Indian Concrete Journal

Review of structural systems for tall buildings Prateek Dewangan, Bhupinder Singh

The effects of lateral loads on tall buildings are pretty significant. Therefore the influence of these actions must be considered from the very beginning of the design. In high-rise building, the structure’s construction is greatly influenced by the type of lateral system provided. The selection of an appropriate lateral structural system plays an essential role in the structure’s response. The taller and slenderer a building, the more critical the structural factors become, and the more necessary it is to choose an appropriate structural form. This article reviews the rigid-frame structural system, braced-frame structural system, and wall-frame structural system. Various models of a RCC tall building are made, and the results of each model are observed for considered structural form. The aim is to find the suitability of the structural system with an increase in height, parametric investigation of the wall-frame, and the braced frame structural system. The structural models are analyzed in ETABS software to study the effect of the height of buildings on the performance of these buildings under lateral loads (seismic forces and wind loads). The linear dynamic response spectrum method is used for the analysis of the structure.

Late age mechanical strengths and hydration of ultra high performance concrete blended with metakaolin and high volume limestone Zongyun Mo, Youmin Han, Jiawei Wang, Li Jiang

In this study, late age re-hydration for metakaolin (MK) added ultra high performance concrete (UHPC) with water curing from 90 to 365 days were investigated. And limestone (LS) was also incorporated into UHPC replacing 30 % cement by binder mass for reducing the cement usage. In addition, cement and LS cement specimens without MK were prepared as the references. Mortar specimens were employed for testing the compressive and flexural strength at 90, 150, 210, 270, and 365 days. And paste specimens were used to measure the chemically bound water, differential thermal analysis (DTA) curves, X-ray diffraction (XRD) patterns, pore structures, and micro-morphology at designated ages. Results indicate that the re-hydration causes an increasing tendency for strength of mortars from 90 to 270 days while a decreasing tendency after 270 days. The re-hydration degree for MK contained mixtures are obviously lower than that of the references. MK can stabilize the late age mechanical property and micro-structure of water cured UHPC. Moreover, the combination of LS and MK do not obviously degrade the strength and micro-structure of long term water cured UHPC compared with that of binary MK contained mixture.

Fresh and hardened properties of geopolymer concrete: A review Satya Ranjan Prusty, Sanghamitra Jena, Ramakanta Panigrahi

Conservation of natural resources, and reduction in environmental pollution can be achieved by utilizing industrial waste for the production of new construction materials. Various types of agro and industrial wastes with alkali activation can be used as alternatives to ordinary Portland cement. In recent years, geopolymer binders become the centrepiece for researchers to solve disposal problems and carbon dioxide (CO₂) emissions. The alkaline solutions are sodium hydroxide combined with sodium silicate which produces geopolymer binder or geocement. This can prevent environmental degradation. This paper reviews the physical and chemical properties of industrial wastes along with the other properties of geopolymer concrete.

Non-destructive evaluation of iron slag concrete containing recycled concrete aggregates Navdeep Singh, Nitin Ankur, Tarun Singh, Mahesh Kumar, Akhil Singh, Parveen Kumar

The study investigates the potential of iron slag (IS) and recycled concrete aggregates (RCA) used as replacement of natural fine aggregate (NFA) and natural coarse aggregate (NCA) respectively in concrete. In designed concrete mixes, NCA were replaced with RCA as 25 % and 50 % while NFA was replaced with constant amount of IS with 30 % (both by-weight). The performance of the aforementioned was particularly evaluated through non-destructive testing wherein tests like electrical resistivity (ER), ultrasonic pulse velocity (UPV) and rebound number (RN) hammer tests were performed at various curing ages. In addition to above, properties such as workability, compressive strength (CS), tensile strength (TS), chloride penetrability and surface absorption were also evaluated briefly for reference. The observations indicate the negative effect of RCA resulting in decrement of UPV, ER and RN values although the incorporation of IS improved the performance marginally for RCA based mixes. Above all, linear regression values also indicate admirable relationships between UPV, ER and RN with CS and TS respectively.

Structural retrofitting of rcc urea silo hangers by using innovative design and execution strategies Mangesh V. Joshi, Vivek S. V., Nikhil Yashawant Jadhav

The article discusses a case study of strengthening of bulk urea silo for a leading fertilizer manufacturing company in India. The need for retrofitting of silo, the analysis and design processes followed for arriving at retrofit solutions are summarized herein, alongside a comparative study of various retrofitting systems and specialty materials considered and selected for final execution. Site challenges and solutions for the same to execute the job in the given time frame by maintaining zero safety incident are also presented. Entire work was executed on design-built basis.