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.

Synthesis of KOH-based geopolymers for innovative applications

This study presents an evaluation on compressive strength of metakaolin-based geopolymers synthetized by using different activators, KOH and NaOH. The influence of NaOH/KOH concentration ratio together with curing temperature and time were investigated to find the best results from the compressive strength tests of metakaolin-based geopolymers, synthesized with a commercial metakaolin. Aggregates of small grain size referred as fillers, were added to reduce brittleness, and minimize the pore size and shrinkage of the final mixture creating a stronger network. In this work, silt recovered from industrial processes of wash water used for aggregates production was used as a filler in the production of KOH-based geopolymers, examining the possible influence on the mechanical strength of the final product. The curing temperatures chosen for the synthesis were 85°C, 60°C and 40°C. The samples were tested after 7 days and 28 days, according to the UNI EN 1015-11:2019 applied on Ca-based cements, analyzing the differences in mechanical strength comparing samples with similar and different compositions. The study presented in total 72 synthetized geopolymer specimens that were analyzed with unconfined compression test (UCT). The characterization of the starting materials metakaolin and silt was carried out using X- ray diffraction analysis (XRD). Whereas, the formed geopolymers were analyzed using X- ray diffraction (XRD), and scanning electron microscopy (SEM) with energy dispersive X- ray spectroscopy (EDS).

Creep deflection of low-strength reinforced concrete flexural members strengthened with carbon fiber composite sheets

The low-strength concrete is defined as a concrete where the compressive cubic strength is less than 15 MPa. Since the beginning of the last century, many low-strength concrete buildings and bridges have been built all over the world. Being short of deeper study, composite sheets are prohibited in strengthening of low-strength reinforced concrete members (CECS 146; ACI 440). Moreover, there are few relevant information about the long-term behavior and durability of strengthened RC members. This fact undoubtedly limits the use of the composite materials in the strengthening applications, therefore, it is necessary to study the behaviours of low-strength concrete elements strengthened with composite materials (FRP) for the preservation of historic constructions and innovation in the strengthening technology. Deformability is one of criteria in the design of concrete structures, and this for functionality, durability and aesthetics reasons. Civil engineer possibly encounters more deflection problems in the structural design than any other type of problem. Many materials common in structural engineering such as wood, concrete and composite materials, suffer creep; if the creep phenomenon is taken into account, checks for serviceability limit state criteria can become onerous, because the creep deformation in these materials is in the same order of magnitude as the elastic deformation. The thesis presents the results of an experimental study on the long-term behavior of low-strength reinforced concrete beams strengthened with carbon fiber composite sheets (CFRP). The work has investigated the accuracy of the long-term deflection predictions made by some analytical procedures existing in literature, as well as by the most widely used design codes (Eurocode 2, ACI-318, ACI-435).