P N OJHA, BRIJESH SINGH, V V ARORA, PRAMOD NARAYAN, AMIT TRIVEDI & MANTU GUPTA
The detection of alkali-silica reaction swelling in the concrete from the staining method (colour test) was carried out based on the method proposed by Guthrie et al[20]. The study included the sequential application of solutions of each of the two water-soluble compounds. Concentrated solutions of sodium cobaltinitrite and rhodamine B in water were prepared. The concrete surface to be examined was treated by pre-rinsing with water and subsequently applying each solution to the surface. After 30-60 seconds the concrete was rinsed thoroughly with water. The treated surface showed yellow and pink regions where ASR gel is present: yellow regions indicated the presence of K-rich, Na-K-Ca-Si gels, while the pink regions indicated alkali-poor gels. The final rinse step was required since the yellow sodium cobaltinitrite solution coated the entire concrete surface, as did the pink rhodamine B solution, thereby obscuring the stained gel regions. The best results were obtained when the sample was treated first with the sodium cobaltinitrite solution; however, the application of the rhodamine B solution first gave adequate results. The slice of concrete core samples was rinsed with water and the rinsed surfaces were searched for regions of yellow staining and regions of pink staining whereby K-rich, i.e. Na-K-Ca-Si gels generated from ASR, were identified by yellow staining and alkali-poor Ca-Si, generated from ASR, were identified by pink staining.
Four concrete core samples were selected, keeping in view the total representation of upstream and downstream for the presence of ASR using the colour method. The treated samples were searched for regions of yellow staining (K-rich, i.e. Na-K-Ca-Si gels generated from ASR) or regions of pink staining (alkali poor, i.e. Ca-Si generated from ASR). The colour test results indicated that the concrete core samples were free from alkali-silica reaction (Figure 5). In a few instances, very minor reaction rims had developed on the margins of large size open-air voids. If the total area of the concrete is considered the area shows these reaction rims were negligible. However, detailed analysis of the colour test were carried out both in the optical microscope and scanning electron microscope.
Figure 5. Colour test on downstream and upstream gallery samples
14 DAM ENGINEERING
Vol XXXII Issue 1
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
