Indian Concrete Journal

Precast concrete building construction in India - challenges and opportunities. Nandeesh Babanagar, Resmi Giriraju, Rohini Prabhugaonker, Vellore Gopalaratnam, Amit Barde, Radhakrishna G. Pillai

Widespread use of precast concrete for building construction can address the rapid demands for timeliness, quantity, quality, and affordable housing in India. Precast concrete construction (PCC) has numerous benefits including efficiency in material use, reduced embodied carbon through use of advanced blends of cements, timely construction from parallel processes and pre-finishing options, reduced environmental disruptions and economic impact due to off-site construction. However, there are some challenges to embrace this sustainable technology in India. This paper discusses a few critical challenges. Solutions are also concurrently recommended based on the vast experience in India and worldwide on successful implementation of PCC. Challenges and solutions are discussed by suitably classifying them in technical, logistics, implementation, and perception issues. Some of the solutions recommended can be adopted rather quickly with existing technical knowledge, and thoughtful reviews of code specifications, while others, particularly those related to perception issues may require more systematic efforts to address adequately. These solutions will help India leverage the potential of PCC to transform the building construction industry and address the demands for housing and related infrastructure. The paper also provides case studies of PCC buildings.

Comparison of flexural design of shear walls using idealized and simplified stress-strain relationships of steel as per IRC:112 (2020) Anasuya Mondal, Santanu Bhanja

The present paper explores the benefit of using idealised design bilinear stress strain relationship of steel over the simplified one in design of rectangular reinforced concrete (RC) shear walls. The idealised bilinear stress strain relationship refers to strain hardening of steel for which, stresses also increase with strain beyond the yield point. This significantly complicates the solution process for load-based design approach as adopted in flexure design. This paper is a myth buster of complexity in calculation process with idealised design bilinear stress strain relationship.
In IRC: 112 (2020) inclination of the plastic branch depends upon the tensile strength and the ultimate strain of steel and accordingly steel has been designated in nine grades. For design of section subjected to axial forces with flexure capacity-based approach of design is adopted instead of load-based design. In this paper capacity-based approach has been adopted in the design of RC shear wall section with for all grades of steel and concrete as permitted by IRC:112 (2020). P-M interaction charts with idealised bilinear stress strain relationship flares out in the under reinforced region. Shear walls are generally designed as heavily under reinforced section whereby designing as per proposed P-M interaction charts with idealised design stress strain relationship of steel will produce significant economy over simplified design stress strain relationship of steel.

Enhancing mechanical properties of mortar with polymethyl methacrylate (PMMA) microcapsules for self-healing Urmil V. Dave, Ridhi A. Vora

Enhancing the durability through self-healing technology holds significant promise for mitigating degradation of concrete structure. The present study investigates the application of microcapsules in mortar to determine optimal dosage and selfhealing efficacy. Two types of mortar were used: a control mortar with a cement-to-sand ratio of 1:3 and a water-cement ratio of 0.5, and another mortar incorporating microcapsules made from calcium alginate and Polymethyl Methacrylate Microcapsules (PMMA) were added in dosages ranging from 1 to 5 %. Traditionally mortar specimens were tested at 3, 7, 14, and 28 days primary compressive strength. Additionally, some specimens were pre-cracked at 14 and 28 days, then cured in water for self-healing for 28 days before being tested again for secondary compressive strength. The self-healing efficacy was highly dependent on the healing period, with specimens subjected to a 28 day healing period showing substantially greater improvements compared to those with a 7 and 14 day healing period. Thus, only the results for the 28 day healing period are considered. Results showed that at lower dosages, the addition of microcapsules containing curing agents improved the compressive strength of mortar specimens. The optimal microcapsule concentration for maximizing compressive strength was between 1 and 3 %. For different dosages, the self-healing rate for capsule-impregnated mortar ranges from 20 to 80 %, which is higher than that of the control mortar. Calcium alginate demonstrated excellent compatibility with the PMMA-based self-healing agent as well as with the mortar. These findings provide valuable insights for designing and constructing self-healing concrete structures, highlighting the potential of microcapsule-based systems in enhancing concrete durability and longevity.

Experimental and numerical study on compressive behavior of concrete filled double tube columns N A G K Manikanta Kopuri, S. Anitha Priyadharshani, J. Shivanand, Adnaanullah Khan, Mohammed Abdul Wasay Hakimullah Rashidi, Masroor Ahmed

In this study, the experimental and numerical investigation of concrete filled double tube (CFDTS) columns subjected to axial compressive load is investigated. The parameters studied are load carrying capacity and ductility index. The influence of normal concrete (NC), special concrete (SC) (Fine aggregate is a combination of 60 % river sand and 40 % ferro chrome slag) and fiber reinforced special concrete (FSC) (Fine aggregate is a combination of 60 % river sand and 40 % ferro chrome slag and crimped steel fibers of 2 % of by weight of cement with aspect ratio of 60 is added) on the behaviour of concrete filled double tube (CFDTS) columns are studied experimentally and numerically. In this study, 18 CFDTS columns (6 types) by varying types of concrete in core and shell portions are investigated. Load vs axial deformation obtained from experimental and numerical results are compared among various types. Special concrete and fiber reinforced special concrete has given better performance in CFDTS columns when compared to normal concrete.