Alkali activated cements (AAC) have been extensively studied for different applications as an alternative to Portland cement (which has a high carbon footprint) and due to the possibility of including waste materials such fly ash or slags. However, few works have addressed the topic of stabilised soils with AAC for unpaved roads, with curing at ambient temperature, where the resistance to wetting and drying as well as the mechanical properties evolution over time is particularly relevant. In this paper, a silty sand was stabilized with an AAC synthetized from low calcium fly ash and an alkaline solution made from sodium silicate and sodium hydroxide. The evolution of stiffness and strength up to 360 days, the tensile strength, and the performance during wetting and drying cycles were some of the characteristics analysed. Strength and stiffness results show a significant evolution far beyond the 28 th curing day, but still with a reasonable short-term strength. Strength parameters deduced from triaxial tests were found to be very high with stress-strain behaviour typical of cemented soils. Durability properties related to resistance to immersion and wetting and drying cycles were found to comply with existing specifications for soil-cement, giving validity for its use as soil-cement replacement.

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Microzonation for earthquake-induced liquefaction hazard is the subdivision of a territory at a municipal or submunicipal scale in areas characterized by the same probability of liquefaction manifestation for the occurrence of an earthquake of specified intensity.The liquefaction hazard at a site depends on the severity of expected ground shaking as well as on the susceptibility to liquefaction of that site. This in turn depends on geological, geomorphological, hydrogeological and geotechnical predisposing factors. Thus, liquefaction hazard implies the existence of territories characterized by a moderate to high level of intensity of expected ground shaking. Microzonation charts for ground shaking and liquefaction hazard play a key role for the mitigation of seismic risk of an urban centre as they provide a valuable tool for the implementation of prevention strategies and land use planning. The LIQUEFACT project fully addressed the problem of microzoning a territory for earthquake-induced liquefaction hazard in a specific work package. Four municipal testing areas were selected across Europe as peculiar case studies where to construct microzonation charts for earthquake-induced liquefaction hazard. They are located in Emilia-Romagna region (Italy), Lisbon metropolitan area (Portugal), Brežice territory (Slovenia) and Marmara region (Turkey). Their location was identified based on the following criteria: severity of expected seismic hazard, availability of geological and geotechnical data, presence of liquefiable soil deposits, documented cases of liquefaction manifestations occurred in historical earthquakes, representativeness of different geological settings, density of population in selected areas (exposure). This paper illustrates the general procedure developed in LIQUEFACT for the assessment of earthquake-induced liquefaction hazard at urban scale and presents the main achievements of the microzonation studies carried out at the four previously mentioned European testbeds. Since the microzonation studies have been carried out using a shared framework and methodology, this paper has the ambition to serve as technical guidelines for updating the standards and the operational criteria currently used in different countries worldwide to construct seismic microzonation maps of liquefaction hazard. Keywords Liquefaction • Earthquake • Microzonation • Guidelines • LIQUEFACT projectsite-specific geotechnical investigations with pre-existing geological and geotechnical data from public and private sources.Existing information on quaternary deposits and man-made landfills, geomorphological maps, trench pits, boreholes and piezometric monitoring data, shall be stored and analysed in a georeferenced (GIS) environment to identify homogeneous lithostratigraphic units susceptible to liquefaction. These data shall be complemented with field and laboratory geotechnical and geophysical information from pre-existing investigation campaigns. This will eventually allow to plan and implement the complementary experimental investi...

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Soil improvement with hydraulic binders is currently used in practice because of the advantages of using the local soil enhancing its geotechnical properties. However, environmental issues related to quicklime applications and carbon-dioxide emissions associated to Portland cement production encouraged the development of new binders. In this work, alkaline-activated cement (AAC) synthetized by fly ash and an alkaline solution was used to stabilize silty sand. The behavior of the treated soil was evaluated performing tests on a physical model and the results were compared to laboratory data to define its compaction, strength, and stiffness properties. Those tests include nuclear density gauge measurements, light falling weight deflectometer tests, and plate load tests, whereas unconfined compression tests with unload-reload cycles and seismic wave measurements were performed at the laboratory. These tests, very common in current geotechnical practice, have proved to be also adequate to quality control and to evaluate the geomechanical properties of this material. The results at 28 days show a significant improvement given by the AAC, but still show some sensitivity to water when flooded. The comparison of results from different tests provided the evolution of stiffness with strain level.

In Portugal, particularly in the greater Lisbon area, there are widespread alluvial sandy deposits, which need to be carefully assessed in terms of liquefaction susceptibility and risk zonation. For this purpose, a pilot site has been set up, as part of the European H2020 LIQUEFACT project. An extensive database of geological and geotechnical reports was collected and a comprehensive site investigation campaign was carried out, including boreholes with standard penetration (SPT), piezocone penetrometer (CPTu) and seismic dilatometer (SDMT) tests as well as geophysical methods, complemented by undisturbed soil sampling for laboratory characterisation. The assessment of liquefaction susceptibility based on field tests was made using the simplified procedure, considering the factor of safety against liquefaction (FSliq), which relates the cyclic resistance ratio (CRR) with the cyclic stress ratio (CSR). While the computation of the CSR is relatively straightforward, the reliability of the CRR strongly depends on the adopted in situ testing technique. Alternative approaches to liquefaction assessment have been proposed, based on quantitative liquefaction damage indexes, namely the Liquefaction Potential Index (LPI) and Liquefaction Severity Number (LSN). In this paper, the geotechnical field data is integrated in these distinct approaches to liquefaction assessment. A comparative and in-depth analysis of the conventional approach is presented and the inclusion of specific information on soil type, as a means to overcome the observed differences, is discussed particularly for SPT and VS results. The combination of these criteria enabled to clearly identify the most critical layers, in terms of liquefaction potential and severity.

Over the past 15 years, there have been some research outcomes in other disciplines, that could be used to produce new, more accurate, and realistic numerical models to characterise pedestrian loads and to significantly improve predictions of response for multiple pedestrian scenarios. However, the disconnection between fields has not facilitated this further research. Using this, the paper presents (1) a new sophisticated load model that includes the description of vertical and lateral loads, including pedestrian-structure interaction, (2) the numerical description of relationships to describe the key parameters of the proposed model, and (3) the evaluation of the effects of pedestrian characteristics that are relevant for serviceability response of footbridges. The proposed new load model enables inherent variability of individual pedestrian actions (intrasubject variability), probabilistic description of how pedestrian characteristics vary among subjects (inter-subject variability), and collective human behaviour (pedestrian-pedestrian interaction). Some of these characteristics are not currently considered in design approaches and can have a substantial impact upon structural response assessment. Finally recommendations are made for many of these characteristics to be introduced in analyses to evaluate the vibration serviceability limit state of footbridges in a more accurate and realistic manner.