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Silica fume mixed concrete in acidic environment
Materials Today: Proceedings xxx (xxxx) xxx
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Silica fume mixed concrete in acidic environment Deep Tripathi ⇑, Rakesh Kumar, P. K. Mehta, Amrendra Singh MNNIT Allahabad, Prayagraj 211004, India
a r t i c l e
i n f o
Article history: Received 18 November 2019 Received in revised form 8 January 2020 Accepted 15 January 2020 Available online xxxx Keywords: Silica fume Acidic environment Ordinary portland cement Durability Normal concrete
a b s t r a c t When concrete is exposed to aggressive environment, its durability may get affected. Earlier, people were more concerned about the strength of concrete without thinking about its durability. But at present the durability of concrete and concrete structures has become a major concern. In this experimental study, the effect of Nitric Acid on concrete made using Silica Fume (SF) was investigated. The optimum replacement level of Ordinary Portland Cement (OPC) with Silica Fume in respect of compressive strength was found i.e. 20%. After obtaining the optimum replacement level, cubes of size 100 mm were cast for both the Normal Concrete (NC) and Silica Fume Mixed Concrete (SFMC) for further studies. All the concrete samples were tested for the strength and durability under acidic environment (8% Nitric acid exposure for a maximum of 90 days). It was found that the compressive strength of all the concrete mixtures decreases in acidic environment for all the exposure periods. The weight loss in both the specimen (NC and SFMC) is more in Nitric acid and it increases with exposure period. It was concluded that Silica Fume Mixed Concrete was more durable than Normal Concrete in acidic environment. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the First International conference on Advanced Lightweight Materials and Structures.
1. Introduction Concrete is the second most consumed material on the earth after water. It is an artificial construction material which is widely used for different types of construction work. Cement is the most important ingredient in concrete, which is produced artificially and during cement production large amount of Carbon dioxide (CO2) is also produced. Due to its high CO2 emission and critical importance to society, it is desirable to reduce greenhouse gas emissions from cement industry. So there is a need to search alternative material which may be used in place of cement or may be used to partially replace cement, with a positive effect on the strength and durability of the concrete and thus reducing the CO2 emission. Researchers have identified some pozzolanic materials which may be used to partially replace cement and contribute to development of strength of the concrete and durability etc. Fly ash (FA), Ground granulated blast furnace slag (GGBS), Rice husk ash (RHA), Metakaolin (MK) and SF are some of the pozzolanic materials which can be used for partial replacement of cement in concrete production. Aggressive environment may be caused due to sulphate attack, sea-water, sewage, effluents from the indus⇑ Corresponding author. E-mail address: [email protected] (D. Tripathi).
tries, acid rain, and high mineral contained water and direct contact with acids. Corrosion of concrete is caused by the acids like Nitric acid, Sulphuric acid, Hydrochloric acids and other types of organic and inorganic acids. Now a days durability of concrete has a important concern for construction professionals. To improve the durability of concrete SF was used by many researchers as a mineral admixture and a positive result was found. Xiaofeng Cong [1] have reported that the replacement of OPC by Silica Fume improves the fresh and hardened properties of concrete. Concrete with incorporation of SF have improved compressive strength due to additional C-S-H gel formation. The optimum replacement level of OPC by Silica Fume was reported as 12% with respect to compressive strength [2]. It was reported that to enhance the abrasion and impact resistance of concrete, fibers and SF (i.e. 20%) was used remarkably [3]. EI-Hadj Kadri et al. [4] investigated the effect of SF on concrete compressive strength and rate of hydration for that OPC was partially replaced by SF (10 to 30% by mass). The optimum replacement percentage was found i.e. 15%. Kolapo O. et al. [5] carried out experiments to investigate the effect of Nitric Acid on the compressive Strength of Laterized Concrete and it was found that the compressive strength of the concrete reduces with acid concentration, curing period and laterite content. V. Pavlik et al. [6] carried
https://doi.org/10.1016/j.matpr.2020.01.311 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the First International conference on Advanced Lightweight Materials and Structures.
Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311
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D. Tripathi et al. / Materials Today: Proceedings xxx (xxxx) xxx
out experiments to study the corrosion of hardened cement paste by acetic and nitric acids and found better performance with SF. Güneyisi et al. [7] reported that the inclusion of mineral admixtures improves the permeability and the compressive strength in comparison to the NC. The compressive strength of concrete is found to increased with curing period with a considerable improvement after 56 days due to additional formation of C-S-H gel at later ages [8]. The micro and macro level properties of concrete are enhanced on inclusion of pozzolanic materials (MK) [9]. The use of Fly Ash and Silica fume in SCC as part replacement of OPC is found to reduce the surface water absorption and sorptivity. The reduction in sorptivity is noticeable beyond 20% replacement level [10]. Percentage change in compressive, Split tensile and Flexural strength for 15% replacement of cement with silica fume gives optimum results and workability was inversely proportional to the % of silica fume [11]. It was found that the increase in the percentage of the silica fume increases the strength reduces the workability and permeability to a high extent [12]. The combination of silica fume and fly ash can be used in the mixture concrete, especially concrete which was in contact with sulphuric acid [13]. 2. Materials and experimental methodology The properties of different materials used and experimental methodology adopted in the present study are included herein. 2.1. Materials The OPC of 43 grade (Brand-M P Birla) obtained from a single batch was used throughout this investigation. The physical properties of OPC confirmed the requirements of IS 8112–1989 [14] and are as follows: Normal consistency = 28%; Initial setting time = 60 min; Final setting time = 480 min; Compressive strength at 3, 7 and 28 day = 23.6, 33.3 and 47.8 N/mm2, respectively. The chemical composition of OPC as supplied by the company is presented in Table 1. The Silica Fume was procured from KGR AGRO Private Ltd. Ludhiyana, Punjab with the following properties: Colourblack/dark grey; Specific gravity = 2.25; Specific surface area = 1500000–1800000 cm2/gm. The chemical composition of Silica Fume as supplied by manufacturer is also included in Table 1. Natural river sand was used for making all concrete samples, conforming to zone II [IS-383-1987] [15]. The other properties of sand follows: Fineness modulus = 2.492; Specific gravity = 2.48; Bulk density = 1680 kg/m3. The coarse aggregates of size 10 and 20 mm conforming to IS: 383–1987 [15] were used (procured from Maa Sharda Traders, Teliyarganj, Prayagraj). The relevant properties are: Bulk density = 1590 kg/m3 and 1560 kg/m3 for 10 and 20 mm, respectively; Specific gravity = 2.67 and 2.8 for 10 and 20 mm, respectively. Fineness modulus = 6.23 and 7.29 for 10 and 20 mm, respectively; Water absorption 1.2 and 1.1% for 10 and 20 mm, respectively. Nitric Acid [Brand-RENKEM] used for creating the acidic environment was procured from The Scientific Tra-
Table 1 Chemical Compositions of Ordinary Portland Cement (OPC) and Silica Fume.
1. 2. 3. 4. 5. 6. 7. 8.
Chemical compositions (%)
OPC
Silica Fume
Silicon dioxide (SiO2) Aluminum oxide (Al2O3) Iron oxide (Fe2O3) Calcium oxide (CaO) Magnesium oxide (MgO) Sodium oxide (Na2O) Potassium oxide (K2O) Loss on ignition
19.45 4.64 3.23 52.55 2.15 0.22 0.76 2.76
89.80 1.40 1.80 0.2–0.7 0.3–0.8 0.4–1.3 — 3.0
Source: As per manufacturers’ data.
Table 2 Final Mix Proportions Obtained per m3 of Concrete. Sl. No.
Materials
Quantity (kg/m3)
1. 3. 4. 5. 6. 7.
Cement Coarse Aggregate Fine Aggregate Water Water/Cement Superplastisizer
321 1311 726 152 0.45 –
ders, Civil lines, Prayagraj. The Specific gravity and Normality of nitric acid were 1.41 and 72%, respectively. 2.2. Experimental methodology The procedures adopted for the mix design and various tests are presented herein. 2.2.1. Mix proportion The M25 grade Normal concrete was prepared using OPC, as per the procedures given in IS: 10262-2009 [16]. The final mix proportion was: Cement:Fine Aggregate:Coarse Aggregate::1:2.26: .08; Water/Cement ratio (w/c) = 0.45; Water content = 152 L/m3, presented in Table 2. To find the compressive strength of Normal Concrete, cubes of size 100 mm were cast after specified curing periods (7 and 28 days). 100 mm cubes were also cast for both the Normal Concrete and Silica Fume Mixed Concrete mixes for further study. These samples were submerged in Tap water as well as in HNO3 solution (8%) for 7, 28, 56 and 90 days. The compressive strength of concrete cubes were determined using compression testing machine (Capacity- 2000 kN) with loading rate of approximately 140 kg/cm2/min, as per the provisions contained in IS: 516–1959 [17]. 3. Results and discussion 100 mm size cubes were cast for Normal Concrete and tested for compressive strength after curing of 7 and 28 days. After, the satisfactory performance of Normal Concrete, the OPC was replaced in part with Silica Fume (5, 10, 15, 20 and 25%) to get the optimum replacement level with respect to compressive strength. The optimum replacement levels were determined at both 7 and 28 days. After obtaining the optimum replacement level, cubes of size 100 mm were cast for both the Normal Concrete and Silica Fume Mixed Concrete for further studies. After demoulding, the specimens were immersed separately in tap water and 8% HNO3 solution for 7, 28, 56 and 90 days. The results and discussions thereon are presented below. 3.1. Fresh concrete properties The variation of workability of Normal Concrete is presented in Fig. 1, with increasing percentage of Silica Fume. The slump was recorded at different percentages (0, 5, 10, 15, 20, and 25%) of SF content. The workability of concrete mixes is found to decrease with increase in Silica Fume content [12]. The slump of concrete mix was decreased by 33 mm (42%) when the replacement level was changed from 0 to 25%. 3.2. Hardened concrete properties 3.2.1. Silica Fume optimization In this study, the replacement level of OPC with Silica Fume was varied from 0 to 25%, at an interval of 5%. It is found that the compressive strength of Silica Fume Mixed Concrete increases with the
Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311
D. Tripathi et al. / Materials Today: Proceedings xxx (xxxx) xxx
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Silica Fume content upto 20%, and thereafter it decreases. Thus the optimum replacement level of OPC by Silica Fume is 20%. The maximum gain in compressive strength of Silica Fume Mixed Concrete is 11.85 and 8.22% with respect to Normal Concrete at 7 and 28 days, respectively. All the mechanical properties of concrete were improved with inclusion of silica fume [18]. This gain in strength is primarily due to the formation of additional C-S-H gel in Silica Fume Mixed Concrete. The compressive strength at 7 and 28 days with varying percentages of Silica Fume in concrete is illustrated in Table 3 and Fig. 2. Fig. 1. Variation of workability of with replacement level.
Table 3 Compressive Strength of Concrete at Different % of Silica Fume. Sl. No.
Silica Fume (%)
7-Days Compressive Strength (MPa)
28-Days Compressive Strength (MPa)
1 2 3 4 5
0 10 15 20 25
21.34 22.34 23.34 23.87 22.33
36.34 37.67 38.67 39.33 33.33
3.2.2. Compressive strength The compressive strength of different concrete specimen, cured for 7, 28, 56, 90 days was determined as per the provisions contained in IS: 516-1959 [10] and results are shown in Table 4 and Fig. 4. Test set up and compression failure of the specimen are shown in Fig. 3. It is observed that the concrete specimens cured in 8% Nitric Acid solution have lower compressive strengths than those cured in tap water. It is also found that the inclusion of Silica Fume in concrete enhanced the compressive strength in compar-
Fig. 4. Variation of compressive strength with age in water and Nitric acid (8%).
Fig. 2. Variation of compressive strength with replacement level for different days.
Table 4 Compressive strength (N/mm2) of all mixes in tap water and HNO3 Solution. Sl. No.
Period (Days)
Exposure Condition Tap Water
1. 2. 3. 4.
7 28 56 90
8% HNO3 Solution
NC
SFMC
NC
SFMC
23.60 34.00 35.30 36.30
27.77 35.33 36.66 37.77
20.00 29.00 30.30 30.70
24.00 30.66 32.00 33.00 Fig. 5. Variation of Weight loss with age in Water and Nitric acid (8%).
Fig. 3. Compression failure of the specimen.
Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311
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D. Tripathi et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 6. Visual Change in Specimen of concrete at 7 and 90 days with acid and water curing.
ison to the Normal Concrete at all the ages. The loss in compressive strength of Normal Concrete after 7, 28, 56 and 90 days exposure in Nitric acid is 15.25, 14.70, 14.16 and 15.43%, respectively, with respect to those cured in water, while for Silica Fume Mixed Concrete the respective changes are 13.57, 13.21, 12.71 and 12.62%. Similar trend was also reported by Rao et al. [19]. Compressive strength increases with inclusion of silica fume upto a optimum replacement level [20]. 3.2.3. Weight change The weights of both Normal Concrete and Silica Fume Mixed Concrete were measured after demoulding and after 7, 28, 56 and 90 days of immersion in water and 8% Nitric acid solution. The results are presented in Fig. 5. For Normal Concrete samples cured in water a weight loss of 0.11, 0.16, 0.16 and 0.27% is found at 7, 28, 56 and 90 days, respectively, while for Silica Fume Mixed Concrete the respective values are 0.1, 0.22, 0.3 and 0.4%. For Normal Concrete samples exposed to Nitric acid (8%), the weight loss is 0.6, 1.12, 1.35 and 1.4% at 7, 28, 56 and 90 days, respectively, while for Silica Fume Mixed Concrete the respective values are 0.61, 0.7, 0.85 and 1.2%. This is similar to the findings of Rao et al. [19].
At optimum replacement level, the gain in compressive strength at 28 days is about 8.22%. The compressive strength of water cured Silica Fume Mixed Concrete is higher than the Normal Concrete. The loss in compressive strength of Normal Concrete after 7, 28, 56 and 90 days of Nitric acid exposure is 15.25, 14.70, 14.16 and 15.43%, respectively, with respect to the strength in water, while for Silica Fume Mixed Concrete the respective changes are 13.57, 13.21, 12.71 and 12.62%. The weight loss in Normal Concrete samples in water is 0.11, 0.16, 0.16 and 0.27% at 7, 28, 56 and 90 days, respectively, while in case of Silica Fume Mixed Concrete the respective changes are 0.1, 0.22, 0.3 and 0.4%. The weight loss in NC samples in Nitric acid solution is 0.60, 1.12, 1.35 and 1.4% at 7, 28, 56 and 90 days, respectively, while for SFMC the respective values are 0.61, 0.7, 0.85 and 1.2%. There is a gradual change in colour from grey to dark orange as the exposure period in acid solutions was increased from 7 to 90 days which might be due to the corrosion of the surface of concrete samples. CRediT authorship contribution statement
3.2.4. Visual inspection Visual inspection of concrete specimens immersed in 8% nitric acid solution was carried out at 7, 28, 56, and 90 days and the photographs are shown in Fig. 6. It is evident that all type of concrete specimens cured in acidic solution get deteriorated to a varying degree. Further, a number of small holes were observed on the surface of specimen cured in Nitric acid. The specimen immersed in Nitric acid had mud like formation on cube surface. This may be the cause of the loss of strength. 4. Conclusion The following are concluded from the above experimental study; It was found the optimum replacement level of OPC by Silica Fume in concrete, on equal weight basis, is 20% with respect to compressive strength. Workability of concrete decreases with increase in replacement level and at optimum replacement level it is lower by about 33%.
Deep Tripathi: Writing - original draft, Investigation. Rakesh Kumar: Conceptualization, Methodology, Supervision. P.K. Mehta: Writing - review & editing, Supervision. Amrendra Singh: Visualization, Investigation. Declaration of competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement The authors acknowledge the Motilal Nehru National Institute of Technology Allahabad, Prayagraj for providing their support. References [1] Xiaofeng Cong, The University Of Kansas, Role of Silica Fume in compressive strength of cement paste, mortar and concrete, April 1990.
Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311
D. Tripathi et al. / Materials Today: Proceedings xxx (xxxx) xxx [2] Rachel J. Detwiler, P. Kumar Mehta, Chemical and physical effects of silica fume on the mechanical behavior of concrete, ACI Mater. J. 86 (6) (1989) 609–614. [3] , MRS Proc. 114 (1987), https://doi.org/10.1557/PROC-114-105. [4] EI-Hadj Kadri, Roger Duval, Salima Aggoun, and Said Kenai, Silica Fume Effect on Hydration Heat and Compressive Strength of High-Performance Concrete, ACI Materials Journal (Title no 106 M13). [5] Kolapo O. Olusola and Opeyemi Joshua, ‘‘Effect of Nitric Acid on the Compressive Strength of Laterized Concrete”. Civil and Environmental Research, ISSN 2222-1719 (Paper) ISSN 2222-2863 (Online) Vol 2, No. 10, 2012. [6] V. Pavlik, Corrosion of hardened cement paste by acetic and nitric acids, Cem. Concr. Res. 26 (3) (1996) 475–490. [7] Erhan Güneyisi, Mehmet Gesog˘lu, Emad Booya, Kasım Mermerdasß, Strength and permeability properties of self-compacting concrete with cold bonded fly ash lightweight aggregate, Constr. Build. Mater. 74 (2015) 17–24. [8] B. Mahalingam, K. Nagamani, L.S. Kannan, K. Mohammed Haneefa, A. Bahurudeen, Assessment of hardened characteristics of raw fly ash blended self-compacting concrete, Perspect. Sci. 8 (2016) 709–711. [9] O.R. Kavitha, V.M. Shanthi, G.P. Arulraj, P. Sivakumar, Fresh, micro-and macrolevel studies of metakaolin blended self-compacting concrete, Appl. Clay Sci. 114 (2015) 370–374. [10] Hau Yan Leung, Jong Kim, Abid Nadeem, Jayaprakash Jaganathan, M.P. Anwar, Sorptivity of self-compacting concrete containing fly ash and silica fume, Constr. Build. Mater. 113 (2016) 369–375.
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[11] Patil Hiteshkumar Santosh, A.K. Dwivedi, A.M. Chatterjee, Optimize properties of concrete with silica fume, J. Mater. Sci. 2 (2017) 1–4. [12] T. Karthik Prabhu, K. Subramanian, P. Jagadesh, V. Nagarajan, Durability properties of fly ash and silica fume blended concrete for marine environment, Indian J. Geo Marine Sci. 48 (11) (2019) 1803–1812. [13] D. Sandy, L. Febriani, S.R. Tonapa, Combination of silica fume and fly ash in concrete with sulfuric acid-curing, Int. J. Eng. Sci. Appl. 6 (1) (2019). [14] IS, 8112, ‘‘Specification for 43 grade ordinary Portland cement”. Bureau of Indian standards 1989 New Delhi, India. [15] IS, 383, ‘‘Specification for coarse and fine aggregate from natural sources for concrete” 1987 of Indian Standards New Delhi: Bureau. [16] IS, 10262, Concrete mix proportioning- Guidelines. Bureau of Indian Standards 2009 New Delhi, India. [17] IS: 516, Methods of Tests for Strength of Concrete, 1959. [18] Piotr Smarzewskia, Influence of silica fume on mechanical and fracture properties of high performance concrete, Elsevier-Proc. Struct. Integrity 17 (2019) 5–12. [19] S. Venkateswara Rao, M.V. Seshagiri Rao, D. Ramaseshu, Strength and durability studies of conventional concrete and self compacting, Concrete 10 (2011) 271–280. [20] A.M. Falmata, A. Sulaiman, R.N. Mohamed, A.U. Shettima, Mechanical properties of self-compacting high-performance concrete with fly ash and silica fume, Springer Nature Appl. Sci. 2 (2019) 33.
Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Silica fume mixed concrete in acidic environment Deep Tripathi ⇑, Rakesh Kumar, P. K. Mehta, Amrendra Singh MNNIT Allahabad, Prayagraj 211004, India
a r t i c l e
i n f o
Article history: Received 18 November 2019 Received in revised form 8 January 2020 Accepted 15 January 2020 Available online xxxx Keywords: Silica fume Acidic environment Ordinary portland cement Durability Normal concrete
a b s t r a c t When concrete is exposed to aggressive environment, its durability may get affected. Earlier, people were more concerned about the strength of concrete without thinking about its durability. But at present the durability of concrete and concrete structures has become a major concern. In this experimental study, the effect of Nitric Acid on concrete made using Silica Fume (SF) was investigated. The optimum replacement level of Ordinary Portland Cement (OPC) with Silica Fume in respect of compressive strength was found i.e. 20%. After obtaining the optimum replacement level, cubes of size 100 mm were cast for both the Normal Concrete (NC) and Silica Fume Mixed Concrete (SFMC) for further studies. All the concrete samples were tested for the strength and durability under acidic environment (8% Nitric acid exposure for a maximum of 90 days). It was found that the compressive strength of all the concrete mixtures decreases in acidic environment for all the exposure periods. The weight loss in both the specimen (NC and SFMC) is more in Nitric acid and it increases with exposure period. It was concluded that Silica Fume Mixed Concrete was more durable than Normal Concrete in acidic environment. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the First International conference on Advanced Lightweight Materials and Structures.
1. Introduction Concrete is the second most consumed material on the earth after water. It is an artificial construction material which is widely used for different types of construction work. Cement is the most important ingredient in concrete, which is produced artificially and during cement production large amount of Carbon dioxide (CO2) is also produced. Due to its high CO2 emission and critical importance to society, it is desirable to reduce greenhouse gas emissions from cement industry. So there is a need to search alternative material which may be used in place of cement or may be used to partially replace cement, with a positive effect on the strength and durability of the concrete and thus reducing the CO2 emission. Researchers have identified some pozzolanic materials which may be used to partially replace cement and contribute to development of strength of the concrete and durability etc. Fly ash (FA), Ground granulated blast furnace slag (GGBS), Rice husk ash (RHA), Metakaolin (MK) and SF are some of the pozzolanic materials which can be used for partial replacement of cement in concrete production. Aggressive environment may be caused due to sulphate attack, sea-water, sewage, effluents from the indus⇑ Corresponding author. E-mail address: [email protected] (D. Tripathi).
tries, acid rain, and high mineral contained water and direct contact with acids. Corrosion of concrete is caused by the acids like Nitric acid, Sulphuric acid, Hydrochloric acids and other types of organic and inorganic acids. Now a days durability of concrete has a important concern for construction professionals. To improve the durability of concrete SF was used by many researchers as a mineral admixture and a positive result was found. Xiaofeng Cong [1] have reported that the replacement of OPC by Silica Fume improves the fresh and hardened properties of concrete. Concrete with incorporation of SF have improved compressive strength due to additional C-S-H gel formation. The optimum replacement level of OPC by Silica Fume was reported as 12% with respect to compressive strength [2]. It was reported that to enhance the abrasion and impact resistance of concrete, fibers and SF (i.e. 20%) was used remarkably [3]. EI-Hadj Kadri et al. [4] investigated the effect of SF on concrete compressive strength and rate of hydration for that OPC was partially replaced by SF (10 to 30% by mass). The optimum replacement percentage was found i.e. 15%. Kolapo O. et al. [5] carried out experiments to investigate the effect of Nitric Acid on the compressive Strength of Laterized Concrete and it was found that the compressive strength of the concrete reduces with acid concentration, curing period and laterite content. V. Pavlik et al. [6] carried
https://doi.org/10.1016/j.matpr.2020.01.311 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the First International conference on Advanced Lightweight Materials and Structures.
Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311
2
D. Tripathi et al. / Materials Today: Proceedings xxx (xxxx) xxx
out experiments to study the corrosion of hardened cement paste by acetic and nitric acids and found better performance with SF. Güneyisi et al. [7] reported that the inclusion of mineral admixtures improves the permeability and the compressive strength in comparison to the NC. The compressive strength of concrete is found to increased with curing period with a considerable improvement after 56 days due to additional formation of C-S-H gel at later ages [8]. The micro and macro level properties of concrete are enhanced on inclusion of pozzolanic materials (MK) [9]. The use of Fly Ash and Silica fume in SCC as part replacement of OPC is found to reduce the surface water absorption and sorptivity. The reduction in sorptivity is noticeable beyond 20% replacement level [10]. Percentage change in compressive, Split tensile and Flexural strength for 15% replacement of cement with silica fume gives optimum results and workability was inversely proportional to the % of silica fume [11]. It was found that the increase in the percentage of the silica fume increases the strength reduces the workability and permeability to a high extent [12]. The combination of silica fume and fly ash can be used in the mixture concrete, especially concrete which was in contact with sulphuric acid [13]. 2. Materials and experimental methodology The properties of different materials used and experimental methodology adopted in the present study are included herein. 2.1. Materials The OPC of 43 grade (Brand-M P Birla) obtained from a single batch was used throughout this investigation. The physical properties of OPC confirmed the requirements of IS 8112–1989 [14] and are as follows: Normal consistency = 28%; Initial setting time = 60 min; Final setting time = 480 min; Compressive strength at 3, 7 and 28 day = 23.6, 33.3 and 47.8 N/mm2, respectively. The chemical composition of OPC as supplied by the company is presented in Table 1. The Silica Fume was procured from KGR AGRO Private Ltd. Ludhiyana, Punjab with the following properties: Colourblack/dark grey; Specific gravity = 2.25; Specific surface area = 1500000–1800000 cm2/gm. The chemical composition of Silica Fume as supplied by manufacturer is also included in Table 1. Natural river sand was used for making all concrete samples, conforming to zone II [IS-383-1987] [15]. The other properties of sand follows: Fineness modulus = 2.492; Specific gravity = 2.48; Bulk density = 1680 kg/m3. The coarse aggregates of size 10 and 20 mm conforming to IS: 383–1987 [15] were used (procured from Maa Sharda Traders, Teliyarganj, Prayagraj). The relevant properties are: Bulk density = 1590 kg/m3 and 1560 kg/m3 for 10 and 20 mm, respectively; Specific gravity = 2.67 and 2.8 for 10 and 20 mm, respectively. Fineness modulus = 6.23 and 7.29 for 10 and 20 mm, respectively; Water absorption 1.2 and 1.1% for 10 and 20 mm, respectively. Nitric Acid [Brand-RENKEM] used for creating the acidic environment was procured from The Scientific Tra-
Table 1 Chemical Compositions of Ordinary Portland Cement (OPC) and Silica Fume.
1. 2. 3. 4. 5. 6. 7. 8.
Chemical compositions (%)
OPC
Silica Fume
Silicon dioxide (SiO2) Aluminum oxide (Al2O3) Iron oxide (Fe2O3) Calcium oxide (CaO) Magnesium oxide (MgO) Sodium oxide (Na2O) Potassium oxide (K2O) Loss on ignition
19.45 4.64 3.23 52.55 2.15 0.22 0.76 2.76
89.80 1.40 1.80 0.2–0.7 0.3–0.8 0.4–1.3 — 3.0
Source: As per manufacturers’ data.
Table 2 Final Mix Proportions Obtained per m3 of Concrete. Sl. No.
Materials
Quantity (kg/m3)
1. 3. 4. 5. 6. 7.
Cement Coarse Aggregate Fine Aggregate Water Water/Cement Superplastisizer
321 1311 726 152 0.45 –
ders, Civil lines, Prayagraj. The Specific gravity and Normality of nitric acid were 1.41 and 72%, respectively. 2.2. Experimental methodology The procedures adopted for the mix design and various tests are presented herein. 2.2.1. Mix proportion The M25 grade Normal concrete was prepared using OPC, as per the procedures given in IS: 10262-2009 [16]. The final mix proportion was: Cement:Fine Aggregate:Coarse Aggregate::1:2.26: .08; Water/Cement ratio (w/c) = 0.45; Water content = 152 L/m3, presented in Table 2. To find the compressive strength of Normal Concrete, cubes of size 100 mm were cast after specified curing periods (7 and 28 days). 100 mm cubes were also cast for both the Normal Concrete and Silica Fume Mixed Concrete mixes for further study. These samples were submerged in Tap water as well as in HNO3 solution (8%) for 7, 28, 56 and 90 days. The compressive strength of concrete cubes were determined using compression testing machine (Capacity- 2000 kN) with loading rate of approximately 140 kg/cm2/min, as per the provisions contained in IS: 516–1959 [17]. 3. Results and discussion 100 mm size cubes were cast for Normal Concrete and tested for compressive strength after curing of 7 and 28 days. After, the satisfactory performance of Normal Concrete, the OPC was replaced in part with Silica Fume (5, 10, 15, 20 and 25%) to get the optimum replacement level with respect to compressive strength. The optimum replacement levels were determined at both 7 and 28 days. After obtaining the optimum replacement level, cubes of size 100 mm were cast for both the Normal Concrete and Silica Fume Mixed Concrete for further studies. After demoulding, the specimens were immersed separately in tap water and 8% HNO3 solution for 7, 28, 56 and 90 days. The results and discussions thereon are presented below. 3.1. Fresh concrete properties The variation of workability of Normal Concrete is presented in Fig. 1, with increasing percentage of Silica Fume. The slump was recorded at different percentages (0, 5, 10, 15, 20, and 25%) of SF content. The workability of concrete mixes is found to decrease with increase in Silica Fume content [12]. The slump of concrete mix was decreased by 33 mm (42%) when the replacement level was changed from 0 to 25%. 3.2. Hardened concrete properties 3.2.1. Silica Fume optimization In this study, the replacement level of OPC with Silica Fume was varied from 0 to 25%, at an interval of 5%. It is found that the compressive strength of Silica Fume Mixed Concrete increases with the
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Silica Fume content upto 20%, and thereafter it decreases. Thus the optimum replacement level of OPC by Silica Fume is 20%. The maximum gain in compressive strength of Silica Fume Mixed Concrete is 11.85 and 8.22% with respect to Normal Concrete at 7 and 28 days, respectively. All the mechanical properties of concrete were improved with inclusion of silica fume [18]. This gain in strength is primarily due to the formation of additional C-S-H gel in Silica Fume Mixed Concrete. The compressive strength at 7 and 28 days with varying percentages of Silica Fume in concrete is illustrated in Table 3 and Fig. 2. Fig. 1. Variation of workability of with replacement level.
Table 3 Compressive Strength of Concrete at Different % of Silica Fume. Sl. No.
Silica Fume (%)
7-Days Compressive Strength (MPa)
28-Days Compressive Strength (MPa)
1 2 3 4 5
0 10 15 20 25
21.34 22.34 23.34 23.87 22.33
36.34 37.67 38.67 39.33 33.33
3.2.2. Compressive strength The compressive strength of different concrete specimen, cured for 7, 28, 56, 90 days was determined as per the provisions contained in IS: 516-1959 [10] and results are shown in Table 4 and Fig. 4. Test set up and compression failure of the specimen are shown in Fig. 3. It is observed that the concrete specimens cured in 8% Nitric Acid solution have lower compressive strengths than those cured in tap water. It is also found that the inclusion of Silica Fume in concrete enhanced the compressive strength in compar-
Fig. 4. Variation of compressive strength with age in water and Nitric acid (8%).
Fig. 2. Variation of compressive strength with replacement level for different days.
Table 4 Compressive strength (N/mm2) of all mixes in tap water and HNO3 Solution. Sl. No.
Period (Days)
Exposure Condition Tap Water
1. 2. 3. 4.
7 28 56 90
8% HNO3 Solution
NC
SFMC
NC
SFMC
23.60 34.00 35.30 36.30
27.77 35.33 36.66 37.77
20.00 29.00 30.30 30.70
24.00 30.66 32.00 33.00 Fig. 5. Variation of Weight loss with age in Water and Nitric acid (8%).
Fig. 3. Compression failure of the specimen.
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Fig. 6. Visual Change in Specimen of concrete at 7 and 90 days with acid and water curing.
ison to the Normal Concrete at all the ages. The loss in compressive strength of Normal Concrete after 7, 28, 56 and 90 days exposure in Nitric acid is 15.25, 14.70, 14.16 and 15.43%, respectively, with respect to those cured in water, while for Silica Fume Mixed Concrete the respective changes are 13.57, 13.21, 12.71 and 12.62%. Similar trend was also reported by Rao et al. [19]. Compressive strength increases with inclusion of silica fume upto a optimum replacement level [20]. 3.2.3. Weight change The weights of both Normal Concrete and Silica Fume Mixed Concrete were measured after demoulding and after 7, 28, 56 and 90 days of immersion in water and 8% Nitric acid solution. The results are presented in Fig. 5. For Normal Concrete samples cured in water a weight loss of 0.11, 0.16, 0.16 and 0.27% is found at 7, 28, 56 and 90 days, respectively, while for Silica Fume Mixed Concrete the respective values are 0.1, 0.22, 0.3 and 0.4%. For Normal Concrete samples exposed to Nitric acid (8%), the weight loss is 0.6, 1.12, 1.35 and 1.4% at 7, 28, 56 and 90 days, respectively, while for Silica Fume Mixed Concrete the respective values are 0.61, 0.7, 0.85 and 1.2%. This is similar to the findings of Rao et al. [19].
At optimum replacement level, the gain in compressive strength at 28 days is about 8.22%. The compressive strength of water cured Silica Fume Mixed Concrete is higher than the Normal Concrete. The loss in compressive strength of Normal Concrete after 7, 28, 56 and 90 days of Nitric acid exposure is 15.25, 14.70, 14.16 and 15.43%, respectively, with respect to the strength in water, while for Silica Fume Mixed Concrete the respective changes are 13.57, 13.21, 12.71 and 12.62%. The weight loss in Normal Concrete samples in water is 0.11, 0.16, 0.16 and 0.27% at 7, 28, 56 and 90 days, respectively, while in case of Silica Fume Mixed Concrete the respective changes are 0.1, 0.22, 0.3 and 0.4%. The weight loss in NC samples in Nitric acid solution is 0.60, 1.12, 1.35 and 1.4% at 7, 28, 56 and 90 days, respectively, while for SFMC the respective values are 0.61, 0.7, 0.85 and 1.2%. There is a gradual change in colour from grey to dark orange as the exposure period in acid solutions was increased from 7 to 90 days which might be due to the corrosion of the surface of concrete samples. CRediT authorship contribution statement
3.2.4. Visual inspection Visual inspection of concrete specimens immersed in 8% nitric acid solution was carried out at 7, 28, 56, and 90 days and the photographs are shown in Fig. 6. It is evident that all type of concrete specimens cured in acidic solution get deteriorated to a varying degree. Further, a number of small holes were observed on the surface of specimen cured in Nitric acid. The specimen immersed in Nitric acid had mud like formation on cube surface. This may be the cause of the loss of strength. 4. Conclusion The following are concluded from the above experimental study; It was found the optimum replacement level of OPC by Silica Fume in concrete, on equal weight basis, is 20% with respect to compressive strength. Workability of concrete decreases with increase in replacement level and at optimum replacement level it is lower by about 33%.
Deep Tripathi: Writing - original draft, Investigation. Rakesh Kumar: Conceptualization, Methodology, Supervision. P.K. Mehta: Writing - review & editing, Supervision. Amrendra Singh: Visualization, Investigation. Declaration of competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement The authors acknowledge the Motilal Nehru National Institute of Technology Allahabad, Prayagraj for providing their support. References [1] Xiaofeng Cong, The University Of Kansas, Role of Silica Fume in compressive strength of cement paste, mortar and concrete, April 1990.
Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311
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Please cite this article as: D. Tripathi, R. Kumar, P. K. Mehta et al., Silica fume mixed concrete in acidic environment, Materials Today: Proceedings, https:// doi.org/10.1016/j.matpr.2020.01.311