Indian Concrete Journal

Utilization of air-cooled blast furnace slag as a 100 % replacement of river sand in mortar and concrete Smrati Jain, Manu Santhanam, Rakesh S., Anil Kumar, Ajay Kumar Gupta, Ritesh Kumar, Subhadra Sen, R. V. Ramna

The steel industries generate millions of tons of slag as byproduct during their production stages. This slag is classified according to its origin and form of cooling conditions. The slag that is slowly cooled is called air-cooled blast furnace slag (ACBFS). Crystalline nature is observed in ACBFS slag because of slow cooling by air. As per IS: 383 (2016), a maximum of 50 % replacement of natural sand with iron slag sand is allowed in plain concrete. The aim of this study is to evaluate the feasibility of using ACBFS as a replacement of river sand in mortar and plain concrete at replacement levels of 0 %, 25 %, 50 %, 75 %, and 100 % by weight. The effect of ACBFS replacement levels of river sand on workability, pull-off strength, and compressive strength of mortar system is studied. Further, the effect of ACBFS replacement levels on fresh, mechanical and durability properties of concrete is studied. Compressive strength, elastic modulus, and split tensile strength of concrete at different replacement levels is evaluated. A detailed study on durability properties such as water sorptivity, water absorption, porosity, and total charge passed in rapid chloride permeability (RCPT) is conducted. The replacement of river sand with ACBFS sand has shown no detrimental effect on the properties studied for both mortar and concrete. The concrete with increasing replacement levels of ACBFS sand showed reduction in porosity and absorption, although, the ACBFS sand has higher water absorption. The ACBFS can be considered as a suitable substitute for river sand for even 100 % replacement.

Flexural behavior of FA/GGBFS based reinforced geopolymer concrete beams Sanjay Kumar, S. Jeeva Chithambaram

Geopolymers are innovative and eco-friendly construction materials that are produced by the activation of aluminosilicates with alkaline activator solutions. Experimental work is done to create geopolymer concrete using industrial by-products that are readily available locally and to analyse the flexural behavior of GPC that has been cured at room temperature. To enable ambient curing of geopolymer concrete, Fly ash is utilised as the main source material and is partially substituted by 10 percent, 20 percent, 30 percent, and 40 percent ground granulated blast furnace slag (GGBFS) content. Alkaline activator solutions have been created by mixing Sodium silicate (Na₂SiO₃) with sodium hydroxide (NaOH) in a ratio of 2.5. The qualities of freshly-prepared and hardened geopolymer concrete (GPC) are investigated using the slump test and the compressive strength test. To evaluate the flexural behavior, 150 mm × 200 mm × 1500 mm geopolymer concrete beams were cast, cured at room temperature, and tested after 28 days. According to experimental findings, a GPC mix with a 12 M NaOH concentration and 30 percent GGBFS content as a partial replacement for fly ash had the highest compressive strength of 40 N/mm². Furthermore, it is evident that the spread of flexural cracks was found to be the cause of the collapse of reinforced geopolymer concrete beams.

The behavior of different RCC joints under various loading conditions: A review Pranoy Roy, Amiya Kumar Samanta

For the analysis of reinforced concrete frames, beams-column joints are generally assumed as rigid. In practice much attention is not given and the joint is usually neglected for specific joint core design, with attention being restricted to anchorage for longitudinal reinforcement in beams. This is quite acceptable for structures designed for gravity loading only, where the frame is not subjected to seismic loads. The collapse of structures during the past earthquakes has indicated the importance of proper joint design for lateral forces. Hence an attempt is made to understand the behavior of joints under different loading conditions and summarize their behavior through this study.

Load transfer mechanism for jointed plain concrete pavements: A review Jeetendra Singh Khichad, Rameshwar J. Vishwakarma, Ramakant K. Ingle

Sustainable and efficient transportation infrastructure is the main requirement of developing countries like India. Road construction plays an important role for the development. Among the numerous pavement types used in road construction, the rigid pavements are proved superior than others in factors like durability, reduction in maintenance, and temperature susceptibility. The initial cost of construction of concrete pavements is more but it can be optimized by proper design and construction practices. Jointed plain concrete pavements (JPCP) are constructed with the joints at certain spacing on the road. Various factors such as concrete properties, loading types, wheels positioning, and joint spacing between slabs affect the load transfer mechanism at the joints. In JPCP effective load transfer at the joints take place either by shear action using aggregate interlock or by providing mechanical devices such as dowel bars. This paper critically reviews the load transfer mechanism at joints. A detailed study is carried out on the behavior of pavement considering factors which affect the efficiency of joints. The article concludes with important recommendations which can enhance the performance of concrete pavements. The factors like aggregate interlocking, dowel bars, misalignment of dowels, size of voids beneath the slab, and crack width are considered to analyse the effect on the load transfer at joints. From the review of literature, it is seen that the dowel bars must be provided for thicker pavements carrying heavy traffic. Proper alignment of the dowel is necessary for the better load transfer at joints. Misalignment of the dowel may lead to failure due to cracking of slab.

Design and detailing of shear studs in composite beams: A critical review N. Subramanian

The advantages of concrete, which is strong in compression, and steel, which is better to resist tensile forces, are better utilized in composite steel-concrete construction. This will result in a considerable economy for bridges and high-rise buildings. To connect the beam and concrete elements, automaticallywelded headed studs are used extensively. These shear studs prevent vertical separation of the concrete and the steel element and transmit longitudinal shear along the contact surface. The behavior of the shear studs while resisting the shear flow is explained both with respect to composite slabs and composite slabs with profiled sheeting, which are often used for the advantage of eliminating the formwork. Although the draft IS: 11384 (2019)^[13] contains equations for the design of shear studs for composite solid slabs, these equations are not applicable to composite slabs using the profiled deck. Hence, the provisions available in other national codes are discussed. The rules for detailing shear studs based on empirical methods and also given in other national codes are compared.