Indian Concrete Journal

Effect of aspect ratio on response reduction factor of RC framed structures with semi-interlocked masonry and unreinforced masonry infill Mangeshkumar Shendkar, Ramancharla Pradeepkumar, Pabitra Ranjan Maiti

In building construction, reinforced concrete (RC) Frame structures are frequently used due to ease of construction and rapid progress of work. In this study, two types of infill’s are used i.e., unreinforced masonry infill and semi-interlocked masonry infill. For the analysis purpose of infill, a double strut nonlinear cyclic model is used. The main objective of the study is to investigate the importance of interlocked brick infill in the RC frame structure. For understanding the same, nonlinear static pushover analysis is carried out on analytical models using finite element based software, SeismoStruct. The response reduction factor components such as ductility reduction factor and overstrength factors were computed from nonlinear static pushover analysis and finally, the response reduction factor is calculated for all models. The primary focus is given to numerical modeling, nonlinear behavior of brick masonry RC buildings subjected to lateral loads and calculation of the response reduction factor of 'RC' infilled frames with different aspect ratios.

Flexural behavior of reinforced high performance self-compacting alkali activated slag concrete beams Manjunath R., Prashanth M. H., Mattur C. Narasimhan, Bala Bharathi U.K.

The present manuscript discusses the results of a series of tests conducted to study, in detail, the performance of reinforced, alkali activated slag concrete beams in terms of their flexural behavior. The present authors have developed and evaluated the performance of a new class of high-performance, self-compacting, alkali-activated slag concrete (HPAASC) mixes, using three industrial by-products, all from the iron and steel industry. While these HPAASC mixes have higher compressive strengths (around 70-90 MP_a), reasonable splitting and flexural strengths along with moduli of elasticity, here, in this investigation, reinforced concrete beams made of these mixes are evaluated for their flexural performances in order to promote their applicability in large-scale infrastructural applications. Twelve under-reinforced concrete beams, were cast and were tested. Their flexural behaviors were experimentally evaluated in terms of loads at first crack, ultimate loads, strain-distributions, their load-deflection characteristics along with ductility values. Results of the present study indicate that, all the reinforced beams made of HPAASC mixes exhibit comparable flexural performances, as compared to that of beams cast with a reference OPC-based concrete mix, making a strong case for the possible application of these HPAASC mixes as structural elements in large-scale infrastructure projects.

Mechanical properties of hybrid fiber reinforced concrete with steel and polypropylene fibers Needhi Kotoky, Anjan Dutta, Sajal K. Deb

The present study reports experimental works on Hybrid Fiber Reinforced Concrete (HyFRC) using a combination of steel and two types of polypropylene fibers available in India. In addition to routine testing of standard cube and cylinder specimens, displacement controlled flexural tests under monotonic loading arrangement are conducted on prism specimens using servo-hydraulic actuator to track the post crack behavior. Toughness and post-peak slopes are identified as parameters for the assessment of performance. It is also observed that a specimen with the lower post-peak slope and higher maximum defections exhibits higher flexural toughness. HyFRC is found to be superior to conventional concrete specimen and the best fiber proportion is assessed utilizing the parameters identified for performance evaluation. The microstructure of HyFRC matrix is studied to explore the possible reasons for improved performance of such specimens after initiation of cracking.

Challenges - sustainability and solutions for constituent materials of structural concrete D. Sree Ramachandra Murty, G. Papa Rao

There is growing realisation worldwide that our planet earth is being threatened by malefic twins of uncontrolled use of natural resources and increasing amount of environmental pollution. It is most appropriately valid in the case of concrete-making materials. Population growth coupled with urbanisation, industrialisation at unprecedented scale and climate change, resulted in significant impact on infrastructure development. Relative to structural engineering in civil engineering construction materials are subject to heavy demand to satisfy infrastructure needs. Concrete has become unquestionably the material of choice for obvious reasons. The unlimited construction activity places heavy demand on concrete. Consequently, the concrete-making materials, cement, aggregates and water have become currently unavailable, inaccessible and increasingly in depletion; but reachable only at unaffordable prices. Industrial development, though revolutionised, the improvements in living standards of humans, has not left environment clean; industrial wastes are accumulating in frightening magnitudes, incurring huge amounts of time, effort and finances for their disposal. Diminishing quantities of concrete-making materials and the growing industrial waste disposal problems can be solved simultaneously, beneficially and economically following certain systems. The aforementioned two categories of materials, namely the diminishing quantities of concrete making materials, and the unprecedently growing industrial wastes, eliminate their ill effects, by one category of materials, helping the other category of materials. The details that follow in the paper, unfold the strategy involved in the solution of the above problem.

Self-compacting concrete containing ground granulated blast furnace slag: A review Ran Bir Singh

This paper presents a review on performance of self-compacting concrete (SCC) containing ground granulated blast furnace slag. SCC is considered as a high-performance concrete in terms of its strength, workability and durability. It has several advantages over normal vibrated concrete as it deforms under its own weight and no vibrations are needed for placing the concrete. The primary objective of this study is to understand the effect of Ground Granulated Blast-furnace Slag (GGBS) on the fresh, the hardened and the durability properties of self-compacting concrete. The study also proposed to suggest optimum dose of GGBS as cement replacement in the SCC. Several papers have been studied to take an overview of recent innovations in SCC containing various mineral admixtures and this paper is aimed to review the application of GGBS and its performance on the quality of SCC to set a benchmark for future research work in this field.

Utilization of copper metallurgical waste for alkali activated binder synthesis Jagmeet Singh, S. P. Singh

This paper focuses on the synthesis of alkali-activated binder using copper slag as aluminosilicate source and evaluates the influence of different synthesis parameters such as alkali dosages (4, 6, 8, and 10%) and silicate modulus (1.0, 1.25, and 1.5) on the compressive strength, microstructure and efflorescence (a durability aspect) of Alkali-activated Copper Slag (AACS) mortar. Fourier Transform Infrared Spectroscopy (FTIR), Mercury Intrusion Porosimeter (MIP) and Scanning Electron Microscopy (SEM) were used to examine different characteristics of AACS mortar. The test results indicate that the compressive strength of AACS mortar mixes was improved with an increase in alkali dosage and silicate modulus. However, high degree of efflorescence was observed when alkali dose was increased beyond 6%. Heat curing was effective to increase the strength properties of AACS mortar at the early age of curing. Aluminosilicate gel phase was detected in the FTIR spectra of AACS mortar mixes with high alkali dosage and silicate modulus. The microstructure and pore structure of AACS mortar mixes was also improved with an increase in alkali dosage and silicate modulus. The optimum alkali dosage for the synthesis of AACS may be taken as 6% keeping in view the degree of efflorescence. However, with the increase in the silicate modulus, a marginal decrease in the efflorescence of AACS mortar has also been observed.

Statistical nature of concrete – Part 1, constituent materials S. B. Kulkarni, Kiran K., Chetan Hazaree

Conforming only to materials’ specifications is often inadequate while dealing with concrete quality on large projects. These materials, extracted from Nature and processed further are subject to inhomogeneities and temporal variations, understanding which is pivotal to realizing the design intent of the built structure. Properly employed statistical methods can provide efficient, economic, and effective means of quality control of constituent materials and concrete. The aim of this paper is to present some statistical explorations and ways of understanding the inherent nature of variations of the constituent materials of concrete, which can in-turn be used in assuring and controlling concrete quality.