scholarly journals Properties of High-Performance Concretes made of Black Sand at High Temperature

2021 ◽  
Vol 7 (1) ◽  
pp. 24-39
Author(s):  
Khaled A. Eltawil ◽  
Ahmed M. Tahwia ◽  
Mohamed G. Mahdy ◽  
Ahmed H. Abdelraheem
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Sem Analysis ◽  
Heavy Minerals ◽  
Fine Aggregate ◽  
Black Sand ◽  
Before And After ◽  
Insulating Properties ◽  
Better Than ◽  
Curing Age

To modify high-performance concrete (HPC) fireproofing properties, black sand (BS) was partially substituted as fine aggregate at various levels. This study aims at evaluating the BS reliability in improving HPC durability properties for various construction applications based on its unique heavy minerals. To achieve this, five HPC series blends were setup to substitute fine aggregate independently with BS. Substitution percentages ranged from 15 to 100% with consistent supplementary cementing materials (SCMs) proportion for each gathering. Tests were performed to assess compressive strength before and after fire exposure under various temperatures of 250, 500 and 750 °C at different curing age. Generally, blending FA with BS was better than using SF with BS. Utilizing BS in the range of 15 to 60% as fine aggregate with 10% FA improves HPC fire-insulating properties. Besides, Z1 SEM analysis observed homogenously and compacted HPC microstructure at 250 and 500 °C. Doi: 10.28991/cej-2021-03091634 Full Text: PDF

The Durability Study of Concrete in Sulfate Environment

2012 ◽  
Vol 204-208 ◽  
pp. 3137-3141
Author(s):  
Hong Xia Qiao ◽  
Yu Li ◽  
Zhong Mao He ◽  
Jin Mei Dong
Keyword(s):  
Portland Cement ◽  
High Performance ◽  
Elastic Moduli ◽  
High Performance Concrete ◽  
Salt Resistance ◽  
Fine Aggregate ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Sulfate Solutions ◽  
Better Than

Aiming at determining the durability of concrete in very salty regions, this study examines the performance of various high performance fine aggregate concretes in a sulfate environment, such as high performance concrete inside a composite additive, and Portland cement concrete and sulfate resistant cement concrete, all of which experienced dry-wet cycles in sodium sulfate solutions. By examining the changes of elastic moduli and analyzing the SEM of the concrete, this paper has found that the salt resistance of sulfate resistant cement concrete is no better than that of Portland cement concrete in the extremely aggressive dry-wet cycle environment but high performance concrete containing a composite additive has better resistance in a sulfate environment. Besides, the composite additive can create the environment for a second hydration to reduce the amount of Ca(OH)2 inside the concrete, and build additional C-S-H gel to reform the microstructure of concrete effectively. Finally, the paper offers some advice for mixing concrete in salt regions.

scholarly journals The Influences of Iron Ore Tailings as Fine Aggregate on the Strength of Ultra-High Performance Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Zhigang Zhu ◽  
Beixing Li ◽  
Mingkai Zhou
Keyword(s):  
Particle Size ◽  
Frost Resistance ◽  
High Performance ◽  
Iron Ore ◽  
High Performance Concrete ◽  
Fine Aggregate ◽  
Ultra High Performance Concrete ◽  
Iron Ore Tailings ◽  
Better Than

The present study looks for the feasibility of preparing UHPC with iron ore tailings (IOT for short) as fine aggregate. To enhance outstanding high performances, some influences on UHPC mortars were investigated such as different kinds of sands, different mix ratio of sands, and different largest particle size of fine aggregate. The results show that IOT have negligible poorer aggregate performance than silica sands but better than river sands. The strength of UHPC reaches the highest point when silica sands were instead 60% by IOT. As the largest particle size of fine aggregate is decreasing, the strength and frost resistance of UHPC were improved, but the liquidity was decreased. Micropowder of IOT affects the strength and the optimal content was 4%.

scholarly journals Producing Heavyweight High-Performance Concrete by Using Black Sand as Newly Shielding Construction Material

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5353
Author(s):  
Khaled A. Eltawil ◽  
Mohamed G. Mahdy ◽  
Osama Youssf ◽  
Ahmed M. Tahwia
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Elevated Temperatures ◽  
Gamma Ray ◽  
High Performance Concrete ◽  
Construction Material ◽  
Construction Materials ◽  
Linear Attenuation Coefficient ◽  
Fine Aggregate ◽  
Black Sand

Experimental work was carried out to study new fine aggregate shielding construction materials, namely black sand (BS). The BS effect on the mechanical, durability, and shielding characteristics of heavyweight high-performance concrete (HWHPC) was evaluated. This study aimed at improving various HWHPC properties, concertedly. Fifteen mixtures of HWHPC were made, with various variables, including replacing 10% and 15% of the cement with fly ash (FA) and replacing normal sand by BS at various contents (15%, 30%, 45%, 60%, 75%, and 100%). The test specimens were subjected to various exposure conditions, including elevated temperatures, which ranged from 250 °C to 750 °C, for a duration of 3 h; magnesium sulfate (MS) exposure; and gamma-ray exposure. The effects of elevated temperature and sulfate resistance on concrete mass loss were examined. The results revealed that BS is a promising shielding construction material. The BS content is the most important factor influencing concrete compressive strength. Mixes containing 15% BS demonstrated significantly better strength compared to the control mixes. Exposure to 250 °C led to a notable increase in compressive strength. BS showed a significant effect on HWHPC fire resistance properties, especially at 750 °C and a significant linear attenuation coefficient. Using 10% FA with 15% BS was the most effective mixing proportion for improving all HWHPC properties concertedly, especially at greater ages.

scholarly journals Mechanical Properties of High-Performance Concrete with Guinea Corn Husk Ash as Additive

2020 ◽  
Vol 5 (1) ◽  
pp. 131-145
Author(s):  
S.O Odeyemi ◽  
M.A Anifowose ◽  
R. Abdulwahab ◽  
W.O. Oduoye
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Sem Analysis ◽  
Target Strength ◽  
Construction Work ◽  
Split Tensile Strength ◽  
Corn Husk ◽  
Curing Age

Consideration on High Performance Concrete (HPC) has risen drastically because of the requirement for application of concrete volume with high strengths for construction work. In this study, the mechanical properties of HPC with Guinea Corn Husk Ash (GCHA) as supplement of cement was investigated. The proportioning of Ordinary Portland Cement (OPC) with GCHA is from 0 - 20%. Design of the concrete mix was done to achieve a characteristic strength of 50 N/mm². The chemical composition of the GCHA was determined using X-ray Fluorescence (XRF)  Slump and compacting factor of fresh HPC were determined. Concrete cubes (for compressive strength), beams (for flexural strength) and cylinder (for split tensile strength) samples were cast and cured in water for 7 - 56 days. Density, compressive, flexural, and split tensile strengths were determined on the hardened HPC and were further examined using SEM analysis. Compressive strength at 56 days showed that control and inclusion of 5% GCHA gave strength 56.85 N/mm2 and 57.76 N/mm2, respectively above the designed target strength of 56.56 N/mm2 while inclusion of 10% GCHA met characteristics strength of 50 N/mm2. However, 5% GCHA-concrete had the highest flexural and split tensile strengths at 56 days of curing. Integration of 10% GCHA as replacement of OPC would produce concrete of higher strengths compared to conventional HPC at longer curing age. Based on the SEM results, uniform distribution of filler was obtained at 10% GCHA inclusion. At higher percentage of GCHA, resulting composite presents multiple and distinct grains with possible weak interfaces.

The Dynamic Elastic Modulus and Microstructure Study of High Performance Concrete in Sulfate Environment

2010 ◽  
Vol 113-116 ◽  
pp. 1371-1374 ◽  
Author(s):  
Hong Xia Qiao ◽  
Hong Fa Yu ◽  
Zhong Mao He
Keyword(s):  
Portland Cement ◽  
High Performance ◽  
Elastic Moduli ◽  
High Performance Concrete ◽  
Fine Aggregate ◽  
Test Results ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Sulfate Solutions ◽  
Better Than

Aimed at determining the durability of concrete in very salty regions, this paper describes a study carried out to examine the performance of various high performance fine aggregate concrete in a sulfate environment, such as high performance concrete inside a composite additive, and Portland cement concrete, and sulfate resistant cement concrete. They experienced dry-wet cycles in sodium sulfate solutions. By examining the changes of elastic moduli and analyzing the SEM of the concrete, the test results show that the salt resistances of sulfate resistant cement concrete is no better than Portland cement concrete in the extremely aggressive dry-wet cycle environment, and high performance concrete containing a composite additive has better resistance to a sulfate environment. Besides, the composite additive can create the environment for a second hydration to reduce the amount of Ca(OH)2 inside the concrete, and build additional C-S-H gel to reform the microstructure of concrete effectively. Finally, the paper offers some advice for mixing concrete in salt regions.

Effect of Copper Slag as a Fine Aggregate on the Durability Characteristics of High-Performance Concrete (HPC) Containing Silica Fume

2020 ◽  
Vol 07 (02) ◽  
pp. 1-10
Author(s):  
Rizwan Ahmad Khan ◽  
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
High Performance Concrete ◽  
Copper Slag ◽  
Chloride Penetration ◽  
Interfacial Transition Zone ◽  
Fine Aggregate ◽  
Fresh Properties ◽  
Fine Aggregates ◽  
Effect Of Copper

This paper investigates the fresh and durability properties of the high-performance concrete by replacing cement with 15% Silica fume and simultaneously replacing fine aggregates with 25%, 50%, 75% and 100% copper slag at w/b ratio of 0.23. Five mixes were analysed and compared with the standard concrete mix. Fresh properties show an increase in the slump with the increase in the quantity of copper slag to the mix. Sorptivity, chloride penetration, UPV and carbonation results were very encouraging at 50% copper slag replacement levels. Microstructure analysis of these mixes shows the emergence of C-S-H gel for nearly all mixes indicating densification of the interfacial transition zone of the concrete.

scholarly journals Abrasion Resistance of Ultra-High-Performance Concrete for Railway Sleepers

2021 ◽  
Author(s):  
Ariful Hasnat ◽  
Nader Ghafoori
Keyword(s):  
Prestressed Concrete ◽  
Abrasion Resistance ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Positive Influence ◽  
Cementitious Material ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Ultra High Performance Concrete

AbstractThis study aimed to determine the abrasion resistance of ultra-high-performance concretes (UHPCs) for railway sleepers. Test samples were made with different cementitious material combinations and varying steel fiber contents and shapes, using conventional fine aggregate. A total of 25 UHPCs and two high-strength concretes (HSCs) were selected to evaluate their depth of wear and bulk properties. The results of the coefficient of variation (CV), relative gain in abrasion, and abrasion index of the studied UHPCs were also obtained and discussed. Furthermore, a comparison was made on the resistance to wear of the selected UHPCs with those of the HSCs typically used for prestressed concrete sleepers. The outcomes of this study revealed that UHPCs displayed excellent resistance against abrasion, well above that of HSCs. Amongst the utilized cementitious material combinations, UHPCs made with silica fume as a partial replacement of cement performed best against abrasion, whereas mixtures containing fly ash showed the highest depth of wear. The addition of steel fibers had a more positive influence on the abrasion resistance than it did on compressive strength of the studied UHPCs.

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