Carbonate concretions

Galvanised steel provides increased corrosion resistance in carbonated concrete. In concrete with more than 0.4% chloride ion with respect to the cement content, there is an increased risk of corrosion and at high chloride contents the rate of corrosion approaches that of plain carbon steel. In test conditions the rate of corrosion is greater in the presence of sodium chloride than calcium chloride. Fusion-bonded epoxy-coated steel performs well in chloride-contaminated concrete up to about 3.9% chloride ion in content. 

Mozley PS, Bums SJ (1993) Oxygen and carbon isotopic composition of marine carbonate concretions an overview. J Sed Pet 63 73-83... 

Raiswell R, Fisher QJ (2000) Mudrock-hosted carbonate concretions a review of growth mechanisms and their influence on chemical and isotopic composition. J Geol Soc 157 239-251 Roden EE, Lovley DR (1993) Dissimilatory Fe (111) reduction by the marine microorganism Desulfuromonas acetoxidans. App Environ Microbio 59 734-742... 

Sass E, Kolodny Y (1972) Stable isotopes, chemistry and petrology of carbonate concretions (Mishash formation, Israel). Chem Geol 10 261-286 Sauer PE, EgUnton Tl, Hayes JM, Schimmelmann A, Sessions AL (2001) Compound-specific D/H ratios of hpid biomarkers from sediments as a proxy for environmental and climatic conditions. Geochim Cosmochim Acta 65 213-222... 

Valley JW, EUer JM, Graham CM, Gibson EK, Romanek CS, Stolper EM (1997) Low temperature carbonate concretions in the martian meteorite ALH 84001 evidence from stable isotopes and mineralogy. Science 275 1633-1637... 

Coal ball carbonate concretion formed during peat formation, usually around... 

Fresh concrete is relatively strongly alkaline, caused by the high content of calcium hydroxide, which, however, gets bound as calcium alumosilicates rather quickly. However, depending on the type of cement, a certain amount of it is released as time goes by. The pH value of non-carbonated concrete is around 12.5. It later falls, however, due to the binding of carbon dioxide from the air. 

Berner, R.A., 1968. Calcium carbonate concretions formed by decomposition of organic matter. Science, 159 195—197. 

Analysis of samples taken from different parts of the carbonate concretions, and from the adjacent host sediment at site 93LD, showed that organic carbon content is higher within the concretions than in the surrounding sediments (Figure 7.17a). Little difference was found between... 

Allison, P.A. Pye, K. (1994) Early diagenetic mineralization and fossil preservation in modern carbonate concretions. Palaios 9, 561-75. 

Pye, K. (1988) An occurrence akaganeite (P-FeO-OH.Cl) in recent oxidized carbonate concretions, Norfolk, England, Mineralogical Magazine 52, 125-6. 

Matsumoto, R. Matsuda, H. (1987) Occurrence, chemistry and isotopic composition of carbonate concretions in the Miocene to Pliocene siliceous sediments of Aomori, northeastern Japan. J. Fac. Sci., Univ. Tokyo, 21, 351-377. 

Coleman, M. (1993) Microbial processes controls on the shape and composition of carbonate concretions. Mar. Geol., 113, 127-140. 

Colton, G.W. (1967) Orientation of carbonate concretions in the Upper Devonian of New York. US geol. Surv. Prof Pap., 575-B, B57-59. 

Fig. 8.8 Ring-shaped carbonate concretion from a cold seep. The unusual shape of the concretion is likely a result of pressure and sediment outgassing effects. Reproduced with permission. Mark Leet for MBARI 1997.

Compaction of mudstones is, as for sand, mostly a function of effective stress at low temperatures (<80°C) (Aplin et al. 1999, Bjprlykke 1997). Carbonate cementation sourced by biogenic carbonate may, however, occur at rather shallow depth so that carbonate concretions or layers can be rendered almost incompressible at shallow depth. The precipitation of quartz cement in mudstones follows much the same principles as in sandstones and is primarily controlled by the temperature. Dissolution of biogenic silica has a strong effect as a source of silica on quartz cementation at temperatures exceeding about 80 C. When modelling the compaction of mudstones the... 

Next, all that was left was a mangled, jerking body pumping gallons of blood onto the bare carbon-concrete floor. The craterous wounds were smoking, as if the bullets had been incendiaries. 

There was an ugly sound of bone shattering. Dead silence. The man flew backwards five yards through the air, hitting the sidewalk in a crumpled sprawl. He slid along the carbon concrete composite for another couple of yards before coming to rest, completely inert. Blood began to splatter from his mouth where serrated bone had punctured his cheek and lip. 

San Angeles spaceport was situated on the southern rim of the metropolis. A square ten kilometres to a side, a miniature city chiselled from machinery. Vast barren swathes of carbon concrete had been poured over the levelled earth and then divided up into roads, taxi aprons, and landing pads. Hundreds of line company hangars and cargo terminals hosted a business which accounted for a fifth of the entire planet s ground-toorbit traffic movements. 

Few results are available for carbonated concrete in tests on Portland cement pastes [7] a very diluted solution was found after carbonation, with only small amounts of the alkali ions Na and (Table 2.1). 

Analogously, correlations exist between the coefficient of water permeabihty k and that of capillary absorption S, but these lose their validity if the surface of the concrete is subjected to a hydrophobic treatment, which will reduce considerably capillary absorption but not permeation. For concrete obtained with Portland cement, correlations between the coefficient of water permeability (k) and conductivity (o = 1/p) measured for a given value of relative humidity are available. On the other hand, conductivity varies greatly in concrete made with blended cements or carbonated concrete, while there is no significant change in water permeability. 

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