Indian Concrete Journal

Comparative study of OPC and PPC-based concrete properties containing bottom ash and fly ash as fine aggregate Soumyaranjan Panda, Monalin Pradhan, Saubhagya Kumar Panigrahi

Utilization of industrial wastes like bottom ash (BA) and fly ash (FA) as a complete replacement for natural fine aggregate (NFA) can solve their disposal issues and protect against the NFA depletion, leading to sustainable concrete production. The current manuscript aims to evaluate experimentally the effect of complete replacement of NFA by BA and FA combination at different proportions in ordinary Portland cement (OPC) and Portland pozzolana cement (PPC)-based M25 grade concrete through various fresh and hardened concrete properties. The optimal mix combination ratio between BA and FA is established and compared with the OPC and PPC-based control concrete with NFA. Noticing the concrete consistency both the slump cone (SC) and compaction factor (CF) tests were executed to monitor the workability changes. Performing the non-destructive test (NDT) (ultrasonic pulse velocity and rebound hammer test), destructive test (DT) (compressive and tensile testing), and durability (sorptivity, acid, and sulfate resistance testing) tests the optimal mix combination ratio was decided. The elucidation of different concrete property variations were established through scanning electron microscopy (SEM) tests. A dense, compact, uniform C-S-H gel distribution, ettringite needles formation, and deposits of portlandite big crystals are responsible factors for the notable hardened property development. The test results confirmed the complete replacement of NFA either by BA or FA yielded poor concrete and the BA (60 %) along with FA (40 %) combination yielded the most suitable concrete.

Self compacting concrete containing coarse recycled concrete aggregate an eco-friendly material Dinesh Kumar, V. V. L. Kanta Rao, Lakshmy Parameswaran

Utilization of recycled aggregates (RA) extracted from construction and demolition waste (CDW), for production of cement concrete, is a viable way to effectively dispose this waste and promote sustainability. This paper presents the experimental test results on the flow, mechanical and durability properties of a self compacting concrete (SCC) containing unprocessed coarse recycled concrete aggregate (CRCA) extracted from CDW. A SCC with a compressive strength of 40 MPa was prepared for the purpose. An aggregate mixture, containing CRCA and coarse and fine aggregates from natural sources, with least void ratio was obtained using aggregate packing density (APD) method. SCC mixes with CRCA (SCC-CRCA) content at 0, 20, 45, and 100 % (of the total coarse aggregate content), by weight, were prepared. Flow, mechanical and durability properties of the SCC mixes were investigated. The flow properties at 90 minutes were also tested to take into account the transit time of concrete to site. The test results indicated that the properties of SCC-natural coarse aggregate (NCA)-CRCA mixes were not significantly different vis-a-vis the SCC-NCA mix properties when NCA was replaced by CRCA up to 45 %, suggesting that higher quantities of un-processed CRCA can be used in cement concrete as against that recommended in IS specifications (i.e. 20 %) for normal (non-SCC) concrete.

Characterisation of alccofine cement paste with graphene oxide C. L. Jejurkar, S. R. Korake, V. Sairam, Sneha Joseph

Cement is one of the fundamental constituents of the construction industry. Since the production of cement leads to large emissions of greenhouse gases and many other environmental issues, attempts have been made to partially or fully replace cement for sustainable construction. In addition to this, researchers are done to incorporate pozzolans and nanomaterials to cement to enhance the cement composite’s strength and durability properties. However, only a few of these researchers study the effect on cement paste’s durability and microstructural behavior by integrating both graphene oxide and pozzolana. In this study, an experimental investigation is carried out on cement paste by replacing cement with Alccofine (AL) and Graphene Oxide (GO). The study was conducted with 10 % of Alccofine and 0, 0.01 and 0.02 % GO in cement paste. Reinforcement of GO in Alccofine cement paste improved its mechanical and durability properties.

A simplified model for analysis of RCC foundation resting on elastic subgrade Indrajit Chowdhury, Ronkoyel Tarafdar

It is an established fact that the behavior of a raft foundation or an isolated footing is governed by relative stiffness of the slab and underlying soil. Despite this appreciation, an isolated footing is usually designed as a rigid slab ignoring influence of the underlying soil deformation in most cases. This practice is in vogue due to ease of computation, as ascertaining the foundation behaviour considering deformation of soil and the interaction between them (often called soil structure interaction) is considered far too complex and laborious for day-to-day design office practice unless,finite difference or finite element numerical methods are considered through a computer analysis.

The present paper presents a simplified model for analysis of such foundations, considering soil-structure interaction(SSI) that can consider both flexible and rigid foundation under one generic formulation. No FEM analysis is required for the proposed method. A simple spreadsheet or a MathCad shell is sufficient to arrive at an acceptable result. The results reflect that conventional design gives a different result than when actual soil structure interaction between the foundation slab and soil is considered.