scholarly journals Sulphide oxidation mortar tests for evaluation of the oxidation potential of sulphide-bearing aggregate

2021 ◽  
Author(s):  
Mona El-Mosallamy ◽  
Medhat Shehata
Keyword(s):  
Fly Ash ◽  
Relative Humidity ◽  
Sodium Hypochlorite ◽  
Room Temperature ◽  
Oxidation Potential ◽  
The Other ◽  
Oxidizing Agent ◽  
Sulphate Attack ◽  
Sulphide Oxidation ◽  
Mortar Bar

This paper proposes two new sulphide mortar bar tests. The two tests involve two exposure conditions: the first one relies on soaking the sample in an oxidizing agent (6% sodium hypochlorite) for three hours at room temperature to promote oxidation while the other test adopts a range of temperatures and relative humidity that promote oxidation and sulphate attack. Both tests were effective in discriminating between aggregates with oxidizable sulphide and those without. Moreover, the use of low-calcium fly ash at 25% and slag at 30% reduced the expansion but not to the level of samples with non-sulphide aggregates. On the contrary, 10% of metakaolin produced more expansion.<br>

scholarly journals Sulphide oxidation mortar tests for evaluation of the oxidation potential of sulphide-bearing aggregate

2021 ◽  
Author(s):  
Mona El-Mosallamy ◽  
Medhat Shehata
Keyword(s):  
Fly Ash ◽  
Relative Humidity ◽  
Sodium Hypochlorite ◽  
Room Temperature ◽  
Oxidation Potential ◽  
The Other ◽  
Oxidizing Agent ◽  
Sulphate Attack ◽  
Sulphide Oxidation ◽  
Mortar Bar

This paper proposes two new sulphide mortar bar tests. The two tests involve two exposure conditions: the first one relies on soaking the sample in an oxidizing agent (6% sodium hypochlorite) for three hours at room temperature to promote oxidation while the other test adopts a range of temperatures and relative humidity that promote oxidation and sulphate attack. Both tests were effective in discriminating between aggregates with oxidizable sulphide and those without. Moreover, the use of low-calcium fly ash at 25% and slag at 30% reduced the expansion but not to the level of samples with non-sulphide aggregates. On the contrary, 10% of metakaolin produced more expansion.<br>

scholarly journals Sulphide oxidation mortar tests for evaluation of the oxidation potential of sulphide-bearing aggregate

2021 ◽  
Author(s):  
Mona El-Mosallamy ◽  
Medhat Shehata
Keyword(s):  
Fly Ash ◽  
Relative Humidity ◽  
Sodium Hypochlorite ◽  
Room Temperature ◽  
Oxidation Potential ◽  
The Other ◽  
Oxidizing Agent ◽  
Sulphate Attack ◽  
Sulphide Oxidation ◽  
Mortar Bar

This paper proposes two new sulphide mortar bar tests. The two tests involve two exposure conditions: the first one relies on soaking the sample in an oxidizing agent (6% sodium hypochlorite) for three hours at room temperature to promote oxidation while the other test adopts a range of temperatures and relative humidity that promote oxidation and sulphate attack. Both tests were effective in discriminating between aggregates with oxidizable sulphide and those without. Moreover, the use of low-calcium fly ash at 25% and slag at 30% reduced the expansion but not to the level of samples with non-sulphide aggregates. On the contrary, 10% of metakaolin produced more expansion.<br>

Evaluating Sulphate Resistance of Cement-Based Systems by Sulphate Content Determination after Exposure

2016 ◽  
Vol 711 ◽  
pp. 1037-1044 ◽  
Author(s):  
Vivek Bindiganavile ◽  
Chi Qian Ou ◽  
Zheng Chen ◽  
Yaman Boluk
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Pore Size ◽  
The Other ◽  
Sulphate Attack ◽  
Cement Type ◽  
Sulphate Content ◽  
Ettringite Formation ◽  
Content Determination ◽  
Median Pore

This paper describes approaches to evaluating the resistance of cement-based composites to sulphate attack. The conventional approach of evaluation by means of measuring expansion is discussed in comparison with the sulphate diffusion, which was quantified as a function of depth. Besides CSA Types GU and HS, a 30:70 blend of fly ash and cement Type GU was also examined. The specimens so produced were immersed in a sulphate solution as per ASTM C1012 and retrieved variously after 7, 14, 28, 56 and 84 days of exposure. As expected, Type HS cement performed best with minimum expansion and sulphate ingress. On the other hand, the Type GU cement showed lower expansion and sulphate ingress in comparison to the fly ash blended binder. Although bearing identical porosity, the blended binder had the smallest median pore size. Therefore, the sulphate ingress and consequent ettringite production likely cracks the blended system more than the other two. Significantly, after longer durations of sulphate exposure, the blended system showed higher tensile strength which implies a healing of cracks through ettringite formation.

scholarly journals The Application of a New Oxidation Mortar Bar Test to Mixtures containing Different Cementing Systems

2021 ◽  
Author(s):  
Bassili Guirguis ◽  
Medhat Shehata ◽  
Josée Duchesne ◽  
Benoît Fournier ◽  
Benoît Durand ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Heat Of Hydration ◽  
Iron Sulphide ◽  
Oxidizing Agent ◽  
Field Exposure ◽  
Bar Test ◽  
Reactive Alumina ◽  
Mortar Bar

The effects of different cementing systems on the expansion of mortars containing iron sulphide-bearing aggregate was studied. Using a recently developed oxidation mortar bar test, the results showed that cementing systems containing low-calcium fly ash, metakaolin, slag, high-sulphate resisting Portland cement, or low heat of hydration Portland cement could reduce the expansion by 50–85%. The main suggested mechanisms behind the reduced expansion is the more refined pore structure of samples with SCMs, and the reduced C3A of low heat of hydration Portland cement. The refined pore structure reduces the permeation of the oxidizing solution into the samples. The similarity of this to penetration of oxygen into concrete under field exposure needs to be determined. Soaking the samples for >3 h in the oxidizing agent can produce excessive expansion – not related to oxidation of iron sulphide phases – in samples with cementing blends containing reactive alumina such as metakaolin.

scholarly journals Antibacterial Ability of Sodium Hypochlorite Activated with PUI vs. XPF File against Bacteria Growth on Enterococcus faecalis Mature Biofilm

2021 ◽  
Vol 9 (6) ◽  
pp. 67
Author(s):  
Nerea Herce-Ros ◽  
Alejandro Álvarez-Sagües ◽  
Laura Álvarez-Losa ◽  
Estanislao Nistal-Villan ◽  
Ulises Amador ◽  
...  
Keyword(s):  
Body Temperature ◽  
Sodium Hypochlorite ◽  
Room Temperature ◽  
Positive Control ◽  
The Other ◽  
Passive Ultrasonic Irrigation ◽  
Bacteria Growth ◽  
Biofilm Removal ◽  
Ultrasonic Irrigation ◽  
Heating Up

The objectives of the present study were to assess the antibacterial effectiveness of two sodium hypochlorite (NaOCl) concentrations (2.5% and 5.25%) activated by means of two techniques, passive ultrasonic irrigation (PUI) and XP-endo® Finisher (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) (XPF) against bacteria growth in intracanal mature biofilm. Our aim was to determine if the effect of heating up NaOCl at body temperature (BT) contributed to an improvement of the efficacy of XPF. Sixty-two single-canal human roots previously instrumented were infected with E. faecalis inoculum at 0.5 McFarland and incubated at 37 °C for two weeks. Twelve specimens were randomly selected as positive control, and the remaining fifty were divided into five experimental groups (n = 10). The first two were irrigated with 2.5 vs. 5.25% NaOCl at room temperature (RT), activated with PUI, and the other three were irrigated with XPF. Of these three, two were irrigated using 2.5 vs. 5.25% NaOCl at RT and one was irrigated with 5.25% NaOCl at BT. Our results showed that NaOCl was effective in biofilm removal for all experimental groups (p > 0.05), especially in the groups irrigated with 5.25% NaOCl at room temperature (RT) activated with PUI and the group treated with 5.25% NaOCl at BT with XPF. These groups were the most successful ones (p < 0.001). NaOCl, activated with XPF, was as effective as PUI in biofilm removal from the apical third of the canal when it was used at higher concentration and heated up. This study indicates that XPF only reached the efficacy of PUI when NaOCl was heated up.

Immobilization Index of Liquid LLW in Cementitious Grouts

1995 ◽  
Vol 412 ◽  
Author(s):  
Sadananda Sahu ◽  
Sidney Diamond
Keyword(s):  
Fly Ash ◽  
Room Temperature ◽  
Liquid Waste ◽  
Chemical Species ◽  
Ionic Species ◽  
Cementitious Materials ◽  
The Other ◽  
Waste Solution ◽  
Low Level ◽  
The Individual

AbstractThe ability of grouts formulated from mixtures of cementitious materials and attapulgite clay to immobilize various chemical species in the projected off-gas waste stream from vitrification of Hanford low level tank wastes was studied. Three different solid blends were evaluated, with cement :fly ash : slag clay weight ratios of 3:3:3:1, 3:0:6:1, and 0:0:9:1. The blended solids were mixed with a simulated low level liquid waste solution containing Na+, NO2-, NO3-, PO43- and OH- ions, in the proportion of 1 liter of solution to 1 kg of solid blend, and were cured either at 22°C (room temperature), 50°C or 90°C. Pore solutions were expressed at various ages and were analyzed to determine the reductions in concentrations of the individual ionic species. The results were expressed in the form of immobilization index (I) calculated for each species. The immobilization indices for Na+ (I Na+ ) and for OH- (IOH-)were similar in each case, and were found to be highest when only slag and clay was present (blend 0:0:9:1). The immobilization index for phosphate, , was 1 in all cases, i.e. phosphate was completely removed from solution. On the other hand removal of NO2- and NO3- ions was generally ineffective.

scholarly journals The Application of a New Oxidation Mortar Bar Test to Mixtures containing Different Cementing Systems

2021 ◽  
Author(s):  
Bassili Guirguis ◽  
Medhat Shehata ◽  
Josée Duchesne ◽  
Benoît Fournier ◽  
Benoît Durand ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Heat Of Hydration ◽  
Iron Sulphide ◽  
Oxidizing Agent ◽  
Field Exposure ◽  
Bar Test ◽  
Reactive Alumina ◽  
Mortar Bar

The effects of different cementing systems on the expansion of mortars containing iron sulphide-bearing aggregate was studied. Using a recently developed oxidation mortar bar test, the results showed that cementing systems containing low-calcium fly ash, metakaolin, slag, high-sulphate resisting Portland cement, or low heat of hydration Portland cement could reduce the expansion by 50–85%. The main suggested mechanisms behind the reduced expansion is the more refined pore structure of samples with SCMs, and the reduced C3A of low heat of hydration Portland cement. The refined pore structure reduces the permeation of the oxidizing solution into the samples. The similarity of this to penetration of oxygen into concrete under field exposure needs to be determined. Soaking the samples for >3 h in the oxidizing agent can produce excessive expansion – not related to oxidation of iron sulphide phases – in samples with cementing blends containing reactive alumina such as metakaolin.

scholarly journals Properties of Indonesian plantain cultivars during ripening and recommendation for flour ingredients

2021 ◽  
Vol 39 (No. 1) ◽  
pp. 35-41
Author(s):  
Rima Kumalasari ◽  
Luki Vanadiani ◽  
Riyanti Ekafitri ◽  
Ina Siti Nurminabari ◽  
Dewi Desnilasari ◽  
...  
Keyword(s):  
Weight Loss ◽  
Relative Humidity ◽  
Room Temperature ◽  
Reducing Sugars ◽  
Starch Content ◽  
The Other ◽  
Physicochemical Changes ◽  
Ripening Stages ◽  
Stage 4 ◽  
Banana Flour

This research aims to examine the physicochemical changes in five Indonesian cultivars of plantain during the normal ripening and determine the optimal ripeness stage for flour. Cultivars 'Kapas', 'Tanduk', 'Raja Bulu', 'Siam', and 'Kepok Kuning' were selected for the research. The cultivars were stored at room temperature of 24.8–31.7 °C and relative humidity of 59.5%–99.9%. Peel colour, weight loss, pulp to peel ratio, firmness, pH, TSS, moisture content, starch, reducing sugars, and titratable acidity were evaluated. The results showed that the best unripe flour based on the starch content for 'Kapas', 'Raja Bulu', 'Tanduk', and 'Siam' cultivars was at stages 1–3 and 'Kepok Kuning' cultivar at ripening stages 1–2. On the other hand, in ripe banana flour, the best stage for 'Kepok Kuning', 'Tanduk', and 'Siam' cultivars was stage 4, for 'Raja Bulu' cultivar stages 4–5 and for 'Kapas' cultivar stages 4–7.

scholarly journals The Application of a New Oxidation Mortar Bar Test to Mixtures containing Different Cementing Systems

2021 ◽  
Author(s):  
Bassili Guirguis ◽  
Medhat Shehata ◽  
Josée Duchesne ◽  
Benoît Fournier ◽  
Benoît Durand ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Heat Of Hydration ◽  
Iron Sulphide ◽  
Oxidizing Agent ◽  
Field Exposure ◽  
Bar Test ◽  
Reactive Alumina ◽  
Mortar Bar

The effects of different cementing systems on the expansion of mortars containing iron sulphide-bearing aggregate was studied. Using a recently developed oxidation mortar bar test, the results showed that cementing systems containing low-calcium fly ash, metakaolin, slag, high-sulphate resisting Portland cement, or low heat of hydration Portland cement could reduce the expansion by 50–85%. The main suggested mechanisms behind the reduced expansion is the more refined pore structure of samples with SCMs, and the reduced C3A of low heat of hydration Portland cement. The refined pore structure reduces the permeation of the oxidizing solution into the samples. The similarity of this to penetration of oxygen into concrete under field exposure needs to be determined. Soaking the samples for >3 h in the oxidizing agent can produce excessive expansion – not related to oxidation of iron sulphide phases – in samples with cementing blends containing reactive alumina such as metakaolin.

Electron microscope studies of the plastic deformation of ternary alloys based on GaAs

1990 ◽  
Vol 48 (4) ◽  
pp. 1120-1120
Author(s):  
R. Haswell ◽  
U. Bangert ◽  
P. Charsley
Keyword(s):  
Plastic Deformation ◽  
Electron Microscope ◽  
Room Temperature ◽  
Stacking Faults ◽  
The Other ◽  
Ternary Alloys ◽  
Dislocation Mobility ◽  
Semiconducting Materials ◽  
Micro Indentation

A knowledge of the behaviour of dislocations in semiconducting materials is essential to the understanding of devices which use them . This work is concerned with dislocations in alloys related to the semiconductor GaAs . Previous work on GaAs has shown that microtwinning occurs on one of the <110> rosette arms after indentation in preference to the other . We have shown that the effect of replacing some of the Ga atoms by Al results in microtwinning in both of the rosette arms.In the work to be reported dislocations in specimens of different compositions of Gax Al(1-x) As and Gax In(1-x) As have been studied by using micro indentation on a (001) face at room temperature . A range of electron microscope techniques have been used to investigate the type of dislocations and stacking faults/microtwins in the rosette arms , which are parallel to the [110] and [10] , as a function of composition for both alloys . Under certain conditions microtwinning occurs in both directions . This will be discussed in terms of the dislocation mobility.

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