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1

Prediction of microstructural evolution in fly ash-modified cementitious system: A computational study

Yadeta Andualem E., Goyal Pradeep K., Sarkar Raju

Materials Science Poland

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2023

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Vol. 41, No. 4

68--77

EN

The intricate interaction between supplementary cementitious materials (SCMs) and cementitious systems profoundly influences the performance and sustainability of cementitious composites. This study explores the microstructural evolution of fly ash (FA)-modified cement paste by employing a three-dimensional cement hydration and microstructure development (CEMHYD3D) modeling package. Through comprehensive simulations, the influence of varying FA content on hydration phase evolution and pore structure within the cementitious system is revealed. As the proportion of FA within the cementitious mixtures increases, there is a substantial enhancement in the rate of hydration. Notably, the incorporation of FA introduces a significant augmentation in the hydration rate, a phenomenon with potential implications for the long-term performance of FA-modified cementitious materials. The prediction results also highlight that increasing FA substitution in cement leads to finer and more interconnected pore networks due to the pozzolanic reaction. These perceptions hold significant implications for optimizing cementitious mixes and advancing sustainable construction practices. The model-predicted results have been validated with experiments, and they are successful in predicting the microstructural evolution in FA-modified cement paste. In summary, the prediction model bridges the theoretical and practical implementation gaps by providing a thorough understanding of the microstructural evolution of FA-modified cement paste. Furthermore, it provides invaluable guidance for tailoring FA-blended cement compositions, thus promoting their enhanced performance and sustainability in the realm of cementitious materials.

2

Electromagnetic properties of cement paste after microwave pretreatment

Li Yue, Liu Yunze, Jin Caiyun

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e185, 2023

EN

In this paper, the effect of microwave pretreatment on the electromagnetic properties of cement paste was investigated. Four different durations of microwave pretreatment were carried out after the standard conditioning of cement paste specimens for 3 days. Subsequently, the electromagnetic properties of the cement paste were tested, the electromagnetic losses of the specimens were calculated and the changes in the dielectric constants were analyzed. Finally, the mechanism by which microwave pretreatment affects the electromagnetic properties was analyzed based on the pore characteristics and hydration results. The results show that microwave pretreatment can improve the electromagnetic loss as well as the dielectric constant of cement paste specimens, but has no significant effect on the magnetic permeability. With the increase of microwave pretreatment time, the reflection loss, absorption loss, and total loss of electromagnetic waves increase significantly, and the multiple reflection loss decreases. The real part of the dielectric constant, imaginary part, and loss angle tangent all increased. There are two main reasons for the increase in electromagnetic loss and dielectric properties of the specimens after microwave pretreatment. One is the significant increase in the percentage of micropores less than 50 nm in the specimen, which increases the reflection loss and absorption loss of electromagnetic waves. On the other hand, microwave pretreatment significantly increased the degree of hydration of the specimen, making the specimen intermediate electrical properties of the larger proportion of the material phase (such as gel), which in turn increased the electromagnetic loss.In this paper, the effect of microwave pretreatment on the electromagnetic properties of cement paste was investigated. Four different durations of microwave pretreatment were carried out after the standard conditioning of cement paste specimens for 3 days. Subsequently, the electromagnetic properties of the cement paste were tested, the electromagnetic losses of the specimens were calculated and the changes in the dielectric constants were analyzed. Finally, the mechanism by which microwave pretreatment affects the electromagnetic properties was analyzed based on the pore characteristics and hydration results. The results show that microwave pretreatment can improve the electromagnetic loss as well as the dielectric constant of cement paste specimens, but has no significant effect on the magnetic permeability. With the increase of microwave pretreatment time, the reflection loss, absorption loss, and total loss of electromagnetic waves increase significantly, and the multiple reflection loss decreases. The real part of the dielectric constant, imaginary part, and loss angle tangent all increased. There are two main reasons for the increase in electromagnetic loss and dielectric properties of the specimens after microwave pretreatment. One is the significant increase in the percentage of micropores less than 50 nm in the specimen, which increases the reflection loss and absorption loss of electromagnetic waves. On the other hand, microwave pretreatment significantly increased the degree of hydration of the specimen, making the specimen intermediate electrical properties of the larger proportion of the material phase (such as gel), which in turn increased the electromagnetic loss.

3

Analysis of the degradation process of sand-lime plasters under the impact of crystallization pressure

Ślusarek Jan, Słomka-Słupik Barbara, Bochen Jerzy

Architecture Civil Engineering Environment

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2023

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Vol. 16, no. 2

137--149

EN

A masonry basement wall was heavily dampened due to the lack of waterproofing in the ground contact area. Internal sand-lime wall plaster samples were subjected to chemical, physical and strength tests. The main phases of the damaged plaster were quartz and calcite. A measuring method of the tensile strength of plasters was proposed. A polar-symmetric deformation problem of a thick-walled spherical tank, allowing for the estimation of circumferential stresses in the spherical model was used for the analysis. It was found that the same values of porosity correspond to identical values of circumferential stresses, regardless of the values of the radii of the analyzed model. Thus the purpose of the presented research was to demonstrate that the mentioned dependence applied in the adopted model may be useful for the analysis of problems involving the resistance of internal plaster structure to the expansion caused by crystallization pressure.

4

Parametry strukturalne błękitu pruskiego na tle innych sorbentów pochodzenia naturalnego i antropogenicznego

Gajda Aleksandra, Sierant Anna, Jodłowski Przemysław

Prace Instytutu Mechaniki Górotworu PAN

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2022

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T. 24, nr 1-4

37--44

PL

W artykule zaprezentowano wyniki badań niskociśnieniowej adsorpcji gazowej błękitu pruskiego z użyciem N2 jako adsorbatu w celu określenia parametrów strukturalnych oraz CO2 w celu określenia parametrów sorpcyjnych. Zgodnie z danymi literaturowymi błękit pruski pod względem adsorpcji kationów porównywany jest do zeolitów, a jego struktura krystaliczna do MOFów. Z uwagi na ten fakt przeprowadzono badania porównawcze, wyznaczając parametry strukturalne zeolitu SN oraz MOFa MIL-140. Powierzchnia właściwa modelu adsorpcji wielowarstwowej BET dla błękitu pruskiego dla zoptymalizowanej temperatury odgazowania osiągnęła wartość 85,02 m2/g, przy całkowitej pojemności sorpcyjnej BET 19,53 cm3/g, co pozwoliło na uszeregowanie go jako sorbentu pomiędzy zeolitem a MOFem. Otrzymane wyniki porównano także z pracami innych autorów.

EN

This paper presents the results of a low-pressure gas adsorption study of Prussian blue using N2 as adsorbate to determine structural parameters and CO2 to determine sorption parameters. According to the literature, Prussian blue is compared to zeolites in terms of cation adsorption, and its crystal structure to MOFs. In view of this fact, a comparative study was carried out, determining the structural parameters of zeolite SN and MOF MIL-140. The specific surface area of the BET multilayer adsorption model for Prussian blue for the optimized degassing temperature reached 85.02 m2, with a total sorption capacity (BET) of 19.53 cm3/g, which allowed it to be ranked as a sorbent between zeolite and MOF. The obtained results were also compared with the works of other authors.

5

Pore structure and surface properties of diatomite with mechanical grinding and its influence on humidity control

Hu Zhibo, Zheng Shuilin, Li Jinyu, Zhang Shuaiqian, Liu Min, Wang Zhicheng, Li Jiaxin, Sun Hongjuan

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 6

art. no. 153509

EN

Mechanical grinding (MG) is an effective method to regulate the pore structure and surface properties of mineral material. Grinding diatomite samples were prepared by horizontal sander under different grinding time. The pore structure and surface properties of grinding samples were characterized systematically by the particle size analysis, low temperature nitrogen adsorption, MIP, fractal theory, XRD, SEM, TEM, FTIR and surface hydroxyl density analysis. The humidity control performance (HCP) of grinding diatomite was tested under different temperature and relative humidity. The relationship among pore structure, surface properties and HCP was analyzed. The results show that macroporous is more easily damaged by mechanical force than mesoporous, and the internal blind holes structure can be opened. The HCP of diatomite is positively correlated with the specific surface area, mesoporous volume, the inhomogeneity of macroporous structure and the number of hydroxyl groups, while negatively correlated with the proportion of macroporous volume.

6

Wpływ struktury porowatości na odporność na korozję betonu wysokowartościowego zawierającego metakaolin

Philip Nivin, Jędrzejewska Agnieszka, Varughese Abynoah E., James Jomy

Cement Wapno Beton

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2022

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R. 27, nr 5

302--319

PL

Chociaż beton jest uważany za trwały materiał, środowisko, na które jest narażony, ma duży wpływ na jego trwałość. Trwałość betonu może być zagrożona ze względu na jego porowatość, szczególnie w trudnych warunkach ekspozycji, którymi jest na przykład środowisko morskie. Żelbetowe elementy konstrukcji morskich, do których należą między innymi mosty, nabrzeża i doki, są poddawane różnego rodzaju oddziaływaniom. Należą do nich cykliczne nawilżanie i suszenie, stan pełnego zanurzenia oraz kontakt z chlorkami. Aby poprawić strukturę porów w betonie i wytrzymałość takich konstrukcji, niezbędne jest stosowanie betonu wysokowartościowego. W badaniach przedstawionych w niniejszej pracy, do produkcji betonu wysokowartościowego zastosowano metakaolin [MK], jako częściowy zamiennik cementu. Wyniki tych badań pokazały, że zastosowanie metakaolinu zmniejsza porowatość betonu, a wraz ze spadkiem porowatości znacznie zmniejsza się szybkość procesu korozji. Beton wysokowartościowy zawierający metakaolin badano przez 365 dni, w celu określenia zmian struktury porowatości po długim okresie ekspozycji, z wykorzystaniem metody iCOR® NDT. Metoda ta służy do określania odporności na korozję i rezystywności betonu bogatego w metakaolin, o dużej wytrzymałości, w warunkach symulowanego nawilżania i suszenia, w środowisku wody morskiej, w kilku okresach. Efekt pogorszenia właściwości betonu, spowodowany symulowanym nawilżaniem i suszeniem w środowisku wody morskiej, był również badany dla przyczepności próbek poddanych normalnym i korozyjnym warunkom ekspozycji.

EN

Even though concrete is considered to be durable, the environment to which the concrete is exposed plays an important role in its durability. The durability of concrete is challenged due to its porous nature, which is especially important in harsh exposure conditions such as marine environment. The reinforced concrete elements of marine structures such as bridges, wharves, docks, etc. are subjected to various types of exposures such as wetting and drying action [WDA], fully submerged condition, and in contact with chlorides. To refine the pore structure of concrete and to improve the durability characteristics of such structures, it is essential to use high performance concrete [HPC]. In this study, metakaolin [MK] is used as partial replacement of cement to produce HPC. The use of metakaolin is found to be very effective in reducing the porosity of concrete. As the porosity of concrete decreases, the corrosion rate can be reduced considerably. The durability characteristics of metakaolin-incorporated HPC is studied for 365 days to investigate the changes in its pore structure in long term. The iCOR® NDT method is used to find the corrosion performance and concrete resistivity of high performance metakaolin concrete under a simulated wetting and drying action [WDA] of seawater over several periods. The deterioration effect caused by the simulated WDA of seawater is also studied by considering the bond strength of specimens subjected to normal and corrosive exposure conditions.

7

Effects of early‑age temperature and salt ion corrosion on the macroproperty deterioration of concrete and corresponding micromechanism

Xue Weipei, Fan Hongjun, Liu Xiaoyuan, Shen Lei

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e98, 1--16

EN

This paper experimentally examines variations in the macroscopic properties of concrete under the interaction of early-age temperature and salt ion corrosion and investigates the microscopic mechanism of these variations from the perspective of pore structure and microcracks. The results show a prominent initial defect compaction stage of the compressive stress-strain curves of the specimens under the interaction of two factors, an increase in the number of pores and a high degree of crack development. Accordingly, the peak strength, secant elastic modulus and porosity of the specimens are greatly affected by the interaction between early-age temperature and salt ion corrosion, as reflected by the obvious deterioration trend. Based on a theoretical analysis, the concept of the initial defect strain ratio is proposed, the relationship between the total deformation and two indicators (initial defect deformation and matrix deformation) is clarified, and a constitutive model that reflects the initial defect compaction characteristics is established.

8

Changes in fractal dimension and durability of ultra‑high performance concrete (UHPC) with silica fume content

Luan Congqi, Wang Jingyu, Gao Jinxu, Wang Jinbang, Du Peng, Zhou Zonghui, Huang Yongbo, Du Shuang

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e123

EN

The combined utilization of silica fume (SF) and steel fiber in UHPC is an inevitable trend to improve its mechanical properties and durability. In this study, the influence of SF dosage on mechanical property, permeability, drying shrinkage as well as the pore structure and fractal dimension (Ds) of UHPC was investigated. Finally, the relationships between the durability of UHPC and the porosity as well as the Ds were revealed and discussed. The results demonstrate that the synergistic effect of SF and fiber increased mechanical properties of UHPC due to the friction and mechanical interlocking of the steel fiber to the fiber-matrix and the adhesion between fiber and paste provided by the silica fume. In addition, incorporating 20% enhanced the mechanical property, decreased the chloride diffusion coefficient, and increased the Ds value. Moreover, increasing Ds value linearly raised compressive strength and drying shrinkage but nonlinearly depressed permeability in UHPC, so Ds can be served as a navel parameter to characterize the permeability and drying shrinkage of UHPC.

9

Petrophysical properties prediction of deep dolomite reservoir considering pore structure

Gui Jinyong, Yin Xingyao, Jianhu Gao, Li Shengjun, Liu Bingyang

Acta Geophysica

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2022

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Vol. 70, no 4

1507--1518

EN

Prediction of petrophysical properties of deep dolomite reservoir using elastic parameter data is challenging and of great uncertainty. Changes in the petrophysical properties generally induce perturbations in elastic properties. Rock-physics model, which plays a role as a bridge between petrophysical properties and elastic properties, determines the accuracy of inversion for petrophysical properties using elastic properties. Different pore structures lead to variations of rock-physics relationships, and in dolomite reservoir, the influence of pore structure on elastic properties is larger than that of petrophysical properties. We first propose a statistical rock-physics model, in which we consider the effect of pore structure on the nonlinear rockphysical relationship between petrophysical properties and elastic properties of dolomite reservoirs. Then, we propose a Bayesian inversion approach of using elastic properties to predict petrophysical properties and use weight factors to address the difference in accuracy of the input elastic properties in the Bayesian inversion framework. Examples illustrate the proposed approach may produce petrophysical properties of high accuracy for deep dolomite reservoirs.

10

The impact of changes in pore structure on the compressive strength of sulphoaluminate cement concrete at high temperature

Tchekwagep J. J. K., Zhao P., Wang S., Huang S., Cheng X.

Materials Science Poland

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2021

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Vol. 39, No. 1

75--85

EN

The internal pore structure of sulphoaluminate cement concrete (SACC) significantly affects its mechanical properties. The main purpose of this study was to establish the relationship between pore structure changes and compressive strength after exposure to elevated temperatures. SACC samples that had been cured for 12 months were dried to a constant weight and then exposed to different temperatures (100 °C, 200 °C and 300 °C), after which the compressive strength and pore structure were measured. The pore structure of SACC was quantitatively described by mercury intrusion porosimetry (MIP) and nitrogen adsorption results. The results showed that with increased temperature, the porosity of the SACC samples also increased and the pore structure was gradually destroyed. Moreover, the SACC’s compressive strength gradually decreased with increasing temperature. The relationship between compressive strength and porosity was in close agreement with the compressive strength–porosity equation proposed by Schiller. Therefore, after extensive exposure to elevated temperature, the changes in SACC’s compressive strength can be quantitatively described by the Schiller equation.

11

Effect of the ground granulated blast furnaceslag on the pore structure of concrete

Chalid Abdul

Archives of Civil Engineering

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2021

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Vol. 67, nr 1

203--214

EN

The objective of this study is to analyze effect of ground granulated blast furnace slag (GGBFS) in concrete on the pore structure, this research will contribute to the knowledge regarding the use of GGBFS as a cementitious material in terms of the future reference and potential improvement to the properties of concrete. To this aim, on the one hand a control specimens (CS) and another samples with 40% and 60% of GGBFS as replacement cement with moist cured at 20°C, 27°C, and cured at site. The compressive strength and the Mercury intrusion porosimetry (MIP) test were done. The result indicates that the strength of concrete with GGBFS at early ages tend to be lower in comparison with the CS. However, the GGBFS reaction plays important roles at the later ages. The samples cured at higher temperature produce higher strength value. The total pore volume (TPV) of the concrete use GGBFS decreases with increasing age.

12

Multi parameter logging evaluation of tight sandstone reservoir based on petrophysical experiment

Li Haitao, Deng Shaogui, Xu Feng, Niu Yunfeng, Hu Xufei

Acta Geophysica

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2021

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Vol. 69, no. 2

429--440

EN

Acoustic, resistivity and nuclear magnetic resonance (NMR) logging are important means of reservoir evaluation. In this paper, the information of pore structure, such as the aspect ratio and the shape, is obtained by rock physical experiments like constant velocity mercury injection and casting thin section. Taking pore structure information as a link, the theoretical relations among acoustic-NMR, acoustic-resistivity and resistivity-NMR of rocks are studied, respectively, based on the diferential equivalent model and fractal theory, and the theoretical derivation results are verifed by AE acoustic emission experiment, rock resistivity experiment and NMR experiment. It is found that there is a power function relationship between the P/S wave velocity and the geometric mean value of NMR T2. Moreover, there are also power function relationships between the slowness of P/S wave and resistivity, and between the value of NMR T2 and the increase rate of resistance. Based on the above relationship, the gas reservoir can be identifed by acoustic-resistivity-NMR multi-parameters in well G of the study area. Compared with the conventional P/S velocity ratio and P-wave slowness intersection method, the separa tion efect of gas and water is more obvious.

13

Badania wytrzymałości, struktury porów i przemian fazowych materiału podsadzkowego zawierającego odpady po przeróbce rud żelaza, poddanego działaniu wysokiej temperatury

Tang Jianhui, Li Ping, Chen Xudong, Bai Yin

Cement Wapno Beton

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2020

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R. 25, nr 2

78--94

PL

Wraz ze zwiększaniem głębokości wydobycia kopalin, temperatura, na którą narażona jest podsadzka stale wzrasta, a więc zwiększa się także ryzyko samozapłonu minerałów zawierających siarkę. Nagłe pożary narażają podsadzkę na działanie wysokich temperatur, co zagraża bezpieczeństwu jej konstrukcji. Z tego względu, aby w pełni określić zmiany właściwości podsadzki, wystawionej na działanie wysokich temperatur, zbadano wytrzymałość na ściskanie i wytrzymałość na rozciąganie przy rozłupywaniu podsadzek z dodatkiem spoiwa cementowego, po różnym czasie dojrzewania: 7 dni, 28 dni i 60 dni oraz przy trzech stosunkach spoiwo/odpad: 1:6, 1:8 i 1:10, po prażeniu próbek w piecu wysokotemperaturowym, w temperaturze: 100°C, 200°C, 400°C, 600°C i 800°C. Zbadano także zmiany fazowe i strukturę porów w podsadzce po prażeniu w tych temperaturach. Uzyskane wyniki wykazały, że wytrzymałość i struktura porów w podsadzce z dodatkiem odpadów po przeróbce rud żelaza w wysokiej temperaturze zależą od czasu dojrzewania. Wytrzymałość podsadzki dojrzewającej przez 7 dni początkowo rośnie, a następnie maleje ze wzrostem temperatury. Wytrzymałość na ściskanie i wytrzymałość na rozciąganie przy rozłupywaniu osiągają maksimum odpowiednio w 200°C i 100°C. Bez względu na czas dojrzewania podsadzki, materiał wyprażony w temperaturze przekraczającej 400°C nie ma praktycznie żadnej wytrzymałości na rozciąganie. Cechy te są ściśle powiązane z rozkładem produktów hydratacji spoiwa, przede wszystkim ettringitu i fazy C-S-H.

EN

With the deepening of mining depth, the geothermal temperature faced by the pit backfill is getting higher and higher, so the spontaneous combustion probability of sulfur-bearing minerals increases. In addition, sudden fires can expose the backfill to high temperatures, which will endanger the structural safety of the backfill. Therefore, in order to fully understand the mechanical response and pore structure evolution characteristics of backfills under high-temperature loading, the compressive strength and splitting tensile strength of backfills with different ages: 7 days, 28 days and 60 days and cement-tailings ratios: 1:6, 1:8 and 1:10 were tested using high-temperature furnace to simulate different temperature loads: 100, 200, 400, 600 and 800°C. The pore structure characteristics of the backfill after high temperature are analyzed by mercury intrusion porosimetry. To further understand the mechanism of backfill transformation at high temperature, the phase evolution characteristics of iron tailings and cementitious materials are analyzed by X-ray diffractometer and differential thermal/thermogravimetric analyzer. The results show that the strength and pore structure of iron tailings backfill at high temperature are related to the curing age. The strength and most probable pore size of backfill cured at 7 days increased first and then decreased with the increase of temperature. Among them, the compressive strength and splitting tensile strength reached their peak values at 200°C and 100°C, respectively. While after 28 days, the pore size increased with the increase of high temperature, and the strength of backfill decreased continuously with increasing temperature. No matter what age of backfill is, it almost loses its tensile strength after being subjected to a high temperature above 400°C. These characteristics are closely related to the expansion of mica in iron tailings and the dehydration and decomposition of cementing material hydration products, such as ettringite and C-S-H phase at high temperature.

14

Prediction of porosity and gas saturation for deep‑buried sandstone reservoirs from seismic data using an improved rock‑physics model

Yaneng Luo, Handong Huang, Morten Jakobsen, Yadi Yang, Jinwei Zhang, Yanjie Cai

Acta Geophysica

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2019

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Vol. 67, no. 2

557--575

EN

In recent years, many important discoveries have been made in global deep oil and gas exploration, which indicates that deep exploration has gradually become one of the most important areas in current and future hydrocarbon exploration. However, the prediction of deep reservoirs is very challenging due to their low porosity and complex pore structure characteristics caused by the burial depth and diagenesis. Rock physics provides a link between the geologic reservoir parameters and seismic elastic properties and has evolved to become a key tool of quantitative seismic interpretation. Based on the mineral component and pore structure analysis of studied rocks, we propose an improved rock-physics model by introducing a third feldspar-related pore for deep-buried sandstone reservoirs to the traditional Xu–White model. This modelling process consists of three steps: first, rock matrix modelling using time-average equations; second, dry rock modelling using a multipore analytical approximation; and third, fluid-saturated rock modelling using a patchy distribution. It has been used in total porosity estimation, S-wave velocity prediction and rock-physics template establishment. The applicability of the improved rock-physics model is verified by a theoretical quartz-water model test and a real data total porosity estimation compared with the traditional Xu–White model and the density method. Then, a rock-physics template is generated by the improved rock-physics model for porosity and gas saturation prediction using seismic data. This template is carefully calibrated and validated by well-log data at both the well-log scale and seismic scale. Finally, the feasibility of the established rock-physics template for porosity and gas saturation prediction is validated by a deep-buried sandstone reservoir application in the East China Sea.

15

Diagnostyczne badania wykwitów solnych na restaurowanych elewacjach. Cz. 2, Badania zapraw i tynków

Bochen J., Słomka-Słupik B., Podwórny J.

Ochrona przed Korozją

|

2018

|

nr 2

43--47

PL

W budynku nieczynnej już kopalni wykonano kompleksowe modernizacyjne prace budowlane. Po wbudowaniu nowych materiałów elewacyjnych i wykonaniu tynków wewnętrznych pojawiły się problemy z wykwitami solnymi. W celu rozpoznania przyczyn wysoleń pobrano próbki cegły i zapraw i poddano je badaniom fizycznym, chemicznym a także wykonano analizy rentgenograficzne (XRD). Zaprawy murarskie okazały się mniej porowate i szczelniejsze w porównaniu z cegłami. Analizy chemiczne wykazały powstawanie siarczanów i węglanów mających swoje główne źródło w nowych zaprawach spajających wbudowane cegły. W celu sprawdzenia skuteczności zabiegów ochronnych dla tynków zwrócono uwagę na ich właściwości kapilarne na tle wybranych materiałów referencyjnych. Badania wykazały ich odporność mimo znacznych różnic w strukturze w stosunku do typowego makroporowatego tynku renowacyjnego.

EN

Complex modernization of building works were carried out in industrial building of unemployed coal mine. Some problems with salt efflorescsnces took place after putting new elevation materials and internal wall plasters. In order to find the reasons of the efflorescences, samples of bricks and mortars were taken and subjected to physical and chemical examinations. Additionally X-ray diffraction analyses were made. Masonry mortars appeared to be less porous and tighter in comparison to bricks. Chemical analyses proved the formation of sulphates and carbonates, having their main source in new mortars sticking new bricks built into. In order to control the efficiency of protective operations of plasters attention were focused into capillary properties among of selected reference materials. The tests proved their resistance in spite of substantial differences in theirs structure in comparison to typical large porous renovation plasters.

16

Charakterystyka mikrostruktury pianobetonu o różnych gęstościach przy zastosowaniu technik mikroskopowych

Chung S. Y., Lehmann C., Elrahman M. A., Stephan D.

Cement Wapno Beton

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2018

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R. 21/83, nr 3

216--225

PL

W pracy przedstawiono wyniki badań próbek pianobetonów z użyciem skaningowej mikroskopii elektronowej oraz mikrotomografii rentgenowskiej. Scharakteryzowano porowatość oraz właściwości matrycy cementowej betonów po różnych czasach dojrzewania. Gęstość decyduje w pierwszej kolejności o mikrostrukturze matrycy cementowej, a co za tym idzie właściwości pianobetonów. Jak można się było spodziewać, matryca cementowa jest bardziej zwarta w pianobetonach o większej gęstości i dojrzewających przez dłuższy okres. Średnica porów zmniejsza się, wraz ze zwiększaniem się gęstości betonów i jest bardziej stabilna w późniejszych okresach.

EN

In this paper a set of foamed concrete specimens with different densities was prepared, and microscopic techniques such as scanning electron microscopy and X-ray micro-computed tomography were used to characterize the specimens. The pore and solid characteristics of the foamed concrete at different ages were also examined to investigate the effect of aging on the materials. The microstructure of cement matrix and thus the properties of foamed concrete are strongly affected by the density of concrete. As it should be expected, the cement matrix is denser in concrete of higher density and concrete cured for longer period. The pore size distribution of the foamed concrete shows the tendency to be composed of smaller pores as the density of the specimens is increasing and to became more stable after longer curing period.

17

Effect of water solution of chloride salts on ceramic bricks drying

Stryszewska T.

Ochrona przed Korozją

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2017

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nr 4

110--113

EN

The article presents the results of a multi-faceted research on the impact of chloride salts on the texture of bricks, and the effects of these interactions. The change of pore structure was determined using mercury intrusion porosimetry. The dominant category pores for process of accumulation of salts was determine too. In addition, observations of the microstructure of bricks exposed in NaCl, KCl and MgCl2 solution were made. For comparison, the observation of the microstructure of samples taken from the bricks existing facilities exposed in real sea water are presented, too. The presence of chloride salts also has a significant impact on the process of drying ceramic masonry but the studies have shown no significant differences in drying bricks, depending on the type of cation. The article results systematize and organize information on the durability of bricks in an environment of chloride salts.

PL

W artykule przedstawiono wyniki wieloaspektowych badań dotyczących wpływu soli chlorkowych NaCl, KCl i MgCl2 na teksturę cegieł oraz wybrane właściwości, w tym proces suszenia. Celem badań było określenie zmian zachodzących w teksturze cegieł pod wpływem roztworów soli chlorkowych. W tym celu wykonano badanie struktury porowatości metodą porozymetrii rtęciowej, obserwacje w mikroskopie skaningowym, badanie składu fazowego metodą XRD oraz zmiany masy metodą termograwimetryczną. Badanie struktury porowatości pozwoliło na określenie kategorii porów będących priorytetowym miejscem kumulacji krystalizujących soli. W badaniach wykazano, że obecność soli spowoduje istotne zmiany w procesie suszenia badanych cegieł w odniesieniu do materiału czystego, jednakże nie zaobserwowano istotnych różnic w zależności od rodzaju kationu. W artykule przedstawiono również obserwacje mikroskopowe cegieł poddanych działaniu naturalnej wody morskiej.

18

Wpływ domieszki superchłonnego polimeru (SAP) na wybrane właściwości zaprawy cementowej

Zachariasz T., Śliwiński J.

Materiały Budowlane

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2017

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nr 8

91--93

PL

W artykule poddano analizie wpływ domieszki superchłonnego polimeru (SAP) na wytrzymałość i strukturę porów normowej zaprawy cementowej. Jako domieszkę stosowano ogólnie dostępny na rynku SAP będący usieciowanym poliakrylanem potasu powstałym w wyniku polimeryzacji blokowej i rozdrobnionym na proszek o wymiarze ziaren 10 ÷ 800 µm. Wyniki badań wykazały, że domieszka ta ma istotny wpływ na badane cechy zaprawy. Stwierdzono efekt tzw. wewnętrznej pielęgnacji oraz wpływ na strukturę porów powietrznych w zaprawie.

EN

In the paper the impact of the superabsorbent polymer (SAP) on the basic strength properties and pore structure of standard cement mortar was analyzed. As an admixture, commercially available SAP is a crosslinked potassium polyacrylate produced by block polymerization and ground to a powder size of about 10 to 800 µm. The results show that this admixture has a significant effect on the tested mortar characteristics. The effect of the so-called internal curing was observed and its effect on the pore structure in the mortar was specified.

19

Wpływ dodatku metakaolinitu na wybrane właściwości kompozytów cementowych

Małaszkiewicz D., Świderski M.

Materiały Budowlane

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2016

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nr 10

25--27

PL

W ostatnich latach odnotowuje się coraz większe zainteresowanie wykorzystaniem kalcynowanej gliny w postaci metakaolinitu (ang. metakaolin) jako pucolanowego dodatku do zapraw i betonów, który pozwala na poprawę parametrów mechanicznych i trwałości kompozytów cementowych. W artykule przedstawiono wyniki badań zaczynów i zapraw, w których cement częściowo zastępowano metakaolinitem. We wszystkich badanych kompozytach zastosowano stały współczynnik w/s = 0,4. Do oceny struktury porowatości zaczynów wykorzystano porozymetrię rtęciową.

EN

The utilization of calcined clay in the form of metakaolin, as a pozzolanic addition for mortars and concretes has received considerable attention in recent years. It enhances mechanical performance and exhibits considerable improvement of durability properties. This paper presents the experimental results of properties of cement pastes and mortars. Cement was partially replaced by metakaolin. The constant water: binder ratio w/b = 0.4 was applied in all tested compositions. Mercury intrusion porosimetry was used for evaluation of paste microstructure.

20

An Estimation Method of Pore Structure and Mineral Moduli Based on Kuster–Toksöz (KT) Model and Biot’s Coefficient

Peng D., Yin C., Zhao H., Liu W.

Acta Geophysica

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2016

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Vol. 64, no. 6

2337--2355

EN

Pore structure and mineral matrix elastic moduli are indispensable in rock physics models. We propose an estimation method of pore structure and mineral moduli based on Kuster-Toksöz model and Biot’s coefficient. In this technique, pore aspect ratios of five different scales from 100 to 10-4 are considered, Biot’s coefficient is used to determine bounds of mineral moduli, and an estimation procedure combined with simulated annealing (SA) algorithm to handle real logs or laboratory measurements is developed. The proposed method is applied to parameter estimations on 28 sandstone samples, the properties of which have been measured in lab. The water saturated data are used for estimating pore structure and mineral moduli, and the oil saturated data are used for testing these estimated parameters through fluid substitution in Kuster–Toksöz model. We then compare fluid substitution results with lab measurements and find that relative errors of P-wave and S-wave velocities are all less than 5%, which indicates that the estimation results are accurate.