Curing of slag concretes at low temperatures: effect on selected durability properties

AbstractThe influence of low curing temperatures (5, 10 and 15 ± 2 °C) on the strength and durability properties of ground granulated blastfurnace slag (GGBS) and ground granulated Corex slag (GGCS) concretes was studied. A standard curing temperature of 23 ± 2 °C) was also used for comparative purposes. Test specimens were cast using 100% CEM I 52.5N (PC), and three PC/Slag (GGBS or GGCS) replacement ratios of 50/50, 65/35 and 80/20, and a w/b ratio of 0.40. The specimens were cured for 28 days by submersion in water at the respective curing temperatures and then tested for durability. Durability was assessed using oxygen permeability, water sorptivity and chloride conductivity tests. The results showed that durability of the concretes decreased as the curing temperature decreased – gas permeability and water sorptivity increased while chloride resistance decreased. It was also observed that at a given curing temperature, the slag blended concretes showed superior durability performance than the plain PC concretes.

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Coal gasification and composite ashes as partial replacements for Portland cement in concrete – strength and selected durability performance

MRS Advances ◽

10.1557/adv.2020.411 ◽

2020 ◽

Vol 5 (54-55) ◽

pp. 2807-2816

Author(s):

Mike Otieno ◽

Dikeledi Maboea

Keyword(s):

Portland Cement ◽

Coal Gasification ◽

Gas Permeability ◽

Concrete Strength ◽

Replacement Level ◽

Chloride Resistance ◽

Weathered Coal ◽

Negative Environmental Impact ◽

Strength And Durability ◽

Durability Performance

AbstractThis study investigated the use of mixed weathered coal fine ash (MWA) and coal gasification ash (CGA), sourced from Sasol® Ltd, South Africa, as partial replacements (10%, 15% and 30% by mass) of Portland Cement (PC) in concrete. The objective was to assess the feasibility of using the ashes, which are generally of lower quality than FA, in concrete in order to avert their negative environmental impact i.e. disposal in heaps and landfills. Companion reference concretes were made using conventional fly ash (FA). Two water-to-binder (w/b) ratios (0.50 and 0.60) were used. The concretes were tested for compressive strength (7, 28 and 56 days) and durability (gas permeability and chloride resistance at 28 and 56 days). In general, the results strongly suggest that the ashes can be used in conventional structural concrete – both from strength and durability viewpoints. Aspects that require attention when they are used include decrease in both workability and rate of strength gain. The gas permeability of the CGA and MWA concretes were similar to those for FA at all replacement levels but a 15% replacement level gave higher chloride resistance.

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Utilization of kimberlite tailings as aggregates in concrete – strength and selected durability properties

MRS Advances ◽

10.1557/adv.2020.153 ◽

2020 ◽

Vol 5 (25) ◽

pp. 1259-1266

Author(s):

Mike Otieno ◽

Esina Ndoro

Keyword(s):

Compressive Strength ◽

Water Demand ◽

Concrete Strength ◽

High Water ◽

Negative Effects ◽

Coarse Aggregates ◽

Durability Properties ◽

Mix Proportioning ◽

Water Sorptivity ◽

Strength And Durability

AbstractThe feasibility of using kimberlite tailings as aggregates in concrete was assessed. Compressive strength and selected durability tests were carried out on concretes made using various replacement levels (0, 40, 60 and 100%) fine and/or coarse blended crushed andesite and kimberlite tailings as aggregates. A w/b ratio of 0.50 and a CEM I 52.5R were used. The results show that the kimberlite tailings as aggregates have a relatively high water demand which was manifested as a reduction in workability of the fresh concretes with kimberlite tailings as a proportion of either fine and/or coarse aggregates. The results also showed that the use of the kimberlite tailings as a proportion of either fine or coarse aggregates in concrete resulted in a decrease in both compressive strength and durability properties viz water sorptivity and oxygen permeability. This was partly attributed to the low workability of the concretes which is known to limit the degree of compaction of fresh concrete. It is envisaged that careful concrete mix proportioning including the use of admixtures and pre-wetting of the aggregates can be used to offset the negative effects of high water demand of the kimberlite aggregates.

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A critical review of the Water Sorptivity Index (WSI) parameter for potential durability assessment: Can WSI be considered in isolation of porosity?

Journal of the South African Institution of Civil Engineering ◽

10.17159/2309-8775/2021/v63n2a4 ◽

2021 ◽

Vol 63 (2) ◽

Author(s):

A J Moore ◽

A T Bakera ◽

M G Alexander

Keyword(s):

Oxygen Permeability ◽

Concrete Durability ◽

Permeability Index ◽

Cover Layer ◽

Durability Index ◽

Durability Assessment ◽

Water Sorptivity ◽

Sorptivity Test ◽

Chloride Conductivity ◽

Two Parameters

ABSTRACT The Durability Index (DI) approach used in South Africa is linked to transport-related properties of the cover layer of concrete. This performance-based approach utilises three different durability-related parameters, namely Water Sorptivity Index (WSI), Oxygen Permeability Index (OPI) and Chloride Conductivity Index (CCI). In the water sorptivity test, both the sorptivity and the water-penetrable porosity of the concrete are measured. Until now, porosity has not been considered directly as a separate durability-related parameter. This paper analyses these implications and suggests that porosity should be adopted as a further index. The paper concludes that sorptivity cannot be interpreted without also reflecting the porosity value since these two parameters are inter-related. Keywords: concrete durability, durability index, water sorptivity, porosity, absorption

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Durability Index Performance of High Strength Concretes Made Based on Different Standard Portland Cements

Advances in Materials Science and Engineering ◽

10.1155/2012/410909 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Stephen O. Ekolu ◽

Sheena Murugan

Keyword(s):

Oxygen Permeability ◽

High Strength ◽

Test Methods ◽

Index Test ◽

Concrete Mixtures ◽

Chloride Resistance ◽

Durability Index ◽

Normal Strength ◽

Strength And Durability ◽

High Chloride

A consortium of three durability index test methods consisting of oxygen permeability, sorptivity and chloride conductivity were used to evaluate the potential influence of four (4) common SANS 10197 cements on strength and durability of concrete. Twenty four (24) concrete mixtures of water-cement ratios (w/c's) = 0.4, 0.5, 0.65 were cast using the cement types CEM I 42.5N, CEM II/A-M (V-L) 42.5N, CEM IV/B 32.5R and CEM II/A-V 52.5N. The concretes investigated fall in the range of normal strength, medium strength and high strength concretes. It was found that the marked differences in oxygen permeability and sorptivity results observed at normal and medium strengths tended to vanish at high concrete strengths. Also, the durability effects attributed to use of different cement types appear to diminish at high strengths. Cements of low strength and/or that contained no extenders (CEM 32.5R, CEM I 42.5N) showed greater sensitivity to sorptivity, relative to other cement types. Results also show that while concrete resistance to chlorides generally improves with increase in strength, adequately high chloride resistance may not be achieved based on high strength alone, and appropriate incorporation of extenders may be necessary.

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Chloride Induced Corrosion and Carbonation in 3D Printed Concrete

Infrastructures ◽

10.3390/infrastructures7010001 ◽

2021 ◽

Vol 7 (1) ◽

pp. 1

Author(s):

Jean De’M Malan ◽

Algurnon Steve van Rooyen ◽

Gideon P. A. G. van Zijl

Keyword(s):

Carbon Dioxide ◽

Flexural Strength ◽

Bond Strength ◽

Lack Of Fusion ◽

Durability Properties ◽

Chloride Induced Corrosion ◽

3D Printed ◽

Strength And Durability ◽

Durability Performance ◽

Interlayer Bond

The durability of reinforced concrete structures is dependent on the ability of the concrete cover to combat the ingress of chlorides and carbon dioxide in marine and urban environments. In recent years, interest in additive manufacturing), specifically referring to extrusion based three-dimensional concrete printing (3DCP), has been growing in the construction industry. Despite this being a promising technology that can save construction time, costs and resources, certain issues regarding the lack of fusion between subsequent printed layers have been brought to light. Research has shown that the lack of fusion at the interlayer regions can act as ingress pathways for corrosion contaminants, such as carbon dioxide and chloride aqueous solution, that can cause deterioration. This study investigates the interlayer bond strength (flexural strength) and durability performance of 3D printed concrete subjected to pass times between 0 and 30 min and compares the results to reference cast concrete of the same concrete mixture. The durability study includes Durability Index testing (oxygen permeability, water sorptivity and chloride conductivity index), accelerated concrete carbonation and chloride-induced corrosion. The results show that the cast samples outperform printed samples, yielding greater flexural strength and durability properties, and emphasize the importance of improving the 3DCP interfacial bond. Cast samples are shown to have randomly distributed, compact voids compared to the interconnected and elongated pores located at the interlayer regions of printed samples. In addition, printed samples yield lower interlayer bond strength and durability properties with an increase in pass time, which is attributed to surface moisture evaporation as well as the thixotropic behaviour of the concrete mixture. Good relationships between the mechanical strength and durability performance are also presented.

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Effect of Influence of Metakaolin and Shredded Plastic Waste on Strength and Durability Properties of M20 Grade Concrete

International Journal of Recent Technology and Engineering - 2 ◽

10.35940/ijrte.b3242.078219 ◽

2019 ◽

Vol 8 (2) ◽

pp. 4170-4175

Keyword(s):

Natural Resources ◽

Industrial Waste ◽

Coarse Aggregate ◽

Environmental Problems ◽

Plastic Waste ◽

Strength Parameters ◽

Durability Properties ◽

Natural Aggregates ◽

Strength And Durability ◽

Durability Performance

The production of cement liberates the equal amount of CO2 into the environment. This will results in various social and environmental problems. There is a need in determining the new cement materials from waste or industrial waste. Second, the extraction of natural aggregates from natural resources poses other environmental problems. So in this article, the experimental programme is conducted to determine the strength and durability performance of cement partially replaced with Metakaolin (MK) (0%, 2.5%, 5%, 7.5% and 10%) and coarse aggregate substituted by shredded plastic waste (SPW) at 0.5% by weight. The main objective of this article was limited to analyzing the strength parameters along with the durability parameters.

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Effects of Nanosilica on Compressive Strength and Durability Properties of Concrete with Different Water to Binder Ratios

Advances in Materials Science and Engineering ◽

10.1155/2016/8453567 ◽

2016 ◽

Vol 2016 ◽

pp. 1-16 ◽

Cited By ~ 26

Author(s):

Forood Torabian Isfahani ◽

Elena Redaelli ◽

Federica Lollini ◽

Weiwen Li ◽

Luca Bertolini

Keyword(s):

Compressive Strength ◽

Diffusion Coefficient ◽

Reference Value ◽

Chloride Diffusion ◽

Gravimetric Analysis ◽

Chloride Diffusion Coefficient ◽

X Ray Diffraction ◽

Durability Properties ◽

Water Sorptivity ◽

Strength And Durability

The effects of the addition of different nanosilica dosages (0.5%, 1%, and 1.5% with respect to cement) on compressive strength and durability properties of concrete with water/binder ratios 0.65, 0.55, and 0.5 were investigated. Water sorptivity, apparent chloride diffusion coefficient, electrical resistivity, and carbonation coefficient of concrete were measured. The results showed that compressive strength significantly improved in case of water/binder = 0.65, while for water/binder = 0.5 no change was found. Increasing nanosilica content, the water sorptivity decreased only for water/binder = 0.55. The addition of 0.5% nanosilica decreased the apparent chloride diffusion coefficient for water/binder = 0.65 and 0.55; however, higher nanosilica dosages did not decrease it with respect to reference value. The resistivity was elevated by 0.5% nanosilica for all water/binder ratios and by 1.5% nanosilica only for water/binder = 0.5. The carbonation coefficient was not notably affected by increasing nanosilica dosages and even adverse effect was observed for water/binder = 0.65. Further information of microstructure was also provided through characterization techniques such as X-ray diffraction, thermal gravimetric analysis, mercury intrusion porosimetry, and scanning electron microscopy. The effectiveness of a certain nanosilica dosage addition into lower strength mixes was more noticeable, while, for the higher strength mix, the effectiveness was less.

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