samples were made in the laboratory mostly using an already prepared mixtures, the others preparing the asphalt concrete from the grading curve and bitumen content. The same procedure was performed for each specimen: preparation, compaction using the roller compactor, cooling and heating before the test. The tests were carried out at 40 - 50 - 60°C in order to obtain the evolution of deformation with temperature variation, except some mixtures for which the tests were carried out only at 50°C. In the elaboration of the results were considered testing parameters, component properties and the characteristics of the mixture. Among the testing parameters, temperature was varied for each sample. The mixtures responded to this variation with a different behavior (linear logarithmic and exponential) not directly correlated with the asphalt characteristics; the others parameters as load, passage frequency and test condition were kept constant. According to the results obtained, the main contribution to deformation is due to the type of binder used, it was found that the modified bitumen have a better response than the same mixtures containing traditional bitumen; to the porosity which affects negatively the behavior of the samples and to the homogeneity ceteris paribus. The granulometric composition did not seem to have interfered with the results. Overall has emerged at working temperature, a decisive importance of bitumen composition, than the other characteristics of the mixture, that tends to disappear with heating in favor of increased dependence of rutting resistance from the granulometric composition of the sample considered. In particular it is essential, rather than the mechanical characteristics of the binder, its chemical properties given by the polymeric modification. To confirm some considered results, the maximum bulk density and the air voids content were determined. Tests have been conducted in the laboratories of the Civil Engineering Department at NTNU in Trondheim according to European Standards.

Experimental and computational study of methane and methyl formate pyrolysis and oxidation in a flow reactor

A study of the pyrolysis and oxidation (phi 0.5-1-2) of methane and methyl formate (phi 0.5) in a laboratory flow reactor (Length = 50 cm, inner diameter = 2.5 cm) has been carried out at 1-4 atm and 300-1300 K temperature range. Exhaust gaseous species analysis was realized using a gas chromatographic system, Varian CP-4900 PRO Mirco-GC, with a TCD detector and using helium as carrier for a Molecular Sieve 5Å column and nitrogen for a COX column, whose temperatures and pressures were respectively of 65°C and 150kPa. Model simulations using NTUA [1], Fisher et al. [12], Grana [13] and Dooley [14] kinetic mechanisms have been performed with CHEMKIN. The work provides a basis for further development and optimization of existing detailed chemical kinetic schemes.

Study of a beam-column joint of a precast system by nonlinear numerical analysis

The present work consists of a detailed numerical analysis of a 4-way joint made of a precast column and two partially precast beams. The structure has been previously built and experimentally analyzed through a series of cyclic loads at the Laboratory of Tests on Structures (Laboratorio di Prove su Strutture, La. P. S.) of the University of Bologna. The aim of this work is to design a 3D model of the joint and then apply the techniques of nonlinear finite element analysis (FEA) to computationally reproduce the behavior of the structure under cyclic loads. Once the model has been calibrated to correctly emulate the joint, it is possible to obtain new insights useful to understand and explain the physical phenomena observed in the laboratory and to describe the properties of the structure, such as the cracking patterns, the force-displacement and the moment-curvature relations, as well as the deformations and displacements of the various elements composing the joint.