Percentage Of Substitution Research Articles

Utilização do Resíduo de Areia Verde de Fundição no Desenvolvimento de Concreto Espumígeno

O principal objetivo deste trabalho foi avaliar a substituição da areia natural pelo resíduo de areia verde de fundição na fabricação de concreto espumígeno. O projeto experimental foi constituído de dois fatores com diferentes níveis: proporção de resíduo de areia verde de fundição em cinco níveis (0%, 25%, 50%, 75%, 100%) e quantidade de espuma em quatro níveis (5%, 10%, 15%, 20% em relação à massa total). A substituição da areia natural foi feita em relação a massa de material. As influências de cada fator sobre a resistência à compressão, densidade (seca e saturada), índice de vazios e absorção de água foram avaliadas. A partir dos resultados, pode-se observar que todos os fatores tiveram influência significativa sobre as variáveis respostas, isto é, aumentando a quantidade de espuma, a resistência à compressão, a densidade seca e a densidade saturada diminuíram em média 32,9%, 21,0% e 14,5%, respectivamente. Já o índice de vazios e a absorção de água tiveram um aumento, em média, de 44,1% e 76,9%, respectivamente, com o aumento da quantidade de espuma. Também se observou que aumentando o percentual de substituição do resíduo em relação a quantidade de areia natural a densidade seca aumentou, em média 23,7% e a densidade saturada aumentou, em média, 14,1%. A resistência à compressão, o índice de vazios e a absorção de água diminuíram, 29,1%, 31,0% e 43,5%, respectivamente, com o aumento do percentual de substituição. De acordo com os resultados é possível verificar que o resíduo de areia verde de fundição tem potencial para ser utilizado na fabricação de blocos de concreto espumígenos, porém estudos avaliando a durabilidade e os efeitos ambientais devem ser realizados, assim como em estudos anteriores que utilizam esse resíduo em concreto e argamassas convencionais e também em pavimentos.

Physicochemical, antioxidant and microbial properties of whole wheat breads formulated with the incorporation of vegetable paste

Whole wheat is an important source of dietary fiber and its consumption is known to lower the risk of colon cancer, diabetes mellitus and cardiovascular disease. Also, World Health Organization (WHO) has recommended increased consumption of vegetables to overcome micronutrient deficiencies and prevent chronic diseases. Thus this study aimed at formulation of whole wheat breads fortified with vegetable paste (made with equal quantities of peas, cauliflower and mushrooms). Four types of breads were formulated; one with 100% whole wheat flour (WWF) (B1) and others by substituting WWF with vegetable paste at the level of 15% (B2), 30% (B3), and 45% (B4). The breads were analysed for their proximate composition, antioxidant properties, physical properties, microbial count and sensory attributes. The incorporation of vegetable paste increased the moisture, ash and protein contents of breads which were 83.5%, 45.9% and 30.2%, respectively, higher in B4 breads than in B1 breads. The 45% substitution of vegetable paste in whole wheat flour increased the total phenolic content of breads by 45% and antioxidant activity by 61.5%. Whereas, the loaf volume decreased and hardness of breads increased with the increase in the percentage of vegetable paste substitution. The aerobic plate count and yeast and mold count of the formulated breads were in acceptable range even after 5 days of storage. Sensory scores revealed that B2 bread was having the highest overall acceptability score of 7.5 which was even higher than the score of commercially available wheat bread (7.3).

Numerical modelling of the mechanical behaviour of rubbercrete

Several finite element models have been analysed to numerically investigate the effects on the compressive strength and on the elastic modulus of a concrete with partial replacement of natural aggregates with different amounts and types of rubber particles from waste tyres. Percentages of substitution from 0% to 83% have been considered with rubber particles size ranging from 3 mm to 30 mm. Analytical relationships have been proposed to analyse the reduction factor of the compressive strength (SRF) and the reduction factor of the elastic modulus (ERF) of this material, known as rubbercrete. Results are confirmed similar to those from experimental campaigns reported in the literature. Results from the reference compressive strength variation are confirmed to depend on the size of the rubber particles, regardless the amount. A sensitivity analysis has been also carried out on the elastic modulus of the rubber and rubbercrete final properties are demonstrated not to clearly depend on it.

Effects of Ni incorporation on the reactivity and stability of hausmannite (Mn3O4): Environmental implications for Mn, Ni, and As solubility and cycling

Trace metal structural impurities are common in Mn (II/III) oxides, yet their effects on the oxides' reactivity and stability have not been experimentally assessed. The present investigation quantifies such effects for the first time by measuring the extent of mineral dissolution of pristine and Ni-substituted hausmannite (MnIIMnIII2O4) (at 1 and 2 wt% Ni) in 8-h batch reactions at pH 5 with/without arsenite (As(III)). Ni substitution occurred at Mn(III) octahedral sites, causing noticeable structural modification in lattice parameters with a decrease in Jahn-Teller distortion, particularly at 2 wt%. In both acidic and reductive dissolution (with As(III)), the Ni-substituted hausmannite exhibited enhanced Mn release relative to the pristine mineral, with concurrent release of structural Ni increasing with substitution percentage. When As(V) release was normalized by surface area, Ni-substituted hausmannite showed a higher As(III) oxidation percentage than the pristine phase. Further, higher ratios of Mn(II):As(V) were observed in Ni-substituted hausmannite. As K-edge X-ray absorption spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy analyses indicated that As(III) oxidation lead to the formation of binuclear bidentate As(V) surface complexes. Enhanced reactivity of Ni-substituted hausmannite may be attributed to lowered mineral stability, which promotes accelerated mineral dissolution and increased structural Mn release, resulting in formation/exposure of highly reactive sites. Thus, structural impurities dictate the properties, reactivity, and stability of the Mn(II/III) oxides, affecting the level of dissolution and the extent of redox reactions, which together impact the fate and cycling of transition metals and metalloids in surface environments.

A Computational Investigation of the Impact of Multiple Injection Strategies on Combustion Efficiency in Diesel–Natural Gas Dual-Fuel Low-Temperature Combustion Engines

AbstractDual-fuel diesel–methane low-temperature combustion (LTC) has been investigated by various research groups, showing high potential for emissions reduction (especially oxides of nitrogen oxide (NOx) and particulate matter (PM)) without adversely affecting fuel conversion efficiency in comparison with conventional diesel combustion. However, when operated at low load conditions, dual-fuel LTC typically exhibits poor combustion efficiencies. This behavior is mainly due to low bulk gas temperatures under lean conditions, resulting in unacceptably high carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions. A feasible and rather innovative solution may be to split the pilot injection of liquid fuel into two injection pulses, with the second pilot injection supporting CO and UHC oxidation once combustion is initiated by the first one. In this study, diesel–methane dual-fuel LTC is investigated numerically in a single-cylinder heavy-duty engine operating at 5 bar brake mean effective pressure (BMEP) at 85% and 75% percentage of energy substitution (PES) by methane (taken as a natural gas (NG) surrogate). A multidimensional model is first validated in comparison with the experimental data obtained on the same single-cylinder engine for early single pilot diesel injection at 310 crank angle degrees (CAD) and 500 bar rail pressure. With the single pilot injection case as baseline, the effects of multiple pilot injections and different rail pressures on combustion and emissions are investigated, again showing good agreement with the experimental data. Apparent heat release rate and cylinder pressure histories as well as combustion efficiency trends are correctly captured by the numerical model. Results prove that higher rail pressures yield reductions of HC and CO by 90% and 75%, respectively, at the expense of NOx emissions, which increase by ∼30% from baseline still remaining at very low level (under 1 g/kWh). Furthermore, it is shown that postinjection during the expansion stroke does not support the stable development of the combustion front as the combustion process is confined close to the diesel spray core.

The synergic influence of carbon nanotube and nanosilica on the compressive strength of lightweight concrete

Nanomaterials, owing to their extraordinary properties are known to improve the performance of concrete, are widely used in cementitious materials. Many studies have been conducted so far to understand the effects of inclusion of nanomaterials on the concrete while less studies have been conducted on Light Wight Concrete (LWC) especially on the synergic effect of nanomaterials.The influence of carbon nanotubes (CNT) and nanosilica (NS) as reinforcement fillers to increase the compressive strength of lightweight concrete using expanded clay were investigated in this study. Eight batches of samples were made by mixing CNT and NS using ultrasonication technique into the concrete mix, with one being a control system without nano reinforcement fillers to be used as a reference batch. The optimum substitution percentage of 3% for nano reinforcements was incorporated into the concrete by varying the ratio of CNT and NS. The compressive strength tests were conducted according to BS EN 12390: 2000 and BS EN 12350: 2009. From the results, it was found that incorporating 1% NS and 2% CNT, the highest compressive strength of 10.72 MPa can be achieved at 28 days, with percentage of 39% as compared to control sample. However, the incorporation of 3% CNT resulted in a negative effect on the compressive strength gain by a significant drop in compressive strength of −16% at 28 days. Field emission scanning electron microscope (FESEM) test was conducted to further observe the compressive strength behaviour for the obtained results.

Hybrid Perovskites with Larger Organic Cations Reveal Autocatalytic Degradation Kinetics and Increased Stability under Light

Hybrid organic-inorganic perovskites have shown incredible promise as active materials for photovoltaic devices, but their instability to light remains a significant roadblock in realizing these applications. Changing the organic cation has been shown to affect light-induced degradation. As a strategy for increasing the stability of these materials, we replaced varying percentages of methylammonium ion in the archetypical methylammonium lead iodide (MAPbI3) hybrid organic-inorganic perovskite with three significantly larger organic ammonium cations: imidazolium, dimethylammonium, and guanidinium. We were able to synthesize hybrid organic-inorganic perovskites with the same 3D perovskite structure as MAPbI3 with substitution of the larger ions as high as 20-30%. These substituted hybrid organic-inorganic perovskites retained similar optoelectronic properties. We discovered that the light-induced degradation in MAPbI3 and its substituted derivatives is autocatalytic, and we calculated rate coefficients for the degradation. All of the substituted hybrid organic-inorganic perovskites showed light-induced degradation slower than that of MAPbI3, up to a 62% decrease in degradation rate coefficient, at all substitution percentages up to 20%. This work provides evidence that a high percentage of a variety of large ammonium cations can be substituted into the hybrid organic-inorganic perovskite lattice without compromising its desirable optoelectronic properties. Insight into the autocatalytic mechanism of light-induced degradation will be valuable for designing additional strategies to improve the stability of hybrid organic-inorganic perovskites. We also offer insights into how factors other than size, such as hydrogen bonding, influence the stability of the materials. Overall, we have shown that substitution of methylammonium ion for the much larger imidazolium, dimethylammonium, and guanidinium cations in MAPbI3 is a valid strategy for creating stable hybrid organic-inorganic perovskite derivatives by slowing the rate of light-induced degradation.

Partial substitution of chemical nitrogen with organic nitrogen improves rice yield, soil biochemical indictors and microbial composition in a double rice cropping system in south China

Substitution of chemical fertilizers with organic amendments recycle organic wastes and minimizes adverse environmental effects of mineral-fertilizer overuse. In China, cropping systems which utilize two rice plantings per year are the most important planting pattern for ensuring food security. To date, few studies have comprehensively evaluated the responses of soil fertility and rice performance in double rice cropping systems to the partial substitution of chemical nitrogen (N) with organic N under the same input rates of N, P and K. In addition, the influences of the mineral-to-organic substitution ratio and season on these responses remain poorly understood. Here, a 34-year field fertilizer trial was sampled to determine the impacts of organic substitution regime and growing season on soil biochemical properties and rice yield. Compared with the mineral NPK fertilizer regime, the replacement of 30 %, 50 % and 70 % of total N with organic N increased the yield of early rice by 4.5 %–8.3 %, respectively and that of late rice by 6.7 %–9.6 %. Moreover, the organic substitution regimes significantly improved soil biochemical indicators. The higher organic N substitution percentage resulted in higher values of many soil properties with the exception of TC:TN, fungi:bacteria and G+:G−, which tended to decrease with increasing substitution. Both fertilizer regime and growing season affected soil nutrient contents, enzyme activity and microbial community structure. The relative abundances of identified PLFA biomarkers 16:1ω5c, 16:1ω7c and 18:1ω7c were markedly higher (p ≤ 0.05) in the organic alternative treated soils than the NPK-treated soils in both seasons. Our results suggest that the substitution of 70 % chemical N with organic N is the most effective fertilizer practice for improving soil fertility and rice yield in double rice cropping systems.

Statistical modeling of mechanical and transport properties of concrete incorporating glass powder

The objective of this study is to model the effect of the partial replacement of cement by glass powder (GP), w/cm, and supplementary cementitious materials (SCM) content, as well as their coupled effects on key engineering properties of concrete using a statistical design of experiments. The modeled experimental domain includes concrete mixtures with w/cm ranging between 0.27 and 0.69, GP percentages of 0–50%, and SCM content of 310 to 440 kg/m3. The modeled responses include the compressive strength and rapid chloride ions permeability (CIP) at various ages. The comparison between predicted and measured responses determined on eight selected mixtures included in the experimental domain indicates good accuracy of the established models to describe the effect of the independent variables on the targeted properties. The derived statistical models indicate that the CIP is dominated by substitution percentage of GP, while the compressive strength is dominated by w/cm, regardless of the age of concrete. The increase in GP content to 30% resulted in a significant reduction in CIP. However, it reduces the compressive strength at early age, which may necessitate a decrease in w/cm to compensate for strength reduction. Trade-off between mixture parameters to achieve targeted compressive strength and CIP properties were established.

Synthesis of Hg<sub>2</sub>Sr<sub>2-x</sub>Ba<sub>x</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>10 </sub>Superconductor and Study the Structure and Electrical Properties

Compound Hg2Sr2-xBaxCa2Cu3O10 high temperature superconductor looks like (HTSC) has been prepared as a pellet by two step solid state reaction with a certain substitution percentages (0.5, 1,1.5,2) of Ba compensation rate of Sr respectively using appropriate weight of pure material Hg2O3, Sr(NO3)2, Ba(NO3)2, CaCO3, and Cu(NO3)2 proportional to their molecular weight. XRD used for study structure properties, a computer program was used to calculation of spike dimensions the lattice parameters a, b and c shows Tetragonal, Electrical resistivity at x= 1.5 of Ba are obtained when the best value of Tc= 142 K.

Concrete performance evaluation of coarse aggregate replacement by civil construction waste

The construction sector is considered a major generator of environmental impacts due to the high consumption of natural resources and waste generation. Thus, this article aims to evaluate the performance of a concrete produced by the partial and total replacement of natural coarse aggregate by recycled coarse aggregate, derived from the concrete residue of buildings and demolitions. The study was made by comparing the compressive strength and absorption of three different concrete traces, keeping the water/cement factor of 0.60 and changing only the proportions of recycled coarse aggregate between 0%, 50% and 100%. The results showed that the higher the percentage of substitution, the greater the water absorption and the lower the resistance results concrete compression. This result was obtained due to the lighter characteristic of the recycled aggregate compared to the natural aggregate. It was concluded that the concrete produced with recycled aggregates could be used in nonstructural functions, giving an adequate destination to the construction and demolition waste and consequently reducing the extraction and consumption of natural resources and contributing for the sustainable development.

Parametric study on effects of methanol injection timing and methanol substitution percentage on combustion and emissions of methanol/diesel dual-fuel direct injection engine at full load

The effects of methanol injection timing (MIT) and methanol substitution percentage (MSP) on the combustion and emissions of a methanol/diesel dual-fuel direct injection engine were investigated, followed by a comparative analysis with the conventional methanol/diesel dual-fuel mode. A single-cylinder, air-cooled, naturally aspirated common rail diesel engine was modified into a dual-fuel direct injection engine with a methanol direct injection system. The engine was operated at a maximum torque speed of 2500 rpm and a mean effective pressure of 0.75 MPa. The engine performance was analyzed for different methanol/diesel fuel mixtures using four MSPs: 10%, 20%, 30%, and 40%. Meanwhile, the MIT was adjusted from −60 to −300 °CA after top dead center (ATDC). The results indicated that methanol addition and retarded MIT allowed the diesel injection timing to be properly advanced. A higher MSP increased the ignition delay (CA0-10) and decreased the combustion duration (CA10-90), leading to increases in the brake thermal efficiency (BTE), coefficient of variation of the indicated mean effective pressure (IMEP) (COVIMEP), and knock intensity (KI), along with increases in the total hydrocarbon (THC) and nitrogen oxide (NOX) emissions and decreases in the carbon monoxide (CO) and soot emissions. Additionally, for a specific MSP, the retarded MIT increased the peak cylinder pressure and decreased the maximum heat release rate. Concurrently, it decreased the CA0-10 and increased the CA10-90. Moreover, increases in the BTE, COVIMEP, and KI; decreases in the THC and CO emissions; and increases in the NOX and soot emissions were achieved using the retarded MIT.

Carbonated binder systems containing reactive MgO and Portland cement: Strength, chemical composition and pore structure

A sustainable binder system with a capacity to mineralize CO2 can be formulated by reactive MgO and Portland cement (PC). This research studies the properties of mortar specimens made with carbonated MgO-PC systems with a MgO substitution range of 0%–100% in order to evaluate and compare the compressive strength, chemical composition and pore structure. Key results indicate that the carbonation front of mortar subjected to the same curing regime is primarily controlled by the percentage of MgO. The carbonation depth together with the MgO substitution percentage impacts the type of the hydration and carbonation products and their quantity. This affects the mechanical properties and microstructure of the matrix. The compressive strength and pore volume are between of 27.5–84.7 MPa and 2.9%–8.7%, respectively. MgO substitution percentages of 60% and 70% were optimal to achieve both relatively high strength and low porosity. Carbonated MgO-PC binder with 60% MgO was found to possess 20% lower embodied CO2 than that of PC.

Improvement of Fatty Acid Profile in Durum Wheat Breads Supplemented with Portulaca oleracea L. Quality Traits of Purslane-Fortified Bread.

The addition of functional ingredients to breads could have effects on preventing cardiovascular diseases, cancers and inflammation. The incorporation of 0–5–10–15% of three populations of dried purslane flour on the rheological, sensorial and nutritional quality of fortified durum wheat breads were evaluated. The increase in dried purslane (up to 15%) caused an increase in the resistance to the mixture and a consequent reduction in its extensibility. The “panel test” gave a largely positive evaluation in 10% of enrichment. The fatty acids in breads resulted higher with the 5% substitution. Contrary to what has been imagined, the increase in percentage of substitution to 10 and 15% did not lead to an increase in linoleic (omega-3) and α-linolenic (omega-6) acid and probably the cause is in the cooking. The total phenols content and the antioxidant potential, evaluated by ferric reducing antioxidant potential (FRAP) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays of the enriched breads increased with the percentage of the dry purslane substitution. The enrichment of the durum wheat flour with 5% purslane resulted in a good compromise to obtain good rheological characteristics of loaves and breads with decreased omega-6/omega-3 ratio and good antioxidant properties.

TiO2 nanoparticles influence on the environmental performance of natural and recycled mortars: A life cycle assessment

The World Meteorological Organization has recently reported that greenhouse gases have reached their highest level since 3–5 million years ago. A continuing rise would cause serious consequences e.g., rising temperatures, death of living beings, or water pollution. Cement is associated with those levels since its production encompasses around 8% of global CO2 emissions. To increase the environmental performance of cementitious materials, different approaches could be followed, for instance, the reuse of waste materials such as recycled aggregate (RA) or the addition of TiO2 nanoparticles due to its proactive effect during service life. However, no research has been found that examined the effect of nano-TiO2 addition on recycled mortars in terms of environmental impact. Consequently, the main objective of this research is to evaluate the sustainability of TiO2 nanoparticles in mortars made with either natural or recycled aggregate. Twelve mixtures with different percentages of nano-TiO2 substitution (0%, 0.5%, 1%, 2% by the weight of cement) and RA replacement (0%, 50%, 100%) were studied. A life cycle assessment focused on material production (cradle-to-gate) was performed. The functional unit (FU) used was 1 m3 of mortar with a given compressive strength. The mix design was modified to meet the fixed strength defined in the FU. In terms of global warming potential, mortars with RA reduced the environmental impact when 0.5% of nano-TiO2 was added. Considering waste generation and depletion of natural resources play a crucial role in the sustainability assessment of mortars with RA. Furthermore, when the compressive strength factor was considered in the FU, RA increased the total CO2 emissions due to the higher amount of cement needed. Finally, despite the apparent harmful effect of nano-TiO2 using a cradle-to-gate approach, these nanoparticles could highly enhance environmental performance due to their effects during service life.

PENGARUH SUBSTITUSI AMPAS TAHU DAN PENAMBAHAN PISANG AMBON PADA SNACK BARKEDELAI UNTUK OLAHRAGAWAN (ASPEK DAYA TERIMA, EKONOMI DAN KANDUNGAN GIZI) <br><i>Effect of Bean Curd Substitution and Addition of Ambonese Banana on Soybean Snack bar Formula for Athletes (Acceptability, Economic Value, and Nutritional Aspects)</br></i>

Degradation of sport performance in Indonesian athletes was recorded in Sea Games 2017 and FIFA rank in 2015. Some of athletes’ main problem are lack of stamina and endurance. These problem are caused by insuffi cient carbohydrate and energy intake. In addition, selection of tofu curd waste and banana are purposed to provide adequate potasium intake. This study was aimed to reveal the eff ect of bean curd waste and the addition of Ambonese bananas to the acceptability, nutritional value and economic value of the formulated snack bars.The used design was true experiment with completely randomized design. This study employed untrained panelists including athletes with weight restrictions (gymnastics and sports combat with weight classes) as many as 30 people.The percentage of bean curd waste substitution was P1: 12%; P2: 16%; P3: 25%, and 10% added banana. Statistical test results Friedman confi rmed a signifi cant diff erence in the level of preference on the texture and taste aspects between control and other formula. The results of the acceptability, nutritional value and economic value ranking obtained the optimum value in formula two (P2).Nutritional value for 100 grams of snack bar P2 (cohydrate: 41.6 g; fi ber: 8.7 g; potassium: 514 mg) has been able to contribute at least 10% of the daily energy needs of athletes. Laboratory test results for fi ber and potassium can meet 16.7% and 10.9% of the daily needs of athletes. Hence, formulated snack bar can be claimed to be high in fi ber and potassium products. The most aff ordable price of the formulated product was 7,000 IDR per 125 g which is more economical than the commercial soybean-based snack bar. Therefore, the formulated snack bar can be recommended as a complementary meal of athlete with weight restrictions.

Residual Compressive Strength of Recycled Aggregate Concretes after High Temperature Exposure.

Sustainability requirements are gaining importance in the construction industry, which needs to take specific measures in the design and construction of concrete structures. The use of recycled aggregates in concrete may be of special interest. Recycling a construction waste will close the life cycle of the original materials (e.g., concrete). Thus, environmental benefits would come from the lower waste generation, and from a lower necessity of raw materials for new structures. The current Spanish code for structural concrete considers the use of recycled aggregates in replacement rates up to 20% by aggregate mass, assimilating their properties with those of concretes without aggregate replacement. Higher substitution percentages would require further testing. In this work, substitution of coarse aggregate for recycled aggregates (with replacement percentages of 25%, 50% and 100%) has been studied, and the concrete’s residual properties after exposure to high temperatures (between 350 °C and 850 °C) have been assessed. Compressive strength and capillary water absorption tests were made after heating, and the experiments showed higher residual strength in concretes with the greatest content of recycled aggregates. However, a statistical analysis made with additional data available in the literature seemed to predict otherwise, and the recycled aggregate replacement would have a negative effect on the residual strength.

The Dynamic Mechanical Properties for Recycled Aggregate Concrete under Tensile-Compressive States

The experiments under biaxial tensile-compressive (T-C) complex stress were carried out for two kinds of substitution percentages of recycled coarse aggregate (RCA) on biaxial proportional loading (α = σ1:σ3 =1:0, 0: −1, 0.05: −1, 0.1: −1, 0.25: −1, 0.5: −1, 1: −1 and−1: −1) and four loading deformation rates of 10−5/s, 10−4/s, 10−3/s, and 10−2/s. The research was completed in the static-dynamic true triaxial machine. The experimental phenomena indicate the tensile failure appears in these specimens of recycled aggregate concrete (RAC) under biaxial T-C stress states. The dynamic mechanical behavior for RAC under biaxial T-C loadings was affected by the strain rates, stress ratios and its substitution percentages of RCA. Accompanied by the increase of strain rates, its strength of RAC is improved. As the tensile stress increases, its compressive strength decreases. The T-C strengths for RAC under biaxial T-C states are less than its corresponding uniaxial T-C strengths at a certain identical strain rates, respectively. Considering the effect of loading rates, a new tensile-compressive failure criterion is established under complex stress states.

Mid Infrared Spectroscopy and Multivariate Analysis Evaluation of Adulteration in Whey Protein Powder

Mid infrared (MIR) spectroscopy was combined with multivariate approaches Principal Component Analysis (PCA) and Partial Least Squares (PLS) regression to assess modifications in spectral profile of whey protein concentrate (WPC) powder due to changes in formulation level using caffeine, creatine and lactose, simulating fraud. Adulterations were made by replacing WPC in different levels from 5 to 50% (w/w - 5% steps) with three adulterants in separate. The spectra comparison of the samples allowed the identification of peaks associated to characteristic chemical bonds of each adulterant. PCA was carried out and 89% of the total variability of the spectral data was explained by three principal components, which allowed the confirmation of variables influencing each sample mixture and validating the spectral observations. Above 20% decrease in WPC content (20% adulteration), it was possible to differentiate all the three substances used. Predictions of percentage of WPC substitution were made through PLS regressions. The best prediction models were: lactose > creatine > caffeine. However, predictions resulted in overall good accuracy, low relative errors and coefficients of determination of fitting of calibration and validation curves above 0.97 in all cases. Therefore, techniques employed here aid the quality assessment of food products as alternative analytical tools.

Contribution to the Study of the Durability of Rubberized Concrete in Aggressive Environments

Today, much of the world’s waste, in particular used tires, is accumulating as a potential source of major environmental and economic problems. In order to better preserve the environment, and in the face of changes in the legislation in force, many recovery actions have been carried out especially in the field of building materials. The present research aims to contribute to the study of the mechanical properties and durability of concretes based on rubber aggregates. To achieve this objective, we have contemplated incorporating therein amounts of rubber granules according to different volume substitution percentages being 10%, 17.5%, and 25%. A comparison of the results with a control concrete has been established. The obtained results make it possible to demonstrate that the substitution of a percentage of sand by rubber granules decreases the mechanical strengths and increases the expansion in water. On the other hand, it improves the resistance to attack from H<sub>2</sub>SO<sub>4</sub>, Na<sub>2</sub>SO<sub>4</sub>, and seawater. The latter is evaluated by the loss and gain in mass as well as the loss in mechanical resistance, especially in the long term (more than 90 days), decreases drying shrinkage, thus decreasing microscopic cracks and providing better durability.