Durability aspects

Concrete may deteriorate if adequate precautions are not exercised to protect it from adverse effects that could result from exposure to natural or artificial conditions. Several physical, chemical, and electrochemical processes are known to induce cracking of concrete. Concrete can have durability problems as a consequence of its exposure to seawater, sulfates, chlorides, freeze-thaw action, carbon dioxide, etc., or when it is attacked by artificially induced processes such as exposure to acids and salts in chemical plants or to fire. In recent years, a new type of durability problem was encountered that involved use of steam cured concrete products. The distress was caused by the formation of delayed ettringite. If the raw materials in concrete are not carefully controlled, there may be an eventual failure of concrete elements, eg., the presence of excess alkali in concrete that promotes alkali-aggregate expansion reaction, harmful impurities in the aggregates, or the presence of excess amounts of dead-burnt MgO. Thermal techniques in combination with others have been employed with success to examine the raw materials as well as the failed concrete. The knowledge gained from such work has been applied to produce more durable concrete. 

The causes leading to the failure of concrete near the construction joints have been evaluated by The concrete sample exhibited peaks 

and X-ray microanalysis techniques were applied to identify the materials that formed around the rim of sandstone or silt stone aggregate in a thirty-year old concrete.An alkali-substituted okenite (C5 S9H9), a precursor phase characterized by a 1.22 nm XRD spacing, was identified. 

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Gobel, U., Hoehne, J., Lox, E.S. et al. (1999) Durability Aspects of NOx Storage Catalysts for Direct Injection Gasoline Vehicles, SAE Technical Paper 99FL-103. 

Tjeerdsma, B.F., Stevens, M. and Militz, H. (2000). Durability aspects of (hydro)thermal treated wood. International Research Group on Wood Preservation, Doc. No. IRG/WP 00A 0160. 

Figures 30.11-30.16 depict the aging aspects of LPCAT-treated TPOs, and Figures 30.17-30.19 depict the durability aspect of LPCAT treatments investigated with three kinds of commercially available TPOs. In figures, LPCAT-air is abbreviated as air plasma, and likewise argon plasma and methane plasma. The results shown in Figures 30.11-30.16 indicate that the wettability or the contact angle of water on a plasma-treated surface is not the major factor that accounts for...

A. Vrouwenvelder, P. Schiessl, Durability aspects of probabilistic ultimate limit state design . Heron, 1999, 44 (1), 19-30. 

Further work could be carried out in order to extend the durability of the antimicrobial property by using different cross-linking agents. The fabric can be functionally enhanced by applying other surface finishes, such as to improve the handle of the fabric. The durability aspect of the antimicrobial finish can be studied over larger number of washes than those conducted during this study. The fabric can also be functionally enhanced by applying other types of finishes. 

The main durability aspects of bonded joints may now be summarised... 

Tezuka, Y. et al. (1992) Durability aspects of cements with high limestone filler content, in Proceedings 9th ICCC, New Delhi. Vol. 5, pp. 53-59. 

Mehta, P.K., and Folliard, K.J. (1995) Rice husk ash—a unique supplementary cementing material durability aspects. ACI SP-154, pp. 531-541. 

Seehra, S.S., Gupta, S., and Kumar, S. (1993) Rapid hardening magnesium phosphate cement for quick repair of concrete pavements characterization and durability aspects. Cement and Concrete Research 23,254-266. 

Debe MK, Hendricks SM, Schmoeckel AK, Atanasoski RT, Vemstnnn GD, Haugen GM (2006) Durability aspects of nanostructured thin film catalysts for PEM fuel cells. ECS Trans... 

Superior durability aspects of the NSTF electrode in comparison to carbon-support-dispersed catalysts are related to (i) its non-electron-conducting support that eliminates carbon corrosion that can cause significant increases in gas transport resistance and (ii) its bulk-like-Pt surface that is more resistant to Pt dissolution [67, 75, 76]. However, NSTF faces higher sensitivity to contaminants due to its lower Pt surface area [77] and other operational challenges related to its unique structure [78-81], notably its electrode thickness which is l/30th of conventional electrode. Figure 13.8... 

Cellulose fibres have been commercially used in asbestos-free fibre cement for many years. Most of the current research still deals with durability aspects of cellulose fibres and other alternative fibres. Improved durability of natural fibre composites has been achieved with the employment of mineral admixtures, such as rice husk ash or metakaolin in order to reduce the alkalinity of the cement paste [Rodrigues et ah, 2006, 2010). 

FIGURE 11.10 Single fiber contact angles of Toray TGP-H materials (hydrophobized to 17 wt% fluorinated ethylene propylene, FEP) aged in accelerated fashion in different liquid-water environments. (With kind permission from Springer Science+Business Media Polymer Electrolyte Fuel Cell Durability, Durability aspects of gas-diffusion and microporous layers, 2009, pp. 159-195, Wood, D.L. and Borup R.L.)... 

The performance of concrete depends on the quality of the ingredients, their proportions, placement, and exposure conditions. For example, the quality of the raw materials used for the manufacture of clinker, the calcining conditions, the fineness and particle size of the cement, the relative proportions of the cement phases, and the amount of mixing water influence the physico-chemical behavior of the hardened cement paste in concrete. In addition, the cementtype, nature of fine and coarse aggregates, water, temperature of mixing, admixture, and the environment will determine the physical, chemical, and durability aspects of concrete. Thermal analysis techniques are widely applied to investigate the physico-chemical behaviors of cement compounds, cement, and concrete subjected to various conditions. 

A study of the hydration of cement and cement compounds in the presence of superplasticizers is useful for theoretical and practical considerations. Many t5 es of thermal techniques including DTA, DSC, TG, DTG, Conduction Calorimetry, and EGA have been used for such studies. They have yielded important results that could be correlated with physical and mechanical characteristics of cement systems. Investigations have included the measurementofheat of hydration, the mechanism of reactions, strength development, microstmcture, permeability, durability aspects, compatibility problems between cement and superplasticizers, the prediction of some properties, material characterization and selection, mathematical modeling of hydration, development of test methods, and cement-superplasticizer interactions. 

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