Durability properties of fly ash and silica fume blended concrete for marine environment

1803-1812The improvement in durability and strength by replacing the conventional components with supplementary materials in concrete is one of the recently focused areas in concrete technology. From the previous till the recent times serious efforts have been taken to improve the structural adequacy and durability characteristics of concrete so as to efficiently replace the usual conventional concrete. In this present research work, the mechanical and durability properties of the concrete blended with fly ash (FC) and silica fume (SC) are studied in detail. The partial replacement of cement with silica fume and fly ash in the concrete improves the overall property of the concrete, gives a way for the reuse of the supplementary material to be efficiently brought back giving a cleaner environment. The fly ash is used with the replacement percentages of 10, 15 and 20 of the cement whereas for silica fume the replacement percentages are 8, 10 and 12, respectively. Also the study is extended to combination mixes to test the strength and durability and it has been found that the increase in the percentage of the silica fume increases the strength reduces the workability and permeability to a high extent and the inclusion of the fly ash paves a way for the increase in the durability property. The effect of the cementitious material with FC and SC on the concrete is compared with the nominal concrete and also the suitability in the usage of marine environment is validated in accordance with the International codes

A Study on the Prediction of Compressive Strength of Self-Compacting Recycled Aggregate Concrete Utilizing Novel Computational Approaches

[EN] A considerable amount of discarded building materials are produced each year worldwide, resulting in ecosystem degradation. Self-compacting concrete (SCC) has 60–70% coarse and fine particles in its composition, so replacing this material with another waste material, such as recycled aggregate (RA), reduces the cost of SCC. This study compares novel Artificial Neural Network algorithm techniques—Levenberg–Marquardt (LM), Bayesian regularization (BR), and Scaled Conjugate Gradient Backpropagation (SCGB)—to estimate the 28-day compressive strength (f’c) of SCC with RA. A total of 515 samples were collected from various published papers, randomly splitting into training, validation, and testing with percentages of 70, 10 and 20. Two statistical indicators, correlation coefficient (R) and mean squared error (MSE), were used to assess the models; the greater the R and lower the MSE, the more accurate the algorithm. The findings demonstrate the higher accuracy of the three models. The best result is achieved by BR (R = 0.91 and MSE = 43.755), while the accuracy of LM is nearly the same (R = 0.90 and MSE = 48.14). LM processes the network in a much shorter time than BR. As a result, LM and BR are the best models in forecasting the 28 days f’c of SCC having RA. The sensitivity analysis showed that cement (28.39%) and water (23.47%) are the most critical variables for predicting the 28-day compressive strength of SCC with RA, while coarse aggregate contributes the least (9.23%).S

Utilization of steel slag in development of sustainable and durable concrete.

This paper reflects the results of an experimental investigation of the strength, permeability, abrasion, carbonation, and shrinkage characteristics of concrete containing various percentages of steel slag as partial replacement of natural fine aggregates. M 30 Grade concrete was designed as per specific national specifications. Steel slag was used to replace natural sand in the range of 0– 50%. It was observed that the steel slag blended concrete with up to 50% substitution exhibited a comparable compressive and flexural strength when compared to the control specimens. From the Dorry’s abrasion test, it was noted that the specimens could be implemented in heavy-duty floor tiles and even extended to pavement construction. The shrinkage strains, water permeability, and carbonation of steel slag blended concrete were observed to be increasing with increasing replacement amounts of steel slag in the place of natural fine aggregates. The concrete containing steel slag replacing up to 40% of natural fine aggregates can be recommended for all heavy load involving structural applications, and substitution levels beyond 40% could be recommended for non-structural applications, pavements, etc

Influence of Design Parameters on Fresh Properties of Self-Compacting Concrete with Recycled Aggregate—A Review

[EN] This article presents an overview of the bibliographic picture of the design parameter’s influence on the mix proportion of self-compacting concrete with recycled aggregate. Design parameters like water-cement ratio, water to paste ratio, and percentage of superplasticizers are considered in this review. Standardization and recent research on the usage of recycled aggregates in self-compacting concrete (SCC) exploit its significance in the construction sector. The usage of recycled aggregate not only resolves the negative impacts on the environment but also prevents the usage of natural resources. Furthermore, it is necessary to understand the recycled aggregate property’s role in a mixed design and SCC properties. Design parameters are not only influenced by a mix design but also play a key role in SCC’s fresh properties. Hence, in this overview, properties of SCC ingredients, calculation of design parameters in mix design, the effect of design parameters on fresh concrete properties, and the evolution of fresh concrete properties are studied.S

Impact of Design Parameters on the Ratio of Compressive to Split Tensile Strength of Self-Compacting Concrete with Recycled Aggregate

[EN] Most concrete studies are concentrated on mechanical properties especially strength properties either directly or indirectly (fresh and durability properties). Hence, the ratio of split tensile strength to compressive strength plays a vital role in defining the concrete properties. In this review, the impact of design parameters on the strength ratio of various grades of Self-Compacting Concrete (SCC) with recycled aggregate is assessed. The design parameters considered for the study are Water to Cement (W/C) ratio, Water to Binder (W/B) ratio, Total Aggregates to Cement (TA/C) ratio, Fine Aggregate to Coarse Aggregate (FA/CA) ratio, Water to Solid (W/S) ratio in percentage, superplasticizer (SP) content (kg/cu.m), replacement percentage of recycled coarse aggregates (RCA), replacement percentage of recycled fine aggregates (RFA), fresh density and loading area of the specimen. It is observed that the strength ratio of SCC with recycled aggregates is affected by design parameters.S

Effect of Design Parameters on Compressive and Split Tensile Strength of Self-Compacting Concrete with Recycled Aggregate: An Overview

[EN] One of the prime objectives of this review is to understand the role of design parameters on the mechanical properties (Compressive and split tensile strength) of Self-Compacting Concrete (SCC) with recycled aggregates (Recycled Coarse Aggregates (RCA) and Recycled Fine Aggregates (RFA)). The design parameters considered for review are Water to Cement (W/C) ratio, Water to Binder (W/B) ratio, Total Aggregates to Cement (TA/C) ratio, Fine Aggregate to Coarse Aggregate (FA/CA) ratio, Water to Solid (W/S) ratio in percentage, superplasticizer (SP) content (kg/cu.m), replacement percentage of RCA, and replacement percentage of RFA. It is observed that with respect to different grades of SCC, designed parameters affect the mechanical properties of SCC with recycled aggregates

Effect of pores on the mechanical and durability properties on high strength recycled fine aggregate mortar

[EN] Larger consumption of natural fine aggregates (NFA) leads to an increase in cost, energy, and negative environmental impact. On the contrary, the larger production of construction waste results in the generation of recycled fine aggregate (RFA), which requires safe disposal. The aim of study, is to the hunt for such alternatives, compares the mortar mechanical and durability properties with and without RFA. High strength mortar specimens were produced with mix proportion as 1:3 using RFA as partial replacement for NFA as 0%, 25%, 50% and 100%. The mechanical and durability performance of all specimens was assessed in the terms of compressive strength, flexural strength, water absorption and mercury intrusion porosimetry. Mechanical performance is confirmed by microscopic studies. The main results display that the mortar with 25% of RFA, performed better, which are related to pore structures and their distribution. It is noted that the, pores also increase with the increase in RFA content. The effect of pores on the strength and their relationships are assessed.SIAuthor wish to thank for the supports and guidance given by faculties from University of Leon, Leon, Spain and Coimbatore Institute of Technology, Coimbatore, Indi

Outcome of delayed versus immediate casting on spasticity of lower limb muscles in cerebral palsy post-botulinum toxin injection

Background: Botulinum toxin type A (BTX-A) is widely used to treat spasticity in children. The optimal strategy for the combined treatment of casting and BTX-A injections is not known. This prospective study is conducted to know the functional outcome of immediate versus delayed casting post-BTX-A injection in children with cerebral palsy (CP). Aims and Objectives: The aim of this study is to compare delayed versus immediate casting as an adjunct to botulinum toxin therapy for spasticity of lower limb muscles in CP. The objectives of the study are to test the hypothesis that delayed casting is superior to immediate casting post-botulinum toxin injection and to know the feasibility of using the Edinburgh visual gait score (EVGS) as a single qualitative and quantitative outcome measure. Materials and Methods: A prospective study is conducted to compare immediate casting with delayed casting post-botulinum toxin injection to spastic lower limb muscles in patients with CP from July 2018 to February 2019. Inclusion criteria: A diagnosis of CP with associated spastic monoplegia, diplegia, or hemiplegia with aided or unaided ambulation. Exclusion criteria: History of orthopedic surgery in the preceding 12 months; selective dorsal rhizotomy; mixed CP; ataxia; athetosis; non-ambulatory subjects. Results: The botulinum toxin injection + delayed POP casting group fared better in terms of clinical and functional outcome (as shown by improved EVGS scores) in our study. Conclusion: There is a clear benefit in delaying casting after the injection of Botulinum toxin in the recurrence of spasticity

Enhanced fresh and hardened properties of foamed concrete modified with nano-silica

Nowadays, the application of nanotechnology has gained increased attention in the concrete technology field. Several applications of concrete require light weight; one such concrete used is foamed concrete (FC), which has more voids in the microstructure. In this study, nano-silica (NS) was utilized, which exhibits a pozzolanic nature, and it reacts with other pozzolanic compositions (like lime, alumina, etc.) to form hydrated compounds in concrete. Apart from these hydrated compounds, NS acts as a filler material and enhances properties of concrete such as the fresh and hardened properties. This research examines the fresh, hardened, and microstructural properties of FC blended with NS. The ratio of binder and filler used in this research is 1:1.5, with a water-to-binder ratio of 0.45 and a density of 880 kg/m3. A total of six different weight fractions of NS were added to FC mixes, namely 0%, 1%, 2%, 3%, 4%, and 5%. Properties assessed for FC blended with NS were the slump, bulk density, strength parameters (flexural, splitting tensile, and compressive strengths), morphological analysis, water absorption, and porosity. It was concluded from this study that the optimum NS utilized to improve the properties was 3%. Apart from this, the relationship between the mechanical properties and NS dosages was developed. The correlations between the compressive strength and other properties were analyzed, and relationships were developed based on the best statistical approach. This study helps academicians, researchers, and industrialists enhance the properties of FC blended with NS and their relationships to predict concrete properties from other properties

Development of ultra-lightweight foamed concrete modified with silicon dioxide (SiO2) nanoparticles: Appraisal of transport, mechanical, thermal, and microstructural properties

Over the last few decades, researchers have devoted significant consideration to the use of nanoscale elements in concrete. Silicon dioxide nanoparticles (SDNs) have been a popular subject of study among the several types of nanoparticles. This article describes the findings of a laboratory investigation that examined the properties of ultra-lightweight foamed concrete (ULFC) including different proportions of SDNs. Wide range of the properties was evaluated specifically the slump flow, density, consistency, flexural strength, modulus of elasticity, compressive strength, split tensile strength, thermal properties, porosity, water absorption, sorptivity, intrinsic air permeability, and chloride diffusion. Additionally, the scanning electron microscopy (SEM) and pore distributions analyses of different mixes were done. Results confirmed a noticeable increase in the mechanical properties of ULFC, with respective improvements in the 28-day compressive, split tensile, and flexural strengths of up to 70.49%, 76.19%, and 51.51%, respectively, at 1.5% of the SDNs inclusion. However, further increases in the SDNs percentage did not result in remarkable enhancements. As the SDN percentage increased from 1.5% to 2.5%, the ULFC's sorptivity, porosity, water absorption, intrinsic air permeability, and chloride diffusion showed substantial improvements. When compared to the control sample, ULFC with SDNs demonstrated higher thermal conductivity values. The reason for this occurrence was determined to be the smaller pore size observed in the ULFC specimens containing SDNs. A great adjustment in the distribution of pore diameters was witnessed in the ULFC mixes when the percentages of SDNs were adjusted. The ULFC specimens, which included SDNs at the percentages of 0.5%, 1.0%, and 1.5%, indicated a reduction in the total number of large voids measuring 500 nm or more, compared to the control ULFC specimen. The findings of this study highlight the potential benefits of incorporating SDNs into ULFC, which may improve its overall properties