Retrofitting of seismically damaged open ground storey RCC framed building with geopolymer concrete

Abstract

Retrofitting is a technique in damaged structure is strengthened to original design requirements. The recent earthquake occurred in India during 2001 in Gujarat, damaged many buildings that were seismically deficient. So there is an urgent need for retrofitting of damaged buildings. This calls for techniques that are technically sound and economically feasible to upgrade deficient and damaged structures. Also, Portland cement (PC) production is under critical review due to high amount of carbon dioxide gas released to the atmosphere and Portland cement is also one among the most energy-intensive construction materials. The current contribution of greenhouse gas emission from Portland cement production is about 1.5 billion tons annually or about 7 % of the total greenhouse gas emissions to the earth’s atmosphere. So retrofitting of existing deficient building using eco-friendly material which could promise higher structural performance than the original building is essential. Many retrofitting methods such as epoxy injection, CFRP, GFRP wrappings etc. are used currently, but there is a mismatch in tensile strength and stiffness of these materials with that of concrete structure. The Geopolymer concrete (GPC) is fire and acid resistant, highly durable, less shrinkage, low permeable and attains strength within 3 days of ambient air curing. So the feasibility study of geopolymer concrete in retrofitting of damaged reinforced concrete (RC) beams and RC building is presented in this paper. An open ground three storey seismically damaged RCC building is retrofitted with GPC at cracked portions. And free vibration test is carried out using reaction mass shaker to obtain the natural frequencies and mode shapes. Also using finite element method in ANSYS software modal analysis is done on the building for natural frequencies and mode shapes. This paper presents the experimental and analytical results of natural frequencies and mode shapes.