<p>Hydrated portland cement provides the solid adhesive matrix necessary to bind aggregate (sand and gravel) into concrete. The hydration reaction requires water, however the products of the reaction limit further diffusion of water to unreacted cement. Superabsorbent polymer (SAP) hydrogel particles absorb mixing water, then subsequently desorb when the relative humidity drops, serving as internal water reservoirs within the cement matrix to shorten diffusion distances and promote the hydration reaction in a process called internal curing. Internally cured cementitious mixtures exhibit an increased degree of hydration and reduced shrinkage and cracking, which can increase concrete service life. Increased service life can, in turn, reduce overall demand for portland cement production, thereby lowering CO2 emissions.</p> <p>This dissertation addresses practical implementation questions key to the translation of SAP hydrogel internal curing technology to from the benchtop to the field in transportation applications, including: (1) What effects do mix design adjustments made to increase mixture flow when using SAP have on cementitious mixture properties? and (2) What effect do cementitious binder characteristics have on SAP performance?</p> <p>The addition of SAP to a cementitious mixture changes the mixture’s flow behavior. Flow behavior is an important aspect of concrete workability and sufficient flow is necessary to place well consolidated and molded samples. Often, additional water is added to mixtures using SAP to account for the absorbed water, however cementitious mixture workability is often tuned using high range water reducing admixtures (e.g., polycarboxylate ester-based dispersants). Fresh and hardened properties of mortars were characterized with respect to flow modification method (using the mortar flow table test; compressive strength at 3, 7, and 28 days; flexural strength at 7 and 28 days; and microstructural characterization of 28-day mortars). At typical doses, it was found that the addition of extra water lowers the resulting compressive and flexural strength, while high range water reducing admixtures administered at doses to achieve sufficient mortar flow did not compromise compressive or flexural strength.</p> <p>The SAPs used in cement are generally poly(acrylamide-acrylic acid) hydrogels and are not chemically inert in high ionic-load environments, such as cement mixtures. The behavior of an industrial SAP formulation with characterized across five different cement binder compositions with respect the cement hydration reaction (using isothermal calorimetry, thermogravimetric analysis of hydration product fraction, and scanning electron microscopy (SEM)/energy dispersive x-ray spectroscopy (EDS) microstructural analysis), the absorption behavior of the SAP, and the fresh and hardened properties of SAP-cement composites (mortar flow and compressive and flexural strength). The change in properties induced by the addition of SAP was similar across ASTM Type I cements from three manufacturing sources, suggesting that SAP internal curing can be implemented predictably over time and geography. Excitingly, in analysis of cement systems meeting different ASTM standards (Type III and Type I with 30% replacement by mass with ground blast furnace slag), synergistic and mitigating reaction behaviors were observed, respectively, in Type III and slag cement, suggesting that further study of SAP with these cement systems could be of particular interest.</p>

The increase of population results in more housing buildings and infrastructure, which increases the need for stable concrete structures that can safely accommodate people. In countries like Sweden, where temperatures are below zero for several months a year, housing construction cannot come to a halt. If a concrete structure is exposed to low temperatures, the phenomenon of early freezing can occur. This can damage the structure when forms are removed. To ensure that forms can be removed at the right time without causing damage, various methods have been developed by the industry, such as the prediction tool HETT 22. This program uses mathematical models to estimate when a safe form removal can be performed, considering factors such as concrete composition and surrounding conditions during casting and curing. A comparative study was conducted between obtained measurement data from two different building projects and simulations in the software. The results of wall simulations with HETT 22 were positive and show that the program can predict with good accuracy when the removal of formwork can be performed. However, the results from the floor slab simulations were indeterminate due to lack of documentation of infrared heating, making it difficult to draw a suitable conclusion about HETT 22:s capacity for floor slab simulations.

Indiana University-Purdue University Indianapolis (IUPUI) / Provisional restorative treatment is an essential part of fixed prosthodontics. Incorporation of adequately constructed provisional restorations will enhance the success rate of definitive restorations. Repairing or replacing failed provisional restorations is a concern for both clinicians and patients. The objective of this investigation was to study the effects of alumina nanofibers reinforcement on the mechanical properties of commercially available provisional fixed partial denture PMMA material. The hypothesis was that the addition of alumina nanofibers to commercially available PMMA resin will significantly increase its flexural strength, fracture toughness, and microhardness. Alumina nanofibers at 0.0 wt %, 0.5 wt %, 1.0 wt %, and 2.5 wt % were added to commercially available provisional fixed partial material (Jet Tooth Shade). A quaternary ammonium acetate dispersant (CC-59, Goldschmidt, Janesville, WI) was added to the acrylic monomer at 0.0 wt %, 1.0 wt %, 2.0 wt % and 5.0 wt % of the nanofiber weight (12 test groups, 1 control). Samples from each group were evaluated for flexural strength, flexural modulus, fracture toughness, and microhardness. The samples were tested after storing in distilled water for 24 hours and 7 days at 37ºC. Two-way analysis of variance (ANOVA) was used to test the effects of storage time and combinations of alumina nanofiber level and quaternary ammonium acetate dispersant level on the flexural strength, fracture toughness, and microhardness of the provisional PMMA resin. Pair-wise comparisons between groups were performed using Tukey’s multiple comparisons procedure to control the overall significance level at 5 percent. Three fracture toughness samples/group were randomly selected for Energy Dispersive Spectrometry (EDS) to qualitatively evaluate the dispersion of the fibers. The data obtained from this study showed that control sample values were in the acceptance range compared with previous research. The experimental samples did not reinforce the provisional resin in the flexural strength, modulus, fracture toughness, or microhardness. There are several factors may attribute to these results, such as poor bonding at the filler/matrix interface. The more homogeneous the mixture of PMMA and fiber, the stronger the acrylic resin. In fact, the presence of poorly bonded fibers, to which little load is transferred, can be almost equivalent to voids. In addition, as seen with EDS images, alumina nanofibers had a tendency to agglomerate. The use of a magnetic stirrer was not effective in physically separating nanofibers agglomerates. Direct dispersion of alumina nanofibers in methyl methacrylate monomer and quaternary ammonium acetate dispersant was not effective in separating the nanofibers into nano-scaled single crystals. The presence of fiber agglomerates acts as a structural defect that detrimentally affects the mechanical properties. Further studies are needed to evaluate the effectiveness of fibers, dispersion techniques, and coupling agents to enhance the mechanical properties of the provisional PMMA resin.

The primary objective of this research was to quantify the improvement in service life of a flexible pavement constructed using full-depth reclamation (FDR) in conjunction with cement stabilization when specified reductions in the spatial variability of specific construction-related parameters are achieved. This study analyzed pavement data obtained through field and laboratory testing of a reconstruction project in northern Utah. Data analyses included multivariate regression, Monte Carlo simulation, and mechanistic-empirical analyses of a model pavement structure. The results of the research show a steadily increasing trend in 28-day unconfined compressive strength of the cement-treated base (CTB) layer with increasing reductions in variability for cement content, moisture content, and reclaimed asphalt pavement (RAP) content across each of five different reliability levels. The most significant increases in CTB strength occurred with reductions in the standard deviations of moisture content and RAP content. Decreasing the variability of cement content did not provide significant additional strength to the CTB layer. Therefore, when involved on FDR projects, members of the pavement industry should focus energy on reducing the variability of both moisture content and RAP content, which both significantly impact pavement life, to achieve high-quality, long-lasting pavements.

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The Phase change materials (PCM) have the ability to absorb and release heat as the temperature changes from high to low temperature and vice versa. The use of phase change materials has increased in the construction sector due to the established environmental requirements and the various application benefits, especially in the thermal comfort of building applications and construction of sustainable infrastructure around the world (Berardi and Gallardo, 2019). Over the past decade, many studies have been conducted on the thermal properties of PCM (phase change material), however, few studies have focused on the study effect of PCM on mechanical and physical properties, although of great importance. In this work, three different microencapsulated types of phase change material (PCM) have been studied, while its effect on the mechanical and hydration properties of the cement paste with regard to constant ratio of water to cement ratio has been taken into account. The PCMs that have been studied are the following: Microencapsulated PCM, which is Nextek 24 D, Nextek 57D (Microtek Laboratories) and Croda Therm ME29P (Croda). In this study, various tests were performed on cementitious paste mixed with different doses of PCM to test the effect that PCM has on the cement hydration (under semi-adiabatic and isothermal conditions), the physical properties (setting time, slump flow, density) and the mechanical properties ( compressive strength). The results of this study indicated that both the melting point of the PCM and its amount have a decisive effect on the properties of the cement paste. Finally, the following conclusions have been drawn: • Additions of different dosage levels of the 24D and Croda PCM types showed that an increase in the dosage resulted in impaired mechanical and physical properties such as compressive strength of the cement paste (mechanical) decreased, and the density and random flow decreased (physical). While Nextek 57D did not show a great effect on cement paste according to density and random flow, which gives reduced negative impact on cement paste workability (physical). According to the mechanical properties, Nextek57D PCM with different levels of levels showed immediate positive effect on cement paste compressive strength compared to reference paste (no addition of PCM), and other cement pastes with other PCM types used in this study. • Mikrotek 57D PCM also gives a positive effect at different dose levels compared to two other types of Nextek 24D and Croda PCM regarding the effect of heat flow, which gives rise to hydration heat during the cement hydration process. However, other types of Nextek 24D and Croda in all quantities showed negligible effect on the heat flow during the cement hydration process.

<p dir="ltr">Corn, a vital cereal grain extensively used in various industries, exhibits viscoelastic properties when subjected to compressive forces. The effect of moisture content on the mechanical behavior of corn is crucial for understanding its storage, processing, and transportation requirements. Understanding the mechanical properties of bulk corn is crucial for ensuring a smooth flow of grains from the bin, thereby helping to prevent confined space-related accidents such as grain bin entrapment and engulfment, which can occur when workers enter the bin to facilitate grain flow. The objective of this study is to investigate the stress and strain relaxation of different bulk corn kernels qualities. In the first study various qualities of bulk corn, including clean corn, corn with impurities, and moldy corn samples were compressed at 42, 77, 106, and 130 N force levels. The compressive behavior of samples was measured at 13.22, 16.16, 18.93, and 21.70% wet basis moisture contents. The samples were compressed at a strain rate of 1.25mm/min, and the strain was kept constant for 200 s to determine the stress relaxation properties. For moldy corn, the energy absorbed increased with force resulting in clump formation irrespective of the force level. In the clean corn, the energy absorbed increased with moisture content, and formation of clumps was observed at 21.70% moisture content. Solidity decreased with moisture content, resulting in high cohesion at moisture contents 18.93% and 21.70% for clean corn. In corn with impurities, even though the energy absorbed increased with moisture content, no clump formation was observed. This study provides insights into the mechanical behavior of bulk corn under compression, such as solidity and compressive strength. An increase in the compressive strength or a decrease in the solidity of stored shelled corn in a grain bin increases compaction, cohesion, and the formation of clumps, and thereby affects the flow of grains during discharge from the bin. The study also highlights potential risks in grain bins when the kernels are moldy and stored at high moisture content.</p><p dir="ltr">The second study investigates the creep behavior of bulk corn kernels and its relationship with moisture content. Clean corn reconditioned to 16.23%, 19.02%, and 21.63% from the initial moisture content of 10.81% were compressed at 42, 77, 106, and 130 N. The viscoelastic behavior of the sample was measured by fitting the experimental data to a four-element Burgers model to obtain the model parameters E₀, E₁, η₀, and η₁. The results showed that the ranges of the elastic modulus (E₀) increase with an increase in moisture content, indicating an increase in compaction and elastic deformation of the sample. Retarded elastic modulus (E₁) values were also high at high moisture content, implying a high absorption of energy. The viscous component shows a dominance of the elastic component due to the low value of η₁ at high moisture content. The findings highlight the importance of considering moisture content in optimizing the handling of corn to enhance safety and efficiency in agricultural operations. Increase in the elastic modulus, retarded elastic modulus, and decrease in the viscous component leads to poor discharge of grains from the bin due to grain bridging or crust, or formation of clump due to out-of-conditioned grain, leading to a potential risk of grain entrapment and engulfment when the grain bin workers get inside the bin. This research contributes to the ongoing efforts to improve grain storage conditions.</p>

Dans un contexte accru d’économie circulaire et de valorisation des matières premières recyclées, les mâchefers d’incinération de déchets non dangereux (MIDND) constituent des déchets granulaires minéraux identifiés comme ressources renouvelables potentiellement valorisables dans la filière construction, notamment dans le domaine des matériaux cimentaires (type mortier/béton). Compte tenu de l'origine et de la nature des granulats de mâchefers, dans une finalité de concourir à une meilleure compatibilité mâchefer/ciment, il apparait essentiel en premier lieu de considérer des fractions minérales de mâchefers au mieux épurées par l’optimisation de l’enlèvement des métaux ferreux, non-ferreux et indésirables. En second temps, tenant compte des spécificités physico-chimiques résultantes des mâchefers, le choix de la base cimentaire constitue le second facteur prépondérant en sus de la nécessité de meilleure qualité de la fraction minérale de mâchefer. Le présent travail doctoral traite spécifiquement de l’apport de l’utilisation d’un ciment sulfo-alumineux dans le contexte de valorisation des mâchefers en matrice cimentaire. Des sables de mâchefers améliorés de fraction 0/2 mm ont été élaborés et utilisés pour l’étude. Dans une première partie, les résultats de formulation de mortiers cimentaires (ciment Portland, noté OPC / ciment sulfo-alumineux, noté CSA) à base de mâchefers en substitution volumique partielle du sable naturel (25, 50 et 75 %) et totale (100 %), mettent en évidence l’apport bénéfique du ciment CSA sur les résistances en compression par comparaison aux mortiers OPC. Une analyse expérimentale du réseau poreux des mortiers à 90 jours révèle que la frange de porosité supérieure à 50 nm est nettement plus faible pour les mortiers CSA. La thèse met en évidence un résultat majeur et pionnier : en interaction mâchefer, le niveau de basicité du milieu réactionnel joue un rôle prépondérant sur le potentiel de dégagement gazeux (hydrogène) après la mise en œuvre et avant la prise. Ce gaz impacte le niveau de porosité de la frange la plus grossière des mortiers durcis. La seconde partie concerne l’étude physique et microstructurale des mortiers soumis à l’attaque à l’eau pure ou à attaque sulfatique pour des substitutions volumiques de 50 et 100 %, avec les témoins pour référentiels. Les observations MEB sur les différentes matrices mettent en évidence une nette moindre sensibilité des mortiers mâchefer/CSA que des mortiers mâchefer/OPC, traduit par des porosités, fissurations et épaisseurs dégradées moindres. / In a world where circular economy and the valorization of raw materials is taking a greater importance, municipal solid waste incineration (MSWI) bottom ash is identified as potentially renewable resource in the construction field and more specifically in cementitious materials like mortar and concrete. Given the origin of the bottom ash and in order to have a better cement/MSWI bottom ash compatibility, the fraction used was as refined as possible by removing ferrous, non-ferrous and unwanted materials. The choice of the cement used is a critical factor as well because it affects the quality of the end product since MSWI bottom ash has particular physicochemical properties. The work in this PhD studies the advantages of using a sulfo-aluminate cement to valorize an improved 0/2 mm fraction of bottom ash that has been developed to be used in cementitious matrices. The first part presents the results of the mortar sample mixes containing bottom ash in a substitution by volume of the standard sand. To better highlight the effect of using a sulfo-aluminate (CSA), CSA mortars containing bottom ash were compared to a Portland cement (OPC) mortars, with substitution rates of 25 %, 50 %, 75 % and 100 % were used. A study of the porosity was then conducted at 90 days ; it shows that the pores larger to 50 nm are remarkably less present for CSA mortars. This thesis brings forward a major and innovative result : the level of alkalinity of the mortar plays an important role in the release of hydrogen gas after mixing and before setting. The presence of these gases creates large porosity in the hardened mortar samples. The second part studies the physical and microstructural aspects of the mortars after being immersed in aggressive environments : pure water and sulfate solution. The substitution rates used in this experiment were 50 % and 100 % by volume as well as the reference mortars with no bottom ash. These samples were then studied in the SEM which showed that CSA/bottom ash mortars were clearly less affected than the OPC/bottom ash mortars. This was highlighted by the porosity, the cracking and the depth of degraded zone.

Self-consolidating concrete (SCC) has wide use for placement in congested reinforced concrete structures in recent years. SCC represents one of the most outstanding advances in concrete technology during the last two decades. In the current work a great deal of cognizance pertaining to mechanical properties of SCC and comparison of fracture characteristics of notched and unnotched beams of plain concrete as well as using acoustic emission to understand the localization of crack patterns at different stages has been done. An artificial neural network (ANN) is proposed to predict the 28day compressive strength of a normal and high strength of SCC and HPC with high volume fly ash. The ANN is trained by the data available in literature on normal volume fly ash because data on SCC with high volume fly ash is not available in sufficient quantity. Fracture characteristics of notched and unnotched beams of plain self consolidating concrete using acoustic emission to understand the localization of crack patterns at different stages has been done. Considering this as a platform, further analysis has been done using moment tensor analysis as a new notion to evaluate fracture characteristics in terms of crack orientation, direction of crack propagation at nano and micro levels. Analysis of B-value (b-value based on energy) is also carried out, and this has introduced to a new idea of carrying out the analysis on the basis of energy which gives a clear picture of results when compared with the analysis carried out using amplitudes. Further a new concept is introduced to analyze crack smaller than micro (could be hepto cracks) in solid materials. Each crack formation corresponds to an AE event and is processed and analyzed for crack orientation, crack volume at hepto and micro levels using moment tensor analysis based on energy. Cracks which are tinier than microcracks (could be hepto), are formed in large numbers at very early stages of loading prior to peak load. The volume of hepto and micro cracks is difficult to measure physically, but could be characterized using AE data in moment tensor analysis based on energy. It is conjectured that the ratio of the volume of hepto to that of micro could reach a critical value which could be an indicator of onset of microcracks after the formation of hepto cracks.