scholarly journals Evaluation of Methods to Correct the Effect of Temperature on Electrical Conductivity of Mortar

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Milena Rangelov ◽  
Somayeh Nassiri
Keyword(s):  
Electrical Conductivity ◽  
Cementitious Materials ◽  
Temperature Correction ◽  
Supplementary Cementitious Materials ◽  
Embedded Sensors ◽  
Degree Of Saturation ◽  
Effect Of Temperature ◽  
Temperature Range ◽  
Durability Assessment ◽  
Higher Temperature

Nondestructive methods to obtain the electrical conductivity (σ) or resistivity (ρ) of concrete are gaining popularity for durability evaluation. However, these methods are susceptible to the effects of curing and conditioning, primarily temperature and degree of saturation. Before σ of concrete at varied temperatures can be used for durability assessment, appropriate corrections must be made to account for the effect of temperature (T). In this study, two existing and one new temperature correction methods were evaluated for 12 mortar mixtures varying in water-to-cementitious material ratio (w/cm) and the content and types of supplementary cementitious materials (SCM). Mortar specimens instrumented with embedded sensors were cured in sealed conditions for 11–13 months. After this period, the sealed specimens were subjected to stepwise temperature change in 5–50°C range while σ was recorded using the embedded sensors. Linear, bilinear, and Arrhenius temperature correction (LTC, BLTC, and ATC, respectively) were fitted to the obtained σ-T datasets and were evaluated for fitness. LTC provided an acceptable fit to the σ-T data (R2 > 0.81) but was found the most suitable in 5–30°C temperature range. BLTC was defined as a combination of two distinct LTC below and above the reference temperature at 23°C and had a better fit to the data (R2 > 0.96). Lastly, ATC showed the best fit among the tested methods (R2 > 0.98) and was found applicable for the full tested temperature range. Comparison of correction coefficients among the mixtures indicated that increase in w/cm results in less sensitivity of σ to temperature. Mixtures with SCM generally exhibit higher temperature sensitivity compared to the corresponding plain mixture. Since the variations in correction coefficients were not substantial (less 18% variation among 10 of 12 mixtures), a single value of activation energy of conduction (Ec) at 32 kJ/mol was identified as the general recommendation for all the tested mixtures.

scholarly journals Effect of temperature on the production of cellulases, xylanases and lytic enzymes by selected Trichoderma reesei mutants

2014 ◽  
Vol 30 (2) ◽  
pp. 255-264 ◽  
Author(s):  
Piotr Janas ◽  
Zdzisław Targoński
Keyword(s):  
Trichoderma Reesei ◽  
Effect Of Temperature ◽  
Cellulolytic Enzymes ◽  
Lytic Enzymes ◽  
Complex Composition ◽  
Temperature Range ◽  
Mutant Strains ◽  
Higher Temperature ◽  
C 30 ◽  
Xylanolytic Enzymes

The effect of temperature in the rangę of 26-38°C on the production of cellulases, xylanases and lytic enzymes by four mutant strains of <i>Trichoderma reesei</i> was analysed. On the basis of these investigations three thermosensitive strains (M-7. RUT C 30 and VTT-D-78085) which showed reduced excretion of the above mentioned enzymes as well as protein and a thermoresistant mutant (VTT-D-79I24) which grew within a temperature range of 26-34°C were characterized. Higher temperature caused an increase in the level of xylanolytic enzymes produced by the four mutants. In addition. it effected the complex composition of cellulolytic enzymes secreted by VTT-D-79l 24 (i.c. increased and reduced excertion of (β-glucosidase and β-1,4-endoglucanase respectively).

scholarly journals Porosity Evaluation of Concrete Containing Supplementary Cementitious Materials for Durability Assessment through Volume of Permeable Voids and Water Immersion Conditions

Buildings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 378
Author(s):  
Manish Kewalramani ◽  
Ahmad Khartabil
Keyword(s):  
Water Absorption ◽  
Water Immersion ◽  
Cementitious Materials ◽  
Chloride Penetration ◽  
Supplementary Cementitious Materials ◽  
Partial Replacement ◽  
Testing Method ◽  
Durability Assessment ◽  
Astm C1202 ◽  
The Impact

Concrete containing supplementary cementitious materials (SCMs) as partial replacement of ordinary Portland cement is regarded as green and durable concrete, with several advantages such as improved strength gain mechanism, resistance to degradation and extended service life of structure. Water absorption or porosity of concrete is directly related to the durability of concrete. In this present study, five concrete mixes involving three different SCMs are investigated for water absorption and rapid chloride penetration rating. A comparison between porosity values obtained using four standard testing methods, i.e., BS 1881-122, RILEM CPC 11.1, RILEM CPC 11.3, and ASTM C642 are presented for three different concrete mixes containing varied compositions and proportions of two SCMs. The testing method by RILEM CPC 11.3 includes distinctive sample preparation and is regarded as a stringent method to represent the degree of concrete porosity. Two additional concrete mixes with three SCMs are further investigated for their water absorption and immersion following the testing method by RILEM CPC 11.3. The impact of SCMs on concrete porosity is discussed. A linear correlation between porosity and rapid chloride penetration (RCP) ratings obtained as per ASTM C1202-19 on specimens of all investigated concrete mixes is proposed as a rapid approach to assess chloride penetration of concrete specimens containing SCMs.

scholarly journals The effect of temperature on the viscosity of air

1926 ◽  
Vol 113 (763) ◽  
pp. 233-237 ◽  
Keyword(s):  
Present Author ◽  
Effect Of Temperature ◽  
Appreciable Change ◽  
Temperature Range ◽  
Higher Temperature ◽  
The Difference ◽  
Experimental Values ◽  
Coefficient Of Viscosity ◽  
Slight Alteration

In a recent paper Prof. A. 0. Rankine has put forward a number of criticisms of the results obtained from, and the experimental method employed in, the determination of the temperature coefficient of viscosity of air by the present author. In the first place, a comparison is drawn between the author’s results and those of other observers in the lower part of the temperature range, and the conclusion is drawn therefrom that there is a possibility of an error of 3 percent, in the author’s measurements throughout the whole range of temperature used. This inference is reached from the figures quoted in Table II of Rankine’s paper, in which the temperature range from 15° to 183° C. is considered. That some difference exists between the author’s results and those of other observers in the lower part of the temperature range is clear, but it must again be emphasised that the values given for low temperatures are not experimental values, but were obtained by an extension of the graph (fig. 2) for higher temperature measurements to the value of the viscosity as given by Millikanj for room temperatures. A slight alteration of the curvature of this extension would make an appreciable change in the ratios η100/η15 and η183/η15 , but this would not be sufficient to account for the curvature at B in fig. 3 of the original paper. If the values of T ⅜ /η for Breitenbach’s results at 182° C. and 302° C. are plotted on this curve, they lie above the present results and on a curve which would intersect AB at about 600° C. That part of the difference is due to this cause seems to be indicated by the fact that the difference diminishes as the temperature rises. Thus at 300° C. the following values of η300/η15 are obtained by Breitenbach, the only other worker at this temperature, and the author. The figures used are those given by Rankine.

Probabilistic Modelling and the k-Value Concept

2014 ◽  
Vol 635 ◽  
pp. 198-203
Author(s):  
Břetislav Teplý ◽  
Markéta Chromá ◽  
Pavla Rovnaníková ◽  
Alfred Strauss
Keyword(s):  
Mathematical Models ◽  
Concrete Structures ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Probabilistic Modelling ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Class A ◽  
Durability Assessment ◽  
Value Concept

The durability of concrete structures is an important issue. Eurocode EN 206-1 introduces the k-value concept for concretes made with supplementary cementitious materials; a prescriptive concept that recommends limiting water/cement ratio values for a specified exposure class. A more advanced performance-based concept directly requires that concrete be designed in terms of performance-related parameters, an approach which seems to be more suitable when durability must be achieved. The application of mathematical models in durability assessment is advocated, and an example is shown.

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

Effect of ground granulated blast funrnace slag and fly ash on strength, permeability, and under-water abrasion of fine-grained concrete

2020 ◽  
Vol 71 (7) ◽  
pp. 775-788
Author(s):  
Quyet Truong Van ◽  
Sang Nguyen Thanh
Keyword(s):  
Fly Ash ◽  
Concrete Strength ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chloride Permeability ◽  
Cement Replacement ◽  
Fine Grained ◽  
Granulated Blast Furnace Slag ◽  
Compressive Strength Test ◽  
Economic Ground

The utilisation of supplementary cementitious materials (SCMs) is widespread in the concrete industry because of the performance benefits and economic. Ground granulated blast furnace slag (GGBFS) and fly ash (FA) have been used as the SCMs in concrete for reducing the weight of cement and improving durability properties. In this study, GGBFS at different cement replacement ratios of 0%, 20%, 40% and 60% by weight were used in fine-grained concrete. The ternary binders containing GGBFS and FA at cement replacement ratio of 60% by weight have also evaluated. Flexural and compressive strength test, rapid chloride permeability test and under-water abrasion test were performed. Experimental results show that the increase in concrete strength with GGBFS contents from 20% to 40% but at a higher period of maturity (56 days and more). The chloride permeability the under-water abrasion reduced with the increasing cement replacement by GGBFS or a combination of GGBFS and FA

Evaluation of strength of concrete on different initial exposure condition

2020 ◽  
Vol 13 ◽  
Author(s):  
Sri Ram Krishna Mishra ◽  
Pradeep Kumar Ghosh ◽  
Manoj Kulshreshtha
Keyword(s):  
Portland Cement ◽  
High Strength ◽  
Cementitious Materials ◽  
General Purpose ◽  
Supplementary Cementitious Materials ◽  
Exposure Condition ◽  
Portland Cement Concrete ◽  
Initial Exposure ◽  
Skilled Manpower ◽  
Standard Practices

Background: The previous studies have focused curing effect of mainly on high strength concrete, where strict supervision is maintained. This study is based upon general purpose concreting work for commercial and residential construction in absence of skilled manpower and supervision. Objective: The objective of this study is to establish a thumb rule to provide 7 days initial curing for maintaining quality for unsupervised concreting irrelevant to type of cement and grading. Methods: In this study concrete samples made with locally available commercial cements were cured for various initial exposure. Results: The results shows that concrete cured after a gap of 4 days from the time of de-moulding have given lowest strength as compared to concrete cured in standard practices i.e. where proper curing protocol had been followed. Conclusion: Initial curing is most important aspect of gaining desired strength. The findings after this study shows that curing affects the strength of concrete in variable grading. Initial curing has great importance for concrete with all types of Portland cement. Concrete with supplementary cementitious materials gives lowest strength initially but results higher strength after 28 days as compared to Portland cement.

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