Satellite geodesy for sea level and climate change

This habilitation thesis presents the findings of the sea level change studies conducted at the Institute of Geodesy of the Technischen Universität Darmstadt betweeen 2001 and 2013. Sea level is an important indicator of climate change. It has been traditionally measured by coastal tide gauges and by satellite altimetry since 1993. Tide gauge measurements indicate a coastal average sea level rise of 1-2 millimeters per year over the 20th century. Over the last two decades the average sea level rise increased to 3.3±0.7 millimeters per year, consistently measured by tide gauges and satellite altimetry. The 2013 Intergovernmental Panel on ClimateChange (IPCC AR5) predicts a global mean rise of 50 ± 20 cm by 2100 for a medium warming scenario for the interval 2081-2100. Sea level rise is not uniform and some regions will be more affected than others. It can possibly exacerbate the effects of other factors, such as flooding and ground subsidence. Because of its potential impact on coastal regions, rising sea level is one of the major threatsof climate warming. Changes in each component of the climate system, ocean, land and ice sheets, affects sea level. The two primary contributors of sea level rise, thermal expansion due to ocean warming and melting of continental glaciers and ice sheets, have been identifiedbut large uncertainties remain. Locally non-climatic components, as subsidence, can causerelative sea level rise much larger than the global average mean sea level rise. The global and highly accurate analysis of sea level variations is made possible by spacebasedtechniques. Their main innovation is the use of the same accurate and global reference frame ensuring long-term, precise monitoring and integration in a Global Geodetic ObservingSystem, which is crucial for many practical applications. This thesis focuses on the use of geodetic techniques. Its aim is a comprehensive analysis of the regional sea level variability and of its causes with particular attention to the coastalzone. The three main scientific objectives are: improvement of multi-mission satellite altimetry records, quantification of global and regional sea level change and attribution of sea level rise. Firstly the altimeter data from different missions are unified, improved in the coastal zoneand validated with in-situ and model data. Secondly global and regional estimations of sea level variability from altimetry and tide gauge data are made. The third part of the work is dedicated to the analysis of the reason for sea level change. Here satellite altimetry andgravity missions data are combined with model data to detect the causes of this variation. The analysis includes the separation of mass and volume sea level change and the closing of the water budget. This work shows the challenges of merging satellite data of different types for the understanding of physical processes in sea basins. It also deals with the challenges of new satellite altimetry missions in the coastal zone, where altimetry provides a consistent link to tide gauge stations co-located with Global Navigation Satellite System observations. It finally discusses the importance of highly accurate sea level variability and trends for modeling coastal processes and for long-term predictions

influence of pyrolysis parameters on the efficiency of the biochar as nanoparticles into cement based composites

Abstract In this research, a particular kind of biochar provided by UK Biochar Centre has been added as nanoparticles into cementitious composites. Its principle characteristic lies in the standardization of its process production, that makes it suitable to been used as filler in cement-matrix composites, ensuring the reproducibility of the cement mix (I. Cosentino "The use of Bio-char for sustainable and durable concrete", 2017). The pyrolysis parameters and the content of carbon in the standardized biochar influenced its efficiency to enhance the mechanical properties of the cement composites: the results, in terms of flexural strength and fracture energy, have been worse than those obtained in previous studies (L. Restuccia "Re-think, Re-use: agro-food and C&D waste for high-performance sustainable cementitious composites", 2016), in which particles have been produced with higher temperature. However, also with standardized biochar a general enhancement of mechanical properties has been recorded, a sign that they can be used to create new green building materials

new self healing techniques for cement based materials

Abstract: In recent years, researches concerning cement-based materials has been focused not only on the strength and the toughness but also on the durability. In fact, the interest on concrete's self-healing process is increasing, due to the rapidly deterioration of that material which tends to crack and thus quickly deteriorate. In this paper, a new self-healing technology for cement-based materials is proposed. This technology is based on the encapsulation method of repairing agent inserted in randomly distributed shell inside the material during its preparation. Two different kind of shells were used: glass spheres and pharmaceutical capsules. The material the shells are made of has to be endowed with a series of fundamental characteristics. That material has to be inert with respect to the repair agent so that it doesn't react with it, resisting to the severe stress condition that the shells undergo during the mixing, and at the same time being capable of breaking down when the crack intercept them, having a good compatibility with the cement mixture. The results demonstrate that it is possible to use this kind of shell to encapsulate the repairing agent: the crack breaks them and they release the healing agent, which allows patching up the crack

Recycled Mortars with C&D Waste

Nowadays an environmental problem that cannot be underestimated is the increasing amount of waste of different nature. Certainly, an environmental friendly solution is to use waste directly or indirectly in the production of concrete or mortar, which are the most used building materials in the world. In the production of coarse recycled aggregates (RA), the fine fraction, also called recycled sand (RS), is involuntarily produced and it represents a large amount of the weight of the crushed C&D waste. Generally, the problem of fine fraction has not been much analysed until now. For this reason, in this work, an innovative mortar mix design for using recycled sand from C&D has been analysed, by partial replacement of standardized sand (SS) with recycled sand (RS) or washed recycled sand (RSW) and by using a fixed w/c ratio equal to 0.5. The main aim of this research has been to investigate if washing and sieving of recycled aggregates can improve the quality of the recycled aggregate. Analyses allowed concluding that the quality of the recycled aggregate could be improved by washing and sieving of recycled aggregates and that in any case the bending strength and the fracture energy increase or decrease simultaneously

Improvements in self-consolidating cementitious composites by using micro carbonized aggregates

There is growing interest in the use of self-consolidating cementitious systems in construction industry. The present research was conducted to enhance the mechanical performance of cement composites by the utilization of micro-sized inert particles. This paper deals with the synthesis of micro-sized inert carbonized particles from hemp hurds. The synthesized carbonized particles were characterized by field emission scanning electron microscope (FESEM). These particles were further used as additive in self-consolidating cement composites. Total of four different wt% additions (i.e. 0.08, 0.20, 1.00 and 3.00 by wt% of cement) were investigated. The cement composites containing carbonized particles inclusions were characterized by three point bending and compression tests. The results indicate that the carbonized particles additions enhanced the flexural and compressive strengths of the cement composites. It was also observed that the fracture properties and the energy absorption capability of the cement composites were enhanced substantially

Enhancing Cement Paste Properties with Biochar: Mechanical and Rheological Insights

Biochar, the solid sub-product of biomass pyrolysis, is widely considered an effective water retention material thanks to its porous microstructure and high specific surface area. This study investigates the possibility of improving both mechanical and rheological properties of cement pastes on a micro-scale. The results show that using biochar as a reinforcement at low percentages (1% to 5% by weight of cement) results in an increase in compressive strength of 13% and the flexural strength of 30%. A high fracture energy was demonstrated by the tortuous crack path of the sample at an early age of curing. A preliminary study on the rheological properties has indicated that the yield stress value is in line with that of self-compacting concrete

Modified fracture properties of cement composites with nano/micro carbonized bagasse fibers

A novel cost-effective alternative in the form of nano/micro carbonized particles produced from waste bagasse fibers has been explored to modify the mechanical properties and fracture pattern of the resulting cementitious composites. Carbonized bagasse particles were produced at Politecnico di Torino and characterized by Raman spectroscopy and scanning electron microscopy. When added with cement paste up to 1 wt% in six different proportions, the carbonized bagasse particles were found effective in significant enhancement of mechanical strength as well as fracture toughness. From micro-graphical observations it is evident that these heterogenic inclusions either block the propagation of micro cracks which has to deviate from its straight trajectory and has to follow the carbon nano/micro particles contour or distribute it into multiple finer cracks. Crack contouring along the carbonized particle, crack pinning, crack diversions and crack branching are the mechanisms which can explain the increase of toughness in the composite samples

Influence of biochar additions on the fracture behavior of foamed concrete

The present study concerns the experimental investigation of foamed concretes with 1600 kg/m3 density that incorporate biochar additions in the mix. A series of small notched beams are prepared to determine the fracture energy in CMOD (crack mouth opening displacement) mode and the mechanical properties in terms of flexural and compressive strength. Besides the evaluation of such properties for classical foamed concrete, the influence of the addition of biochar in the lightweight cementitious paste is comparatively investigated. Two different concentrations of biochar are analyzed, namely 2% and 4% of the cement weight, and two different curing conditions are studied, namely in air and in water at controlled temperature for 28 days. The results demonstrate that better fracture behavior are obtained with 2% biochar and air curing conditions. The biochar additions in moderate concentrations (e.g. 2%) seems to make the fracture surface more tortuous, thus justifying the numerical outcomes, and does not impair the flexural strength. Further microstructural investigation is underway to confirm the experimental observations. This research paves the way for a promising construction material that is more environmentally friendly and sustainable than traditional materials used in the building industry

Investigation on the fracture behavior of foamed concrete

Abstract The fracture behavior of lightweight foamed concrete (LWFC) is significantly influenced by microstructural properties, which are ascribed to the arrangement of air bubbles and pores as well as to the presence of different hydration products. In this contribution, an experimental investigation on the fracture behavior of LWFC is performed. Notched beams made of LWFC were tested in three-point bending to determine the fracture energy based on the load-CMOD (Crack Mouth Opening Displacement) curve. The influence of the dry density is explored considering one density for non-structural purposes (equal to 800 kg/m3) and another density for structural applications (1600 kg/m3). Moreover, two curing conditions are considered (air and water). The load-CMOD curves reveal that for lower dry densities the fracture behavior of LWFC is particularly affected by the curing conditions, with better results achieved in air curing conditions, but this influence decreases with higher dry densities. The improved performance in air curing conditions for lower dry densities is also observed in terms of flexural strength, but is not particularly evident for the compressive strength. Micrographs across the crack surface determined via Scanning Electron Microscopy (SEM) are finally presented to analyze the experimental findings and justify the results in terms of microstructural configuration of the specimens