Desarrollo de nueva metodología para la estimación de propiedades mecánicas de eco-hormigones, mediante ensayos no destructivos en función de la temperatura

Programa Oficial de Doutoramento en Enxeñaría Civil. 5011V01[Resumen] La utilización de las cenizas de biomasa como adición del cemento o la utilización del árido reciclado fino y grueso de hormigón como sustitución parcial del árido natural en la fabricación del hormigón, son dos ejemplos de valorización de residuos, que pasan a ser subproductos. Esto reduce el impacto ambiental de la fabricación del hormigón. Con el fin de contribuir al avance de las normativas hacia una regulación más sostenible, en esta tesis se estudia la influencia de estos eco-materiales en la evolución de propiedades mecánicas del hormigón y en sus correlaciones con los resultados de ensayos no destructivos, en función de la temperatura de curado. Se observa que la temperatura de curado influye en el efecto que tienen los eco-materiales en la evolución de las propiedades mecánicas, y afecta también a sus correlaciones con ensayos no destructivos, sobre todo, a edades tempranas. Se proponen modelos de estimación de la resistencia a compresión mediante combinación de ensayos no destructivos que mejoran los resultados de los modelos utilizados habitualmente. Por último, se realiza una propuesta de nuevo procedimiento para mejora del control de calidad, que podría conllevar grandes ventajas tanto a corto plazo, como a largo plazo.[Abstract] The use of biomass ashes as an additive to cement or the utilization of fine and coarse recycled aggregate for concrete as a partial substitution of natural aggregate in concrete fabrication, constitute two examples of waste recovery, as the wastes eventually become by-products. This reduces the environmental impact of concrete fabrication. With the goal of contributing to the advancement of standards toward more sustainable protocols, this Thesis studies the influence of these eco-materials on the evolution of the mechanical properties of concrete and on the correlations with the results of non-destructive tests, as a function of the curing temperature. It is observed that curing temperature has an impact on the effect of these eco-materials on the evolution of the mechanical properties and also affects their correlations with non-destructive tests, especially at early ages. Estimation models of the compressive strength are proposed by combining non-destructive tests. The proposed models achieve better results that those usually utilized. Finally, a new procedure for the improvement of quality control is proposed. This may lead to significant advantages both on the short- and the long-term time scales.[Resumo] A utilización das cinzas de biomasa como adición do cemento ou a utilización do árido reciclado fino e groso de formigón como substitución parcial do árido natural na fabricación do formigón, son dous exemplos de valorización de residuos que pasan a ser subprodutos. Isto reduce o impacto ambiental da fabricación do formigón. Co el fin de contribuír ao avance das normativas cara unha regulación máis sostible, nesta tese se estudia a influencia destes eco-materiais na evolución de propiedades mecánicas do formigón e nas súas correlacións cos resultados de ensaios non destrutivos, en función da temperatura de curado. Observase que a temperatura de curado inflúe no efecto que teñen os eco-materiais na evolución das propiedades mecánicas e afecta tamén a súas correlacións con ensaios non destrutivos, sobre todo, a idades temperás. Propóñense modelos de estimación da resistencia a compresión mediante combinación de ensaios non destrutivos que melloran os resultados dos modelos utilizados habitualmente. Por último, realizase unha proposta de novo procedemento para mellora do control de calidade, que podería implicar grandes vantaxes tanto a curto prazo, como a longo prazo

The Effects of Curing Temperature on the Hydration Kinetics of Plain and Fly Ash Pastes and Compressive Strength of Corresponding Mortars with and without nano-TiO2 Addition.

Incorporation of fly ash in cementitious systems containing ordinary portland cement (OPC) increases their long-term strength and durability. However, replacement of cement by fly ash also reduces the heat of hydration of such systems and reduces early-age strength development. The reduced rate of strength development can increase the risk of durability problems, e.g. scaling, in cases when young concrete is exposed to low temperatures and deicing chemicals. This study investigated the potential of nano-titanium dioxide (nano-TiO2) particles to modify the hydration kinetics of fly ash pastes and compressive strength development of corresponding mortars cured under low (4°C) and standard (23°C) temperatures. The kinetics of the hydration study was performed on paste specimens using the thermogravimetric analysis (TGA) and isothermal calorimetry (IC) methods. The mortar specimens used for compressive strength testing were prepared using the same w/cm values and the same types of binders as those used to prepare the paste specimens. It was found that although the addition of nano-TiO2 accelerated the hydration rate of all pastes, that treatment was, however, more effective in the fly ash pastes than in the ordinary portland cement (OPC) pastes, especially for the cases of low temperature curing. These findings were confirmed by the results of strength testing as the specimens experiencing accelerated rates of hydration were also found to be stronger

Improving Scaling Resistance of Pavement Concrete Using Titanium Dioxide (TiO\u3csub\u3e2\u3c/sub\u3e) and Nanosilica

This project focused on the evaluation of the influence of nanoadditives on the hydration kinetics, mechanical properties, and durability of concretes with and without supplementary cementitious materials (SCMs). The types of nanomaterials used in the course of this study included nano-titanium dioxide (nano-TiO2) and two forms of nanosilica. A series of experimental tasks, including fabrication, curing, and conditioning of specimens, microstructure analysis, mechanical strength testing, and durability testing were conducted in the laboratory. Based on experimental results, it can be concluded that the addition of nanoparticles can accelerate the early-age hydration process of cementitious pastes, especially those containing fly ash and cured at low temperatures. Both the compressive and flexural strength of mortars and concretes were also enhanced by the addition of nanoparticles. In addition, incorporation of nanoparticles reduced the total amount and connectivity of pores present in concretes. That resulted in lowering the water permeability of concretes, regardless of the cementitious systems and curing temperatures used. The resistance of concretes to freeze-thaw cycles and scaling was also improved by the addition of nanoparticles, especially those containing fly ash. However, an excess of nanoparticles additions may reduce the scaling resistance of concretes

High Performance Mortar with 100% Recycled Aggregate using Titanium Dioxide Nanoparticles

Concrete and mortar are materials commonly used in construction. Their main compounds are cement, aggregates (sand and gravel) and water. In an effort to increase the sustainability of these materials, the idea of using recycled aggregates from ground old concrete and using it to make mortar and concrete has gained more interest. It has two advantages: it reduces the need to mine for raw materials and lessens the amount of old and defective concrete that is typically put in landfills. But, the use of recycled concrete aggregate lowers the strength of mortars and concretes because the residual compounds in the recycled sand reduces bonding with the cement paste. This research studies the use of Titanium Dioxide nanoparticles (TiO2) as a potential additive to increase the strength and improve the bonding of mortar with 100% recycled aggregates. Using mixtures with different percentages of TiO2 by the weight of cement (0% -reference-, 0.5%, 1% and 2%) the compressive and flexural strength was studied. With 0.5% of TiO2 nanoparticles, an improvement of 10 % of the compressive strength and 7% of the flexural strength with respect to the reference mortar at 7 days were achieved. Results of compressive and flexural strength at 90 days will be obtained during the next weeks. The effect of TiO2 on the hydration product through Thermogravimetric analysis (TGA) is being studied. Additionally, the effect of TiO2 on the microstructure of the mortar will be investigated using scanning electron microscope (SEM) analysis (ongoing analysis)

Synthesis Study of Best Practices for Cleaning Tools and Paving Equipment: Asphalt Release Agents (ARAs) and Asphalt Cleaners (ACs)

Diesel has been used widely as an asphalt cleaning agent due to its effectiveness for many years. However, its negative impact on health and the environment calls for more sustainable and safe alternatives. Asphalt Release Agents (ARAs) are products for preventing or mitigating undesirable adhesion of HMA to the asphalt equipment, and Asphalt Cleaners (ACs) are products for remediation when the adhesion has already happened. In this study, commercially ARAs and ACs reported by NTPEP and U.S. DOTs are quantitatively and qualitatively examined based on the following criteria: (1) cost-effectiveness, (2) functionality, (3) environmental, and (4) safety considerations. The results provided valuable insights into cost-effective products; and ultimately led to developing an interactive decision-making dashboard to help INDOT make more informed decisions regarding testing and investing in these alternatives

Definición empírica de la relación agua / cemento efectiva en morteros con árido reciclado en función de la absorción

The use of recycled aggregates from construction and demolition wastes for the manufacture of mortars and concretes is a subject of great interest from the point of view of sustainable construction since it can reduce the exploitation of quarries replacing natural aggregate by recycled aggregate and it can reduce the volume of wastes in landfills. In order to study the influence of recycled aggregate on concrete and mortar strength, the effective water/cement ratio must be the same in concretes or mortars compared. The effective water/cement ratio is defined as the amount of water available to react with the cement of the mixture. Discrepancies among authors arise in the definition of how much is the amount of available water, which depends on the absorption and moisture of the aggregates at the time of the batch. Therefore, in this research, an experimental study is developed empirically to find the amount of water which reacts with the cement mortar in various mixtures with different ratios of recycled aggregate depending on the absorption of the aggregates. Subsequently, the relations between the amount of water which doesn’t react with the cement and aggregate absorption of each of the mixtures were analyzed. Finally, a definition of the effective water/cement ratio depending on absorption is proposed, based on the empirical study developed.La utilización de áridos reciclados procedentes de construcción y demolición, para la fabricación de morteros y hormigones es un tema de gran interés desde el punto de vista de la construcción sostenible puesto que, además de disminuir la explotación de las canteras al sustituir el árido natural por árido reciclado, también se reduce el volumen de residuos depositados en vertederos. Para poder estudiar la influencia que tiene el uso de árido reciclado en la resistencia de los hormigones y morteros, es necesario que la relación agua/cemento efectiva sea a misma en todas las mezclas comparadas, La relación agua/cemento efectiva se define como la cantidad de agua disponible que reacciona con el cemento de la mezcla. Las discrepancias entre autores surgen en la definición de cuál es esa “cantidad de agua disponible”, La cantidad de agua disponible que reacciona con el cemento depende de la absorción de los áridos Por ello, en esta investigación, se desarrolla un estudio experimental para hallar de forma empírica la cantidad de agua que reacciona con el cemento en varias mezclas de mortero con distintos porcentajes de sustitución de árido reciclado, en función de la absorción de los áridos. Posteriormente se analiza qué relaciones existen entre la cantidad de agua que no reacciona con el cemento y el agua total de absorción de los áridos de cada una de las mezclas. Finalmente se propone una definición de la relación agua/cemento efectiva en función de la absorción basada en este estudio empírico

Improving Scaling Resistance of Pavement Concrete Using Titanium Dioxide (TiO2) and Nanosilica

SPR-4336This project focused on the evaluation of the influence of nanoadditives on the hydration kinetics, mechanical properties, and durability of concretes with and without supplementary cementitious materials (SCMs). The types of nanomaterials used in the course of this study included nano-titanium dioxide (nano-TiO2) and two forms of nanosilica. A series of experimental tasks, including fabrication, curing, and conditioning of specimens, microstructure analysis, mechanical strength testing, and durability testing were conducted in the laboratory. Based on experimental results, it can be concluded that the addition of nanoparticles can accelerate the early-age hydration process of cementitious pastes, especially those containing fly ash and cured at low temperatures. Both the compressive and flexural strength of mortars and concretes were also enhanced by the addition of nanoparticles. In addition, incorporation of nanoparticles reduced the total amount and connectivity of pores present in concretes. That resulted in lowering the water permeability of concretes, regardless of the cementitious systems and curing temperatures used. The resistance of concretes to freeze-thaw cycles and scaling was also improved by the addition of nanoparticles, especially those containing fly ash. However, an excess of nanoparticles additions may reduce the scaling resistance of concretes

Anisotropy vs Isotropy in Living Cell Indentation With AFM

The measurement of local mechanical properties of living cells by nano/micro indentation relies on the foundational assumption of locally isotropic cellular deformation. As a consequence of assumed isotropy, the cell membrane and underlying cytoskeleton are expected to locally deform axisymmetrically when indented by a spherical tip. Here, we directly observe the local geometry of deformation of membrane and cytoskeleton of different living adherent cells during nanoindentation with the integrated Atomic Force (AFM) and spinning disk confocal (SDC) microscope. We show that the presence of the perinuclear actin cap (apical stress fibers), such as those encountered in cells subject to physiological forces, causes a strongly non-axisymmetric membrane deformation during indentation reflecting local mechanical anisotropy. In contrast, axisymmetric membrane deformation reflecting mechanical isotropy was found in cells without actin cap: cancerous cells MDA-MB-231, which naturally lack the actin cap, and NIH 3T3 cells in which the actin cap is disrupted by latrunculin A. Careful studies were undertaken to quantify the effect of the live cell fluorescent stains on the measured mechanical properties. Using finite element computations and the numerical analysis, we explored the capability of one of the simplest anisotropic models – transverse isotropy model with three local mechanical parameters (longitudinal and transverse modulus and planar shear modulus) – to capture the observed non-axisymmetric deformation. These results help identifying which cell types are likely to exhibit non-isotropic properties, how to measure and quantify cellular deformation during AFM indentation using live cell stains and SDC, and suggest modelling guidelines to recover quantitative estimates of the mechanical properties of living cells

Synthesis Study of Best Practices for Cleaning Tools and Paving Equipment: Asphalt Release Agents (ARAs) and Asphalt Cleaners (ACs)

SPR-4652Diesel has been used widely as an asphalt cleaning agent due to its effectiveness for many years. However, its negative impact on health and the environment calls for more sustainable and safe alternatives. Asphalt Release Agents (ARAs) are products for preventing or mitigating undesirable adhesion of HMA to the asphalt equipment, and Asphalt Cleaners (ACs) are products for remediation when the adhesion has already happened. In this study, commercially ARAs and ACs reported by NTPEP and U.S. DOTs are quantitatively and qualitatively examined based on the following criteria: (1) cost-effectiveness, (2) functionality, (3) environmental, and (4) safety considerations. The results provided valuable insights into cost-effective products; and ultimately led to developing an interactive decision-making dashboard to help INDOT make more informed decisions regarding testing and investing in these alternatives