Suhas Vijay Patil, K. Balakrishna Rao and Gopinatha Nayak
Recycling construction waste is a promising way towards sustainable development in construction. Recycled aggregate (RA) is obtained from demolished concrete structures…
Abstract
Purpose
Recycling construction waste is a promising way towards sustainable development in construction. Recycled aggregate (RA) is obtained from demolished concrete structures, laboratory crushed concrete, concrete waste at a ready mix concrete plant and the concrete made from RA is known as RA concrete. The purpose of this study is to apply multiple linear regressions (MLRs) and artificial neural network (ANN) to predict the mechanical properties, such as compressive strength (CS), flexural strength (FS) and split tensile strength (STS) of concrete at the age of 28 days curing made completely from the recycled coarse aggregate (RCA).
Design/methodology/approach
MLR and ANN are used to develop a prediction model. The model was developed in the training phase by using data from a previously published research study and a developed model was further tested by obtaining data from laboratory experiments.
Findings
ANN shows more accuracy than MLR with an R2-value of more than 0.8 in the training phase and 0.9 in a testing phase. The high R2-value indicates strong relation between the actual and predicted values of mechanical properties of RCA concrete. These models will help construction professionals to save their time and cost in predicting the mechanical properties of RCA concrete at 28 days of curing.
Originality/value
ANN with rectified linear unit transfer function and backpropagation algorithm for training is used to develop a prediction model. The outcome of this study is the prediction model for CS, FS and STS of concrete at 28 days of curing.
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Adithya Tantri, Gopinatha Nayak, Adithya Shenoy and Kiran K. Shetty
This study aims to present the results of an experimental evaluation of low (M30), mid (M40) and high (M50) grade self-compacting concrete (SCC) with three nominal maximum…
Abstract
Purpose
This study aims to present the results of an experimental evaluation of low (M30), mid (M40) and high (M50) grade self-compacting concrete (SCC) with three nominal maximum aggregate sizes (NMAS), namely, 20 mm, 16 mm and 12.5 mm, with Bailey gradation (BG) in comparison with Indian standard gradation (ISG).
Design/methodology/approach
This study was conducted in a laboratory by testing the characteristics of fresh and hardened properties of self-compacting concrete.
Findings
Rheological and mechanical properties of SCC were evaluated in detail and according to the results, a concrete sample containing lower NMAS with BG demonstrated improvement in modulus of elasticity and compressive strength, while improving the rheological properties as well. Meanwhile, SCC demonstrated poor performance in split tensile and flexural strengths with lower NMAS gradations and a direct correlation was evident as the increase in NMAS caused an increase in the strength and vice-versa.
Originality/value
Upon comparison of BG with ISG, it was revealed that BG mixes succeeded to demonstrate superior performance. From the material optimization, rheological and mechanical performance study, it is recommended that BG with NMAS 16 mm can be used for conventional SCC.
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Amrutha, Gopinatha Nayak, Mattur Narasimhan and S. Rajeeva
Quite often, concrete in structures is likely to get exposed to high temperatures, including an incident of fire. The strength-retention properties of concrete after such an…
Abstract
Quite often, concrete in structures is likely to get exposed to high temperatures, including an incident of fire. The strength-retention properties of concrete after such an exposure are of great importance in terms of the serviceability of buildings. This paper presents an experimental study on the strength retention and impermeability aspects of a set of self compacting, high-volume fly ash concrete mixes under elevated temperatures. Five selfcompacting concrete mixes with a higher 60% level of cement replacement with fly-ash, are designed and the effects of elevated temperatures, in the range of 200-800°C, on the physical, mechanical and durability properties of these mixes are assessed. The assessment is in terms of the weight losses and the reduction in the compressive strengths of concrete cubes and split tensile strengths of concrete cylinders. The durability characteristics are assessed in terms of RCPT test results on these mixes. Performances of these self compacting concrete mixes (SCC) at elevated temperatures are also compared with two normally-vibrated concrete mixes (NCs) of an equivalent M30 strength grade. Test results indicate that weight of the specimens significantly get reduced with an increase in the level of elevated temperature, with sharp variations beyond 600°C. The experimental results also show that large improvements against chloride-ion penetration and better strength-retention at higher temperatures can be realized with self-compacting high-volume fly-ash concrete mixes additionally admixed with GGBFS and silica fume.