Indian Concrete Journal

Engineering behaviour of graphene nanoengineered concrete Suehail Aijaz Shah, and M. A. Tantray

Graphene, the material of the 21^st century, possesses exceptional qualities such as high flexibility, Young’s modulus, and tensile strength, making it an ideal material for reinforced cementitious composites. Incorporating graphene nanoplatelets (GNPs) into concrete has shown great promise in improving concrete’s mechanical properties and durability. This study examines the effect of different dosages of GNPs on concrete’s compressive strength, split tensile strength, and permeability. The findings reveal that adding GNPs can significantly enhance concrete’s mechanical properties and reduce its permeability, which is crucial for improving its durability. The modified concrete underwent microstructure analysis to determine the optimal dosage required to achieve the desired properties. This study provides valuable guidance on the utilization of GNPs in concrete. Finally, the paper discusses the challenges and limitations of using GNPs concretely and suggests future research directions. Overall, the paper offers valuable insights into the potential of GNPs as nanofillers in concrete and their potential impact on the future of construction materials.

Numerical modelling and shear capacity of steel reinforced ECC beams with short shear span Hamsavathi K., S. B. Singh, and Madappa V. R. Sivasubramanian

This research study investigates the shear capacity of steelreinforced engineered cementitious composite (ECC) beams with a short shear span. Three steel-reinforced ECC beams that failed in shear are chosen, and shear stress - shear deformation simulation is performed to realize the response of the beams through finite element analysis. Further, an interpretation model is developed to understand the shear load transfer mechanism, including ECC’s tensile capacity, using a strut and tie model. Finally, a detailed parametric study is conducted to understand the tensile load carrying capacity of ECC for a range of shear span to depth ratio and amount of shear reinforcement. From the parametric study, it is learned that for all the shear span to depth ratio, the tensile load carrying capacity of ECC has decreased with the increased shear reinforcement.

Mechanical properties of geopolymer concrete made at ambient temperature with fly ash and GGBFS Satalingappa P. Deshamukh, and G. S. Manjunatha

The geopolymer concrete is formed by reacting alkaline solutions with silicon, alumina, and calcium products. Here, a number of experiments were conducted by ambient curing to find the suitable percentage proportion of flyash and GGBFS to get the desired strength with conventional concrete. Here By conducting short-term and long-term tests, efforts to find the most suitable proportion of flyash and GGBFS give the closest strength results to conventional concrete. In this study, using geopolymer concrete (GPC) mixes of 75 : 25, 70 : 30, 65 : 35, and 60 % : 40 % flyash: GGBFS and M20 grade concrete, mechanical and durability tests were conducted.

Effect of Water Dispersed Graphene Oxide in High Performance Mortarincorporating Ultrafine Slag Velchuri Sairam, C. L. Jejurkar, S. R. Korake, and Ankur Laxman Yadav

This study deals with the partial replacement of cement with ultrafine slag and addition of 0.1 % wt/volume water dispersed graphene oxide (GO) in 1:3 cement sand mortar at w/c ratio 0.30. The study initially focused on arriving at the optimum ultrafine slag replacement percentage to which varying dosages of water dispersed GO was added. An improvement in the compressive and flexural strength along with pore refinement, attributing to better resistance to water absorption and sorptivity was observed. However, the fluidity decreased with the increasing dosage of GO. The ultimate percentage increase with 0.05 % dosage of GO resulted in an increase of 66.88 % for compressive strength and 31.19 % for flexural strength at 28 days curing age. System with 0.10 % GO dosage exhibits the least water absorption percentage. Lowest sorptivity coefficient of 1.7 x 10-2 mm/sec1/2 was observed for mix with 0.05 % GO. Graphene oxide accelerates the rate of hydration along with acting as nano-scale fibers by filling the micro-pores and voids, attributing to the improved results. However, at higher levels, the agglomeration of GO contributes to the improper filling of voids. Field emission scanning electron microscope (FE-SEM) and X-ray diffraction test, performed to study the microstructure which indicated pore refinement and extensive C-S-H formation, implying improved strength. The optimum results were observed for the system with 15 % ultrafine slag replacement along with 0.05 % water dispersed GO.

Structural design for fire: results of fire load surveys and recommendations of building codes and standards Shreya Jadon, and Deepesh Singh

Fire growth in a compartment is mainly dependent on the amount of combustibles (fire loads) and the ventilation openings. The fire load surveys strongly correlate fire loads with compartment size and use. But the Indian code does not account for these variables and specify a constant value. The present codal values of fire loads need to be revised as the type of construction materials, furnishings and layouts of the modern buildings has been changed significantly in recent years. This paper critically reviews the fire loads recommended in the surveys, and, codes and standards to identify the gaps in the existing survey values and also suggest key parameters to be included in the future load surveys.