Characteristics of concrete produced with burnt clay as coarse aggregate

Aggregate is the principal ingredient for concrete, and studies have predicted that excessive use of it would lead to insufficient quantity for future large constructions. This study investigate the use of burnt clay as alternative aggregates for concrete production. First clay was exposed to elevated temperature in the range of 1200 – 6000 C. Thereafter 3 sets of burnt clay aggregate were prepared then they were subjected to tests to determine the specific gravity, moisture content, water absorption, bulk density, impact value and crushing value test. These aggregates were subjected to compressive strength, impact value and crushing value tests. Result showed that the specific gravity of these aggregates exposed to between 600-1200oC, were between 2.11- 2.43. Whereas the bulk densities were between 973.7-1012 kg/m3 for burnt clay aggregates exposed to between 600 -1200oC. The moisture content of the burnt clay aggregates were in the range 1.749-1.833; Water absorption for the three sets of burnt clay aggregates was between 8.303-8.378 for clay aggregates heated to a range of 600-1200oC. The compressive strength for the three types of 100mm concrete cubes produced using the burnt clay aggregates after 28 days of curing, were between 10-11.2 N/mm2.While the compressive strength after 56days of curing, were between 13.20- 17.40N/mm2 for concrete produced with burnt clay aggregates subjected to elevated temperatures of 600-1200oC. The impact and crushing values of the crushed burnt clay aggregates ranges from 14- 33%. It was concluded that there is no significant difference between the quality of concrete produced with burnt clay aggregate and the conventional concrete (control sample). Hence, study recommended the use of burnt clay aggregate and durability properties of concrete be investigated.Keywords: Coarse Aggregates, Properties, Concrete, Burnt Clay, Water Absorptio

Comparative Study of the Compressive Strength of Cement Laterite Brick Produced with Rice Husk Ash and Wood Ash as Partial Replacement Of Cement

The paper presents an outcome of experimental comparative study on the compressive strength of laterite brick made with rice husk ash and wood ash as partial replacement of cement. First, Rice Husk Ash (RHA) and Wood Ash (WA) were prepared and subjected to the following tests: specific gravity, density and bulk density. This was followed by the production of three types of bricks viz cement laterite-bricks(control), cement-laterite bricks produced using RHA as partial replacement of cement and another brick made with WA as partial replacement of cement. Replacement levels range from 0 - 30% at 10% intervals. The samples were cured by water sprinkling, before testing them for compressive strength at 7, 14, 21 and 28 curing days. Result of the tests showed that the specific gravity of RHA and WA are 2.20 and 2.13 respectively. The Absorption capacity of all the samples is in the range of 4.5 – 9.1%which is within the allowable value of 25% set by the Nigerian Industrial Standard. Compressive strength for 10 % replacements range from 0.75N/mm2 for 7days to 3.7N/mm2 for 28 days for RHA, as against 2.6 N/mm2 for 7days to 5.3N/mm2 for 28days curing for WA. This shows that bricks produced using WA are relatively higher in strength than those made with RHA. Though it is concluded that RHA and WA, can be used as partial replacements of cement in the production of laterite brick. Also, laterite brick produced with 20% and 30% partial replacements of cement with RHA and WA, respectively,, have, satisfied the minimum requirement as contained in BS 6073, and are recommendable.Keywords: Cement, compressive strength, rice husk ash, laterite brick, partial replacement levels, wood ash

The role of magnetic resonance cholangiopancreatography (MRCP) in obstructive jaundice

Objective: To evaluate the diagnostic value of MRCP in studying the sites and cause of obstructive jaundice in comparison with other imaging modalities at the Department of Radiology, Aga Khan University Hospital, from January 1999 to May 2001.Methods: Forty nine consecutive patients included 19 men and 30 women, suspected of obstructive jaundice. Patients underwent ultrasound (n = 49), CT (n = 11), ERCP (n = 25) and biliary surgery (n = 17). Final diagnosis was established by surgical exploration, endoscopic sphincterectomy, cytology and clinical follow up.Results: Of the 49 patients 17 had choledocholithiasis. Twenty five patients had malignant strictures, out of which 11 had non-specific malignant strictures, 7 had pancreatic carcinoma, 3 had Klatskin tumors, 3 had periampullary carcinoma and 1 had gallbladder carcinoma. Six patients had benign strictures and 1 patient had choledochal cyst. Overall, MRCP was sensitive (88%) and specific (96.8%) in detecting choledocholithiasis. MRCP sensitivity and specificity in detecting benign main bile duct stricture was equal to 83.3% and 97.6% respectively, and 92% and 100% for malignant stricture.CONCLUSION: Our prospective study confirms that MRCP, a noninvasive and well tolerated imaging technique is of value in the diagnosis of obstructive jaundice

Health Effects of Radiation Exposure to Human Sensitive Organs Across Some Selected

The interaction of ionizing radiation with human body, either from external sources (i.e. outside the body) or from internal contamination of the body by radioactive substances, leads to biological effects which may later show up as clinical symptoms. The nature and severity of these symptoms and the time at which they appear depend on the amount of radiation absorbed and the rate at which it is received. This study aimed at assessing the Health Effects of Radiation Exposure to Human Sensitive Organs across Some Selected Mining Sites of Plateau State Nigeria. Finding of this study have revealed that the mean Dorgan values for the lungs, ovaries, bone marrow, testes, kidney, liver and whole body for different mining points of Plateau State are 0.29, 0.26, 0.31, 0.36, 0.28, 0.21 and 0.30 mSv/y respectively. From the findings presented, it can be concluded that the background radiation in Plateau State is not an issue of health concern in regards to sensitive organs and may not course immediate health effect except when accumulated over long period of time which may cause cancer to the indoor members on approximately seventy years of exposure

No evidence of an 11.16 MeV 2+ state in 12C

An experiment using the 11B(3He,d)12C reaction was performed at iThemba LABS at an incident energy of 44 MeV and analyzed with a high energy-resolution magnetic spectrometer, to re-investigate states in 12C published in 1971. The original investigation reported the existence of an 11.16 MeV state in 12C that displays a 2+ nature. In the present experiment data were acquired at laboratory angles of 25-, 30- and 35- degrees, to be as close to the c.m. angles of the original measurements where the clearest signature of such a state was observed. These new low background measurements revealed no evidence of the previously reported state at 11.16 MeV in 12C

Detection of mycobacteria in raw cow milk sold in Bwari Area Council, Abuja FCT

Bovine tuberculosis (bTB) is an important zoonotic disease worldwide and hence it is of great public health significance. It is present in most developing countries where surveillance and control activities are often inadequate or unavailable. This study was designed to detect mycobacteria in raw milk of cows using ZN-stain, PCR, and cultural techniques to determine the prevalence of bTB in Bwari area council of FCT Abuja. Out of the 145 raw milk sampled, 6.89% tested positive by ZN-stain and culture while 1.3% were positive by PCR. The herd prevalence per satellite town based on ZN-stain technique was 8.89%, 10.0%, 3.33% and 5.00% for Bwari, Dei-Dei, Kubuwa and Ushafa respectively. While by cultural method, the prevalence was 2.22%, 10.00%, and 5.00% for Bwari, Dei-Dei, Kubuwa and Ushafa respectively. PCR revealed the prevalence of Mycobacterium species for Bwari and Dei-Dei as 2.22% and 3.33% respectively. Detection of Mycobacteria in raw (unpasteurized) pose a serious public health risk to raw milk consumers in Bwari area council.Keywords: Raw milk, bTB, ZN stain, PCR, Cultur

Evidence for Nodal superconductivity in Sr2_{2}ScFePO3_{3}

Point contact Andreev reflection spectra have been taken as a function of temperature and magnetic field on the polycrystalline form of the newly discovered iron-based superconductor Sr2ScFePO3. A zero bias conductance peak which disappears at the superconducting transition temperature, dominates all of the spectra. Data taken in high magnetic fields show that this feature survives until 7T at 2K and a flattening of the feature is observed in some contacts. Here we inspect whether these observations can be interpreted within a d-wave, or nodal order parameter framework which would be consistent with the recent theoretical model where the height of the P in the Fe-P-Fe plane is key to the symmetry of the superconductivity. However, in polycrystalline samples care must be taken when examining Andreev spectra to eliminate or take into account artefacts associated with the possible effects of Josephson junctions and random alignment of grains.Comment: Published versio