Composite materials contribution in strengthening concrete structures affected by alkali–aggregate reaction
by L. Curtil, E. Ferrier, S. Ronel-Idrissi, P. Hamelin
International Journal of Materials and Product Technology (IJMPT), Vol. 19, No. 1/2, 2003

Abstract: Alkali–aggregate reactivity (AAR) is a chemical reaction that occurs in some concrete structures. AAR is a reaction between pore solution alkali hydroxide and some siliceous aggregates. The damage to the concrete induced by AAR is very important with expansion and cracking. The main purpose of this investigation is to evaluate the effectiveness of the use of external bonded FRP on the durability of civil engineering structures damaged by alkali reaction (mechanical behaviour determination, comparison with Larive's model and confinement efficiency). In a first approach, we are working on a mortar specimen containing alkali–silica aggregates. The deterioration of mortar is determined from the expansion measures and from the measure of mechanical properties. To reduce the necessary duration of development of alkali–aggregate reaction, two accelerated mortar bar tests are evaluated: immersion in saturated NaCl solution at 50°C; immersion at 38°C (P 18 585 AFNOR standard). Two types of sample are made: no reactive mortar and reactive mortar with opal sand and siliceous limestone (Tournai sand). Composite skins (FRP reinforcement) are placed at the beginning or after some expansions. The linear expansion of mortar bars exposed to several temperatures (and pressure) in various storage conditions for different testing periods (5 h, 28 days or 3 months) is measured. The mechanical behaviour is also determined on confined and unconfined specimens. Our experiment results are compared with Larive's swelling model. The parameters bring out the contribution of composite materials and show a difference between specimens with FRP reinforced at the beginning (after the cure period but before the maturing phase) or after some expansion (during the ageing phase). We have a good agreement between our experimental results and Toutanji's model predicting mechanical behaviour of wrapped concrete, adding to this analytical model a chemical damage coefficient to characterise AAR level of each specimen.

Online publication date: Sun, 28-Sep-2003

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