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1 – 10 of over 17000
Article
Publication date: 21 May 2021

Shemin T. John, Athul Mohan, Merin Susan Philip, Pradip Sarkar and Robin Davis

Timely removal of formwork is one of the crucial aspects of construction management that directly influences the safety and quality of the structure as well as the economy…

Abstract

Purpose

Timely removal of formwork is one of the crucial aspects of construction management that directly influences the safety and quality of the structure as well as the economy of the project. Code recommendations in this regard are not widely practiced because of the difficulties in their implementations. Also, such code recommendations are not robust for all the possible construction conditions. The present paper proposes an IoT-enabled system that notifies the minimum striking time of vertical formwork based on a specified target compressive strength.

Design/methodology/approach

An IoT device is proposed for the timely removal of vertical formwork by monitoring of early age concrete compressive strength in real-time. The maturity method is utilized for this purpose. The implementation of the proposed system is demonstrated on three concrete columns. The proposed system is found to be suitable for any construction condition.

Findings

The proposed system is a novel, cost-effective, IoT-enabled real-time monitoring system which includes features like cloud connectivity and remote monitoring. This system can be easily implemented at the site without any human intervention.

Practical implications

The study explores the development of an IoT device for the timely removal of vertical formwork which will ensure quality, safety and productivity in concrete construction.

Originality/value

This paper is the first attempt to determine the minimum striking time of vertical formwork using IoT-based technology.

Details

Engineering, Construction and Architectural Management, vol. 29 no. 5
Type: Research Article
ISSN: 0969-9988

Keywords

Article
Publication date: 2 September 2019

Faezeh Nejati and S.A. Edalatpanah

The purpose of this paper is to investigate the effect of steel and carbon fibers on the mechanical properties of light concrete in terms of tension strength, compressive…

73

Abstract

Purpose

The purpose of this paper is to investigate the effect of steel and carbon fibers on the mechanical properties of light concrete in terms of tension strength, compressive strength and elastic modulus under completely dry and wet conditions.

Design/methodology/approach

In this study, the lightweight concrete made of Light Expanded Clay Aggregate (LECA) as coarse aggregate and sand as fine aggregate was used. To achieve a compressive strength of at least 20 MPa, microsilica was used 10 percent by weight of cement. In order to compensate for the reduction of tension strength of concrete, steel and carbon fibers were used with three volume ratio of 0.5, 1 and 1.5 percent in concrete. The results of concrete specimens were studied at the age of 7, 28, 42 and 90 days under controlled dry and wet conditions.

Findings

The results showed that the addition of steel and carbon fibers to the concrete mixture would reduce the drop in slump. Also, the use of steel and carbon fibers plays a significant role in increasing the tension strength of the specimens. Furthermore, the highest increase in tension strength of steel and carbon fiber samples was 83.3 and 50 percent, respectively, than the non-fibrous specimen when evaluated at 90 days of age. Moreover, the steel and carbon fiber increased the water absorption of the samples. Adding steel and carbon fibers to a lightweight concretes mixture containing LECA aggregates plays a significant role in increasing the modulus of elasticity of the samples. The highest increase in the elastic modulus of steel and carbon fibers was 18.9 and 35.4 percent, respectively, than the non-fibrous specimen at 28 days of age.

Originality/value

In this paper, the authors investigated the mechanical properties of steel fiber and carbon reinforced concrete. Also, according to the conditions of storage of samples and the age of concrete (day), the experiments were carried out on samples.

Details

International Journal of Structural Integrity, vol. 11 no. 2
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 25 April 2022

Ayoub Abou Houraira, Abdellah Ouali, Ouafa Elhammoumi and Ahmed Fekri

Morocco is facing climate change, as shown by national studies conducted to date. The purpose of our research work is, on one hand, to develop an experimental protocol;…

Abstract

Purpose

Morocco is facing climate change, as shown by national studies conducted to date. The purpose of our research work is, on one hand, to develop an experimental protocol; simulating the Moroccan climate, through exposing concretes to accelerated aging in different cycles of temperature variation (+5 to +40 C°) and humidity (60–98% RH) and on another hand, to determine the effect of exposure to temperature and humidity variation cycles on the durability indicators (of concrete [with and without thermal cure]).

Design/methodology/approach

For this purpose, three classes of concrete were studied (C35, C40 and C55). Each class of concrete was considered first with no addition of silica fume (SF) and then with a 10% addition of SF. The concrete samples underwent three types of conditioning before performing the tests. The control concretes (Ct) were demoulated after 24 h and stored under stable temperature and humidity conditions (20 ± 2 °C and 80% ± 5 RH). Treated concretes (CV) demouled after 24 h and exposed to 300 cycles of 12 h of temperature and moisture variation in a climate chamber. And finally, concretes that have undergone a heat cure (CTV) for 5 h at 90 °C, were then removed from the mold and exposed to temperature and moisture variations cycles identical to treated concrete (CV).

Findings

The results obtained show that aging accelerated by temperature change, and humidity improves durability indicators compared to Ct. Concretes that have undergone a thermal cure, followed by accelerated aging, show an improvement in durability indicators between 50 and 200 cycles, but the performance of concrete decreases after 200 exposure cycles. The addition of SF plays a beneficial role in the durability of concrete in the three exposure environments.

Originality/value

The originality of the work is, to develop an experimental protocol, simulating the Moroccan climate, through exposing concretes to accelerated aging in different cycles of temperature variation (+5 to +40 C°) and humidity (60–98% RH) and on another hand, to determine the effect of exposure to temperature and humidity variation cycles on the durability indicators of conventional concrete (with and without thermal cure).

Details

International Journal of Building Pathology and Adaptation, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2398-4708

Keywords

Article
Publication date: 19 December 2019

Huijun Wu

The purpose of this paper is to research the hardened properties of non-dispersible concrete in seawater environment, especially in seawater environment.

Abstract

Purpose

The purpose of this paper is to research the hardened properties of non-dispersible concrete in seawater environment, especially in seawater environment.

Design/methodology/approach

The main approach is according to the experiment.

Findings

The findings of this paper are: first, because of the washing effect of water, the strength of underwater non-dispersible concrete is lower than that of terrestrial concrete. Second, the strength of non-dispersible underwater concrete with silica fume increases remarkably at different ages. Third, underwater non-dispersible concrete does not produce new products when it is formed and cured in seawater.

Originality/value

In this paper, underwater non-dispersible concrete is formed and maintained on land, freshwater and seawater by underwater pouring method. The working performance, mechanical properties and durability of underwater non-dispersible concrete mixtures after hardening are tested.

Details

International Journal of Structural Integrity, vol. 11 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 22 June 2012

Xin Wang, Shaoze Luo and Qiang Yuan

A new roller compacted concrete dam of Fengman hydropower station was determined to be built in the toe of the old dam which had been identified as a dangerous dam. The…

Abstract

Purpose

A new roller compacted concrete dam of Fengman hydropower station was determined to be built in the toe of the old dam which had been identified as a dangerous dam. The new dam during construction would be impacted by the high‐speed flow discharged from the old dam. This is an important problem met for the first time in China, which would affect the whole project construction. The purpose of this paper is to describe a series of erosion experiments of the new dam material.

Design/methodology/approach

A kind of high‐speed flow erosion test apparatus was developed for erosion experiment of the new dam material. The maximum jet velocity was up to 40 m/s and the section area of the nozzle was 25 cm2. In the process of experiments, the equipment showed its good performance. Erosive wear tests of two types of materials used in the new dam, a roller compacted concrete and a distorted concrete with four kinds of ages were carried out with the flow velocity in the range of 30‐35 m/s.

Findings

Erosion parameters and erosion laws of the two types of concretes with different ages were obtained, and a general relationship had been found between erosion rate and flow velocity: with velocity exponent between 3.33 and 3.93. It was also concluded that the erosion resistance of the distorted concrete was better than that of the roller compacted concrete and the mechanics properties of the concretes of over 14 days age was influenced slightly by water impacted.

Originality/value

The test results would play a practical technique guide role for the safety of this project during construction in the flood season.

Details

Anti-Corrosion Methods and Materials, vol. 59 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 7 December 2021

Santosh Kumar Karri, Markandeya Raju Ponnada and Lakshmi Veerni

One of the sources for the increase in the carbon footprint on the earth is the manufacturing of cement, which causes a severer environmental impact. Abundant research is…

Abstract

Purpose

One of the sources for the increase in the carbon footprint on the earth is the manufacturing of cement, which causes a severer environmental impact. Abundant research is going on to diminish CO2 content in the atmosphere by appropriate utilization of waste by-products of industries. Alkali-activated slag concrete (AASC) is an innovative green new concrete made by complete replacement of cement various supplementary cementitious raw materials. Concrete is a versatile material used in different fields of structures, so it is very important to study the durability in different exposures along with the strength. The purpose of this paper is to study the performance of AASC by incorporating quartz sand as fine aggregate under different exposure conditions.

Design/methodology/approach

The materials for this innovative AASC are selected based on preliminary studies and literature surveys. Based on numerous trials a better performance mix proportion of AASC with quartz sand is developed with 1:2:4 mix proportion, 0.8 alkali Binder ratio, 19 M of NaOH and 50% concentration of Na2SiO3. Subsequently, AASC cubes are prepared and exposed for 3, 7, 14, 28, 56, 90, 112, 180, 252 and 365 days in ambient, acid, alkaline, sulfate, chloride and seawater and tested for compressive strength. In addition, to study the microstructural characteristics, scanning electron microscope (SEM), energy dispersive X-ray analysis and X-ray diffraction analysis was also performed.

Findings

Long-term performance of AASC developed with quartz sand is very good in the ambient, alkaline environment of 5% NaOH and seawater with the highest compressive strength values of 51.8, 50.83 and 64.46, respectively. A decrease in compressive strengths was observed after the age of 14, 56 and 112 days for acid, chloride and sulfate exposure conditions, respectively. SEM image shows a denser microstructure of AASC matrix for ambient, alkaline of 5% NaOH and seawater.

Research limitations/implications

The proposed AASC is prepared with a mix proportion of 1:2:4, so the other proportions of AASC need to verify. In general plain, AASC is not used in practice except in few applications, in this work the effect of reinforced AASC is not checked. The real environmental exposure in fields may not create for AASC, as it was tested in different exposure conditions in the laboratory.

Practical implications

The developed AASC is recommended in practical applications where early strength is required, where the climate is hot, where water is scarce for curing, offshore and onshore constructions exposed to the marine environment and alkaline environment industries like breweries, distilleries and sewage treatment plants. As AASC is recommended for ambient air and in other exposures, its implementation as a construction material will reduce the carbon footprint.

Originality/value

The developed AASC mix proportion 1:2:4 is an economical mix, because of low binder content, but it exhibits a higher early age compressive strength value of 45.6 MPa at the age of 3 days. The compressive strength increases linearly with age from 3 to 365 days when exposed to seawater and ambient air. The performance of AASC is very good in the ambient, alkaline environment and seawater compared to other exposure conditions.

Details

Journal of Engineering, Design and Technology , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1726-0531

Keywords

Article
Publication date: 15 May 2019

Daniel Paul Thanaraj, Anand N. and Prince Arulraj

This paper aims to explain the influence of Standard Fire as per ISO 834 on the strength and microstructure properties of concrete specimens with different strength grade.

Abstract

Purpose

This paper aims to explain the influence of Standard Fire as per ISO 834 on the strength and microstructure properties of concrete specimens with different strength grade.

Design/methodology/approach

The strength grades of concrete considered for the experimental investigation were Fck20, Fck30, Fck40 and Fck50. The specimens were heated up to 1, 2, 3 and 4 h as per standard fire curve. Effect of elevated temperature on compressive and flexural behavior of specimens with various strength grades was examined. Effects of age of concrete, weight loss, surface characteristics and thermal crack pattern were also investigated.

Findings

Experimental investigation shows that strength grade, duration of exposure and age of concrete are the key parameters affecting the residual strength of concrete. For the beams exposed to 3 and 4 h of heating, the residual flexural strength was found to be so insignificant that the specimens were not able to even sustain their own weight. The loss in compressive and flexural strength of Fck50 concrete specimens heated up to 1 h were found to be 26.41 and 86.03 per cent of the original unheated concrete, respectively. The weight loss was found to be more for higher grade concrete specimens, and it was about 8.38 per cent for Fck50 concrete. Regression analysis was carried out to establish the empirical relation between residual strength and grade of concrete. Scanning electron microscopy and thermogravimetric analysis were carried out to examine the damage level of fire-affected concrete specimens.

Originality/value

Empirical relationship was developed to determine the residual strength of concrete exposed to elevate temperature, and this will be useful for design applications. This database may be useful for identifying member strength of reinforced beams subjected to various durations of heating so that suitable repair technique can be adopted from the available database. It will be useful to identify the proper grade of concrete with regard to fire endurance, in the case of concrete under compression or flexure.

Details

Journal of Engineering, Design and Technology , vol. 17 no. 5
Type: Research Article
ISSN: 1726-0531

Keywords

Article
Publication date: 10 April 2007

Shibli R.M. Khan, J. Noorzaei, M.R.A. Kadir, A.M.T. Waleed and M.S. Jaafar

This paper aims to present a research finding that establishes a regression model between ultrasonic pulse velocity (UPV) tests and actual strength of high performance…

1601

Abstract

Purpose

This paper aims to present a research finding that establishes a regression model between ultrasonic pulse velocity (UPV) tests and actual strength of high performance concrete (HPC).

Design/methodology/approach

In this study, a total of 270 cube samples were made from six different mix proportions. The mixes were grouped in two series that consist of nominal maximum aggregate sizes of 10 mm (A10) and 19 mm (A19). Silica fume were used as mineral admixtures at 5 percent, 10 percent and 15 percent of cement in both series. UPV tests were conducted for each of the specimens, followed by destructive strength tests. The tests were carried out for concrete at different ages of between three to 56 days. The destructive test results were used as the true strength of the mixes and the UPV test results were used as strength estimation.

Findings

Concrete strength correlations between UPV and destructive tests were analysed for each mix proportions and in each series. These correlations are presented in the form of regression equations that displays standard error of between ±2.4 to ±5.7 MPa regardless of mix for the concrete in series A10. Similarly, in series A19 concrete, standard errors of between ±3.2 to ±6.7 MPa were found. Strength prediction models using UPV for high performance concrete are proposed. The models have overall correlation coefficients above 0.80 for all the mixes.

Originality/value

There are no standard relationships that had been established for high performance concrete strength with UPV test methods. The proposed relationship can be used for concrete strength estimation that is normally required in building or structural assessment, especially with the present trend of constructing modern structures using high performance concrete.

Details

Structural Survey, vol. 25 no. 1
Type: Research Article
ISSN: 0263-080X

Keywords

Article
Publication date: 1 June 2020

Hakas Prayuda, Fanny Monika and Martyana Dwi Cahyati

This study aims to discuss the results of fresh properties and compressive strength of self-compacting concrete using ingredients added red brick powder as a fine…

Abstract

Purpose

This study aims to discuss the results of fresh properties and compressive strength of self-compacting concrete using ingredients added red brick powder as a fine aggregate substitute. The results of the study were compared with the properties of fresh properties and compressive strength with ingredients added by rice husk ash, which is also a fine aggregate substitute. In addition, the initial compressive strength of each of these variations was also examined to accelerate the completion time of construction projects using self-compacting concrete.

Design/methodology/approach

This research was conducted in a laboratory by testing the characteristics of fresh and hardened properties of self-compacting concrete.

Findings

Fresh properties testing is carried out in the form of V-funnel, flow table, J-ring and L-box where all specimens produce quite varied flow rates. Compressive strength was estimated at ages 3, 7, 14 and 28 days with cylindrical specimens with a diameter of 150 mm and a height of 300 mm. The variation of fine aggregate substitutes used is 20, 40 and 60 per cent.

Originality/value

From the results of the compressive strength, it can be concluded that the added material is categorized as self-compacting concrete with high initial compressive strength, while at 28 days, the compressive strength test results are categorized as high-strength self-compacting concrete.

Details

World Journal of Engineering, vol. 17 no. 4
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 14 November 2016

Jiang Hu

The multi-scale numerical simulation method, able to represent the complexity of the random structures and capture phase degradation, is an effective way to investigate…

Abstract

Purpose

The multi-scale numerical simulation method, able to represent the complexity of the random structures and capture phase degradation, is an effective way to investigate the long-term behavior of concrete in service and bridges the gap between research on the material and on the structural level. However, the combined chemical-physical deterioration mechanisms of concrete remain a challenging task. The purpose of this paper is to investigate the degradation mechanism of concrete at the waterline in cold regions induced by combined calcium leaching and frost damage.

Design/methodology/approach

With the help of the NIST’s three-dimensional (3D) hydration model and the random aggregate model, realistic 3D representative volume elements (RVEs) of concrete at the micro-, the meso-, and the macro-scales can be reconstructed. The boundary problem method is introduced to compute the homogenized mechanical properties for both sound and damaged RVEs. According to the damage characteristics, the staggering method including a random dissolution model and a thermo-mechanical coupling model is developed to simulate the synergy deterioration effects of interacted calcium leaching and frost attacks. The coupled damage procedure for the frost damage process is based on the hydraulic pressure theory and the ice lens growth theory considering the relationship between the frozen temperature and the radius of the capillary pore. Finally, regarding calcium leaching as the leading role in actual engineering, the numerical methodology for combined leaching and frost damage on concrete property is proposed using a successive multi-scale method.

Findings

On the basis of available experimental data, this methodology is employed to explore the deterioration process. The results agree with the experimental ones to some extent, chemical leaching leads to the nucleation of some micro-cracks (i.e. damage), and consequently, to the decrease of the frost resistance.

Originality/value

It is demonstrated that the multi-scale numerical methodology can capture potential aging and deterioration evolution processes, and can give an insight into the macroscopic property degradation of concrete under long-term aggressive conditions.

Details

Multidiscipline Modeling in Materials and Structures, vol. 12 no. 4
Type: Research Article
ISSN: 1573-6105

Keywords

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