Selecting appropriate and suitable of materials plays an important role in concrete mix design to meet the general requirements of European guidelines for self-compacting concrete and to ensure a balance between deformability and stability. The type of selected materials and the ratios of concrete ingredients can be affected by the fresh and hardened properties of the concrete. In the contract agreement of the Mumbai Metro underground project, the technical specifications clearly state the values of limits set for achieving the durability parameters for the life of 120 years of the structure. According to the requirement of the site conditions Self-compacting concrete was designed with available material, special material like Ultra GGBS- Alccofine 1203 and crystalline waterproofing admixture. Self-compacting concrete is superior concrete than the traditional concrete with high workability, no segregation, no bleeding, and it is also suitable for use in structures with long-distance pumping in the instant case i.e., more than 120-meter length in Underground NATM tunnels, cross-passages, and the concrete structure of the underground metro station box. The paper presents a comparison between concrete mix designs and their achieved test parameters suitable for the contract specification of Mumbai metro underground project
The Mumbai Metro underground project is designed for 120 years of life of concrete structures. In the agreement the technical specifications clearly state the values of limits set for achieving the durability tests parameters like RCPT, Water permeability, moisture moment, drying shrinkage etc. Appropriate and suitable selection of supplementary cementitious materials such like GGBS, Ultrafine GGBS-Alccofine, Crystalline growth admixture etc., is required for improving durability, decreasing permeability, surface finish ability, and improving the overall hardened properties of concrete. Rheological properties of Self-compacting concrete are advanced than traditional normal slump concrete and the hardened properties of concrete are the same as traditional normal slump concrete . Self-compacting concrete is suitable for a fast rate of concrete placement, with faster construction times and ease of flow around dense reinforcement without vibration or a little bit of surface tamping to get a better surface finish. It ensures good homogeneity, pumping ability, best surface finish, consistent concrete strength, and durability of the concrete structure. “The rheology of concrete describes the flowability, mobility, and stability of fresh concrete. The hardened concrete properties like compressive strength, flexural strength, split tensile, etc., are specifically struck by the composition of concrete ingredients. In the Mumbai region, river sand is not available and therefore construction industries are totally depending on crushed stone sand. According to site requirements, only Self-compacting concrete was suitable due to long-distance pipe pumping and congested reinforcement in the structure. Hence Self-compacting concrete was developed by conducting several numbers of concrete mix trials and found that appropriate selection of materials is required for optimizing concrete mix design with low cementitious content and for achieving standards requirements for flowability by slump flow, and sieve segregation resistance tests as per specification mentioned in European standard . Chemical admixtures i.e., high-performance superplasticizers required for optimized the cementitious content and minimize the W/C ratio for production of Self-compacting concrete .Addition of special material like, Ultrafine GGBS (easily available in Indian market at manufacturer) and Crystalline growth waterproofing admixture helps for making economical and durable concrete with less cementitious contents.
II. CONCRETE INGREDIENTS
OPC 53 Grade cement of M/s Ultratech is used. Physical & Chemical tests results values are as given in Table 1 & 2 .
Ground granulated blast furnace slag (GGBS) of M/s JSW obtained from Pen, Raigad, Maharashtra, India. The physical and chemical properties of GGBS are given in the Table 1 and Table 2, respectively .
C. Ultrafine GGBS -Alccofine
Ultrafine GGBS (UFGGBS) commercially available as Alccofine-1203 is a low calcium silicate-based mineral additive which is generally used in lieu of of silica fume in high-performance concrete  due to lower cost and easy availability in Indian market. UGGBS- Alccofine 1203 is a slag based SCM having ultra-fineness with the optimized particle size distribution .
“Ordinary Portland Cement OPC-53 grade, GGBS and UFGGBS-Alccofine are conformed to Indian Standard Specifications IS: 269-2015, IS 16714-2018and IS 16715-2018”   
???????D. Chemical admixtures and crystaline growth waterproofing admixture
“Poly carboxylic ether-based superplasticizer admixture brand name Sika ViscoCrete 5138 M/s Sika are used to bring out the required water reduction and maintain the dispersing effect during the time required for transportation and placement at the site.Sika ViscoCrete 5138 is a high-performance superplasticizer (H.P.S) and specially developed for high workability, flowable, and self-compacting concrete mix. In the product datasheet of Crystalline growth waterproofing admixture brand name SIKA 101 H of M/s Sika. The use of crystalline waterproofing admixtures (CWA) has the potential of improving the durability and reducing the permeability of concrete structures especially those exposed to environments like soil face structures of underground structures” 
III. CONCRETE MIX DESIGN
“The concrete mix is designed as per absolute volume method according to the Indian standard -Concrete mix proportioning Guidelines to meet environmental exposure conditions of Mumbai city, Maharashtra i.e., considered a severe condition” . “The properties of the concrete ingredients differ from one state to another state of the same country, and it is totally depending on the actual environmental exposer condition of the site and quality of available concrete ingredients for making suitable concrete mix” . Concrete mix compositions are presented in Table 6Table 6. Abstract of all trial mixes which were conducted for finalizing the suitable Self-compacting concrete M40 Grade for Mumbai Metro project. Total 8 numbers of concrete trials were conducted using different kinds of materials and found two concrete mixes are matching the requirement of self-compacting concrete as per the requirement of European guideline and durability parameters of the technical specification of contract agreement of underground metro projects.
The authors are thankful to Director Projects of Mumbai Metro Rail Corporation and PMT Head of Shanghai Tunnel Engendering Co., Ltd for their motivational inputs and supports.
1) Selecting appropriate and suitable concrete ingredients and optimization of powder content in concrete mix, helps to improve the results of flowability, passing ability in the structure and for best results of durability parameters of the concrete.
2) Self-compacting concrete can be easily placed for long distance pumping and in congested locations due to dense reinforcement without vibration during the placement.
3) Crystalline waterproofing admixture plays effective role for reducing permeability and to increase durability of the structures.
4) Low values of Water permeability (WPT) and RCPT were due to addition of UFGGBS (Alccofine) and partly may be due to use of crystalline waterproofing admixture.
5) Since SCC allows the use of more powder enabling use of various SCM’s selecting appropriate and suitable mineral admixtures in various forms combined with high level PCE’s and crystalline waterproofing chemical admixture can yield a very low permeability Concrete with high durability and sustainability with longer service life.
A. CRediT authorship contribution statement
Sandip Sonule: Acquisition of data; Analysis and interpretation of data; On site execution; Drafting of manuscript
H. Jayarama: Review and editing of the manuscript; Funding acquisition; Permission and approval
Partha Sarath Ojha: Review and editing of manuscript
C.M Jadhav: Review and editing of manuscript; Funding acquisition; Permission and approval
Dr. K.C Tayade: Analysis and interpretation of data; Review and editing of manuscript.
B. Compliance with ethical standards
Conflict of interest - On behalf of all authors, the corresponding author states that there is no conflict of interest.
 K. C. T. N. V. P. V. &. A. B. G. Sandip Sonule, \"A case study on performance of self-compacting concrete in highly congested reinforcement of cast in situ structure,\" Asian Journal of Civil Engineering, vol. 22, no. 4, pp. 1-10, June 2021.
 The European Guidelines for Self-Compacting Concrete Specification, Production and Use, May2005, 2005.
 A. I. Hassan EL-Chabib, \"The performance of high-strength flowable concrete made with binary,\" Construction and Building Materials 47 (2013) 245–253, vol. 47, no. 47, pp. pp 245-253, 2013.
 P. M. A. S. B. S. V. V. A. P. N. Ojha, \"Optimization and evaluation of ultra high-performance con-crete,\" Journal of Asian Concrete Federation, vol. Vol. 6, no. No. 1, pp. pp. 26-36, June 2020, June 2020.
 M. V. a. P. D. b. V. K. c. B. Venkatesan a, \"Experimental study on concrete using partial replacement of cement by,\" Materials Today: Proceedings, vol. Volume 37, no. Part 2, pp. Pages 2183-2188, 2021.
 IS 269:2015. Ordinary Portland Cement- Specification, 2015.
 IS 16714-2018. GGBS for use in cement, mortar and concrete-specifications, 2018.
 IS: 16715-2018 \"Ultrafine Ground Granulated Blast Furnace Slag\", 2018.
 C. Xue, \"Self-healing efficiency and crack closure of smart cementitious composite with crystalline admixture and structural polyurethane,\" Construction and Building Materials, vol. Volume 260, p. 119955, November 2020.
 IS 9103:1999, Concrete Admixtures: Specification, Bureau of Indian Standard, Delhi, pp. 1–14., 1999.
 IS 383: 201 6 Bureau of Indian Standards (New Delhi) Indian standard coarse and fine aggreagtes for concrete specification, IS 383: 201 6 .
 IS :10262:2009 Concrete mix proportioning - Guidelines, 2009.
 W. OH, \"Why is SCC Different from Country. Fourth International Symposium on SCC,\" Chicago, 2005.
 MSZ EN 12350, Testing fresh concrete, Part 8, Part 9, Part 10, Part 11, Part 12, (2010), 2010.
 K. K. D. C. S. T. Patrick Paultre, \"tructural performance of self-consolidating concrete used in confined concrete columns,\" ACI Struct J, 102 (7) (2005), pp. 560-568, vol. 7, no. 102, pp. pp. 560-568, 2005.
 A. D. Adesina, \"Concrete Sustainability Issues,\" in 38th Cement and Concrete Science Conference, London, 2018.
 Chiara F. Ferraris, \"Measurement of the Rheological Properties of High Performance Concrete: Sate of the Art Report,\" Journal of Research of the National Institute of Standards and Technology, vol. 104(5), no. 8, pp. pp.461-478, 1999.
 B. K. a. W. C. P. Steven H. Kosmatka, \"Design and Control of concrete mixtures,\" Portland Cement Association, United States of America, 2008.