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 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 Preparation of Fly Ash/Epoxy Composites and Its Effects on Mechanical Properties

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 79 ◽  
Author(s):  
Jeesoo Sim ◽  
Youngjeong Kang ◽  
Byung Joo Kim ◽  
Yong Ho Park ◽  
Young Cheol Lee
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Tensile Strength ◽  
Fly Ash ◽  
Critical Point ◽  
Compression Strength ◽  
Industrial Waste ◽  
Epoxy Composite ◽  
The Other ◽  
Epoxy Composites

In this research, a fly ash/epoxy composite was fabricated using fly ash filler classified as industrial waste. The behavior of its mechanical properties was investigated by changing the volume of fly ash to 10, 30 and 50 vol.%. To determine the influence of particle size on the mechanical properties, we used two different sizes of the fly ash, which were separated by sieving to less than 90 μm and 53 μm. To optimize fabrication conditions, the viscosity of the fly ash/epoxy slurry was measured at various temperatures with different fly ash volume fractions. In terms of mechanical properties, tensile strength increased as the amount of fly ash increased, up to a critical point. On the other hand, the compression strength of the composite increased continuously as the amount of fly ash increased. Finally, the fracture surfaces were characterized and correlated with the mechanical properties.

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 Practical Prediction Models of Tensile Strength and Reinforcement-Concrete Bond Strength of Low-Calcium Fly Ash Geopolymer Concrete

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 875
Author(s):  
Chenchen Luan ◽  
Qingyuan Wang ◽  
Fuhua Yang ◽  
Kuanyu Zhang ◽  
Nodir Utashev ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Bond Strength ◽  
Prediction Models ◽  
Splitting Tensile Strength ◽  
Geopolymer Concrete ◽  
Structural Factors ◽  
Test Results ◽  
Portland Cement Concrete ◽  
Low Calcium

There have been a few attempts to develop prediction models of splitting tensile strength and reinforcement-concrete bond strength of FAGC (low-calcium fly ash geopolymer concrete), however, no model can be used as a design equation. Therefore, this paper aimed to provide practical prediction models. Using 115 test results for splitting tensile strength and 147 test results for bond strength from experiments and previous literature, considering the effect of size and shape on strength and structural factors on bond strength, this paper developed and verified updated prediction models and the 90% prediction intervals by regression analysis. The models can be used as design equations and applied for estimating the cracking behaviors and calculating the design anchorage length of reinforced FAGC beams. The strength models of PCC (Portland cement concrete) overestimate the splitting tensile strength and reinforcement-concrete bond strength of FAGC, so PCC’s models are not recommended as the design equations.

scholarly journals Coal Fly Ash Derived Silica Nanomaterial for MMMs—Application in CO2/CH4 Separation

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 78
Author(s):  
Marius Gheorghe Miricioiu ◽  
Violeta-Carolina Niculescu ◽  
Constantin Filote ◽  
Maria Simona Raboaca ◽  
Gheorghe Nechifor
Keyword(s):  
Fly Ash ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Coal Fly Ash ◽  
High Surface ◽  
Industrial Applications ◽  
Mixed Matrix Membranes ◽  
Co2 Removal ◽  
Mcm 41

In order to obtained high selective membrane for industrial applications (such as natural gas purification), mixed matrix membranes (MMMs) were developed based on polysulfone as matrix and MCM-41-type silica material (obtained from coal fly ash) as filler. As a consequence, various quantities of filler were used to determine the membranes efficiency on CO2/CH4 separation. The coal fly ash derived silica nanomaterial and the membranes were characterized in terms of thermal stability, homogeneity, and pore size distribution. There were observed similar properties of the obtained nanomaterial with a typical MCM-41 (obtained from commercial silicates), such as high surface area and pore size distribution. The permeability tests highlighted that the synthesized membranes can be applicable for CO2 removal from CH4, due to unnoticeable differences between real and ideal selectivity. Additionally, the membranes showed high resistance to CO2 plasticization, due to permeability decrease even at high feed pressure, up to 16 bar.

scholarly journals Effects of water absorption on the mechanical properties of hybrid natural fibre/phenol formaldehyde composites

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sekar Sanjeevi ◽  
Vigneshwaran Shanmugam ◽  
Suresh Kumar ◽  
Velmurugan Ganesan ◽  
Gabriel Sas ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Strength ◽  
Water Absorption ◽  
Hybrid Composites ◽  
Phenol Formaldehyde ◽  
Natural Fibre ◽  
The Other ◽  
Fibre Reinforcement ◽  
Dry Conditions

AbstractThis investigation is carried out to understand the effects of water absorption on the mechanical properties of hybrid phenol formaldehyde (PF) composite fabricated with Areca Fine Fibres (AFFs) and Calotropis Gigantea Fibre (CGF). Hybrid CGF/AFF/PF composites were manufactured using the hand layup technique at varying weight percentages of fibre reinforcement (25, 35 and 45%). Hybrid composite having 35 wt.% showed better mechanical properties (tensile strength ca. 59 MPa, flexural strength ca. 73 MPa and impact strength 1.43 kJ/m2) under wet and dry conditions as compared to the other hybrid composites. In general, the inclusion of the fibres enhanced the mechanical properties of neat PF. Increase in the fibre content increased the water absorption, however, after 120 h of immersion, all the composites attained an equilibrium state.

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