Effects of Sulfate and Sulfuric Acid on Efficiency of Geopolymers as Concrete Repair Materials

Various geopolymer mortars (GPMs) as concrete repairing materials have become effective owing to their eco-friendly properties. Geopolymer binders designed from agricultural and industrial wastes display interesting and useful mechanical performance. Based on this fact, this research (experimental) focuses on the feasibility of achieving a new GPM with improved mechanical properties and enhanced durability performance against the aggressive sulfuric acid and sulfate attacks. This new ternary blend of GPMs can be achieved by combining waste ceramic tiles (WCT), fly ash (FA) and ground blast furnace slag (GBFS) with appropriate proportions. These GPMs were designed from a high volume of WCT, FA, and GBFS to repair the damaged concretes existing in the construction sectors. Flexural strength, slant shear bond strength, and compatibility of the obtained GPMs were compared with the base or normal concrete (NC) before and after exposure to the aggressive environments. Tests including flexural four-point loading and thermal expansion coefficient were performed. These GPMs were prepared using a low concentration of alkaline activator solution with increasing levels of GBFS and FA replaced by WCT. The results showed that substitution of GBFS and FA by WCT in the GPMs could enhance their bond strength, mechanical characteristics, and durability performance when exposed to aggressive environments. In addition, with the increase in WCT contents from 50 to 70%, the bond strength performance of the GPMs was considerably enhanced under sulfuric acid and sulfate attack. The achieved GPMs were shown to be highly compatible with the concrete substrate and excellent binders for various civil engineering construction applications. It is affirmed that the proposed GPMs can efficiently be used as high-performance materials to repair damaged concrete surfaces.

Effects of Eight-Week Combined Resistance and Endurance Training on Serum Levels of Prostate Specific Antigen (PSA), Sex Hormone Binding Globulin (SHBG), and Phosphatase and Tensin Homolog (PTEN) in Men with Prostate Cancer

Background: Prostate cancer (PC) is the second most prevalent cancer and the sixth cancer leading to death in men worldwide. Objectives: The purpose of this study was to examine the effect of eight weeks of combined training on specific markers of prostate cancer in older adults. Methods: Twenty older adults (62 ± 7 years) with prostate cancer were divided randomly into the control (n = 10) and training (n = 10) groups. The training group performed exercise training in three sessions a week for eight weeks. Resistance training included two sets of 10 repetitions at 60 - 75% of one-repetition maximum, and endurance training contained treadmill running for 20 - 35 min at 60 - 75% of maximum heart rate. Bruce test, one-repetition maximum, and ELISA technique were used respectively to measure the aerobic performance, strength performance, and serum levels of prostate specific antigen (PSA), sex hormone binding globulin (SHBG), phosphatase and tensin homolog (PTEN), and testosterone (TS). A two-way analysis of variance with repeated measures was used to specify the differences. Results: Weight, fat percentage, Body Mass Index (BMI), waist-hip ratio (WHR), glucose, insulin, and PSA were significantly lower in the training group than the control group (P < 0.05). Furthermore, strength performance, aerobic performance, SHBG, TS, and PTEN were significantly higher in the training group than in the control group (P < 0.05). Conclusions: Combined training can have an influential role in physical condition improvement through decreasing the PSA serum level and increasing SHBG, TS, and PETEN serum levels, which helps patients with prostate cancer to be cured.

Quasi-Static and Dynamic Mechanical Properties of a Ti-6Al-4V Titanium Alloy Produced Using Unconventional Manufacturing Methods

The purpose of this paper was to determine the mechanical properties of a Ti-6Al-4V titanium alloy produced by traditional CIP (Cold Isostatic Pressing) and by LENS (Laser Engineered Net Shaping), an additive manufacturing process. A reference material, being a commercial Ti-6Al-4V alloy, was also tested. The strength test specimens were produced from a high-quality, Grade 5 titanium powder. Each specimen had its density, porosity, and hardness determined. Compression curves were plotted for the tested materials from the strength test results with static and dynamic loads. These tests were performed on an UTS (Universal Testing Machine) and an SHPB (Split Hopkinson Pressure Bar) stand. The test results obtained led to the conclusion that the titanium alloy produced by CIP had lower strength performance parameters than its commercially-sourced counterpart. The LENS-produced specimens outperformed the commercially-sourced alloy both in static and dynamic load conditions.

Combined Effects of Citrulline Plus Nitrate-Rich Beetroot Extract Co-Supplementation on Maximal and Endurance-Strength and Aerobic Power in Trained Male Triathletes: A Randomized Double-Blind, Placebo-Controlled Trial

Citrulline (CIT) and nitrate-rich beetroot extract (BR) are ergogenic aids and nitric oxide (NO) precursors. In addition, both supplements seem to have other actions at the level of muscle metabolism that can benefit strength and aerobic power performance. Both supplements have been studied in numerous investigations in isolation. However, scientific evidence combining both supplements is scarce, and to the best of the authors’ knowledge, there is no current study of endurance athletes. Therefore, the main purpose of this study was to determine the effect of 9 weeks of CIT plus BR supplementation on maximal and endurance-strength performance and aerobic power in male triathletes. This study was a randomized double-blind, placebo-controlled trial where participants (n = 32) were randomized into four different groups: placebo group (PLG; n = 8), CIT plus BR group (CIT- BRG; 3 g/kg/day of CIT plus 3 mg/kg/day of nitrates (NO3−); n = 8), CIT group (CITG; 3 g/kg/day; n = 8) and BR group (BRG; 3 mg/kg/day of NO3−; n = 8). Before (T1) and after 9 weeks (T2), four physical condition tests were carried out in order to assess sport performance: the horizontal jump test (HJUMP), handgrip dynamometer test, 1-min abdominal tests (1-MAT) and finally, the Cooper test. Although, no significant interactions (time × supplementation groups) were found for the strength tests (p > 0.05), the CIT- BRG supplementation presented a trend on HJUMP and 1-MAT tests confirmed by significant increase between two study moments in CIT-BRG. Likewise, CIT-BRG presented significant interactions in the aerobic power test confirmed by this group’s improve estimated VO2max during the study with respect to the other study groups (p = 0.002; η2p = 0.418). In summary, supplementing with 3 g/day of CIT and 2.1 g/day of BR (300 mg/day of NO3−) for 9 weeks could increase maximal and endurance strength. Furthermore, when compared to CIT or BR supplementation alone, this combination improved performance in tests related to aerobic power.

Quantitative Assessment of the Kinetics of Damage Accumulation in the Polymer Matrix Structure Under Full-Scale Climatic Factors and Tensile Loads

Постановка задачи. Изучено изменение упруго-прочностных показателей и кинетики накопления повреждений в эпоксидных полимерах под действием растягивающих нагрузок в контрольном состоянии и после натурного климатического воздействия в течение одного календарного года. Расчет кинетики накопления повреждений осуществлялся на основе авторской методики, основанной на использовании методов фрактального анализа кривых деформирования образцов полимерных материалов при растяжении. Результаты. Предложен удельный показатель θ, позволяющий количественно оценивать суммарное число повреждений на единицу прочности, накопление которого приводит к разрушению полимеров. Получены аппроксимирующие зависимости, описывающие взаимосвязь между удельным показателем θ и пределом прочности эпоксидных полимеров при растяжении. Выводы. Установлено, что наибольшей стабильностью свойств под действием натурного климатического воздействия обладает полимер на основе эпоксидной смолы «Этал-247». Statement of the problem. In the current study we look at the change in the elastic-strength performance and kinetics of damage accumulation in epoxy polymers under tensile loads in the control state and after full-scale climatic exposure during one calendar year were studied. Damage accumulation kinetics was calculated based on the author's method using methods of fractal analysis of deformation curves for polymer materials samples under tension. Results. We proposed specific index θ to quantify the total number of damages per unit of strength where its accumulation leads to the destruction of polymers. The dependences have been obtained that describe the relationship between specific index θ and tensile strength of epoxy polymers. Consclusion. The study has shown that the Etal-247 epoxy resin-based polymer cured with Etal-1440 amine hardener has the most stable properties under the full-scale climatic exposure.

Effect of weightlifting training on jumping ability, sprinting performance and squat strength: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to assess the effect of using weightlifting movement and their derivatives in training on vertical jump, sprint times, and maximal strength performance. Thirty-four studies were used for meta-analysis with a moderate quality on the PEDro scale. Meta-analysis showed positive effects of weightlifting training, especially when combined with traditional resistance training on countermovement jump performance, sprint times, and one-repetition maximum squat (ES = 0.41, ES = −0.44, and ES = 0.81, respectively). In conclusion, results revealed the usefulness of weightlifting combined with traditional resistance training in improving sprint, countermovement jump and maximal strength performance.

A NEW METHOD FOR ASSESSING THE SAFETY OF SHIPS DAMAGED BY GROUNDING

The primary aim of the present study is to propose an innovative method for assessing the safety of ships which have suffered accidental or in-service damages. Only a small number of probable scenarios for accidental or in-service damage representing all possible damage scenarios are selected using a sampling technique in which the random variables affecting the damage are probabilistically characterized. A damage index for the corresponding damage scenario is defined as a function of damage characteristics such as location and extent of the damage. The residual strength performance of a ship with the corresponding damage scenario can then be calculated by analytical or numerical methods. Once this process has been carried out for each of the damage scenarios selected, a diagram relating the residual strength performance to the damage index (abbreviated as the R-D diagram) can be established. This diagram will be very useful for a first-cut assessment of a ship’s safety immediately after it has suffered structural damage. The diagram can also be used to determine acceptance criteria for a ship’s safety against accidental or in-service damage. An applied example is shown to demonstrate the applicability of the proposed method in terms of developing a diagram between the ultimate longitudinal strength versus grounding damage index for four types of double-hull oil tankers – VLCC, Suezmax, Aframax, and Panamax.

Influence of Graphene Nanoplatelets on the Compressive and Split Tensile Strengths of Geopolymer Concrete

Geopolymer is now a more advanced alternative to cement and available substitute for OPC while graphene nanoplatelets (GnP) are new nanomaterials with extraordinary properties that can enhance and improve the strength of cementitious materials. Although graphene reinforced concrete has intriguing potential, its implementation in construction requires better knowledge of the impact of GnP on the properties of concrete related to durability. Studies on the compressive and tensile strength performance of geopolymer concrete (GPC) containing GnP are needed. The present study investigated the influence of reinforcing GPC with varying percentages of GnP on the compressive and split tensile strengths of GPC. The addition of GnP ranged from 0.0%, 0.25% and 0.5% by weight of total binder. It has been observed that the addition of GnP increased the compressive strength by 30% and the tensile strength by 22% in comparison to a reference sample with a specified composition of fly ash and sodium metasilicate. In addition, the effect of GnP on enhancing the compressive strength of the geopolymer was shown to diminish as the amount of sodium metasilicate increased.