International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 12 Issue: 07 | Jul 2025
p-ISSN: 2395-0072
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Investigate the feasibility of thermal treated and untreated RCP as an SCM with addition of nano CaCO3 Rahul Chandel1, Sayantan Ghosh2 1Master's Degree Scholar, Department of Civil Engineering, Maharaja Agrasen University, Baddi (Himachal
Pradesh)
2 Assistant Professor Department of Civil Engineering, Maharaja Agrasen University, Baddi (Himachal Pradesh)
---------------------------------------------------------------------***--------------------------------------------------------------------On the other hand, the problem of C&DW arises, Abstract - Powder obtained from the recycling process of
approximately, 3 billion tonnes of C&DW are generated annually and grow constantly [3] and [1]. India is the second-largest country behind China, which produces approximately 100 to 400 MT C&DW per year reported by Building Material and Technology Promotion Council (BMTPC). Most of C&DW is inert and non-hazardous, other than this minority of C&DW containing environmental unfriendly substances like asbestos, organic pollutant and heavy metals especially, zinc which is responsible for soil and air pollution, second issues with that, it requires land for its dumping which increase its dumping cost as well as covered useful land, [1].
concrete waste is considered an essential product for attaining complete recycling of concrete waste. Powder with a size < 150 μm is considered in the categories with a nomenclature as RCP (recycled concrete powder). However, various studies show that the RCP integrated with cement reduces the performance. Thus, this study aims to investigate the performance of thermally treated RCP at 650 0C, 700 0C, and 7500C for 2h and also investigate the properties of untreated RCP, at 10% and 15% replacement with the addition of 1% nano CaCO3. Various properties of mortar, such as flow ability, SAI (Strength Activity index) at 28 days, and compressive strength, were tested, besides determining the flow ability, affected by an increase in dosage of replacement, an increase in treated temperature, and on addition of Nano CaCO3.The SAI values of mortar mixes 650TR10N, 700TR10, 700TR10N, 700TR15and 700TR15N are 76.8%, 75%, 84.3%, 77.9% and 88% respectively. Thermally treated RCP at 700oC at 15% replacement with 1% nano CaCO3 shows 7% increment at 7days and 11.9% reduction in compressive strength at 28 days as compared to standard mortar (Rf). The effective range of activation of RCP in this study ranges from 6500C to 7000C.This study provides a way to utilize RCP and contribute to sustainable construction practices.
Various studies are available and still ongoing to find the solutions to the above problem. The RCP particles have an irregular shape, a rough surface, and micro pores, which increase water demand and adversely affect the rheological properties [1]. In contrast, the sharp angle and rough surface improve the hydration process by providing nucleation sites, various hydrated products like C-S-H gel, Aft, and CH form due to initial hydration, and CaCO3 due to carbonation, and SiO2 from sand, chemical composition almost similar to cement [1]. Studies found that CaO and SiO2 oxides are major oxides in RCP in which SiO2 is present in majority and Al2O3, which are obtained from hydration products, unhydrated cement, and CaCO3,[4].
Key Words: Construction and demolition waste, nano Calcium carbonate, Recycled Concrete thermally treated Concrete Powder.
Powder,
Rocha, J. H., & Filho, R. D. reported that the strength Activity Index of RCP is enhanced by the particle size of RCP and reported that 87.2% AI at 28 days comes at D50 of 8.22 μm, and AI comes 15% at D50 of 22.7 μm, and comes approximately 100% at D50 of 2.34 μm. Thermal treatment is one of the effective methods to enhance the reactivity of RCP. Several studies found that the effective range of thermal activation of RCP ranges from 650 0C to 700 °C, providing AI of >75% and also reported that, with temperature and replacement dosage increase, the rheological properties are affected, and found that replacement dosage should be <30% to be an adequate replacement [4]. The previous studies on nano CaCO3 found the optimum dosage range of nano CaCO3 as an additive is 1% to 3%; further increments in its dosage cause agglomeration of particles, resulting in improper hydration [5] [6].
1. INTRODUCTION The consumption of concrete worldwide is about 25 billion tons annually, and its demand rises dramatically. Production rate of concrete predicted to be more than 18 billion tons per year, and cement will be 5.5 billion tons by 2050 [1]. Construction industries are promising to take steps to achieve net-zero emissions by 2050. Various studies show, the construction industry contributes approximately 20% CO2 emissions globally. Mostly, 7% to 8% comes from the cement industry alone [2]. Data from various environmental and concrete associations shows that the production of cement in the year of 2023 was 4.1 billion tonnes globally.
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