Concrete alkali-silica reaction

Hobbs, D.W. (1988). Alkali Silica Reaction in Concrete, Thomas Telford Ltd., London. 

Rodrigues, F,A, Monteiro, P.J.M., and Sposito, G., The alkali-silica reaction. The surface charge density of silica and its effect on expansive pressure. Cement Concrete Res., 29, 527, 1999,... 

Fire-, blast-, and earthquake-resistant materials and systems Crosscutting innovations Constituent materials New materials Smart systems for design of fire-, blast-, and heat-resistant alternative reinforced structures Survivability reserach Concrete as part of multimaterials systems Noncorroding steel reinforcement Concrete with predictable performance Materials with reduced shrinkage and cracking Reduction of alkali-silica reactions in concrete... 

Alkali-silica reaction is an expansive reaction in concrete that can occur when a solution of sodium or potassium hydroxide reacts with a siliceous aggregate to form a gel of hydrated alkali silicate. 

H. M. Visser, R. B. Polder, Alkali-silica reaction in concrete penetration of alkalis (in Dutch), TNO Building and Construction Research report 2000-BT-MK-R0207, 2000. 

D. M. Thompson, Electrochemical induction of alkali-silica reaction in concrete . Materials and Structures, 1991, 24, 359-361. 

C. L. Page, S. W. Yu, "Potential effects of electrochemical desalination of concrete on alkali silica reaction . Magazine of Concrete Research, 1995, 47, 23-31. 

Sergi, G. and Page, C.L. (1992). The Effects of Cathodic Protection on Alkali-Silica Reaction in Reinforced Concrete, Contractor Research Report 310, Transport Research Laboratory, Crowthorne, Berkshire, UK. 

The deterioration of concrete can be the consequence of the presence of some aggregates components which, for example, as iron sulphide, decompose to give iron(lll) hydroxide and sulphuric acid [71]. This phenomenon will be presented later. Let us discuss now the studies of concrete deterioration mechanism caused by alkali silica reaction, the most important in practice. The two types of reactions can be distinguish ... 

Fig. 6.32 Relationship between the active alkalis content in cement and cement content in a concrete vs. the alkali-silica reaction susceptibility. (According to 71 )...

Linking of the preventing action of mineral additions, with the sodium and potassium concentration lowering in the liquid phase, is obvious. The progress of alkali silica reaction is strongly dependent on this concentration, as well as on the related pH of this solution. Low alkali content is a warrant of the lack of concrete expansion with reactive aggregate. 

Reduced concrete deterioration due to alkali-silica reaction in mixes in which Portland cement has been partially replaced by fly ash has been widely reported (Hobbs, 1986, 1989 Meland, 1986 Shayan et ai, 1996). Fly ash seems to act mainly as an alkali diluter, lowering the amount of available alkalis in the system. The capability to reduce the alkali-aggregate expansion may vary in different ashes, and depends on their own alkali content and fineness. 

In addition to an increase of strength, the presence of rice husk ash also improves the resistance of concrete to acid attack. The expansion due to alkali-silica reaction and sulfate attack is reduced considerably. Also, the frost resistance has been foimd to be significantly improved by adding rice husk ash to the concrete mix (Mehta and Folhard, 1995). 

Hobbs, D.W. (1986) Deleterious expansion of concrete due to alkali-silica reaction influence of PFA and slag. Magazine of Concrete Research 38 (137), 195-205. 

Nixon, P. J. et al. (1986) The effect of pfa with a high total alkali content on pore solution composition and alkali silica reaction. Magazine of Concrete Research 38,30-35. 

Swamy, R.N. (ed.) (1992) The Alkali-Silica Reaction in Concrete. Blackie Son, Glasgow. 

The deterioration seen in Fig. 22.1(a), (b) and (c) is due to alkali silica reaction. This expansive internal reaction results in deleterious expansion and consequent opening of fissures and cracks in concrete, compromising its durability. It is a relatively frequent anomaly observed in large concrete civil infrastructures. Similarly common are the anomalies shown in Fig. 22.1(d), (e), (f), (g) and (h), where biological degradation leads to a significant reduction of section, loosening of joints, or excess deformation. 

Beside the alkali-silica reaction described above, similar phenomena may occur in the case of reactive dolomites and limestones. The so-called alkali-carbonate reaction (ACR) is less frequent and not completely understood. When the effects of ACR are observed, two similar remedies are also necessary either to keep the content of alkalis in concrete as low as possible, or to decrease the percentage of deleterious aggregate in the concrete mix. 

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