Indian Concrete Journal

Fresh-state behavior of paving concrete reinforced with discarded coconut coir fibres Someen Khute, Surender Singh, Raúl Zerbino, Ravindra Gettu

The present study deals with the fresh state behavior of paving concrete containing discarded coconut coir fibres (DCF). Owing to lower density and hydrophilicity, dispersion of DCF could be a challenging issue and therefore, two approaches are studied for uniformly distributing the DCF in concrete viz. end-stage mixing and intermediate-stage mixing; the parameters of DCF considered are their size (short and long) and proportion (0.1-0.7 % by concrete volume). Thereafter, based on these results, various concrete mixes containing DCF are prepared and studied for their properties – slump, bleeding, plastic shrinkage and compressive strength are the properties investigated. The results favour the adoption of intermediate mixing for better dispersion of DCF in concrete. Concrete mixes containing DCF exhibited lower bleeding as well as the potential to mitigate plastic shrinkage cracking. From this study, it is suggested to include coir at dosages of 0.1 %-0.4 % by concrete volume, depending on the severity of the extreme ambient conditions, for preventing plastic shrinkage cracks in pavement concrete.

Economy in construction with realistic uniformly distributed imposed loads Shreya Jadon, Deepesh Singh, Sunil Kumar

A structural designer requires realistic design loads for safe and economical design of buildings. Recent study of Indian load survey data of office and residential buildings and the revision of foreign building codes and standards has prompted a need for further collection of additional imposed load data to substantiate future revision of Indian code of practice, IS: 875-2 (1987)^[1]. This paper gives a critical assessment of uniformly distributed imposed loads of the Indian code based on the values of load surveys and recommendations of foreign building codes and standards. This assessment identifies the probable areas of reducing imposed loads in Indian code for the design of buildings.

Experimental investigation on durability of concrete incorporating ground granulated blast furnace slag blends Anamika Agnihotri, P. V. Ramana

This paper reports on a clever inquiry regarding endeavors to make building bricks utilizing mechanical by-products and therefore the potential advantages of innovation, economy, and looking after the environment. A preparation of sample-making by employing a result of a mechanical preparation is seen as a step towards a lot of possible building development. This paper shows an experimental study of a ground granulated blast furnace slag (GGBS) based mix that was cured for seven days before being exposed to a mixed resolution of common salt (30 g/l) and sulfate (3 g/l). 2 slags with totally different chemical compositions, known as slags 1 and 2, were mixed with cement with substitution rates of 30 % and 40 %, respectively. The slump and mechanical strength of the concrete, which comprises GGBS, were studied at 3, 7, 14 and 28 days curing period. Mechanical testing of concrete samples was complemented by microstructural studies and chemical characterization of raw resources, all employing a constant w/b quantitative relation of 0.4 to analyze results of the exposed environment. Concrete samples were subjected to temperatures between 20°C and 38°C exposure conditions (to replicate temperate and tropical climates). The outcomes demonstrate that GGBS increase the freshened and hardened performance of the concrete, enhancing its mechanical qualities. Temperature includes an important effect on the sturdiness of the slag based mixture. The decrease in cohesiveness at high temperatures diode to a discount in chloride penetration early. This impact becomes less noticeable at later ages. As chloride penetration increased, it was discovered that compressive strength decreased. Scanning electron microscopy-energy dispersive X-ray (SEM-EDX)

Study of shear failure in concrete filled un-plasticized polyvinyl chloride (UPVC) tubular columns V. K. Verma, P. K. Gupta

In this paper, an effort is made to understand the shear mode of failure of concrete filled un-plasticized polyvinyl chloride tubular (CFUT) columns with the help of Mohr-Coulomb failure criterion. The analytical results are verified with experimental results. The effect of confining pressure on angle of shear failure plane has been investigated, presented, and discussed. To understand the failure mechanism, eighteen specimens of concrete filled unplasticized polyvinyl chloride (UPVC) tubular columns were cast by filling concrete of grade M30 and M40 in the tubes of diameters 160, 200, and 225 mm of class 3, 4 and 5 with nominal pressure of 0.6, 0.8, and 1.0 mPa [as per IS: 4985 (2000)^[12]. All the specimens were tested by applying axial load on concrete core only. It was found that all the specimens failed by development of shear cracks with slight bulging. Mohr-Coulomb failure criterion was used to calculate the angle of failure plane. Present study shows that shear failure of CFUT columns may be avoided using UPVC tubes of higher class.

Properties of controlled low-strength materials developed through common effluent treatment plant sludge B. N. Skanda Kumar, A. Shashishankar

The proper disposal of the wastes generated from the industries is a severe concern in India. The byproducts from industrial waste are used for many civil engineering applications. Amongst them the usage of common effluent treatment plant (CETP) sludge for development of controlled low-wtrength materials (CLSM) is still to be explored. The CLSM or flow-able fill could be used effectively as alternate in preserving or limiting the usage of construction materials. They are used in the areas, where compaction equipments are not feasible. The study aims to investigate fresh and hardened properties of CLSM (constituting proportion of class-F fly ash, CETP sludge, cement, M-sand and water). The work carried facilitate in developing eco-friendly CLSM mix in which byproduct material utilization is maximized, satisfying workability and performance requirements. The developed CLSM constitute for three levels of cement substitution with CETP sludge (i.e. 5, 10, and 15 %) for five classes of mix design (A, B, C, D, and E). The outcome of the results was promising and found that the flowability values were between 20-25 cm and unconfined compressive strength (UCS) was found maximum for Mix E at 28 days. Based on the UCS results, the CLSM developed may be considered for the possible application in pavement bases or for permanent fills.

Experimental investigation on durability properties of ramie fibers and hooked-end steel fibers reinforced high strength concrete incorporating silica fume and metakaolin M. Sriram, K. R. Aswin Sidhaarth, S. Kandasamy

The durability properties of hybrid fiber-reinforced high-strength concrete (HFRHSC) were examined in this research. Ramie fibers and hooked-end steel fibers combination is a new one and these combinations highly enhance the performances of the concrete specimens. Silica fume and metakaolin were added to both HFRHSC and conventional concrete specimens. Ramie fiber usage in concrete is a new trend and it gives good results compared to other types of natural fibers. The optimum contents of silica fume and metakaolin are 10 % and 5 % respectively. A concrete mix of grade M₇₀ is used for this investigation. For developing HFRHSC, different proportions of ramie and steel fibers are mixed with cementitious composites. Ramie fiber fractions of 0.5, 1, 1.5, and 2 % are kept constant with varying fractions of hooked-end steel fibers of 17 different mixes prepared. The durability properties of HFRHSC are determined by different tests such as water absorption, acid test, sorptivity test, drying test, sulfate test, and marine attack test. The water absorption of HFRHSC is decreased by 4.5 %; whereas, the sorptivity and drying shrinkage are decreased by 3.5, and 3 % respectively. Furthermore, the results of the acid test of HFRHSC are decreased by 10 %, the sulphate attack test of HFRHSC is decreased by 12 % and the marine attack test results achieves 11 % compared to the conventional concrete specimens. The hybrid fiber-reinforced concrete specimens exhibit a highly reduced absorption capacity than conventional concrete specimens. The effects of HFRHSC in acid tests show less deterioration compared to conventional concrete specimens.