This paper presents analysis and comparison into mechanical behaviour and microstructural attributes of postweld heat-treated AISI 1020 (0.21%-C) plates joined by the shielded metal arc welding (SMAW) process. The purpose of this work is to heat the welded samples uniformly so that a possible formation of austenite can be obtained, and hence, residual stresses, if any, can be recovered. Four pairs of such steel were taken and welded to form four joints. Welding was followed by heat treatment. The heating temperature and holding time were selected as 1040°C and 60 minutes, respectively. Different cooling media such as sand, water, oil, and air were used to cool the samples. Hence, there were four different samples according to their physical conditions: sand-cooled, water-quenched, oil-quenched, and air-cooled. For analysing mechanical behaviour of all the plates, standard-shaped specimens were prepared out of them. The tensile strength, impact strength, hardness, and the microstructural attributes were analysed in four welded samples after heat treatment. Significant variations in tensile strength and hardness were reported when compared with each other. Oil-cooled sample showed a remarkable enhancement in tensile strength. The sand-cooled sample possessed the highest toughness, whereas water-quenched samples were found to be highly hard. Furthermore, a good combination of strength, hardness, and ductility was reported in oil-cooled sample. Pearlite (coarse and fine) and martensite were the main microstructural findings in the study. A clear vision of ferrite, cementite, and martensite on various heat-treated samples made this study important. All the mechanical properties are in good corroboration with microstructure. A significant refinement into all the mechanical properties was achieved in this work.

This paper presents the experimental investigation of the load-resisting characteristics of damaged columns repaired with glass reinforced polymer (GFRP) jacketing. The high-strength columns were made with ground granulated blast furnace slag (GGBS) used at 15%, 25%, and 35% as a partial substitute for cement. Cube specimens of size 100 mm × 100 mm × 100 mm and columns of size 600 mm × 120 mm were cast to perform the study. Considering the practical difficulties in the construction field in obtaining river sand, industrial sand was used for making the specimens eco-friendly. On completion of the prescribed curing period of 28 days, the cube specimens were subjected to a compression test to ensure the grade of the mix design, and the column specimens were subjected to axial loading and were tested in two categories, with and without wrapping of GFRP sheets’ split tensile strength. Compression tests on cubes and columns were done. The nondestructive test was also performed with the ultrasonic pulse velocity (UPV) method to check the dense nature of the concrete before and after wrapping with GFRP. On comparing the results, it was observed that it is possible to obtain a higher strength using industrial sand when supported with suitable admixtures and strengthening processes.

This paper discusses the possibility of developing a lightweight self-compacting concrete (SCC) with self-curing capabilities. In this regard, a supplementary cementitious material metakaolin, a presoaked lightweight expanded clay aggregate (LECA), and a chemical agent, superabsorbent polymer (SAP), were incorporated in developing a self-compacting self-curing concrete possessing a target strength of 60 MPa through experimental investigations, and the results are reported. The research includes an analysis of basic material properties of constituent materials including fresh properties of concrete and mechanical properties such as compressive and splitting tensile strength. It was inferred from the experimental results that utilization of self-curing agents in SCC has enhanced the mechanical properties when compared with conventional SCC mix. In particular, a combination of 0.3% SAP and 15% LECA gave the optimum strength values. The optimum usage limit of both the materials is presented in this study, and the results prove that SCC can be used as an alternate resource without disturbing the natural resources.

Black cotton soils, which are expansive, are present in abundance in Ethiopia. This type of soil possesses expansion when saturated with water and contraction during hot seasons, due to which it is labelled as “weak soil.” They may remain a threat to the structures if they are constructed over them without precautions. The quality of such soils can be improved by treating them with suitable stabilizers or soil reinforcers. This paper discusses the chances of using the second waste of plastic bottles as a reinforcer to strengthen weak black cotton soils in Ethiopia. Second, plastic bottle waste was added at 1%, 2%, 3%, 5%, 7%, and 9% to the soil, and numerous trials were conducted to ensure the reliability of the results. The effects were analyzed based on the results from the Atterberg limit tests, compaction tests, unconfined compression strength (UCS) tests, and the California bearing ratio test (CBR) for soaked and unsoaked conditions. The results were compared against the natural soil results, and the optimum usage percentage of second waste plastic required to reinforce the soil was reported. The results indicate that among the various properties used, the mix with 2% second waste plastic is effective with numerous trials being conducted to ensure the reliability of the results and decreased values of OMC by 18.5%, increased MDD by 1.9%, increased CBR by 50.9%, and increased UCS by 10.1%. Thus, the research provides a novel technique to recycle plastic waste once again as soil reinforcement, thereby saving the environment from dumped waste.

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