| PSWC-BAR FOR SUSTAINABLE REINFORCED CONCRETE CONSTRUCTION Anil K. Kar1; U. K. Chatterjee2; 1ENGINEERING SERVICES INTERNATIONAL, SALT LAKE CITY, KOLKATA, INDIA., Kolkata 700064, India; 2IIT KHARAGPUR (RETIRED PROFESSOR), Kolkata 700106, India; PAPER: 321/Metals/Regular (Oral) SCHEDULED: 15:55/Wed. 30 Nov. 2022/Arcadia 1 ABSTRACT: Strength, rigidity and durability of reinforced concrete constructions, with plain round bars of mild steel as rebars, made it the number one medium of construction. Later, ribbed bars of high strength carbon steel were introduced in the hope of making reinforced concrete constructions more economical. Proponents of ribbed bars overlooked that the provision and presence of ribs make ribbed bars of carbon steel highly susceptible to corrosion. Consequently, constructions with ribbed bars of carbon steel proved to be less sustainable, as such constructions reached states of distress early. The excessive corrosion destroys or reduces load-carrying capacity of concrete elements, reinforced with ribbed bars. It can also lead to local or total failure of structures during vibratory loadings. Moreover, loose rust on the surface of ribbed bars will prevent any possible passivation of rebars, thereby hastening the process of corrosion in rebars and distress in reinforced concrete constructions. As claimed solutions, fusion bonded epoxy coated ribbed bars, ribbed stainless steel bars, polymer coated glass fibre and granite reinforced bars, have been used. Besides high cost, these bars do not “bond” with concrete, whereas the availability of competent bond between rebars and the surrounding concrete is an essential requirement for the satisfactory performance of reinforced concrete. Use of corrosion inhibitors with concrete and provision of surface protection systems in the nature of waterproofing treatment, so as to prevent corrosion in steel elements inside concrete, are accepted practices today. These alternative solutions cost money, and the performance of concrete elements are dependent upon the performance of the contractor. Moreover, the use of corrosion inhibitors or the provision of surface protection systems cannot solve problems, which may be caused by the lack of bond between rebars and concrete, viz., reduced load-carrying capacities, lack of ductility, and local or total failure of structures during vibratory loadings. PSWC-BAR, characterized by its plain surface and wave-type configuration, provides a zero-cost solution to all the problems and limitations of ribbed bars and alternative solutions. In due consideration of using steel with high elongation properties, it is recommended to limit the use to steel of yield strength not exceeding 550 MPa. The absence of ribs on the surface of PSWC-BAR makes it free of excessive corrosion, that is associated with conventional ribbed rebars, thereby leading to several-fold enhancement of life span of concrete constructions with PSWC-BAR. The several-fold enhancement of life span of concrete structures lowers the life-cycle cost of construction to a fraction of what it is today, and it increases very significantly the financial, social, environmental and global sustainability of reinforced concrete constructions than what it is today. The many benefits of using PSWC-BAR are derived from its physical characteristics of plain surface and wave-type configuration. The use of PSWC-BAR, with its wave-type configuration, leads to enhancement of effective bond between such bars and the surrounding concrete, thereby leading to increased load-carrying capacity, and several-fold increase in ductility and energy-absorbing capacity, making constructions cheaper and safer during earthquake events, adding to the sustainability of reinforced concrete construction. References: REFERENCES : [1] A. K. Kar, New Building Materials & Construction World, Vol 16, July (2010) 180-199. [2] A. K. Kar, The Masterbuilder, Vol 20, September (2018) 136-146. [3] A. K. Kar, Pro of Inst of Civil Engineers --- J. of Construction Materials, https://doi.org/10.1680/jcoma.18.00019 (2019) 1-9. [4] A. K. Kar, The Masterbuilder, Vol 21, September (2019) 102-110. [5] A. K. Kar, Design of Cities and Buildings – Sustainability and Resilience in the Built Environment, IntechOpen, January (2021) 1-26. |
