Indian Concrete Journal

Bending mechanical properties of fiber grid reinforced cement concrete pavement Wei Xu, Lihai Su, Jun Zhang, Bohan Yang, Wang Xu

In order to study the influence of fiber grid type, fiber grid surface treatment and maximum grain size of coarse aggregate on bending mechanical properties of cement concrete pavement, the beam bending tests and fatigue tests were respectively conducted. The reinforcement mechanism of fiber grid and cement concrete pavement was analyzed. The failure processes of the specimens were analyzed, the mechanical mechanism of the interaction between fiber grid and cement concrete was discussed. The research result shows that brittle failure characterizes the damage of the beam bending specimens. Fiber grid greatly improves the bending mechanical properties of cement concrete, and the bending strength of cement concrete is improved by 6.62 to 31.40 %. When coarse aggregate limiting grain size is 20 mm compared with 40 mm, the bending strength of cement concrete increases by 2.72 to 9.97 %. The bending strength of cement concrete is improved by 8.30 to 11.88 % when the fiber grid surface is treated with epoxy resin. The fatigue strength of fiber grid reinforced cement concrete is higher than that of the plain cement concrete, and the fatigue strength limit increases when the stress ration decreases.

Design aids for reinforced concrete circular columns with high strength steel R. K. Desai, N. Subramanian

Circular reinforced concrete columns provide good aesthetics. Circular columns will have same moments of inertia about any diametrical axes, resulting in same strength and stiffness about any of the diametrical axes of bending. Interaction curves are an inevitable requirement for design of columns subjected to axial load and moments. Design aids are available for Fe-415 and Fe-500 grades of steel in many text books and handbooks. Design aids published by Bureau of Indian Standards have been very useful for the designers from the past four decades. However, the design aids in the form of interaction curves for columns with high strength steels like Fe-550 and Fe-600 grades are scarce. With the availability of high strength steels, the usage of the same is increasing. Considering this requirement, an attempt is made in this paper to derive the required mathematical formulae and suggest a systematic step by step procedure to formulate interaction curves for circular columns with any grade of steel. As the procedure suggested involves iterative computations using a systematic approach, it is wellsuited to be developed as a computer program. The typical output of such a program has been validated and presented for circular columns for HYSD Fe-600 grade of steel in the form of interaction curves. The mathematical formulae and the step by step procedure suggested can be easily modified for circular columns subjected to axial tension and moment. The formulae and step by step procedure presented here are so generic in nature that, once the design stress-strain curve of steel is known, interaction curves can be plotted for any grade of steel including mild steel, high yield strength deformed (HYSD) bars and thermo-mechanically treated (TMT) bars.

Study on sintered fly ash aggregate (SFA) properties in comparison to IS: 9142-2 (2018) and its durability Hemanta Kumar Ram

As there is ever increasing demand of coarse aggregate for construction of concrete based infrastructure in India, the Indian construction industry is encountering grave problems due to scarcity of optimum quality coarse aggregate. India as a developing country demands humongous concrete requirements wherein coarse aggregate have a crucial role to play. The coarse aggregates are generally excavated enormously from mountains, hills, stone quarries etc. and crushed into various sizes, which jeopardizes our obligation towards mother earth by depleting our mountains, creating environmental hazards, deforestation on large scale to name a few. Thus we must imperatively contemplate an alternate way out to deal with this precarious menace. Amid all cognizable apparent sources of coarse aggregate, the sintered fly ash aggregate (SFA) can be considered on the cutting age holistically. The production process of SFA utilizes about 90 to 95 % of fly ash, a hazardous waste generated from thermal power stations. Thus, a meticulous evaluation of mechanical and chemical properties of SFA was required to be conducted in respect to the IS: 9142-2 (2018)^[1] to establish its credentials. The study further presents the durability of concrete made with SFA, including compressive strength, splitting tensile strength, flexural strength, setting time and permeability. The obtained test results including the results of concrete durability were found to be within the standard limit.

Performance assessment of steel slag aggregates as partial replacement of river sand in concrete Arjun S., Hemalatha T., Rajasekaran C.

In order to bring sustainability in construction, nowadays, many industrial solid wastes are used as a partial replacement for cement as well as aggregates. Using industrial wastes in construction solves dual problem of waste disposal and depletion of natural resources. Steel aggregate is one such industrial solid waste having potential to replace the conventional river sand. In this study, an attempt has been made to investigate the performance of steel slag aggregates in concrete as a partial replacement for conventional river sand. Three mixes were made for this study, first mix made of ordinary Portland cement (OPC) and 100 % river sand (₀M⁰), second mix (₀M⁵⁰) made of OPC and 50 % river sand replaced by slag aggregates and third mix (₂₅M⁵⁰) made of 25 % fly ash and 75 % OPC, and 50 % slag aggregates. Tests for assessing the mechanical and durability properties were conducted. The results showed that the strength and durability of concrete made with steel slag aggregate and river sand were comparable. This study shows the suitability of using 50% steel slag aggregates as a partial replacement for river sand in concrete.

High dynamic range images and support vector machine algorithm for damage identification on concrete structures Arulmozhi Priya N., Sivasubramanian K., Sofia Rajesh

The present work proposes to adopt and investigate the applicability of high dynamic range (HDR) images for the identification and quantification of damages in concrete structures. In this work, support vector machine (SVM) algorithm which is a popular artificial intelligent algorithm has been used for classification and identification of the damage regions. The SVM algorithm is primarily trained to identify and classify the damage region. Based on the training, a SVM model is developed which is later used for the identification of the damage region. On further processing, the quantification of the damage region becomes possible. In the present work, four images with different types of damage on concrete structures have been selected. The damage identification and quantification have been carried out using the SVM algorithm. From the results, it has been observed that the application of SVM algorithm on HDR images can be used to effectively identify and quantify damages in concrete structures.