Hydration, shrinkage, pore structure and fractal dimension of silica fume modified low heat Portland cement-based materials

2021 ◽  
Vol 272 ◽  
pp. 121952
Author(s):  
Lei Wang ◽  
Minmin Jin ◽  
Yonghua Wu ◽  
Yongxiang Zhou ◽  
Shengwen Tang
Keyword(s):  
Fractal Dimension ◽  
Portland Cement ◽  
Pore Structure ◽  
Silica Fume ◽  
Cement Based Materials

scholarly journals Influence of Different Alkali Sulfates on the Shrinkage, Hydration, Pore Structure, Fractal Dimension and Microstructure of Low-Heat Portland Cement, Medium-Heat Portland Cement and Ordinary Portland Cement

2021 ◽  
Vol 5 (3) ◽  
pp. 79
Author(s):  
Yang Li ◽  
Hui Zhang ◽  
Minghui Huang ◽  
Haibo Yin ◽  
Ke Jiang ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Portland Cement ◽  
Pore Structure ◽  
Ordinary Portland Cement ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Crystal Forms ◽  
Pore Structures ◽  
Cement Based Materials ◽  
Mineral Compositions

In cement-based materials, alkalis mainly exist in the form of different alkali sulfates. In this study, the impacts of different alkali sulfates on the shrinkage, hydration, pore structure, fractal dimension and microstructure of low-heat Portland cement (LHPC), medium-heat Portland cement (MHPC) and ordinary Portland cement (OPC) are investigated. The results indicate that alkali sulfates magnify the autogenous shrinkage and drying shrinkage of cement-based materials with different mineral compositions, which are mainly related to different pore structures and hydration processes. LHPC has the lowest shrinkage. Otherwise, the effect of alkali sulfates on the autogenous shrinkage is more profound than that of drying shrinkage. Compared with the pore size distribution, the fractal dimension can better characterize the shrinkage properties of cement-based materials. It is noted that the contribution of K2SO4 (K alkali) to the promotion effect of shrinkage on cement-based materials is more significant than that of Na2SO4 (Na alkali), which cannot be ignored. The microstructure investigation of different cement-based materials by means of nuclear magnetic resonance (NMR), mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) shows that this effect may be related to the different pore structures, crystal forms and morphologies of hydration products of cement-based materials.

scholarly journals Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

2022 ◽  
Vol 6 (1) ◽  
pp. 40
Author(s):  
Lei Wang ◽  
Xiao Lu ◽  
Lisheng Liu ◽  
Jie Xiao ◽  
Ge Zhang ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Portland Cement ◽  
Pore Structure ◽  
Fractal Analysis ◽  
Concrete Structures ◽  
Mass Concrete ◽  
Pore Structures ◽  
Cement Based Materials ◽  
Induction Stage ◽  
Shrinkage Behavior

Currently, low heat Portland (LHP) cement is widely used in mass concrete structures. The magnesia expansion agent (MgO) can be adopted to reduce the shrinkage of conventional Portland cement-based materials, but very few studies can be found that investigate the influence of MgO on the properties of LHP cement-based materials. In this study, the influences of two types of MgO on the hydration, as well as the shrinkage behavior of LHP cement-based materials, were studied via pore structural and fractal analysis. The results indicate: (1) The addition of reactive MgO (with a reactivity of 50 s and shortened as M50 thereafter) not only extends the induction stage of LHP cement by about 1–2 h, but also slightly increases the hydration heat. In contrast, the addition of weak reactive MgO (with a reactivity of 300 s and shortened as M300 thereafter) could not prolong the induction stage of LHP cement. (2) The addition of 4 wt.%–8 wt.% MgO (by weight of binder) lowers the mechanical property of LHP concrete. Higher dosages of MgO and stronger reactivity lead to a larger reduction in mechanical properties at all of the hydration times studied. M300 favors the strength improvement of LHP concrete at later ages. (3) M50 effectively compensates the shrinkage of LHP concrete at a much earlier time than M300, whereas M300 compensates the long-term shrinkage more effectively than M50. Thus, M300 with an optimal dosage of 8 wt.% is suggested to be applied in mass LHP concrete structures. (4) The addition of M50 obviously refines the pore structures of LHP concrete at 7 days, whereas M300 starts to refine the pore structure at around 60 days. At 360 days, the concretes containing M300 exhibits much finer pore structures than those containing M50. (5) Fractal dimension is closely correlated with the pore structure of LHP concrete. Both pore structure and fractal dimension exhibit weak (or no) correlations with shrinkage of LHP concrete.

scholarly journals Ultrafine portland cement performance

2018 ◽  
Vol 68 (330) ◽  
pp. 157 ◽  
Author(s):  
C. Argiz ◽  
E. Reyes ◽  
A. Moragues
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Portland Cement ◽  
Silica Fume ◽  
Structure Refinement ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Blending Method ◽  
Cement Based Materials ◽  
Ultrafine Cement

By mixing several binder materials and additions with different degrees of fineness, the packing density of the final product may be improved. In this work, ultrafine cement and silica fume mixes were studied to optimize the properties of cement-based materials. This research was performed in mortars made of two types of cement (ultrafine Portland cement and common Portland cement) and two types of silica fume with different particle-size distributions. Two Portland cement replacement ratios of 4% and 10% of silica fume were selected and added by means of a mechanical blending method. The results revealed that the effect of the finer silica fume mixed with the coarse cement enhances the mechanical properties and pore structure refinement at a later age. This improvement is somewhat lower in the case of ultrafine cement with silica fume.

Study on the Influence of Air-Entraining Agent on the Impermeability of Cement-Based Composites Based on its Pore Structure by Fractal Theory

2010 ◽  
Vol 168-170 ◽  
pp. 615-618
Author(s):  
Zhi Qin Du ◽  
Wei Sun
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Mercury Intrusion Porosimetry ◽  
Fractal Theory ◽  
Mercury Intrusion ◽  
Pore Structures ◽  
Cement Based Materials

The effect of different quantity of air-entraining agent on the impermeability of cement-based materials are studied in this paper. Impermeability test and mercury intrusion porosimetry (MIP) method were used to characterize the impermeability and pore structures. The fractal dimension is used to describe the characteristic of pore structure and calculated by the data of MIP experiment. The result shows that owing to the improvement of pore structure, the impermeability performance of the cement-based composites is noticeably enhanced when air-entraining agent is added with appropriate quantity.

Research on Fractal Characteristics of Cement-Based Materials by Nitrogen Adsorption Method

2011 ◽  
Vol 415-417 ◽  
pp. 1545-1552 ◽  
Author(s):  
Ming Tang ◽  
Jing Qi Li
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Surface Area ◽  
Nitrogen Adsorption ◽  
Surface Characteristics ◽  
Adsorption Method ◽  
Surface Fractal Dimension ◽  
Surface Fractal ◽  
Cement Based Materials ◽  
Fractal Characteristics

In order to confirm the surface fractal dimension of the internal pore of complex porous materials by means of the FHH model and nitrogen adsorption method. Study the change rule on fractal characteristics of the pore of cement based materials further. The results shows that, surface area of the complex internal structure of cement based materials has the fractal characteristics observably. Testing and evaluating the fractal characteristics on surface area of the pore of cement-based materials is effective by nitrogen adsorption method. It is good for analyzing surface characteristics of pore structure further. Surface fractal dimension of pore structure and surface area have not good correlation. The characteristics and conclusion that quality fractal dimension of powder and surface area evaluating fineness of powder have not very good correlation is consistent.

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