An Investigation Of A High Speed Shear Mixer On Selected Pastes And Mortars

1988 ◽  
Vol 137 ◽  
Author(s):  
M. L. Brown ◽  
W. B. Ledbetter ◽  
H. M. Jennings
Keyword(s):  
Cement Paste ◽  
High Speed ◽  
Initial Study ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Shear Mixing ◽  
Paddle Mixer

AbstractThe influence of shear mixing on selected properties of cement pastes and mortars was investigated by preparing specimens using an ordinary paddle mixer and a high speed shear mixer. The results appear to indicate that shear mixing influences the bond between paste and aggregate, particularily at low water:cement ratios. The properties of hardened cement paste did not change markedly as a result of high speed shear mixing used in this initial study.

scholarly journals PROPERTY CHANGE OF HARDENED CEMENT PASTE BY HIGH-SPEED IMPACT

2019 ◽  
Vol 72 (1) ◽  
pp. 77-82
Author(s):  
Yuya SAKAI ◽  
Ivwananji SIKOMBE ◽  
Keiko WATANABE
Keyword(s):  
Cement Paste ◽  
High Speed ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Property Change ◽  
High Speed Impact

scholarly journals Microscopic Change in Hardened Cement Paste due to High-Speed Impact

2019 ◽  
Vol 17 (9) ◽  
pp. 518-525
Author(s):  
Yuya Sakai ◽  
Ivwananji Sikombe ◽  
Keiko Watanabe ◽  
Hiroyuki Inoue
Keyword(s):  
Cement Paste ◽  
High Speed ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
High Speed Impact ◽  
Microscopic Change

scholarly journals Microscopic Change in Hardened Cement Paste Due to High-Speed Impact

2018 ◽  
Author(s):  
Yuya Sakai ◽  
Ivwananji Sikombe ◽  
Keiko Watanabe ◽  
Hiroyuki Inoue
Keyword(s):  
Cement Paste ◽  
High Speed ◽  
Impact Load ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
High Speed Impact ◽  
Gas Gun ◽  
Microscopic Change ◽  
The Moment ◽  
The Impact

Impact load was applied to hardened cement paste (HCP) specimens using a gas gun to investigate microscopic changes in the specimens and develop a better response model of concrete subjected to impact load. Plasma emission was observed at the moment of impact at 420 m/s and the colour of the portion near the impact point turned brighter. This brighter portion was analysed, and it was observed that the pore structure was coarser compared to the other portion; however, the results of thermogravimetry and X-ray diffraction analysis were similar. A possible reason is that the generated heat was instantaneous and the rate of the temperature increase in the HCP decreased due to evaporation of water in the HCP. These results indicate that during impact at a few hundred m/s, porosity increase due to heat effect is more dominant than porosity decrease due to mechanical compaction.

scholarly journals On Phase Identification of Hardened Cement Pastes by Combined Nanoindentation and Mercury Intrusion Method

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3349
Author(s):  
Jingwei Ying ◽  
Xiangxin Zhang ◽  
Zhijun Jiang ◽  
Yijie Huang
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Cement Paste ◽  
Phase Distribution ◽  
Gaussian Mixture ◽  
Hardened Cement ◽  
Phase Identification ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Mercury Intrusion

The micro-mechanical properties of hardened cement paste can be obtained by nanoindentation. Phases at different locations can generally be determined by using the Gaussian mixture model (GMM) method and the K-means clustering (KM) method. However, there are differences between analysis methods. In this study, pore structure and porosity of hardened cement paste aged three, seven, and 28 days were obtained by mercury intrusion porosimetry (MIP), and their micro-mechanical properties were obtained by the nanoindentation method. A new method, GMM-MIP and KM-MIP, was proposed to determine the phase of hardened cement paste based on the pore structure and nanoindentation results. The results show that GMM-MIP and KM-MIP methods are more reasonable than GMM and KM methods in determining the phase of hardened cement paste. GMM-MIP can be used to obtain reasonable phase distribution. If the micro-mechanical properties of each phase in hardened cement paste do not satisfy the normal distribution, the GMM method has significant defects.

scholarly journals DISTRIBUTION OF HYDRATION PRODUCTS IN THE MICROSTRUCTURE OF CEMENT PASTES

2020 ◽  
Vol 27 ◽  
pp. 84-89
Author(s):  
Michal Hlobil
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Numerical Study ◽  
Hardened Cement ◽  
Spatial Gradient ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Hydration Model

This case study focuses on the quantification of the amorphous hydrate distribution in the microstructure of hardened cement paste. Microtomographic scans of the hardenend cement paste were thresholded based on histogram image analysis combined with microstructural composition obtained from CEMHYD3D hydration model, to separate unhydrated cement grains, crystalline and amorphous hydrates, and capillary pores. The observed spatial distribution of the amorphous hydrate exhibited a strong spatial gradient as the amorphous gel tended to concentrate around dissolving cement grains rather than precipitate uniformly in the available space. A comparative numerical study was carried out to highlight the effect of the spatially (non)uniform hydrate distribution on the compressive strength of the hardened cement paste.

Hydration and Microstructure of Nano Modified Cement Paste

2021 ◽  
Vol 321 ◽  
pp. 9-14
Author(s):  
Gintautas Skripkiūnas ◽  
Ekaterina Karpova ◽  
Rostislav Drochytka ◽  
Jakub Hodul
Keyword(s):  
Cement Paste ◽  
Cement Hydration ◽  
Aqueous Suspension ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Microstructure Observation ◽  
Multi Walled Carbon Nanotubes ◽  
Hardened Cement Pastes ◽  
Walled Carbon Nanotubes

Hydration of cement systems modified by nano additives requires the understanding of its mechanisms. The present research is focused on the investigation of hydration processes in cement pastes modified by multi-walled carbon nanotubes (MWCNTs) suspension. The ultrasonication method was used for homogenization of MWCNTs in the volume of an aqueous suspension. The hydration of cement pastes was assessed by the calorimetry test. The prolongation of cement hydration in case of modification by MWCNT suspension was observed. The microstructure observation by scanning electron microscopy (SEM) was performed for identification of MWCNT's dispergation in hardened cement pastes and for the observation of cement hydration products. The compressive and flexural strength were tested to evaluate the effect of MWCNT on mechanical properties of hardened cement paste.

scholarly journals Hydration characteristics and structure formation of cement pastes containing metakaolin

2018 ◽  
Vol 149 ◽  
pp. 01013 ◽  
Author(s):  
Leonid Dvorkin ◽  
Nataliya Lushnikova ◽  
Oleksandr Bezusyak ◽  
Mohammed Sonebi ◽  
Jamal Khatib
Keyword(s):  
Pore Structure ◽  
Cement Paste ◽  
Average Diameter ◽  
Cementitious Materials ◽  
Mineral Admixture ◽  
Mineral Admixtures ◽  
Hardened Cement ◽  
Initial Structure ◽  
Hardened Cement Paste ◽  
Cement Pastes

Metakaolin (MK) is one of the most effective mineral admixtures for cement-based composites. The deposits of kaolin clays are wide-spread in the world. Metakaolin is comparable to silica fume as an active mineral admixture for cement-based composites. In this paper, the rheological and mechanical properties of cement paste containing metakaolin are investigated. The effect of MK is more evident at “tight” hydration conditions within mixtures with low water-cement ratio, provided by application of superplasticizers. The cement is replaced with 0 to 15% metakaolin, and superplasticizer content ranged from 0 to 1.5% by weight of cementitious materials (i.e. cement and metakaolin). An equation is derived to describe the relationship between the metakaolin and superplasticizer content and consistency of pastes. There is a linear dependence between metakalolin content and water demand. Second-degree polynomial describe the influence of superplasticizer content. The application of SP and MK may produce cement-water suspensions with water-retaining capacity at 50-70% higher than control suspensions. The investigation of initial structure forming of cement pastes with SP-MK composite admixture indicates the extension of coagulation structure forming phase comparing to the pastes without additives. Crystallization stage was characterized by more intensive strengthening of the paste with SP-MK admixture comparing to the paste without admixtures and paste with SP. Results on the porosity parameters for hardened cement paste indicate a decrease in the average diameter of pores and refinement of pore structure in the presence of metakaolin. A finer pore structure associated with an increase in strength. X-ray analysis data reveal a growing number of small-crystalline low-alkaline calcium hydrosilicates and reducing portlandite content, when MK dosage increases. Scanning electron microscopy (SEM) data confirm, that hardened cement paste containing MK has crystalline structure with dominance of partially crystalized hydrosilicates and gel-like formations.

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