Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies. Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies..
Criteria such as (materials) endurance and lifeexpectancy, or (structural) endurance have a significant impact on the make-up of concrete. That is to say that design and use criteria a factors in determining concrete's useful life. Currently, more and more corrosion inhibitors are used to extend the useful life of a structure. This is analyzed in this paper using the predictive model found in Life-365 Service Life. To carry-out this study use of corrosion inhibitors was modeled and their performance based on a strategic analysis of a structures useful life of a structure taking into account factors such as humidity and salinity (meaning different microenvironments). The impact of the inhibitors in terms of initiating and propagation of corrosion will be compared using the Tuutti model. In this way, this paper's objective is to propose a methodology to evaluate the characteristics for concrete from design taking into account environmental and longevity factors.
Composites of bio-based aliphatic poly-functional epoxy resin reinforced with high concentration of bio-silica were prepared by a solvent free method. The unmodified bio-silica (BS) was obtained from rice husk. Two amine hardeners were used: one was based on polyethylene oxide (PEO) and the other on polypropylene oxide (PPO). The epoxy-amine systems were reinforced with 10, 20, 30 and 40% weight fraction to the unreinforced epoxy resin. The structure and morphology of the BS was analyzed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively. These techniques were also used to determine the silica dispersion degree in the polymer matrix. Thermal characterization was carried out using a Differential Scanning Calorimetry (DSC) and Thermogravimetric Analyses (TGA). The glass transition temperature, Tg, increased significantly for both polyetheramine cured systems incorporating 10 wt% and 20 wt% of the BS; nevertheless, the best performance was observed in PEO networks. The thermal stability at 5% of weight loss temperature increased consistently with reinforcement concentration up to ~ 21% and ~ 10% compared to neat PEO and PPO cured networks, respectively. Tensile strength and Young modulus for PEO systems showed similar results up to 30 wt% of BS, whereas for PPO networks they decreased relentlessly at 20 wt% of BS. PEO composites showed an overall increase in the Shore D hardness testing. Water swelling experiment illustrated greater hydrophilicity of PEO compared to filled and unfilled PPO systems. The water absorption remains unaltered up to 20 wt% of BS, revealing a good interaction between both networks and filler. It was clearly illustrated the difference in the effect of hydrophilicity (PEO) and the hydrophobicity (PPO) in the epoxy composite results. A better compatibility and good correlation between mechanical and thermal properties were observed in 10 wt% of BS in both polyetheramine cured networks. Keywords-Rice husk silica, bio-silica reinforced polymers, bio based thermosets, aliphatic bio-epoxy composites, polymer composites.
This study deals with a comparison between water and air cured blended cement pastes at a Water-to-binder (W/B) ratio of 0.3 after ageing for 91 days. Supplementary Cementitious Materials (SCMs) like zeolitic tuffs are widely used to improve compressive strength by the pozzolanic reaction. In this study, mordenite rich tuff, a mixture of clinoptilolite-heulandite-mordenite-calcite, and calcareous siltstone were blended with Ordinary Portland cement (OPC) at levels ranged from 5 to 27.5%. Using quantitative X-ray diffraction (QXRD), Thermal gravimetric analysis-Differential scanning calorimetry (TGA-DSC), as well as density measurements and compressive strength, some hydration parameters such as content of calcium hydroxide (CH), anhydrous cement phases, calcite, and water in hydrates, density and the mechanical performance were determined. The results showed that hydration process of blended cement pastes was uncomplete at ages as late as 91 days regardless of curing conditions. The air cured cement pastes showed a less content of CH, water in hydrates, and compressive strength, but instead a higher density and content of carbonate-like minerals with respect to their water-cured counterparts. The pozzolanic reaction scarcely proceeded at a W/B ratio of 0.3 regardless of curing condition. Among the SCMs, mordenite rich tuff blended cement pastes presented the best compressive strength values, when was cured under water; the others showed better values of compressive strength in air curing condition.
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