scholarly journals Recycling Blast Furnace Ferronickel Slag as a Replacement for Paste in Mortar: Formation of Carboaluminate, Reduction of White Portland Cement, and Increase in Strength

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2687
Author(s):  
Qingfeng Guan ◽  
Jingliang Xia ◽  
Jing Wang ◽  
Faguang Leng ◽  
Yongxiang Zhou ◽  
...  
Keyword(s):  
Blast Furnace ◽  
Portland Cement ◽  
Performance Enhancement ◽  
Cement Content ◽  
Free Water ◽  
Hydration Products ◽  
Cement Replacement ◽  
Replacement Method ◽  
Ferronickel Slag ◽  
White Portland Cement

Blast furnace ferronickel slag (BFFS) is generated in the production of ferronickel alloys and is used as cement replacement in concrete or mortar. The effectivity in reducing cement consumption and improving performance are limited. By referring to the paste replacement method, this work used BFFS to replace an equal volume of the white Portland cement paste to obtain greater performance enhancement. BFFS was used with five levels of replacement (0%, 5%, 10%, 15%, 20%) and four water-to-cement ratios (0.40, 0.45, 0.50, 0.55) were designed. Fluidity, mechanical strength, hydration products, and pore structure of every mixture were measured. The results showed that the workability of the mortars decreased due to the reduced volume of water, but the 28-day compressive strength of the mortars increased, and the cement content of the mortars was also reduced by 33 wt %. The X-ray diffraction (XRD) patterns revealed that there existed a carboaluminate phase, and the presence of the ettringite was stabilized, indicating that the accumulating amount of the hydration products of the mortar increased. Furthermore, the BFFS could consume the portlandite and free water to form a higher amount of chemically bound water due to its pozzolanic activity. A high degree of hydration and a large volume of the hydration products refined the porosity of the hardened mortars, which explained the enhancement of the strength of the mortars. Compared to the cement replacement method, the paste replacement method was more effective in preparing eco-friendly mortar or concrete by recycling BFFS for reducing the cement content of the mortar while improving its strength.

scholarly journals Utilizing blast furnace ferronickel slag as paste replacement to reduce white Portland cement content and improve performance of mortar

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Qingfeng Guan ◽  
Jingliang Xia ◽  
Faguang Leng ◽  
Yongxiang Zhou
Keyword(s):  
Blast Furnace ◽  
Portland Cement ◽  
Carbon Dioxide Emissions ◽  
Drying Shrinkage ◽  
Improve Performance ◽  
Carbonation Depth ◽  
Replacement Method ◽  
Ferronickel Slag ◽  
Depth Water ◽  
White Portland Cement

AbstractAs a special type of cement that can provide construction with aesthetics, white Portland cement (WPC) is restricted by the high cost of its production. To reduce the consumption of WPC and carbon dioxide emissions without degrading the properties of mortar, this work produced various mortar mixes by replacing an equal volume of the paste (the total volume of WPC and water) with blast furnace ferronickel slag (FNS), the by-product of ferronickel smelting. The workability, 28-day compressive strength, carbonation depth, water permeability, and drying shrinkage test were conducted, and mercury intrusion porosimetry (MIP) test was used to characterize the pore structure. The results show that the paste replacement method is eco-friendlier and more effective than the traditional cement replacement technology in utilizing FNS to reduce WPC consumption, which may promote the development of white concrete construction.

Alkali Activation of Granulated Blast Furnace Slag

2010 ◽  
Vol 158 ◽  
pp. 1-11 ◽  
Author(s):  
Zi Qiao Jin ◽  
Xian Jun Lu ◽  
Shu Gang Hu
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Portland Cement ◽  
Blast Furnace Slag ◽  
Ordinary Portland Cement ◽  
Hydration Product ◽  
Early Age ◽  
Hydration Products ◽  
Granulated Blast Furnace Slag ◽  
Furnace Slag

In order to stimulate the potential cementitious property of granulated blast furnace slag (GBFS), the ground GBFS sample (Wei Fang Iron and Steel Corporation, China) was activated by lime and gypsum under different dosages. The results showed that lime is an effective activator for the slag, and the optimum dosage of lime is about 10% (w/w) of the slag. At the optimum dosage of lime, the 28 days compressive strength of the lime-slag paste is higher than that of 32.5 ordinary Portland cement (OPC). But, the early age strength (3 and 7 days compressive strength) of the lime-slag paste is lower than that of the OPC. Addition of gypsum can effectively improve the early age strength of the lime-slag paste. At the ratio of gypsum:lime:slag of 8.2:9.2:82.6 (w/w), both the early and long-term compressive strengths of the gypsum-lime-slag paste are higher than that of the OPC. According to XRD, TG-DTA and SEM detections of the hydration products of the lime-slag paste, the gypsum-lime-slag paste and the OPC paste, it reveals that the hydration process of the GBFS-based cementitious material is different from the ordinary Portland cement and the presence of ettringite (AFt) contributes to the early age strength of the pastes. The major hydration product of the OPC paste (<7 days) were measured as ettringite (AFt), but the AFt phase was not detected in the hydration product of the lime-slag paste and the major hydration product of the lime-slag paste was determined as amorphous CSH gel. However, AFt was detected in the hydration products of the gypsum-lime-slag paste in the early stages of hydration, and the formation of AFt is favorable for the early strength improvement of the material.

Chemical Activation of Cementing Properties of Granulated Blast Furnace Slags

2012 ◽  
Vol 454 ◽  
pp. 11-16
Author(s):  
Xian Jun Lu ◽  
Shu Gang Hu ◽  
Zi Qiao Jin
Keyword(s):  
Blast Furnace ◽  
Portland Cement ◽  
Amorphous Materials ◽  
Chemical Activation ◽  
Xrd Analysis ◽  
Hydration Products ◽  
X Ray ◽  
Early Strength ◽  
Activated Slag ◽  
Alkali Activated

Using CaO, NaOH and Na2CO3 as activators, the effects of dosage and combination of the activators on the cementing property of granulated blast furnace slags were investigated, and the hydration products of the activated slags were detected by X-ray powder diffraction (XRD) analysis. Results indicate that CaO can be used as an effective activator for the slag samples and its optimum dosage is about 10%, but the CaO activated slags shows much lower early strength than the Portland cement. However, the early strength of the CaO activated slag can be remarkably improved by the addition of NaOH or Na2CO3. Under the addition of about 6% NaOH or Na2CO3, the overall compressive strength of the alkali activated slag is higher than a 42.5MPa Portland cement. XRD analysis revealed that the hydration products of the alkali activated slags are mainly amorphous materials, which is quite different from that of the Portland cement.

scholarly journals Experimental Study on Mechanical Properties and Structural Characteristics of Modified Sludge in Foundation Pit

CONVERTER ◽  
2021 ◽  
pp. 11-21
Author(s):  
Shuren Wang, Et al.
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
High Efficiency ◽  
Cement Content ◽  
Structural Characteristics ◽  
Curing Time ◽  
Hydration Products ◽  
Foundation Pit ◽  
Early Strength

To explore the efficient method of sludge modification, Ultra-fine Portland cement (UPC) was introduced as a sludge modifier regarding Ordinary Portland Cement (OPC) modified sludge as a reference. The mechanical properties and microstructural changes of UPC-modified sludge with different curing time and cement content were carried out by unconfined compressive strength (UCS), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) tests. Results show that the UCS of UPC-modified sludge varies with curing time and cement content in the same way as that of OPC-modified sludge. However, compared with OPC-modified sludge, UPC has a higher sludge modification efficiency, and the UPC-modified sludge has greater compressive strength, significantly early-strength, and stronger resistance to deformation. The stress-strain curves of UPC-modified sludge present significant peak stresses, and which show a brittle failure mode. The combination of the hydration products calcium silicate hydrate (C-S-H) gels and ettringite (Aft) crystals are the essential reason for the improvement of the macroscopic strength of the modified sludge. In contrast to OPC, the UPC hydrates faster and more fully. The UPC-modified sludge can generate more hydration products under the same conditions, this is why that has high efficiency and early-strength. The conclusions obtained in this study can provide a reference for the similar engineering application of ultra-fine cement in modified sludge.

scholarly journals Efficiency of Rice Husk Ash as Cementitious Material in High-Strength Cement-Admixed Clay

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Pornkasem Jongpradist ◽  
Watee Homtragoon ◽  
Raksiri Sukkarak ◽  
Warat Kongkitkul ◽  
Pitthaya Jamsawang
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Cement Content ◽  
High Strength ◽  
Compression Tests ◽  
Cement Replacement ◽  
Soil Cement ◽  
Partial Cement Replacement

The potential and efficiency of using rice husk ash (RHA) to add up or partially replace Portland cement in deep cement mixing technique are examined. A series of unconfined compression tests on cement-RHA-stabilized clay are conducted to investigate the influence of RHA on the mixture properties. Special attention is paid to its efficiency for increasing the strength by partial cement replacement to obtain high-strength soil cement, and it is compared with fly ash. Test results indicate that up to 35% of RHA could be advantageously added up to enhance the strength if the cement content in the mixture is larger than 10%. The RHA enhances the strength of cement-admixed clay by larger than 100% at 28 days. For curing time of 14 and 28 days, the RHA exhibits higher efficiency on Portland cement replacement when the cement and overall cementitious contents are not less than 20 and 35%, respectively. The optimum condition for high-strength mixture is achieved when RHA is added to the 20% cement content mixture. When compared with fly ash of similar grain size, the efficiency of RHA is higher when the content to be added is greater than 15%. This indicates the suitability of RHA for use in high-strength soil-cement.

scholarly journals Surface Characteristics of Portland Cement/Blast Furnace Slag Mixtures

1996 ◽  
Vol 13 (6) ◽  
pp. 461-467 ◽  
Author(s):  
Kh.A. Khalil
Keyword(s):  
Blast Furnace ◽  
Portland Cement ◽  
Blast Furnace Slag ◽  
Surface Characteristics ◽  
Hydration Products ◽  
Cement Pastes ◽  
Degree Of Hydration ◽  
Granulated Blast Furnace Slag ◽  
Granulated Slag ◽  
Furnace Slag

The effect of the degree of hydration and amounts of granulated blast furnace slag on the surface properties of Portland cement pastes were studied. The results obtained showed that the specific surface area SBET (m2/g) and pore volume Vp (cm3/g) decreased on increasing the degree of hydration. The addition of different amounts of granulated slag effected a decrease in SBET and Vp to an extent proportional to the amount present. These results were attributed to a replacement of clinker by the amounts of slag added and the formation of hydration products.

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