No abstract

Self-compacting concrete (SCC) generally requires cement and chemical admixtures of high material cost. The use of mineral admixtures (such as fly ash, metakaolin etc.) as partial replacement of cement in SCC can bring down the cost. The use of industrial wastes such as fly ash, metakaolin etc in the binder of concrete reduces the storage, disposal and environmental problems. In the present study, the effects of partially replacing cement of self-compacting concrete by mineral admixtures (fly-ash and metakaolin) on (i) fresh state flow properties, (ii) 28 days compressive, splitting tensile and flexural strengths at room/standard temperature and (iii) 28 days compressive strengths at elevated temperatures. In the present study the mix design for M40 grade SCC was first carried out in accordance with EFNARC guidelines. The cement in SCC was partially replaced with (a) 5 % of flyash and 3% of metakaolin, (b) 5 % of flyash and 6% of metakaolin, (c) 5 % of flyash and 9% of metakaolin, (d) 15 % of flyash and 3% of metakaolin, (e) 15 % of flyash and 6% of metakaolin, (f) 15 % of flyash and 9% of metakaolin, (g) 25 % of flyash and 3% of metakaolin, (h) 25 % of flyash and 6% of metakaolin and (i) (a) 25 % of flyash and 9% of metakaolin. Tests such as slump flow, V-funnel, L-box, U-box, J-ring were carried out on fresh concrete. Conventional compressive strength test was carried out on hardened self-compacting concrete (SCC). The initial tangent modulus of SCC was also determined during the test. Compressive strength was also determined at 28 days after heating the specimens to 100 o C, 200 o C and 300 o C in a furnace for 6 hours. The splitting tensile test was conducted on SCC cylinders at 28 days at standard temperature to determine the splitting tensile strength. The flexural test was conducted on beam specimens at standard temperature in universal testing machine to determine the flexural strength as well as the loaddeflection characteristics. It is observed that the replacement of cement by a combination of fly ash and metakolin in the range of 8 to 34 percent has no adverse effect on the workability properties of SCC. As the percentage of cement replacement increases, the 7 days and 28 days compressive strength, flexural strength, initial tangent modulus of SCC cubes increase up to 24 % and later decrease. The maximum splitting tensile strength of SCC cylinders at 28 days occurs for a percentage of cement replacement = 14 in the considered range. The minimum splitting tensile strength at 28 days occurs for a percentage of cement replacement = 28 in the considered range. The loss in compressive strength of SCC at elevated temperature is taken as a measure of durability against elevated temperature and it increases as the elevated temperature increases. The maximum loss of compressive strength at elevated temperature occurs at percentage of cement replacement = 8 in the considered range.

Self-compacting concrete (SCC) is a concrete that has a high flowing ability with no segregation. It is considered to be one of the revolutionary developments in concrete technology in recent times. It reduces noise at sites, precast factory and neighborhood. Self-compacting concrete and glass fibers are combined to create glass fiber reinforced self-compacting concrete (GFRSCC). The present work deals with the workability and strength studies on glass fiber reinforced selfcompacting concrete of grade M40 with fly ash and silica fume. The mix proportions for self-compacting concrete were arrived at by performing mix design and then fine-tuning using EFNARC guidelines. The cement was replaced by 20% fly ash and 12% silica fume by weight. This was kept constant for all the mixes. The glass fiber percentage was varied from 0 to 0.8 % by weight of concrete. Addition of glass fibers increased the 7 days compressive strength compared to the reference mix (mix with no glass fibers) but the increase was not significant. There was moderate (15% to 21 %) increase in 28 days compressive strength when fibers were added relative to the reference mix. Addition of fibers to self-compacting concrete increased the 7 days splitting tensile strength by 13% to 69%. Addition of fibers to self-compacting concrete increased the 28 days splitting tensile strength by 5% to 50%. Addition of fibers to selfcompacting concrete increased the 28 days flexural strength by 30% to 48%. The 7 and 28 days compressive strengths of selfcompacting concrete with glass fibers were maximum at a fiber percentage = 0.3. The 7 and 28 days splitting tensile strengths of self-compacting concrete with glass fibers were maximum at a fiber percentage = 0.4. The 28 days flexural strength of selfcompacting concrete with glass fibers was maximum at a percentage = 0.7.

No abstract

No abstract