scholarly journals Development of Eco-Friendly Cement Using a Calcium Sulfoaluminate Expansive Agent Blended with Slag and Silica Fume

2021 ◽  
Vol 11 (1) ◽  
pp. 394
Author(s):  
Taewan Kim ◽  
Ki-Young Seo ◽  
Choonghyun Kang ◽  
Tak-Kee Lee
Keyword(s):  
Silica Fume ◽  
Mechanical Performance ◽  
Hydration Product ◽  
Early Age ◽  
Low Carbon ◽  
Calcium Sulfoaluminate ◽  
Mixing Ratios ◽  
Expansive Agent ◽  
Binder Ratio

This is an experimental study on the development of a low-carbon, eco-friendly cement containing a calcium sulfoaluminate expansive agent (CSAe), slag, and silica fume (SF). The cement to be developed has a low water/binder ratio (w/b) of 0.5 and is designed to be used for structural purposes, with focus on its mechanical performance. CSAe, slag, and SF were mixed at various mixing ratios. The main hydration product of the slag-based CSAe cement in the experiment was ettringite. Substituting less than 30% of CSAe showed a sufficient level of mechanical performance; that is, the material could be used as structural cement. SF controlled the excessive expansion of CSAe. However, since the developed slag-CSAe-SF cement has low early age (1 d) strength, follow-up research is needed for improvement.

Mechanical Performance of Steam-Cured Self-Compacting Concrete Incorporating Silica Fume and Limestone Powder

2021 ◽  
Vol 56 ◽  
pp. 111-122
Author(s):  
Youcef Ghernouti ◽  
Bahia Rabehi ◽  
Sabria Malika Mansour
Keyword(s):  
Heat Treatment ◽  
Silica Fume ◽  
Mechanical Performance ◽  
Limestone Powder ◽  
Maximum Temperature ◽  
Self Compacting Concrete ◽  
Curing Period ◽  
Heat Treated ◽  
Binder Ratio ◽  
Mechanical Strengths

In this paper, influence of heat treatment on evolution of mechanical strengths at early age, less than 24hours of self-compacting concretes containing limestone powder and silica fume as fine materials was investigated experimentally. Two compositions of self-compacting concrete have been studied; the first is elaborated with silica fume addition and the second with limestone powder, each mixture were prepared with a constant water/binder ratio of 0.39. Concrete samples were either cured in water at (23±1°C), or steam cured at 65°C maximum temperature over six hours (6h) curing period. Tests of mechanical strengths were performed on specimens cooled down slowly to room temperature after heating.The obtained results show that all self-compacting mixtures exhibited satisfying fresh properties and check EFNARC specifications of self-compacting concrete (slump flow diameter higher than 650mm, L-box ratio higher than 80% and sieve stability less than 17%).Mechanical strengths of concrete containing limestone addition are slightly lower than those of concrete based on silica fume at all ages. Moreover, heat treatment generates an improvement of compressive and flexural strength. Interesting compressive strengths are obtained. At 24 hours, after heat treatment, the strengths are already greater than 35 MPa. The values ​​are 37 MPa and 40 MPa for self-compacting concrete containing limestone powder and silica fume respectively compared to 40 MPa and 46 MPa obtained at 7 days for the corresponding non-heat treated concretes. Compressive strength gain of SCCs mixtures with limestone powder and with silica fume, undergoing heat treatment at the age of 24hours is 85% and 75% respectively compared to SCCs mixtures cured in water.

scholarly journals Rheological Behavior and Microstructure Characteristics of SCC Incorporating Metakaolin and Silica Fume

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2576 ◽  
Author(s):  
Gang Ling ◽  
Zhonghe Shui ◽  
Tao Sun ◽  
Xu Gao ◽  
Yunyao Wang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Silica Fume ◽  
Mechanical Performance ◽  
Free Water ◽  
Hydration Product ◽  
Replacement Ratio ◽  
Microstructure Characteristics ◽  
Beneficial Effects ◽  
Slump Flow ◽  
Strength And Durability

This study explores the effects of metakaolin (MK) and silica fume (SF) on rheological behaviors and microstructure of self-compacting concrete (SCC). The rheology, slump flow, V-funnel, segregation degree (SA), and compressive strength of SCC are investigated. Microstructure characteristics, including hydration product and pore structure, are also studied. The results show that adding MK and SF instead of 4%, 6% and 8% fly ash (FA) reduces flowability of SCC; this is due to the fact that the specific surface area of MK and SF is larger than FA, and the total water demand increases as a result. However, the flowability increases when replacement ratio is 2%, as the small MK and SF particles will fill in the interstitial space of mixture and more free water is released. The fluidity, slump flow, and SA decrease linearly with the increase of yield stress. The total amount of SF and MK should be no more than 6% to meet the requirement of self-compacting. Adding MK or SF to SCC results in more hydration products, less Ca(OH)2 and refinement of pore structure, leading to obvious strength and durability improvements. When the total dosage of MK and SF admixture is 6%, these beneficial effects on workability, mechanical performance, and microstructure are more significant when SF and MK are applied together.

Influence of Cold Weather on Compressive Strength in High Performance with Silica Fume

2014 ◽  
Vol 627 ◽  
pp. 445-448 ◽  
Author(s):  
Young Il Jang ◽  
Wan Shin Park ◽  
Sun Woong Kim ◽  
Song Hui Yun ◽  
Hyun Do Yun ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Silica Fume ◽  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Weather Condition ◽  
Weather Conditions ◽  
Cold Weather ◽  
Binder Ratio ◽  
Hot Weather

This paper addresses the influence of cold weather on the compressive strength of high performance concrete with silica fume under different curing days. Test variables of this study are weather condition (5°C, -5°C and-15°C) and different curing days (7days and 28 days). In this work, the specimen was designed a water-binder ratio of 0.34. One batches of concrete were prepared for each mixing hour, and the compressive strength of cylindrical concrete specimens was measured after 7 and 28 days. Test results for concrete compressive strength show that the concrete’s best mechanical performance occurred when there was the least difference between ambient temperature and concrete temperature, that is, during the later hours of the day in hot weather conditions.

The Study on the Early Age Cracking due to the Addition of Silica Fume into Concrete and the Trouble-Shooting Strategy

2011 ◽  
Vol 295-297 ◽  
pp. 824-829
Author(s):  
Chao Lung Hwang ◽  
Chun Tsun Chen ◽  
Le Anh Tuan Bui ◽  
Fondly Reymont Kurniawan
Keyword(s):  
Water Absorption ◽  
Silica Fume ◽  
Heat Of Hydration ◽  
Early Age ◽  
Design Algorithm ◽  
Shooting Technique ◽  
Trouble Shooting ◽  
Durability Index ◽  
Binder Ratio ◽  
Water To Binder Ratio

This study is mainly to investigate the early age cracking due to the addition of silica fume (SF) into concrete and to propose Densified Mixture Design Algorithm (DMDA) method as a trouble-shooting strategy. Specimens with different water-to-binder ratio (W/B) and silica fume content were prepared with ACI concrete (W/B = 0.23, 0.35 and 0.47; SF content = 0%, 10%, 20% and 30%) and DMDA concrete (W/B = 0.23, 0.35 and 0.47; coating paste thickness t = 5, 15 and 25 μm). Adding silica fume to the concrete system to replace part of cement may increase the crack intensity, and the rate of water absorption; but reduce the heat of hydration. DMDA method as a problem-shooting technique shows to have a better performance in reducing the crack intensities up to 41% with W/B = 0.23 and the better durability index than that of ACI method.

scholarly journals Hydration of Calcium Sulfoaluminate-Based Binder Incorporating Red Mud and Silica Fume

2019 ◽  
Vol 9 (11) ◽  
pp. 2270 ◽  
Author(s):  
Yubin Jun ◽  
Jae Hong Kim ◽  
Taewan Kim
Keyword(s):  
Compressive Strength ◽  
Silica Fume ◽  
Red Mud ◽  
Drying Shrinkage ◽  
Pozzolanic Activity ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Replacement Level ◽  
Calcium Sulfoaluminate ◽  
Expansive Agent

This study investigated the properties of hardened pastes made with calcium sulfoaluminate expansive agent (CSA), red mud, and silica fume. Five different ratios of 10:90, 20:80, 30:70, 40:60, and 50:50 were applied as the weight ratios of CSA and red mud. Red mud was replaced with 0, 5, and 10% silica fume by weight. Compressive strength, drying shrinkage, XRD, MIP, and SEM/EDS of the hardened pastes were performed. The results indicated that as the amount of CSA increased (i.e., as the amount of red mud decreased) up to 30%, sample strengths showed a tendency to increase. The main reaction product of the pastes was expansive ettringite, which was formed from the consumption of ye’elimite, anhydrite, gypsum, and Ca(OH)2. It was expected that C-S-H would be formed by the reaction of C2S in red mud; however, C-S-H phase was not present, and the pozzolanic activity due to the use of silica fume did not occur. The increase of CSA replacement level was effective for controlling the drying shrinkage of the samples. However, 50% replacement level of CSA induced excessive expansion, leading to the reduction in strength. It was found that the excessive expansion in the sample was reduced by the addition of silica fume.

scholarly journals Electrochemical Performance of Steel Embedded in CSA Concrete and Its Interfacial Microstructure

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Meimei Song ◽  
Qiu Li ◽  
Ke Wu ◽  
Yihua Dou
Keyword(s):  
Corrosion Resistance ◽  
Hydration Product ◽  
Interfacial Microstructure ◽  
Interfacial Zone ◽  
Low Carbon ◽  
Calcium Sulfoaluminate ◽  
Galvanostatic Polarization ◽  
Relationship Of ◽  
The Relationship

Calcium sulfoaluminate cement (CSA) is a low-carbon cementitious material that significantly reduces alkalinity and produces calcium hydroxide-free (CH-free) matrix environment in comparison to ordinary Portland cement (OPC). It might be, however, less efficient towards the passivation of steel in concrete and further investigation before widespread adoption is required. In this project, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) on polished samples was employed to provide the interfacial characterization of steel reinforced CSA concrete and study the relationship of interfacial quality and corrosion resistance of the embedded steel. The galvanostatic polarization behavior indicates that the steel embedded in CSA concrete remains passive for 28 days in absence of Cl− ions and carbonation. Microstructure analysis has shown that there is an Al-enriched layer at interfacial zone in CSA concrete with the main hydration product of AH3, which is also alkaline and is expected to improve the steel passivity. Furthermore, the interfacial zone has markedly reduced porosity compared to the bulk matrix, which leads to reduced possibility of current flow between anode and cathode and therefore improves the corrosion resistance of the embedded reinforcement.

scholarly journals Early-Age Behaviour of Fiber Reinforced High Performance Concretes

2018 ◽  
Vol 4 (2) ◽  
pp. 7
Author(s):  
Valeria Corinaldesi ◽  
Jacopo Donnini ◽  
Glauco Merlonetti
Keyword(s):  
Flexural Strength ◽  
High Performance ◽  
Mechanical Performance ◽  
Mechanical Tests ◽  
Strength Development ◽  
Early Age ◽  
Fiber Reinforced ◽  
Expansive Agent ◽  
Significant Difference ◽  
Hardened State

The aim of this experimental activity was to study the early-age behavior of several Fiber-Reinforced Concretes (FRCs) containing expansive agent. The investigation concerned the evaluation of the influence of different amounts of fibers (dosages of 2.0%, 1.75% and 1.5% by volume of FRCC) on the mechanical performance of FRCs. In particular, hooked brass-coated fibers were used and dead-burnt calcium oxide based expansive agent was employed at a dosage of 40 kg/m3. The attention was focused on the strength development at early ages. Mechanical tests were carried out at 0.25 (i.e. 6 hours, that is time of demolding), 1, 2, 7 up to 28 days of curing. The properties of FRCs were characterized at the fresh state, by measuring flow ability and consistency as well as at hardened state by measuring compressive and flexural strength up to 28 days. Flexural strength was measured on prismatic specimens according to the procedure described in EN 12390-5. The different dosage of fibers did not influence the values of compressive strength, while there is a significant difference in terms of 28-day flexural strength between the several mixtures depending on the different amount of fibers. In all cases at least 20 MPa of 28-day peak flexural strength were achieved.

scholarly journals Effect of Low Temperatures on the Mechanical Performance of GFRC Modified by Low Carbon Cement

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Meimei Song ◽  
Chuanlin Wang
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Low Temperatures ◽  
Mechanical Performance ◽  
Strain Curve ◽  
Hydration Product ◽  
Ultimate Strain ◽  
Low Carbon ◽  
Bending Performance ◽  
Freeze Thaw

Glass fibre reinforced cement (GFRC) is a composite material with great ductility but it undergoes severe strength and ductility degradation with ageing. Calcium sulfoaluminate (CSA) cement is low carbon cement, and more importantly, it exhibits great potential to produce more ductile and durable GFRC. This study focuses on mechanical performance, e.g., compressive strength, stress-strain curve, and freeze-thaw resistance of CSA/GFRC as well as its microstructural characteristics under low temperatures. XRD was applied to investigate the hydration mechanism of CSA cement under −5°C, 0°C, and 5°C. It was found out that low-temperature environments have very little effect on the type of hydration products, and the main hydration product of hydrated CSA cement cured under low temperatures is ettringite. Moreover, low-curing temperatures have an adverse effect on the compressive strength developments of CSA/GFRC but the strength difference compared with that under 20°C reduces gradually with increasing curing ages. In terms of bending performance, both ultimate tensile strength and ultimate strain value indicate considerable degradation with ageing under low temperatures after 14 d. The ultimate strain value reduces to 0.34% at −5°C, 0.39% at 0°C, and 0.44% at 5°C compared with 0.51% for that cured at 20°C for 28 d. The tensile strength of samples cured at −5°C for 28 d is only 15.2 MPa, taking up only 40% of that under 20°C. CSA/GFRC also demonstrated great capability in the antifreeze-thaw performance, and the corresponding strength remains 95.9%, 94.7%, 94.2%, and 94.3%, respectively, for that cured under 20°C, 5°C, 0°C, and −5°C after 50 freeze-thaw cycles. Microstructural studies reveal that densification of the interfilamentary space with intermixtures of C-A-S-H and ettringite is the main reason that causes the degradation of CSA/GFRC, which may result in loss on flexibility when forces are applied, therefore reducing the post-peak toughness to some extent.

Influence of Silica Fume on High-Performance Concrete

2014 ◽  
Vol 670-671 ◽  
pp. 437-440 ◽  
Author(s):  
Fan Wang ◽  
Shan Suo Zheng ◽  
Xiao Fei Wang
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Silica Fume ◽  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Split Tensile Strength ◽  
Binder Ratio ◽  
Water Binder Ratio

With the improvement of concrete materials and the emergence of new materials, adding silica fume to high-performance concrete (HPC) has been one of the important ways in concrete technology. In this paper, through experimental study on the mechanical performance of HPC with 5%, 10%, 15% and 20% silica fume replacing cement for different water-binder ratio, along with polycarboxylates high performance water-reducing admixture, silica fume has large effects on 28d compressive strength, split tensile strength and flexural strength of the HPC. Meanwhile, due to the different level of water-binder ratio, the relationship between split tensile strength, flexural strength and compressive strength is also obvious linear.

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