scholarly journals Effect of Hydrogen Nanobubbles on the Mechanical Strength and Watertightness of Cement Mixtures

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1823
Author(s):  
Won-Kyung Kim ◽  
Young-Ho Kim ◽  
Gigwon Hong ◽  
Jong-Min Kim ◽  
Jung-Geun Han ◽  
...  
Keyword(s):  
Mercury Intrusion Porosimetry ◽  
Cement Mortar ◽  
Stable State ◽  
Pozzolanic Reaction ◽  
Hydration Reaction ◽  
High Concentration ◽  
Mercury Intrusion ◽  
Electron Microscope Analysis ◽  
Mixing Water ◽  
Cement Mixtures

This study analyzed the effects of applying highly concentrated hydrogen nanobubble water (HNBW) on the workability, durability, watertightness, and microstructure of cement mixtures. The number of hydrogen nanobubbles was concentrated twofold to a more stable state using osmosis. The compressive strength of the cement mortar for each curing day was improved by about 3.7–15.79%, compared to the specimen that used general water, when two concentrations of HNBW were used as the mixing water. The results of mercury intrusion porosimetry and a scanning electron microscope analysis of the cement paste showed that the pore volume of the specimen decreased by about 4.38–10.26%, thereby improving the watertightness when high-concentration HNBW was used. The improvement in strength and watertightness is a result of the reduction of the microbubbles’ particle size, and the increase in the zeta potential and surface tension, which activated the hydration reaction of the cement and accelerated the pozzolanic reaction.

Cement render and mortar and their damages due to salt crystallization in the Holy Trinity Dominicans monastery in Cracow, Poland

2020 ◽  
Author(s):  
Mariola Marszałek ◽  
Krzysztof Dudek ◽  
Adam Gaweł ◽  
Jerzy Czerny
Keyword(s):  
Laboratory Tests ◽  
Mercury Intrusion Porosimetry ◽  
Cement Mortar ◽  
Salt Crystallization ◽  
Secondary Minerals ◽  
X Ray ◽  
Mercury Intrusion ◽  
Holy Trinity ◽  
Micro Raman Spectroscopy ◽  
Jurassic Limestone

<p>The presented investigations are focused on a part of the 13<sup>th</sup> century Church of the Holy Trinity Dominicans monastery in Cracow, Poland, and include the wall façade of the 17<sup>th </sup>century Myszkowski chapel. The chapel was probably designed by Santi Gucci Fiorentino and built by his workshop. Southern façade of the chapel is made of Tertiary limestone blocks that make characteristic rusticated wall. Lower part of the façade is covered with cement and the basement is made of irregular fragments of Jurassic limestone and Cretaceous sandstone partly replaced and bound with cement mortar. The façade revealed clear signs of damage ranging from dark gray soiling of the surface, scaling to efflorescences. The last ones – mainly on the border of limestone blocks and the cement in the part of the basement.</p><p>Laboratory tests included mineralogical, chemical and petrophysical analyses. Optical microscopy, scanning electron microscopy (SEM-EDS), micro-Raman spectroscopy and X-ray diffractometry (XRD) were used for analysing materials and deterioration products of the cement render and mortar. The petrophysical properties of the materials have been performed using mercury intrusion porosimetry. The secondary minerals detected include mainly gypsum CaSO<sub>4</sub>·2H<sub>2</sub>O, thenardite Na<sub>2</sub>SO<sub>4</sub>, <sub> </sub>aphthitalite (Na,K)<sub>3</sub>Na(SO<sub>4</sub>)<sub>2</sub>, darapskite, Na<sub>3</sub>(SO<sub>4</sub>)(NO<sub>3</sub>)·H<sub>2</sub>O, nitre KNO<sub>3</sub>, nitratine NaNO<sub>3</sub>, ettringite Ca<sub>6</sub>Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>(OH)<sub>12</sub>·26H<sub>2</sub>O and monosulphite Ca<sub>4</sub>Al<sub>2</sub>O<sub>6</sub>SO<sub>3</sub>·11H<sub>2</sub>O. Lower blocks of the façade covered with cement contain chiefly gypsum, ettringite and monosulphite, cement from the basement – gypsum and nitre; while efflorescences – thenardite, aphthitalite, darapskite, nitre and nitratine. The origin of the salts have been discussed and the differences in their type have been associated with composition of the materials and their physicochemical properties.</p><p>This work has been financially supported by the AGH University of Science and Technology, statutory grant no. 16.16.140.315.</p>

Hydration and microstructure of concrete containing high volume lithium slag

2020 ◽  
Vol 10 (3) ◽  
pp. 430-436
Author(s):  
Zhihai He ◽  
Jingyu Chang ◽  
Shigui Du ◽  
Chaofeng Liang ◽  
Baoju Liu
Keyword(s):  
Mercury Intrusion Porosimetry ◽  
High Volume ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Supplementary Cementitious Materials ◽  
Mineral Admixtures ◽  
Sustainable Construction ◽  
Mercury Intrusion ◽  
Variation Trends ◽  
Lithium Slag

Due to requirements for environmental protection, saving of resources and sustainable construction in the future, investigation on the use of high volume mineral admixtures as supplementary cementitious materials in concrete was carried out in this study. The effect of high volume lithium slag (LS) to partially replace cement by weight on compressive strengths of concrete was experimentally investigated, and the hydration of hardened paste was measured by non-evaporable water. Moreover, the microstructure of concrete was determined by mercury intrusion porosimetry and scanning electron microscope methods. Results showed that the use of high volume LS reduced compressive strengths of concrete at early ages, and compressive strengths were remarkably improved at later ages, with concrete containing 40% LS being close to that of the control concrete. Hydration of hardened paste showed similar variation trends with compressive strengths. The highvolume LS degraded concrete microstructure at early ages, and 40% LS improved concrete microstructure at the later ages, due to the filling effect and pozzolanic reaction of LS. However, there still existed defects in microstructure of concrete containing 60% LS, with increased harmful porosity, especially interfacial transition zone.

May the Piezoresistivity of GNP-Modified Cement Mortar Be Related to Its Fractal Structure?

2021 ◽  
Vol 5 (4) ◽  
pp. 148
Author(s):  
Nanxi Dang ◽  
Jin Tao ◽  
Qiang Zeng ◽  
Weijian Zhao
Keyword(s):  
Fractal Structure ◽  
Mercury Intrusion Porosimetry ◽  
Cement Mortar ◽  
Fractal Dimensions ◽  
Gauge Factor ◽  
Mercury Intrusion ◽  
Multi Scale ◽  
Fractal Models ◽  
Cement Mortars ◽  
Electron Scanning Microscopy

High piezoresistivity of cement-based composites tuned by conductible fillers provides a feasible way to develop self-sensing smart structures and buildings. However, the microstructural mechanisms remain to be properly understood. In the present work, the piezoresistivity of cement mortar with different dosages of graphene nanoplatelets (GNPs) was investigated, and the microstructure was assessed by electron scanning microscopy (SEM) and mercury intrusion porosimetry (MIP). Two surface fractal models were introduced to interpret the MIP data to explore the multi-scale fractal structure of the GNP-modified cement mortars. Results show that the incorporation of GNPs into cement mortar can roughen the fracture surfaces due to the GNPs’ agglomeration. Gauge factor (GF) rises and falls as GNP content increases from 0% to 1% with the optimal piezoresistivity observed at GNP = 0.1% and 0.05%. The GF values of the optimum mortar are over 50 times higher than those of the reference mortar. Fractal dimensions in macro and micro fractal regions change with GNP content. Analysis shows that the fractal dimensions in micro region decrease first and then increase with the increase of GF values. GNPs not only impact the fractal structure of cement mortar, but also alter the tunneling and contact effects that govern the piezoresistivity of composite materials.

scholarly journals Effects of Gamma-Ray Irradiation on Hardened Cement Mortar

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Yuliia Khmurovska ◽  
Petr Štemberk ◽  
Svyatoslav Sikorin ◽  
Jiří Němeček ◽  
Daria Jóźwiak-Niedźwiedzka ◽  
...  
Keyword(s):  
Diffraction Analysis ◽  
Gamma Ray ◽  
Mercury Intrusion Porosimetry ◽  
Cement Mortar ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mercury Intrusion ◽  
Significant Difference ◽  
Gamma Ray Irradiation ◽  
Control Samples

AbstractThe effect of gamma-ray irradiation on cement mortar properties is investigated in this study in order to understand the mechanism behind the strength and stiffness reduction, which may be significant according to the available researches. 60Co irradiation facility with the generating dose rate of 0.1–10 Gy/s and the total activity of 4.4·1015 Bq (120 kCi) was used to perform the irradiation, so that the total observed dose of the irradiated samples reached the values ranging from 12.0 to 15.0 MGy. An identical set of control samples was placed in the same laboratory conditions away from gamma radiation. The results of nanoindentation, X-ray diffraction analysis and mercury intrusion porosimetry of the irradiated and the control samples are shown and explained in detail in this study. The nanoindentation creep compliance and the nanoindentation elastic modulus of the irradiated and the control samples do not show any significant difference. The mineral composition obtained using the X-ray diffraction analysis of the irradiated and the control samples is also similar. The pore structure rearrangement and microcrack occurrence, which were evidenced by the mercury intrusion porosimetry and scanning electron microscopy, led to the porosity increase and may be attributed to the significant decrease of compressive strength.

Influences of Ground Limestone Fineness on the Properties of Cement-Based Materials

2012 ◽  
Vol 517 ◽  
pp. 403-410
Author(s):  
Jia Xiao ◽  
Bao Guo Ma ◽  
Rong Zhen Dong ◽  
Cai Yun Xu
Keyword(s):  
Pore Structure ◽  
Mercury Intrusion Porosimetry ◽  
Cement Mortar ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Mercury Intrusion ◽  
Setting Times ◽  
Cement Based Materials ◽  
Hardened Cement Pastes ◽  
Ground Limestone

The effect of ground limestone fineness on the properties and mechanism of cement-based composite materials was investigated. The setting times, fluidity and strength of cement mortar were measured. In order to identify the mechanism effect of ground limestone fineness on the microstructure of the hardened cement pastes, microstructure analyses such as calorimetry analysis and Mercury Intrusion Porosimetry (MIP) were also performed. Experimental results indicated that the setting times are shortened, and the fluidity and strength of cement mortar are improved with the ground limestone fineness increases. The increase of the ground limestone fineness can effectively inhibit the pore structure of hardened paste, which due to mortar and paste samples incorporating replacement levels of ground limestone, and improve the pore structure of hardened paste.

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