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Geopolymer is known to have many structural and nonstructural benefits, but the attractive characteristic of this novel material is that it depends essentially on a byproduct from different industries, and the use of Portland cement is absent. This concrete is an environmentally friendly product and is essential as the sustainability issue is considered. Compared with the material properties, the behavior of reinforced concrete members made of geopolymer has gained less importance by past researchers. Therefore, this review paper aims to summarize the evidence of the structural behavior of geopolymer concrete beams to provide a better understanding of the characteristics of reinforced geopolymer beams. A total of sixteen published works on geopolymer beams reinforced with steel rebar have been reviewed, and it found that there are 83 beams tested in flexure and 29 beams tested to highlight the shear behavior. For comparison, some researchers have tested control beams made of Portland cement concrete (PCC). It is noted that geopolymer concrete (GPC) beams have a performance, in general, better than that of PCC beams in terms of strength and ductility. Design proposals for PCC beams could be safely used for GPC beams, and the software based on the finite element method accurately predicts the load-deflection response. However, further study is recommended to provide more detailed and cost-effective design methodologies for the potential use of GPC in large-scale field applications.

Tire rubber waste is globally accumulated every year. Therefore, a solution to this problem should be found since, if landfilled, it is not biodegradable and causes environmental issues. One of the most effective ways is recycling those wastes or using them as a replacement for normal aggregate in the concrete mixture, which has high impact resistance and toughness; thus, it will be a good choice. In this study, 135 data were collected from previous literature to develop a model for the prediction of rubberized concrete compressive strength; the database comprised different mixture proportions, the maximum size of the rubber (1–40 mm), and the rubber percentage (0–100%) replacing natural fine and coarse aggregates were among the input parameters in addition to cement content (380–500 kg/m3) water content (129–228 kg/m3), fine aggregate content (0–925 kg/m3), coarse aggregate content (0–1303 kg/m3), and curing time of the samples (1–96 Days); then the collected data were used in developing Multi Expression Programming (MEP), Artificial Neural Network (ANN), Multi Adaptive Regression Spline (MARS), and Nonlinear Regression (NLR) Models for predicting compressive strength (CS) of rubberized concrete. The parametric analysis reveals that as the maximum rubber size increases, the reduction in compressive strength becomes more pronounced. Notably, this strength decline is more significant when rubber replaces coarse aggregate than its replacement of fine aggregate. Among the input parameters considered, it is evident that the fine aggregate content exerts the most substantial influence on the compressive strength of rubberized concrete. Its impact on predicting compressive strength surpasses other factors, with the concrete samples' curing time ranking second in importance. According to the assessment tools, the ANN model performed better than other developed models, with high R2 and lower RMSE, MAE, SI, and MAPE. Additionally, ANN and MARS models predicted the CS of different sizes better than MEP and NLR models. Subsequently, we employed the collected data to develop predictive models using Multi Expression Programming (MEP), Artificial Neural Network (ANN), Multi Adaptive Regression Spline (MARS), and Nonlinear Regression (NLR) techniques to forecast the compressive strength (CS) of rubberized concrete. The statistical analysis tools assessed the performance of these developed models through various evaluation criteria, including the Coefficient of Determination (R2), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Scatter Index (SI), and Mean Absolute Percentage Error (MAPE). In summary, our study underscores the efficacy of recycling rubber materials in concrete production. It presents a powerful predictive model for assessing the compressive strength of rubberized concrete, with the ANN model standing out as the most accurate and reliable choice for this purpose.

This paper aims to experimentally investigate the flexural behavior of concrete beams reinforced with glass fiber reinforced polymer (GFRP) bars made of concrete with and without polyethylene terephthalate (PET) waste fiber addition. The test variable covers the structural application of different PET fiber lengths (20 mm and 40 mm). Firstly, several tests were done on ten concrete mixes containing 1–2% PET waste fiber with a 0.25% increment by volume. The mixture's concrete properties, including stress-strain curves, were studied to obtain the optimum percentage of PET fiber. Furthermore, four GFRP reinforced concrete (RC) beams were cast from concrete containing 0% PET fiber (the control beam), 1% PET fiber volumes of 20 mm and 40 mm, and an equal mixture of both lengths. The beams were designed using ACI 440.1R to fail in GFRP rupture. The results showed that compressive strength increased by 8% and 6% using 1% fiber volume of 20 and 40 mm PET fiber, respectively. It was found that PET fiber addition had a negligible effect on changing the ductility, cracking pattern, or failure mode of under reinforced GFRP RC beams. The cracking and ultimate loads are slightly reduced, however, and the corresponding deflections are well reduced, especially when using 40 mm PET fiber. With the use of PET waste fiber, serviceability increased by up to 12% based on deflection limit control (L/240). The addition of 40 mm of PET fiber was found to enhance the beam stiffness by 25%. An analysis method has been proposed to predict the flexural strength of GFRP RC beams made with PET fiber. Moreover, it is recommended to treat the PET fiber surface to improve the fiber-concrete bond when used in non-ductile RC beams.

Nowadays, the performance criteria for concrete construction are moving toward eco-efficiency, which is a method of producing highly durable and environmentally friendly concrete while minimizing both manufacturing costs and environmental load. Admixtures are commonly used in all concrete construction; however, some of them are harmful to human health and cause leaching, which is responsible for environmental pollution. On this principle, one of the eco-efficiency method's techniques is to use natural materials as additives in concrete. The paper continues to discuss the experi-mental data generated at the author's laboratory as part of exploratory work on the use of natural materials and their impact on the properties of cement, mortars, and concretes in terms of improving fresh, mechanical, and durability properties of concrete , The paper concludes that the observed impacts of using these natural material additions on the properties of mortar and concrete will motivate greater research in these areas, thereby improving the sustainability of concrete constructions.

A combination of fiber reinforced polymer (FRP) and concrete subjected to seawater or crude oil is a desirable solution to reduce resource shortage and environmental issues. In current decades, numerous investigations have considered the utilization of FRP composites as a way for concrete confinement. Such composites have been typically limited to wrapping concrete columns at ambient temperatures. This raises the question of whether such composites can be utilized in some other applications. For that reason, the effectiveness of carbon fiber reinforced polymer (CFRP) wrapped concrete under seawater or crude oil exposure for 90 days and 720 days long-term impacts at ambient temperature concentrations have been tested experimentally. To accomplish this objective, 16 column specimens were prepared and tested. The impacts of exposure conditions, exposure time, loading type, and CFRP thickness were examined. Although it is evident that control columns' load-bearing capacities are reduced when immersed in seawater or crude oil, there is a noticeable improvement in load-bearing capability for columns immersed in seawater for a prolonged period of time for 720 days compared to those immersed in crude oil for the same amount of exposure. The strength of the confined control column and the columns submerged in seawater or crude oil significantly improved as compared to the unwrapped column without soaking in seawater or crude oil under monotonic or cyclic loading. The results of the experiment and the available design-oriented strength models can encourage the widespread use of FRP confined seawater or crude oil concrete in artificial islands and offshore structures. It was determined that these models are insufficient for predicting the strength of RC columns that had been submerged in seawater or crude oil and then encased in CFRP confinement.

Different properties of Self-compacting concrete (SCC) containing plastic waste aggregate (PWA) have been experimentally studied by researchers. However, most of these works focused on examining the properties of one type of PA. In the present paper, the influence of four different types; namely Polyvinyl chloride (PVC), Heat-treated plastic (PEL), Mixed plastic (Mix), and polyethylene terephthalate (PET) as a fine aggregate (FA) replacement; on fresh properties of SCC was examined. Results indicated that changing the PWA geometry influenced different properties of SCC. All concrete samples with PVC and PEL plastic were in the range of EFNARC classification (classified in VS2/PA2 class), causing no blocking in V-funnel and L-box test. Meanwhile, mixed plastic up to 7.5% and PET up to 5% fall within VS2/VF2 class; otherwise, the mixture was outside the range of EFNRAC standards. The best plastic waste aggregate regarding all new properties was PVC confirming all requirements for a successful SCC, causing no blocking or segregation. Thus, 10% was selected as the optimum percentage. Furthermore, PET was the worst, for PET-7.5% significant increase in the V-funnel (57.6 sec) and reduction in H2/H1 ratio (0.58) was obtained besides blocking in L-box tests, segregation, and bleeding in slump flow test. Thus, more than 5% is not recommended when using PET in Self-compacting concrete.

In this study, a model was proposed based on calculating the total surface area of aggregate to assess fresh density, compressive, and splitting tensile strengths of plastic aggregate (PA) recycled concrete. The key factor is the change in the total surface area of the natural aggregate by the PA. For a given PA volume, the change in the property could be assessed. The prediction well depends on the natural and plastic aggregates distribution size, specific gravity, and bulk density. The proposed model prediction was accurate when applied to high-strength, and lightweight concretes. The reason is attributed to the relatively good bond between PA and hardened cement paste in these concretes. However, for the majority of concrete mixes investigated, the model moderately underestimated strength loss, and this underestimation could be attributed to the PA- hardened cement paste bond deficiency. An attempt was made to assess the bond deficiency parameter for a more accurate prediction.

The manufacture of ordinary Portland cement (OPC) produces a lot of CO2 in the atmosphere. Researchers have recently focused on exploring the behaviour of geopolymer concrete (GPC) as an alternative to Portland cement concrete (PCC) in micro and macro dimensions. Geopolymers (GP) are innovative cement-based materials that could totally replace OPC composites. Geopolymer composites (GC) have a reduced carbon footprint and utilize less energy than OPC. The construction industry's main concerns are material characteristics and the performance of reinforced concrete (RC) structural components. Therefore, this review paper is going to look at some important material properties, like fresh characteristics, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity, as well as the evidence of the structural behaviour of GPC beams. According to the findings of this review, GPC offers similar or superior fresh and mechanical properties to conventional concrete composite. In addition, it was mentioned that GPC might be utilized to design GPC members securely in terms of their strength capabilities and standard codes of practice. Nevertheless, further study is suggested to include more detailed and cost-effective design methods for the potential use of GPC for large-scale field applications.

Many environmental and health problems are raised from cement manufacturing processes and other factories because those factories emit large amounts of carbon dioxide (CO2) into the atmosphere. Using supplementary cementitious material reduces the amount of cement used, then the amount of CO2 is also reduced. Metakaolin (MK) is used as a mineral admixture to improve the mechanical properties of concrete because higher strength requires a more densified concrete mixture. Mineral admixtures have a pozzolanic reaction and lower thickness of the transition zone. In this study, four different models, specifically linear regression (LR), nonlinear regression (NLR), multi-logistic regression (MLR), and M5P-tree models, are proposed to predict the compressive strength (compressive strength) of high-strength concrete (HSC) modified with metakaolin admixture. These models are useful since they serve as an effective way to predict compressive strength without waiting for a long time theoretically and are cost-effective and time-saving. For this purpose, 197 experimental data of HSC mixtures with MK from previous research are collected, statistically analyzed, and used to propose the prediction models. The curing time of the tested sample ranged between 1 and 360 days, and water to binder ratios was from 100-206 kg/m3. The highest compressive strength of the HSC samples was 105 MPa at 28 days. The proposed models are assessed by the coefficient of determination (R2), root mean squared error (RMSE), scatter index (SI). And OBJ. The M5P-tree model was the best model among the proposed models with R2, RMSE, SI of 0.77, 6.67 MPa, 0.096, respectively.

In this article, flexural strength and compressive strength of concrete containing polypropylene fiber (PP), polyethylene terephthalate (PET) waste fiber and a combination between them were experimentally investigated. For this reason, laboratory experiments were performed on a total of 40 mixes. Results show that compressive strength property of concrete reinforced with PET waste fiber is not comparable to that of concrete reinforced with PP fiber, in which there is a compressive strength reduction, and the effect of PET fiber length on the strength is not important. Behavior of concrete contained PET waste fiber in flexure was found better. There is a good opportunity to use a hybrid fiber (25% PET and 75% PP) to enhance flexural strength of concrete.

Abstract: Background: The most frequent movement issue seen in clinical practice is tremors. It is known as repetitive, involuntary oscillations. The diagnostic process for tremor patients can be time-consuming and complicated, as the identification of “Essential Tremor” and its distinction from other types of tremor. Objectives: This study aimed to describe the electrophysiological findings of essential, enhanced physiological, and physiological tremors, using surface electromyography and an accelerometer. Patients and Methods: The study included 24 patients with essential tremors, 10 patients with enhanced physiological tremors, and 10 patients with physiological tremors. We assessed the frequency, amplitude, and muscular contraction pattern of tremors during rest, posture, and a 1 kg load. Results: The tremor frequency of essential tremor patients was about 4.2-10.1 Hertz, while enhanced physiological tremor and physiological tremor were increased to 6.1–12.7 Hertz and 5.1-10.2 Hertz, respectively. The essential tremor group muscle contraction pattern was predominantly synchronous, as do all enhanced physiological, and physiological tremor patients, but with more fine low amplitude muscle bursts. By varying the tremor frequency and the weight load effect, tremor analysis could discriminate essential from enhanced physiological, and physiological tremors. Conclusions: The tremor analysis using surface electromyography and an accelerometer is sufficient to differentiate between essential tremors, enhanced physiological tremors, and physiological tremors.

Since nanotechnology can enhance the performance of materials, significant effort has been expended in recent years to incorporate nanoparticles (NPs) into geopolymer concrete (GPC) to improve performance and produce GPC with improved characteristics. Recent efforts have been made to incorporate various nanomaterials, most notably nano-silica (nS), into GPC to improve the composite's properties. Compressive strength (CS) is an important property of all concrete composites, including geopolymer concrete. Several mix proportion parameters and curing temperature and ages influence the CS of geopolymer concrete. As a result, developing a credible model for forecasting concrete CS is critical for saving time, energy, and money while also providing guidance for scheduling the construction process and removing formworks. This paper consists of three phases; in the first phase, a detailed review on the effect of adding nS on the CS of GPC was provided; then, in the second phase, a large amount of mixed design data were extracted from literature studies to create five different models including artificial neural network, M5P-tree, linear regression, nonlinear regression, and multi logistic regression models for forecasting the CS of GPC incorporated nS. Finally, the developed models were validated in the last phase by carrying out experimental laboratory works. Results revealed that the addition of nS improves the CS of GPC, and the ANN model estimated the CS of GPC incorporated nS more accurately than the other models. On the other hand, the alkaline solution to binder ratio, molarity, NaOH content, curing temperature, and ages were those parameters that significantly influenced the CS of GPC incorporated nS.

In this experimental study, physical, strength and durability properties of roller compacted concrete (RCC) containing metakaolin with or without steel fiber are investigated. For this purpose, seven different mixes were designed and tested in the lab. To assess properties of compressive strength, splitting tensile strength, water permeability and freezing and thawing resistance in terms of weight and compressive strength losses. There is an increasing compressive strength of RCC containing MK with or without steel fiber with increasing ages. 15% MK 45 kg/m3 steel fiber was found the best dosage for RCC at the age of 90 days. Also, there is a splitting tensile strength enhancement being increased with increasing MK and steel fiber in the mix. There is a continuous permeability reduction with increasing combined MK and steel fiber addition reaching 77.9% as maximum value for the mix of 20% metakaolin and 60 kg of steel fiber. Also, there is a reduction of weight and compressive strength losses of RCC subjected to freezing and thawing cycles up to 300 due to MK and steel fiber addition. It is concluded that using a combination of MK and steel fiber has a promised future to be used in more durable RCC for road construction.

This study describes two workability tests, compressive strength and tensile strength tests of high strength flowable concrete containing plastic fiber prepared from polyethylene terephthalate (PET) waste bottles. For the high fluidity mix Vebe time and V-funnel time tests were carried out. Results show that there is a Vebe time increase with PET fiber addition to concrete being increased with increasing fiber volume and fiber length. V-funnel time was found to reduce when up to 0.75% fiber volume is added to concrete, followed by an increase for larger fiber volumes. When fiber length is increase, there is more time increase, but in general, V-funnel time increase was lower than that of Vebe time, indicating a different influence of PET fiber on the compactibility and flowability. The measured V-funnel time for all mixes was found to conform to the limits of European specifications on the flowability of self compacting concrete. Small descending in compressive strength was recorded for RPET fiber reinforced concrete that reached 15.74 % for 1.5 percent fiber content with 10 mm fiber length. Attractive results was recorded in split tensile strength of RPET fibrous samples which resulted in improvement up to 63.3 % for 1.5 percent of 40 mm fiber length content.

In this research, physical and mechanical properties of high strength concrete containing PVC waste have been investigated. The fine aggregate was replaced with PVC waste with two different gradings (fine grading and coarse grading) at dosages of 0%, 5%, 10%, 20%, and 40% by the volume of aggregate. The properties include physical properties of density and water absorption, mechanical properties of compressive strength, splitting tensile strength and flexural strength. Results show that in general, using 5% PVC replacement in high strength concrete has no appreciable effect to damage the physical and mechanical properties of concrete. With increasing PVC aggregate content, the deterioration of the concrete properties was observed. The coarse graded PVC aggregate has some more effect on the deterioration of concrete properties compared to the fine graded PVC aggregate.

A variety of ashes used as the binder in geopolymer concrete such as fly ash (FA), ground granulated blast furnace slag (GGBS), rice husk ash (RHA), metakaolin (MK), palm oil fuel ash (POFA), and so on, among of them the FA was commonly used to produce geopolymer concrete. However, one of the drawbacks of using FA as a main binder in geopolymer concrete is that it needs heat curing to cure the concrete specimens, which lead to restriction of using geopolymer concrete in site projects; therefore, GGBS was used as a replacement for FA with different percentages to tackle this problem. In this study, Artificial Neural Network (ANN), M5P-Tree (M5P), Linear Regression (LR), and Multi-logistic regression (MLR) models were used to develop the predictive models for predicting the compressive strength of blended ground granulated blast furnace slag and fly ash based-geopolymer concrete (GGBS/FA-GPC). A comprehensive dataset consists of 220 samples collected in several academic research studies and analyzed to develop the models. In the modeling process, for the first time, eleven effective variable parameters on the compressive strength of the GGBS/FA-GPC, including the Activated alkaline solution to binder ratio (l/b), FA content, SiO2/Al2O3 (Si/Al) of FA, GGBS content, SiO2/CaO (Si/Ca) of GGBS, fine (F) and coarse (C) aggregate content, sodium hydroxide (SH) content, sodium silicate (SS) content, (SS/SH) and molarity (M) were considered as the modeling input parameters. Various statistical assessments such as Root Mean Squared Error (RMSE), Mean Absolute Error (MAE), Scatter Index (SI), OBJ value, and the Coefficient of determination (R2) were used to evaluate the efficiency of the developed models. The results indicated that the ANN model better predicted the compressive strength of GGBS/FA-GPC mixtures compared to the other models. Moreover, the sensitivity analysis demonstrated that the alkaline liquid to binder ratio, fly ash content, molarity, and sodium silicate content are the most affecting parameter for estimating the compressive strength of the GGBS/FA-GPC.

Considering that most studies depend on theoretical equations to determine the minimum reinforcement ratio, only a few studies on this ratio are available. Therefore, a more defined limit should be suggested to design codes by performing additional investigations and experimental studies on this limit. This study examines the behavior of high-strength concrete (HSC) beams with low reinforcing steel ratios to establish a limit for the lowest flexural reinforcement ratio that will ensure ductility. Experiments were performed on 12 reinforced HSC beams with a concrete compressive strength of 99 MPa, which were divided into three categories depending on their size. Each category comprised four beam reinforcement ratios (0%, 0.13%, 0.33%, and 0.65%), and two main parameters (beam size and reinforcement ratio) were investigated. Furthermore, to ensure flexural failure at the middle-span, adequate web reinforcing was used in all the beams and tested under a four-point load until they exhibited failure. Based on regression analysis, an equation was proposed for the rupture modulus of reinforced beams. The findings suggest that, in addition to the yielding strength of the reinforcements and the compressive strength of the concrete, the depth of the beams should be considered when computing the minimum flexural reinforcement of beams.

There is a general belief that admixture can improve some important properties of concrete, and different kinds of admixtures are in use worldwide. In the current investigation, a comparative experimental study has been performed on using grape and mulberry extracts as a natural admixture and chemical admixture for concrete. Increasing of workability and reduction in water absorption were observed due to the addition of natural admixtures to concrete. There was an enhancement of concrete compressive strength tested at 3, 7, and 28 days and the 28 days modulus of elasticity as a result of using different admixtures, but reduction of splitting tensile strength was observed. In general, using the two natural admixtures has a beneficial effect to improve both fresh and hardened properties of concrete and they have a superiority on the chemical admixture with regard the cost and producing environmental-friendly construction material.

Different non-destructive tests are in use for the structural health monitoring. Test variables affecting non destructive behavior of concrete were discussed by some researchers, including the effect of instantaneous loading during testing for ultrasonic pulse velocity (UPV). This study aimed at determining rebound number (RN) using Schmidt hammer and UPV of concrete subjected to short term and continuous loadings. Tests were carried out on concrete cubes and cylinders to study the effect of short term loading, while to apply a continuous loading, reinforced concrete beams were loaded inside a rigid steel frame. Reduction of RN and UPV for concrete subjected to 80% compressive loading was found to be 8.1% and 10% respectively. There is some effect of loading cycle at high loading level especially for lower strength concrete. Also, RN was found to reduce with increasing tensile short term loading, in which for lower strength concrete reached 5%. There is a continuous reduction in UPV percentage with increasing tensile loading level, especially for lower strength concrete but the effect of tensile loading was found to be smaller than that of compressive loading. Analysis of data was made and equations were presented to calculate the changes take place due to short term loading effects. It is concluded that for concrete under continuous tensile stress, equations for UPV-compressive strength relationship should be modified with a reduction factor of 0.87 or calculated from an equation proposed in this study.

Introduction: Poisoning is a major public health issue and a leading cause of admission to the emergency department (ED). There is a paucity of data describing the epidemiology and cost of acute poisoning. Therefore, this study investigated the epidemiology, patterns, and associated costs of acute poisoning in emergency department of the largest tertiary care healthcare centre in Qatar. Method: This study was a retrospective review of the health records of patients admitted to the ED due to poisoning between January 2015 and December 2019. Incidence, clinical characteristics, and costs associated with acute poisoning were assessed. Frequency and percentages were calculated for categorical variables and mean and SD for continuous variables. The relationship between sociodemographic characteristics and poisoning profile was assessed using the chi-square test. A micro-costing approach using the cost of each resource was applied for cost calculations. Result: The incidence of acute poisoning was 178 cases per 100,000 patients. Females (56%) and children below 14 years (44.3%) accounted for the largest proportion. Most of the exposures were accidental involving therapeutic agents (64.2%). The mean length of hospital stay was found to be 1.84 ± 0.81 days, and most patients (76.6%) were discharged within the first 8 h. A statistically significant difference was found between age groups and type of toxin (χ2 = 23.3, p < 0.001), cause and route of exposure (χ2 = 42.2, p < 0.001), and length of hospital stay (χ2 = 113.16, p < 0.001). Admission to intensive care units had the highest cost expenditure (USD 326,008), while general wards accounted for the least (USD 57,709). Conclusion: Unintentional poisoning by pharmacological agents is common in infants and children. This study will assist in the development of educational and preventive programmes to minimise exposure to toxic agents. Further studies are required to explore the impact of medical toxicology services, and post discharge monitoring of poisoning. [ABSTRACT FROM AUTHOR]