Indian Concrete Journal

Towards adoption of composite cements in India, produced using slag-limestone, fly ash-limestone and calcined clay-limestone combinations Yuvaraj Dhandapani, Manu Santhanam

Finely ground limestone is gaining prominence for cosubstitution with conventional supplementary cementing materials (SCMs) due to synergistic interactions in composite cements containing three components, i.e., clinker-limestoneSCM. In this study, concrete performance with composite cementitious blends with fly ash-limestone, slag-limestone and calcined clay-limestone was assessed with varying levels of limestone addition. The results show that choice of SCM is more critical in governing the performance of composite cements. While calcined clay and slag can accommodate up to 20 % limestone with synergistic performance enhancement compared to 30 % binary substitution, limestone addition of 10-15 % is recommended for fly ash to ensure sufficient mechanical and durability performance. As international standards are fast moving towards the standardisation of ternary blends containing SCM like slag, fly ash and calcined clay, along with limestone filler (up to 15-20 %), composite cement standards in India should make provisions for robust ternary binders containing slag-limestone, fly ash-limestone and calcined clay-limestone to allow rapid adoption of sustainable composite cement in the Indian construction industry

Validation and failure mechanism identification of reinforced concrete beam-slab systems with secondary beams using nonlinear finite element analysis tool Farooq Ahamed Shaik, Bijily Balakrishnan

Although experimental investigations on beam-slab systems have been conducted, there is a paucity of research dedicated to the numerical validation of these systems, particularly in predicting their failure mechanisms and complete loaddeflection behavior. The existing numerical investigations have largely concentrated on isolated systems, with little validation of intricate systems that include secondary beams and combined failure mechanisms. Addressing this gap, the current study introduces a numerical validation scheme for reinforced concrete beam-slab systems with secondary beams, utilising non-linear finite element analysis tools like Abaqus. The modelling technique encapsulates the interactive behavior between beams and slabs, including yield line formation in slabs and plastic hinge formation in beams. The obtained results are in good agreement with the experimental results in terms of failure mechanisms, collapse loads, and complete loaddeflection response

Use of hybrid steel fibre-reinforced concrete in construction of elevated slabs Sujatha Jose, Ravindra Gettu

One of the most promising applications of fibre reinforced concrete (FRC) is the construction of pile supported slabs in order to address the issues of differential settlement, cracking, or long-term serviceability problems due to soil structure interactions. As previous studies have shown the advantage of using a hybrid combination of amorphous metallic fibres (AMF) and hooked ended steel fibres (SF) in terms of an enhanced flexural performance due to synergistic effect, a comparative study of the design of pile supported slab with hybrid, as well as steel fibre alone, is described here, demonstrating the implications of hybrid combinations of steel and AMF in slab thickness. AMF increase first peak, contributing in Serviceability Limit State (SLS) and SF increase post cracking capacity, ductility in Ultimate Limit State (ULS) and are more competitive for redundant structural applications (such as slabs on ground). AMF is more advantageous for initial crack formation (extensibility) and it was found that their combinations lead to about 20 % reduction in slab thickness for elevated slabs applications, using similar total content of steel fibres.

Evaluation of mechanical properties of bamboo with different surface treatments and flexural behavior of bamboo reinforced concrete Jaimin Shah, J. D. Rathod

The flexure test was carried out on six bamboo-reinforced concrete beams using a universal testing machine and a linear variable differential transformer (LVDT) setup to determine the neutral axis and moment capacity according to Indian standard code. Mechanical properties of bamboo splints available locally in Gujarat are evaluated experimentally according to the Indian standard codes. The bond strength of bamboo splint with coir rolling, sand coating and epoxy coating on splints is evaluated and compared with plain bamboo splint. Sand coated bamboo splint exhibits 32 percent higher bond strength compared to other kinds of frictional enhancement. Neutral axis is located experimentally which is close to theoretical one. The bamboo reinforced beams displayed a moment capacity that was 100 percent more than the calculated moment capacity according to the working stress method. Tensile strength of bamboo is found to be 109.59 N/mm², while bond strength of sand coated bamboo is found to be 3 times higher than untreated bamboo. The sand coated bamboo beams exhibited load-bearing capacity 76 % higher than bamboo reinforced concrete (BRC) beams while, deflection at ultimate load is found to be 6.8 mm against 12 mm in plain BRC beams. Neutral axis is located between 11 to 73 mm from top experimentally which is in line with theoretical calculation.

Compressive and tensile strengths of ternary blended concrete and their xgboost prediction Ashok Kumar, Virendra Kumar, Sanjay Kumar

The article investigates studies the strength properties of ternary blended concrete (TBC) made of 70 % ordinary Portland cement (OPC), 24 % fly ash, and 6 % silica fume to reduce the environmental impact of concrete production. TBC grades M20 to M40 were tested for compressive, split tensile, and flexural strengths over 7–91 days. The results show that adding fly ash and silica fume to concrete boosts its long-term strength and durability from 7 to 28 days and up to 91 days. The study used the XGBoost algorithm to predict mechanical parameters of ternary blended concrete (TBC), achieving strong correlation values (R² > 0.7) for compressive, tensile, and flexural strength. The findings suggest Ternary blended systems can achieve concrete building sustainability and mechanical performance goals.