Disposal of Sea Bottom Sediments by Use as Raw Material for Concrete Elements

The possibility of using sea bottom sediments as a substitute for fine sand aggregate was investigated for the fabrication of concrete solids and marine reefs. The proportions of raw materials in the concrete mixture were optimized, and the materials were evaluated with by testing their slump, air content, mass change, total shrinkage and compressive strength. In the short term, i.e. a curing age of 3 to 28 days, the compressive strengths of the concrete materials made with the sediments were better than those of the normal concrete blocks. Furthermore, after 187 days of curing, the compressive strengths were 44, 31 and 12 MPa respectively for the concrete products with a water-cement ratio (w/c) by weight of 0.47, 0.69 and 1.15 using the sediments. When the concrete materials were field-tested in the sea for approximately one year, the blocks were not damaged by the sea environment because the compressive strengths were 48, 33 and 14 MPa with w/c = 0.47, 0.69 and 1.15, respectively. Since the concrete blocks constructed with the optimal mix of raw materials had enough solid strength to be used in the sea, it may be unnecessary to add steel reinforcement to this concrete for the specific purpose of constructing marine reefs

Determination of trace lead impurities in pure copper slurry samples by electrothermal atomic absorption spectrometry with molybdenum tube atomizer

A method for direct atomization of slurry sample by electrothermal atomic absorption spectrometry (SS-ETAAS) has been developed for the determination of trace lead impurities in commercially available pure copper using laboratory-made molybdenum tube atomizer. Suitable charring temperature was set and matrix element interference was checked. Lead standard solution in the glycerol-water medium as calibration medium and ultrasonic agitation method of the suspension of the sample powder were used. Typical results of this direct slurry method and wet digestion were close and precision varies over the range RSD 3.9 to 9.0 %. The recovery of Pb added was 98-102 %. Accuracy for certified copper sample agreed within 3 % range. Limits of detection were 34 fg Pb (3S/N), and characteristic mass 170 fg Pb. The method offers rapid calibration, simplified and fast analysis of lead in pure copper at lower cost