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This study aimed to determine the abrasion resistance of ultra-high-performance concretes (UHPCs) for railway sleepers. Test samples were made with different cementitious material combinations and varying steel fiber contents and shapes, using conventional fine aggregate. A total of 25 UHPCs and two high-strength concretes (HSCs) were selected to evaluate their depth of wear and bulk properties. The results of the coefficient of variation (CV), relative gain in abrasion, and abrasion index of the studied UHPCs were also obtained and discussed. Furthermore, a comparison was made on the resistance to wear of the selected UHPCs with those of the HSCs typically used for prestressed concrete sleepers. The outcomes of this study revealed that UHPCs displayed excellent resistance against abrasion, well above that of HSCs. Amongst the utilized cementitious material combinations, UHPCs made with silica fume as a partial replacement of cement performed best against abrasion, whereas mixtures containing fly ash showed the highest depth of wear. The addition of steel fibers had a more positive influence on the abrasion resistance than it did on compressive strength of the studied UHPCs.

In this study, surface resistivity of the non-proprietary ultra-high-performance concretes (UHPCs) using traditional aggregates were evaluated. Four plain UHPCs were batched using various cementitious materials at a constant water-to-cementitious materials ratio of 0.21 with an aggregate-to-cementitious materials ratio of 1.20. The 28-day surface-resistivity was measured for a duration of 60 minutes (10 minutes intervals). The influence of testing time on surface resistivity of the studied UHPCs was also examined. The results of this study highlighted that surface resistivity of UHPC could be used with confidence to assess its chloride penetration resistance. The outcome of the study also revealed that the binary blend UHPC containing silica fume, as a partial replacement of Portland cement, displayed the highest surface resistivity, lowest chloride ion penetration, and highest compressive strength amongst the studied UHPCs. Time of testing had a minor effect on surface-resistivity of the studied UHPCs.

This paper examines the freezing and thawing resistance of high early-strength concrete (HESC) developed for rapid repair of pavements and bridge decks. The cement types chosen for this study included ASTM Type III, ASTM Type V, and Calcium Sulfoaluminate (CSA). A cement content of 386 kg/m 3 was maintained for all studied concretes. Specimens were tested after 24 hours and 28 days of curing in order to evaluate compressive and flexural strengths. In addition, the opening time was determined based on the required time to achieve the minimum compressive strength of 20.7 MPa. The freezing and thawing (F–T) resistance of the test samples were evaluated in accordance with the F–T duration of 96 hours per cycle for a total of 25 cycles. Test results revealed that at the opening time and after 24 hours curing, CSA cement concrete displayed the highest compressive and flexural strengths, but lowest resistance to freezing and thawing with de-icing salt. The 28-day cured Type V cement concrete produced the highest strength and de-icing salt resistance, while CSA cement concrete produced the contrary.

This study examines the suitability of ASTM Type V cement concrete for rapid repair applications. To this end, experimental results on transport and durability properties of high early-strength concretes using ASTM Type V cement were compared with those of a more traditional cement used for rapid repair, i.e. Type III cement. A cement content of 445 kg/m 3 (750 lb/yd 3 ) was maintained for all studied concretes. The experimental program included compressive strength, absorption, rapid chloride migration, corrosion resistance, and mass loss due to freezing and thawing regimes. The results of this study revealed that use of Type III and V cements were both effective for concrete rapid repair applications. The opening time to reach the minimum compressive strength of 21 MPa (3000 psi) was found dissimilar. Type III cement concrete showed better strength properties at early ages due to its high fineness. However, as curing age was extended to 24 hours and 28 days, Type V cement concrete produced higher strength results. Moreover, Type III cement concretes failed to display better performance in transport properties, corrosion, and frost resistance when compared to that of the studied Type V cement concretes.

This paper examines the abrasion resistance of high early-strength concrete developed for rapid repair of highways and bridge decks. The cement types chosen for this study included ASTM Type III, ASTM Type V, and Calcium Sulfoaluminate (CSA) cements. A cement content of 386 kg/m 3 (650 lb/yd 3 ) was maintained for all studied concretes. Test samples were tested after 24 hours and 28 days of curing in order to evaluate compressive strength and depth of wear. Test results revealed that the opening time to attain minimum required compressive strength for CSA cement concrete was one hour, whereas the values for Type V and Type III cement concretes were 8.5 and 6 hours, respectively. After 24 hours curing, CSA cement concrete displayed the highest strength, but lowest resistance to wear. The 28-day cured CSA cement concrete produced the highest strength and resistance to abrasion, while Type III cement concrete showed a similar strength, but lower resistance to wear, when compared to those of the Type V cement concrete.

The study presented herein was intended to (1) compare the optimum (minimum) dosage requirements of four different sources of polycarboxylate-based high-range water-reducing admixtures (HRWRAs) and viscosity-modifying admixtures (VMAs) in attaining slump flows of 508 mm, 635 mm, and 711 mm, and a visual stability index (VSI) of 0 (highly stable concrete) or 1 (stable concrete), and (2) assess the flowability/viscosity, stability, passing ability, and filling ability of the resulting self-consolidating concretes. The test results showed that the optimum dosage requirements to obtain a uniform slump flow and visual stability index varied among the four selected admixture sources. The required dosage amount for HRWRAs was highest for the polycarboxylate-ester (PCE) type and lowest for the polycarboxylate-acid (PCA) type. Acceptable flowability plastic viscosity dynamic and static stability, passing ability, and filling ability of self-consolidating concrete can be achieved with the proper dosing of the four studied admixture sources.

An experimental study was carried out using in pilot-scale constructed wetland systems, operated in parallel to treat raw sewage. Each system consisted of a vertical flow (VF) unit that was filled with biochar as the main media, followed by a horizontal flow (HF) unit filled with crushed cement mortar. Hydraulic loading (HL) ranged 340–680 mm/day was applied on the VF wetland units, where high total nitrogen (TN) mass removal rate (20–23 g N/m 2  d) was obtained, demonstrating that biochar media had a beneficial effect on the degradation of nitrogenous pollutants. Total phosphorus (TP) removal percentage (concentration based) was ≥ 86% in HF wetlands packed with mortar materials. In one system, the flow direction of the sewage was directed by the deployment of downflow pipes and vertical baffles, aiming to facilitate the formation of aerobic and anaerobic zones in the wetland matrices. The effects of such arrangement were analyzed by comparing pollutant removal efficiencies in the two systems. On average, 99, 96, 93, and 86 percentage removals were obtained for ammonia (NH 4 -N), TN, biochemical oxygen demand (BOD), and TP, respectively, during the experiments. Biochar and crushed mortar proved to be a highly effective combination as media in subsurface flow constructed wetlands for wastewater treatment.

Properties of high early-strength concretes (HESCs) containing Type V, Type III, and rapid hardening calcium sulfoaluminate (CSA) cements were investigated at curing ages of opening time, 24 h, and 28 days. Investigated properties included the fresh (workability, setting time, air content, unit weight, and released heat of hydration), mechanical (compressive and flexural strengths), transport (absorption, volume of permeable voids, water penetration, rapid chloride permeability, and accelerated corrosion resistance), dimensional stability (drying shrinkage), and durability (de-icing salt and abrasion resistance) properties. Test results revealed that the HESC containing Rapid-Set cement achieved the shortest opening time to attain the required minimum strength, followed by Type III and Type V cement HESCs. For the most part, Type V cement HESC produced the best transport and de-icing salt resistance, whereas Rapid-Set cement HESC displayed the best dimensional stability and wear resistance.

Snake bite is a neglected public health problem in the world and one of the major causes of mortality and morbidity in many areas, particularly in the rural tropics. It also poses substantial economic burdens on the snake bite victims due to treatment related expenditure and loss of productivity. An accurate estimate of the risk of snake bite is largely unknown for most countries in the developing world, especially South-East Asia. We undertook a national epidemiological survey to determine the annual incidence density of snake bite among the rural Bangladeshi population. Information on frequency of snake bite and individuals' length of stay in selected households over the preceding twelve months was rigorously collected from the respondents through an interviewer administered questionnaire. Point estimates and confidence intervals of the incidence density of snake bite, weighted and adjusted for the multi-stage cluster sampling design, were obtained. Out of 18,857 study participants, over one year a total of 98 snake bites, including one death were reported in rural Bangladesh. The estimated incidence density of snake bite is 623.4/100,000 person years (95% C I 513.4-789.2/100,000 person years). Biting occurs mostly when individuals are at work. The majority of the victims (71%) receive snake bites to their lower extremities. Eighty-six percent of the victims received some form of management within two hours of snake bite, although only three percent of the victims went directly to either a medical doctor or a hospital. Incidence density of snake bite in rural Bangladesh is substantially higher than previously estimated. This is likely due to better ascertainment of the incidence through a population based survey. Poor access to health services increases snake bite related morbidity and mortality; therefore, effective public health actions are warranted.

To determine serum zinc level and other relevant biological markers in normal, prediabetic and diabetic individuals and their association with Homeostasis Model Assessment (HOMA) parameters. This cross-sectional study was conducted between March and December 2009. Any patient aged ≥ 30 years attending the medicine outpatient department of a medical university hospital in Dhaka, Bangladesh and who had a blood glucose level ordered by a physician was eligible to participate. A total of 280 participants were analysed. On fasting blood sugar results, 51% were normal, 13% had prediabetes and 36% had diabetes. Mean serum zinc level was lowest in prediabetic compared to normal and diabetic participants (mean differences were approximately 65 ppb/L and 33 ppb/L, respectively). In multiple linear regression, serum zinc level was found to be significantly lower in prediabetes than in those with normoglycemia. Beta cell function was significantly lower in prediabetes than normal participants. Adjusted linear regression for HOMA parameters did not show a statistically significant association between serum zinc level, beta cell function (P = 0.07) and insulin resistance (P = 0.08). Low serum zinc accentuated the increase in insulin resistance seen with increasing BMI. Participants with prediabetes have lower zinc levels than controls and zinc is significantly associated with beta cell function and insulin resistance. Further longitudinal population based studies are warranted and controlled trials would be valuable for establishing whether zinc supplementation in prediabetes could be a useful strategy in preventing progression to Type 2 diabetes.