Concrete specimens of different sizes and shapes were made with various reactive aggregates and stored under conditions favorable to the development of alkali-silica reactivity (ASR), with their expansion measured with time along the three directions. They have been cast vertically (cylinders and prisms) or horizontally (prisms and larger blocks), using a vibrating table, a vibrating needle, or rodding. The expansion due to ASR was always greater in the direction perpendicular to the casting plane. The higher the number of flat and elongated particles in the reactive aggregate, the higher the coefficient of anisotropy, defined as the ratio between the expansions perpendicular and parallel to the casting plane. This coefficient was constant through the course of the expansion. It was generally higher for the cylinders than for the prisms, and still less for larger blocks. Consolidation by rodding induced anisotropy coefficients distinctly smaller than consolidation using a vibrating table, while a vibrating needle induced intermediate values; however, all methods gave constant volumetric expansion at least up to an important expansion level. For prisms cast horizontally and measured axially in accordance with the concrete test CSA A23.2-14A or ASTM C 1293, consolidation using rodding induced long-term (axial) expansions greater by 71% compared with consolidation using a vibrating table. In order to reduce the experimental variability of the test, only one method of consolidation should be allowed. When evaluating field concrete affected by ASR, it appears important to consider the orientation with respect to the casting plane of the core samples subjected to mechanical or residual expansion tests.
The expansion to date of the concrete from a structure affected by alkali–silica reaction (ASR) is a crucial parameter in the evaluation of the structural integrity of the structure. Three methods have been used to evaluate this expansion: (i) the "stiffness damage test" (SDT), (ii) the "damage rating index" (DRI), and (iii) surface cracking. Concrete cylinders were made using several types of coarse and fine reactive aggregates and subjected to the Canadian Standards Association (CSA) concrete prism test CSA A23.2-14A (or American Society for Testing and Materials (ASTM) test method C1293), i.e., at 38 °C and >95% relative humidity (RH). At various expansion levels, the specimens were subjected to SDT and DRI tests. Very good relationships were obtained between the expansion due to ASR and the SDT. The correlation between the ASR expansion and the DRI was not as good but still of interest. Width measurements of surface cracks were also performed on a number of blocks made with different reactive aggregates and exposed in the laboratory at 38 °C and >95% RH. The expansion estimated from these measurements was much lower than that measured on the blocks.Key words: aggregates, alkali–silica reaction, concrete expansion, damage rating index, petrography, stiffness damage test, surface cracking.
Prototypes of columns were cast with different percentages of rebars and stirrups and various alkali-silica reactive aggregates. The deformations of concrete were measured along the three directions using surface metal studs and internal vibrating wire gauges. The deformations of steel were measured using fiber-optic gauges and short rods welded to rebars and stirrups. Along each direction, the deformations of concrete and steel were quite similar up to 0.08% longitudinal expansion, beyond which the rebars were generally showing less (longitudinal) expansion than concrete. The rebars reduced the longitudinal expansion; the higher the percentage of longitudinal steel, the higher this reduction. On the other hand, the expansion increased in the other two transverse directions to give comparable volumetric expansions for all specimens of the same mixture, with or without relatively spaced-out stirrups. The transverse expansion perpendicular to the casting plane was always higher than the transverse expansion parallel to this plane. The rebars were tensioned up to 280 MPa. The concrete was prestressed parallel to the rebars, up to 3.3 MPa. For their part, the stirrups were highly stressed in tension and flexure, and usually reached plastification. Résumé: Des prototypes de colonnes ont été fabriqués avec différents granulats susceptibles de réactivité alcalis-silice et divers pourcentages de barres longitudinales et d'étriers. Les déformations du béton ont été mesurées selon les trois directions à l'aide de plots métalliques de surface et de jauges à corde vibrante, et les déformations des aciers ont été mesurées à l'aide de tiges métalliques et de jauges à fibre optique soudées aux barres et aux étriers. Pour chacune des trois directions, l'expansion du béton et de l'acier furent comparables jusqu'à environ 0,08 % d'expansion longitudinale, les barres présentant généralement ensuite une expansion (longitudinale) inférieure à celle du béton. Ces barres ont réduit l'expansion longitudinale, et ce, d'autant plus que le pourcentage d'acier longitudinal était élevé. En contrepartie, les déformations ont augmenté dans les deux autres directions transversales de telle sorte que tous les spécimens d'un même mélange ont subi des expansions volumétriques assez comparables, et ce, en présence ou non d'étriers relativement espacés. L'expansion transversale perpendiculaire au plan de coulée a toujours été plus élevée que l'expansion transversale parallèle à ce plan. Les armatures longitudinales ont subi des tensions atteingnant 280 MPa pendant que le béton subissait, parallèlement aux armatures, des compressions atteignant 3,3 MPa. Pour leur part, les étriers ont subi d'importantes contraintes en tension et en flexion, atteignant généralement la plastification.
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