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

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
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.

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

MRS Advances ◽  
2020 ◽  
Vol 5 (25) ◽  
pp. 1267-1275
Author(s):  
Mike Otieno ◽  
Riccardo Opeka
Keyword(s):  
Oxygen Permeability ◽  
Gas Permeability ◽  
Curing Temperature ◽  
Durability Properties ◽  
Chloride Resistance ◽  
Blastfurnace Slag ◽  
Water Sorptivity ◽  
Chloride Conductivity ◽  
Strength And Durability ◽  
Durability Performance

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.

scholarly journals Effect of Using River Sand on The Strength of Normal and High Strength Concrete

2018 ◽  
Vol 7 (4.20) ◽  
pp. 222 ◽  
Author(s):  
Haitham Al-Thairy
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
River Sand ◽  
Strength Concrete ◽  
Concrete Mixtures ◽  
Test Parameters ◽  
Normal Strength ◽  
Compressive And Flexural Strengths

The shortage and high cost of quarries sand in some regions around the world has motivated engineers and researchers to investigate the possibility and feasibility of using other materials to be used as a fine aggregate in concrete mixtures. The main objective of this research is to experimentally investigate the effect of using river sand as a partial replacement of the ordinary quarries sand on the mechanical properties of normal and high strength concrete. Nine concrete mixtures were prepared and tested in terms of fresh and hardened properties using different replacement ratios of the required proportion of the normal sand. Four replacement ratios were used for normal strength concrete (NSC) which are: 0%, 25%, 50% and 75%, whereas, five replacement ratios were used for high strength concrete (HSC) namely: 0%, 35%, 60% and 90%. For each strength grade, the test parameters of the prepared mixtures included compressive and tensile strength. The experimental test results have revealed that it is possible to obtain a normal and high strength concrete with acceptable compressive and flexural strengths values by using river sand with replacement ratios up to 25% and 35% for NSC and HSC, respectively. When the replacement ratios were increased to more than the aforementioned ratios, the strength of the concrete decreased accordingly.  

scholarly journals Role of Polypropylene Fibres in Concrete Spalling Risk Mitigation in Fire and Test Methods of Fibres Effectiveness Evaluation

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3869 ◽  
Author(s):  
Izabela Hager ◽  
Katarzyna Mróz
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Risk Mitigation ◽  
High Strength ◽  
Test Methods ◽  
Reactive Powder Concrete ◽  
Polypropylene Fibres ◽  
Normal Strength ◽  
Reactive Powder ◽  
In Fire

The explosive behaviour of concrete in fire is observed in rapidly heated concrete. The main factors controlling the occurrence of spalling are related to the material’s low porosity and high density as well as the limited ability to transport gases and liquids. Thus, for high-strength, ultrahigh-strength, and reactive powder concrete, the risk of spalling is much higher than for normal-strength concrete. The paper presents the discussion on the leading hypothesis concerning the occurrence of concrete spalling. Moreover, the methods for spalling prevention, such as polypropylene fibre application, which has been found to be an effective technological solution for preventing the occurrence of spalling, are presented. Various tests and testing protocols are used to screen concrete mixes propensity toward spalling and to evaluate the polypropylene fibres’ effectiveness in spalling risk mitigation. The most effective testing methods were selected and their advantages were presented in the paper. The review was based mainly on the authors’ experiences regarding high performance concrete, reactive powder concrete testing, and observations on the effect of polypropylene fibres on material behaviour at high temperature.

Microstructure of an extruded rapidly solidified Al-8Fe-2Mo alloy

1986 ◽  
Vol 44 ◽  
pp. 548-549
Author(s):  
W. T. Donlon ◽  
J. E. Allison ◽  
S. Shinozaki
Keyword(s):  
Electron Microscopy ◽  
Automotive Industry ◽  
Fuel Economy ◽  
High Strength ◽  
Al Alloys ◽  
Light Weight ◽  
Thin Sections ◽  
Strength And Durability ◽  
Rapidly Solidified ◽  
Whitney Aircraft

Light weight materials which possess high strength and durability are being utilized by the automotive industry to increase fuel economy. Rapidly solidified (RS) Al alloys are currently being extensively studied for this purpose. In this investigation the microstructure of an extruded Al-8Fe-2Mo alloy, produced by Pratt & Whitney Aircraft, Goverment Products Div. was examined in a JE0L 2000FX AEM. Both electropolished thin sections, and extraction replicas were examined to characterize this material. The consolidation procedure for producing this material included a 9:1 extrusion at 340°C followed by a 16:1 extrusion at 400°C, utilizing RS powders which have also been characterized utilizing electron microscopy.

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