Effect of Iron Ore Tailing on the Properties of Concrete

Experiments were conducted to determine the suitability of iron ore tailing (IOT) as fine aggregate replacement of sand (RS) for concrete used for rigid pavement. The use of iron ore tailing (IOT) from Itakpe mines near Okene in north-central Kogi state of Nigeria will ensure economy in concrete production as well as a better way of disposing the tailing. Mix design was carried out for concrete of grade 35 using standard practice for selecting proportions for normal weight, and mass concrete [ACI 211.1-91, 1997]. The constituent materials were batched by weight. The mix with only sand as fine aggregate served as the control mix, while sand was replaced in the other mixes by 20%, 40%, 60%, 80% and 100% iron ore tailing (IOT). Consistency and Strength test were conducted on both concrete specimens. It was observed that concrete workability reduced with increase in the percentage of iron ore tailing in the mix. Twenty-eight (28) days compressive strength and indirect tensile strength values of 43.67N/mm2 and 2.69N/mm2 respectively, were obtained for concrete when 20% iron ore tailing (IOT) was used, Values comparable to 28days compressive strength and indirect tensile strength values of 45.02N/mm2 and 2.64N/mm2 respectively, obtained using only sand as fine aggregate. Keywords: concrete; sand (RS); iron ore tailing (IOT); compressive and tensile strength

Fermentation of deproteinized cheese whey powder solutions to ethanol by engineered Saccharomyces cerevisiae : effect of supplementation with corn steep liquor and repeated-batch operation with biomass recycling by flocculation

The lactose in cheese whey is an interesting substrate for the production of bulk commodities such as bio-ethanol, due to the large amounts of whey surplus generated globally. In this work, we studied the performance of a recombinant Saccharomyces cerevisiae strain expressing the lactose permease and intracellular ß-galactosidase from Kluyveromyces lactis in fermentations of deproteinized concentrated cheese whey powder solutions. Supplementation with 10 g/l of corn steep liquor significantly enhanced whey fermentation, resulting in the production of 7.4% (v/v) ethanol from 150 g/l initial lactose in shake-flask fermentations, with a corresponding productivity of 1.2 g/l/h. The flocculation capacity of the yeast strain enabled stable operation of a repeated-batch process in a 5.5-l air-lift bioreactor, with simple biomass recycling by sedimentation of the yeast flocs. During five consecutive batches, the average ethanol productivity was 0.65 g/l/h and ethanol accumulated up to 8% (v/v) with lactose-toethanol conversion yields over 80% of theoretical. Yeast viability (>97%) and plasmid retention (>84%) remained high throughout the operation, demonstrating the stability and robustness of the strain. In addition, the easy and inexpensive recycle of the yeast biomass for repeated utilization makes this process economically attractive for industrial implementation.Fundação para a Ciência e a Tecnologia (FCT)LACTOGAL-Produtos Alimentares S.A.Companhia Portuguesa de Amidos, S.A

Successful and unsuccessful approaches to imaging carcinoids: Comparison of a radiolabelled tryptophan hydroxylase inhibitor with a tracer of biogenic amine uptake and storage, and a somatostatin analogue

A mouse mastocytoma model was used to determine the biodistribution and tumour uptake of four radiopharmaceuticals developed to target the serotonin synthetic pathway in carcinoid tumours. Three of the compounds were competitive inhibitors of the rate-limiting enzyme of serotonin synthesis, tryptophan hydroxylase. Radiolabelled iodo- dl -phenylalanine (iodine-131 PIPA) was found to have the highest uptake and tumourto-liver ratio. Four patients with known carcinoid tumours were then injected with 0.5 mCi 131 I-PIPA and imaged at 1, 4, 24 and 48 h post-injection. The radiopharmaceutical, however, failed to localize in the known tumour sites. This result was in contrast to the authors' experience of 131 I- and 123 I-MIBG imaging of carcinoid tumours. Seven patients with known metastatic carcinoid tumours, two patients with symptoms of recurrence following tumour resection, one patient with completely resected disease, and two patients with a flushing syndrome of uncertain aetiology were studied with 131 I-MIBG. Three of the seven patients with known metastatic disease had positive 131 I-MIBG scans. Both patients with clinical evidence of recurrent disease had negative scans, as did the patient who was considered to have had complete resection of her primary tumour. The two patients with idiopathic flushing syndrome also had negative scans. Among seven patients imaged with 123 I-MIBG there were four true-negative scans and one falsenegative, the latter in a patient with biochemical and CT evidence of recurrence. In a seventh patient with distant metastases there was variable uptake in some of the lesions. Four patients were studied with indium-111 penetetreodide. Two patients with metastatic carcinoid disease had positive scans, although hepatic metastases were not seen in one. Another two with idiopathic flushing syndrome had normal studies. The literature suggests that up 50% of carcinoid tumour cases are detected with 131 I-MIBG, compared to a sensitivity of 87% reported with somatostatin receptor imaging using 111 In-pentetreotide. The experience with 123 I-MIBG is much less extensive. The mechanisms of carcinoid tumour localization for each of the three classes of radiotracers are discussed and contrasted to their varying sensitivities. The relative success of 131 I-MIBG and 111 In-pentetreotide relative to 131 I-PIPA may be related to the fact that 131 I-MIBG is actively taken up and stored by the enterochromaffin cells of the tumours and 111 In-pentetreotide binds to cell surface receptors, whereas 131 I-PIPA binds to tryptophan hydroxylase, which may be present in quantities too small to permit tumours to be imaged.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46840/1/259_2005_Article_BF01731835.pd

An Investigation Into the Use of Groundnut as Fine Aggregate Replacement

The suitability of groundnut shell as a constituent material in concrete was investigated by re- placing proportions by volume of ne aggregate (river sand) with groundnut shells. Physical properties of cement, groundnut shells and aggregates were determined. Concrete cubes measur- ing 150x150x150mm were cast. Groundnut shells were used to replace ne aggregate at 0, 5, 15, 25, 50 and 75% replacement levels. The e ects of the groundnut shells on the workability of fresh concrete were determined by the slump and compacting factor value tests. Compressive strengths and density values of the concrete cubes were evaluated at 28 days at di erent percentage replacement levels obtaining a range of values of 34.37, 40.59, 21.33, 17.78, 12.44, 7.56N/mm2 and 2402.96, 2533.33, 2349.62, 2215.30, 2121.48, and 1854.81Kg/m3 respectively. Increase in percentage of groundnut shells in the cubes led to a corresponding reduction in densities of the cubes and compressive strength values. At a replacement value of 25% and above, of ne aggregate with groundnut shells; lightweight concrete was produced which could be used where low stress is required. Hence groundnut shells can be used for the production of lightweight concrete.Keywords: groundnut shell, lightweight, aggregates, concrete, compressive strengt

Evaluation of the Relationship between Bacteria Concentration and the Strength and Durability of Self-compacting Concrete Incorporating Sporosarcina pasteurii

This research was carried out to evaluate the relationship between the incorporation of calcite precipitation bacteria, sporosarcina pasteurii using calcium lactate as nutrient source and the properties of calcined clay and limestone powder blended self-compacting concrete. Ten mixes were designed and designated S0 to S9 with S0 the control (without bacteria and nutrient) and S1 to S9 at varying bacteria and calcium lactate concentrations and the effect of the bacteria cell density and calcium lactate concentration on the compressive strength, sorptivity and tensile strength with age evaluated using experimental program and statistical packages (ANOVA and post hoc tests). The result of both the experimental program and statistical evaluation shows that the incorporation of sporosarcina pasteurii and calcium lactate as nutrient had a positive impact on the properties of the ternary blended self-compacting concrete

Probabilistic Assessment of a Typical Reinforced Concrete Girder Under Critical Loading

Reinforced concrete bridges are continuously subjected to increased traffic load and exposed to harsh environments causing bridge members to deteriorate, thus, affecting their durability, safety and performance. This work aims at a probabilistic assessment of a reinforced concrete bridge girder under critical loading considering the flexural and shear failure modes of the bridge. A limit state function for the failure modes was generated and, the stochastic variables and statistical parameters were determined. Additionally, the safety indices for each failure mode were determined using First Order Reliability Method (FORM) procedure. Mathematical models were developed and the uncertainties in structural resistance, applied loading as well as structural components were included using the probabilistic method. A computer program in FORTRAN language was developed and deployed for the reliability analysis of the bridge girder to ascertain the level of safety using First-Order Reliability Method. The results revealed that the safety index for shear and flexural failure mode decreases as the span is increased. For concrete strength of 30 N/mm2 and a depth of 1000 mm, the safety index for shear and flexural failure reduced from 4.5 to 2.0 and 10.7 to 3.37 respectively as the span increases from 10 m to 19 m. This indicates that the shear and flexural failure modes are sensitive to increase in span. In order to obtain a minimum safety target of 3.8, it is recommended that the depth of the beam should not be less than 1200 mm while the span should not exceed 16 m, and concrete grade should not be less than 35 N/mm3. &nbsp