Performance Characteristics of Self-Compacting Concrete Containing Iron Slag

Abstract

In India, an approximate production of iron and steel slag is 10 million tons annually. Large quantity of slag is used in cement industry but except that it is dumped on land adjoining sites of iron and steel mills, and becoming environmental hazard to the community. The constructive use of iron slag is the better way to mitigate the issue associated with disposal. The utilization of such material in self compacting concrete helps in reducing the disposal problem. Hence in this study, perceptions for using iron slag as replacement of fine aggregates are explored. The current study has been carried out to evaluate the feasibility of the use iron slag as fine aggregates in self-compacting concrete (SCC). Control SCC was made with fly ash (10% addition as supplementary cementing material) designed to achieve 28-day compressive strength of 30 – 40MPa. In control SCC, fine aggregates were replaced with iron slag at 10, 25 and 40% contents. A total four SCC mixtures SCC-CM, SCC-IS10, SCC-IS25 and SCC-IS40 were developed; SCC-CM (control mix) was developed without replacement of iron slag with fine aggregates, SCC-IS10 with 10% replacement of iron slag, SCC-IS25 with 25% replacement of iron slag and SCC-IS40 with 40% replacement of iron slag. Slump flow, L-box, U-box and V-funnel tests were performed to evaluate passing and filling abilities of SCC in fresh state. Tests for compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, water absorption, sorptivity, sulphate resistance, rapid chloride permeability, abrasion resistance and ultra-sonic pulse velocity were conducted up to the age of 365 days. Test results indicate that fresh properties such as slump flow, L-box, U-box and V-funnel of SCC mixes with or without replacement of iron slag were within the specified range as specified by EFNARC. Compressive strength of SCC mixtures increased with the inclusion of iron slag as well as with age. At the age of 7 days, SCC mixes with iron slag achieved higher compressive strength. 28-day compressive strength of SCC with iron slag varied between 37.1 N/mm2 to 45.1 N/mm2 at 10 to 40% replacement of iron slag as compared to 35.7 N/mm2 of control SCC. Splitting tensile strength increased with the increase in iron slag and with age as well. 28-day splitting tensile strength of SCC with iron slag was varied between 2.8 N/mm2 to 3.4 N/mm2 at from 10 to 40% replacement of vi iron slag. However, 28-days splitting tensile strength of control SCC were 2.7 N/mm2. Flexural strength of SCC increases with the inclusion of iron slag as compared with control SCC. Modulus of elasticity of SCC mix with iron slag mixes was in the range of 28.19 – 28.87 GPa at 28-days age against 27.9 GPa of control SCC. Water absorption and sorptivity decreased with the increase in iron slag content. However, in case of compressive strength loss in sulphate resistance, control SCC performed slightly better than SCC with iron slag content. Chloride permeability of SCC mixes reduced with iron slag. Further, chloride permeability decreased with age, and decreased at faster rate than that of control SCC mixture. Abrasion resistance of SCC with iron slag content was higher than control SCC. The effect of iron slag on pulse velocity value of SCC was significant. All value of pulse velocity was graded as excellent concrete quality. Micro-structural analysis reveals that SCC matrix gets denser and pore structure improves with the inclusion of iron slag content. X-ray diffraction spectrum reveals that the phase composition of powder SCC paste was not changing qualitatively, the change of phases was observed on the use of iron slag dose in SCC. In the statically analysis the correlation of strength properties, strength and durability properties shows that there is good relation between regression curve and data points and good coefficient of determination. Strength and durability results indicate that iron slag could be suitably used in making SCC.