Portland resistivity

In concrete, triethanolamine accelerates set time and increases early set strength (41—43). These ate often formulated as admixtures (44), for later addition to the concrete mixtures. Compared to calcium chloride, another common set accelerator, triethanolamine is less corrosive to steel-reinforcing materials, and gives a concrete that is more resistant to creep under stress (45). Triethanolamine can also neutralize any acid in the concrete and forms a salt with chlorides. Improvement of mechanical properties, whiteness, and more even distribution of iron impurities in the mixture of portland cements, can be effected by addition of 2% triethanolamine (46). Triethanolamine bottoms and alkanolamine soaps can also be used in these type appUcations. Waterproofing or sealing concrete can be accompUshed by using formulations containing triethanolamine (47,48). 

Concrete, Mortar, and Plaster. Citric acid and citrate salts are used as admixtures in concrete, mortar, and plaster formulations to retard setting times and reduce the amount of water requited to make a workable mixture (172—180). The citrate ion slows the hydration of Portland cement and acts as a dispersant, reducing the viscosity of the system (181). At levels below 0.1%, citrates accelerate the setting rate while at 0.2—0.4% the set rate is retarded. High early strength and improved frost resistance have been reported when adding citrate to concrete, mortar, and plaster. 

Cement and Concrete Concrete is an aggregate of inert reinforcing particles in an amorphous matrix of hardened cement paste. Concrete made of portland cement has limited resistance to acids and bases and will fail mechanically following absorption of crystalforming solutions such as brines and various organics. Concretes made of corrosion-resistant cements (such as calcium aluminate) can be selected for specific chemical exposures. 

The specific electrical resistance of concrete can be measured by the method described in Section 3.5. Its value depends on the water/cement value, the type of cement (blast furnace, portland cement), the cement content, additives (flue ash), additional materials (polymers), the moisture content, salt content (chloride), the temperature and the age of the concrete. Comparisons are only meaningful for the... 

Cements are used mainly for jointing brickworks, drainage gullies, pipes and storage tanks. Portland cement has very poor resistance to acids but good resistance to alkaline liquors. 

High-alumina cement is very quick setting, but its acid resistance is only slightly better than Portland cement, and it is rapidly attacked by alkalis. Super-sulfated cement is used for liquors high in sulfates. It is resistant to acidic conditions down to a pH of 3.5 and has alkali resistance similar to Portland cement [50]. 

In addition to the four compounds discussed above, the final Portland cement may contain gypsum, alkali sulfates, magnesia, free lime and other components. These do not significantly affect the properties of the set cement, but they can influence rates of hydration, resistance to chemical attack and slurry properties. 

Portland cement is susceptible to corrosion by CO2 and H2S. The chemical attack by CO2 is called carbonation. A microsample technique has been developed to study the CO2 corrosion in cements, because the corrosion is difficult to monitor with common test procedures [264]. This technique is also advantageous as an accelerated testing method. A polymer-modified cement has been tested in field studies [694]. The addition of silica also improves chemical resistance [146], in particular brine corrosion. 

Y. R. Leonov, M. E. Lamosov, S. A. Ryabokon, V. A. Mosin, F. G. Mamulov, A. R. Akhmadzhanov, and G. D. Varlamov. Plugging material for oil and gas wells—contains Portland cement and additive in form of product of reaction between furfurol and ammonia and has improved corrosion resistance. Patent SU 1818463-A, 1993. 

Direct shear test of soils under consolidated drained conditions pH of soil for use in corrosion testing Field measurement of soil resistivity using the Wenner four-electrode method Optimum S03 in portland cement... 

Corrosion-resistant cements have been developed for use in wells used to inject supercritical carbon dioxide for enhanced oil recovery (32). These are based on Portland cement and high levels (as much as 40% wt.) of additives such as fly ash. Epoxy resins have been successfully used as cements in corrosive environments... 

Fig. 7.1 Effect of entrained air on the resistance to freezing and thawing in laboratory tests (courtesy Portland Cement Association, Skokie, Illinois, USA [2]).

The strength data in Table 7.19 show that using very low amounts of ASTM Type 1 (normal Portland) cement compressive strength of the order of 8 and 35 MPa can be obtained at 1 and 28 days respectively. The concrete s resistance... 

SURYVANSHI, A. K., SCANTLEBURY, J. D. LYON, S. B. 1995. The binding of chloride ions by sulphate resistant portland cement. Cement and Concrete Research, 25, 581-592. 

Chrysotile is a noncombustible fibrous solid that has been widely used as a fireproof thermal insulator, for brake linings, in construction materials, and for filters under the name of asbestos. It decomposes with loss of water at 600-800 °C, eventually forming forsterite and silica at 810-820 °C. Because it is more resistant to attack by alkalis than are the amphibole asbestoses, chrysotile has been used in chloralkali cell membranes and in admixture with Portland cement for making sewer pipes (Chapter 11). 

Sulfur concretes are used in many specialty areas where Portland cement concretes are not completely satisfactory. Because SC can be formulated to resist deterioration and failure from mineral acid and salt solutions, it is used for construction of tanks, electrolytic cells, thickeners, industrial flooring, pipe, and others. In addition, SC is under investigation for many other prospective uses (58,59) (see CEMENT). 

Sulphur concretes resistant to moisture show good durability in the presence of various acid and salt solutions which are normally aggressive to Portland cement concretes (4, J>, 6). Care must nevertheless be exercised with the aggregates to be used. 

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