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1

Projektowanie zapraw cementowych o optymalnej urabialności i stabilności na konkurs ACI - Mortar Workability 2024

Olczyk Norbert, Góra Wiktoria, Góralski Adrian, Iwańska Karolina, Jaczyński Maciej, Kaźmierczak Kacper, Żygadło Alicja

Przegląd Budowlany

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2024

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R. 95, nr 4

41--45

PL

Artykuł przedstawia proces projektowania i wykonywania zaprawy cementowej o optymalnej urabialności, spełniającej regulaminowe kryteria konkursu „Mortar Workability 2024” organizowanego przez American Concrete Institute (ACI) w Nowym Orleanie w USA, dotyczące właściwości reologicznych, parametrów ekologicznych i ekonomicznych.

EN

The article presents the process of designing and manufacturing a concrete mortar with optimal workability, meeting the regulatory criteria of the „Mortar Workability 2024” competition, concerning rheological properties of cement-based mixtures. The event is organized by the American Concrete Institute (ACI) in New Orleans USA.

2

Właściwości samozagęszczalnego betonu z popiołem lotnym poddanego wewnętrznej pielęgnacji

Shanmugapriya J., Chinnaraju K.

Cement Wapno Beton

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2024

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R. 29, nr 1

2--15

PL

Właściwa pielęgnacja i optymalizacja procesu dojrzewania betonu mają znaczący wpływ na jego właściwości transportowe, co z kolei wpływa na jego właściwości mechaniczne i trwałość. W niniejszym artykule zbadano wpływ popiołu lotnego na wewnętrzną pielęgnację i właściwości mieszanki betonu samozagęszczalnego w różnych warunkach otoczenia. Do badań wybrano dwa materiały do wewnętrznej pielęgnacji: lekkie kruszywo keramzytowe [LECA] oraz polimer superabsorbujący [SAP]. Przedstawiono właściwości takie jak sorpcyjność, odporność na penetrację jonów chlorkowych oraz migrację jonów chlorkowych w próbkach betonów ze zmiennym udziałem procentowym popiołu lotnego w zakresie 30% ÷ 50% w różnych warunkach dojrzewania, mianowicie konwencjonalnym dojrzewaniu w warunkach otoczenia, dojrzewaniu z ograniczonym dostępem powietrza z dodatkami do wewnętrznej pielęgnacji oraz dojrzewaniu w warunkach otoczenia z dodatkami do wewnętrznej pielęgnacji. Wyniki wskazują, że szczelność betonu poprawiła się wraz ze zwiększeniem udziału procentowego popiołu lotnego dzięki obecności wody pochodzącej z wewnętrznej pielęgnacji, wpływającej na proces hydratacji oraz popiołu lotnego, który obniża ciepło hydratacji i skurcz spowodowany wysychaniem. Efektywność wewnętrznej pielęgnacji również poprawiła się wraz ze zwiększeniem udziału popiołu lotnego w próbkach. W warunkach otoczenia, mieszanki z zamianą popiołu lotnego powyżej 45% wykazały najlepsze właściwości mechaniczne, z powodu zmiany struktury porowatości prowadzącej do lepszych właściwości transportowych betonu [mniejszej przepuszczalności].

EN

Proper curing of concrete has a major beneficial effect on the transport properties of concrete which in turn influences its durability. This paper attempts to study the effect of fly ash on the transport properties of internally cured Self-Compacting Concrete specimens under ambient conditions. Two internal curing materials, Lightweight Expanded Clay Aggregates [LECA] and Superabsorbent Polymer [SAP] were chosen for the study. Properties such as sorptivity, resistance to chloride ion penetration and chloride ion migration specimens with varying percentages of fly ash replacement from 30% to 50% are presented under different curing conditions namely conventional curing, sealed curing with internal curing materials and ambient curing with internal curing materials. The results showed that the impermeability of concrete improved with an increasing percentage of fly ash replacements owing to the presence of internal curing water to improve hydration along with fly ash that moderates the heat of hydration and drying. The internal curing efficiency also improved with the increase in the percentage of fly ash replacement. Under ambient conditions, the mixes with fly ash above 45% replacement have shown very good mechanical and durability properties indicating a refined pore structure leading to enhanced transport properties.

3

The influence of mineral additives and sands on the performance of self-compacting sand concretes

Djoual Belkacem, Kettab Ratiba Mitiche, Ghrieb Abderrahmane, Bouziani Tayeb, Zaitri Rebih

Advances in Materials Science

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2024

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Vol. 24, nr 1(79)

104--126

EN

The chosen plan for our case study is a network mixture design consisting of 21 mixtures. The application of this method has proven to be immensely useful in studying the influence of composition parameters (composite design) and the utilization of various types of mineral additives (mixture design). The application of the Design of Experiments (DOE) method, based on a statistical approach, allowed for a better understanding of the effect of formulation parameters, including the proportion of alluvial sand (75%), dune sand (25%), the total amount of sand kept at constant percentages, the dosages of brick powder, limestone filler and ceramic powder (all varying from 0 %, 20 %, 40 %, 60 %, 80 %, and 100 %), while keeping the dosage of superplasticizer and the water/binder ratio constant. This approach helped to understand the interactions between these parameters and their impact on the process. Mathematical models relating the variations of these parameters to the workability and compressive strength of such concrete mixtures have been established. The results obtained show that the workability of SCSC (expressed by slump flow and V-funnel flow) improves with the increase in the dosage of limestone filler (FC), brick powder (PB), and ceramic powder (PC), with element having a different impact, be it alone or in a combination. Moreover, they all improved the behavior of SCSC in both the fresh and hardened states. The experiment shows that increasing the proportions of FC and PC in the mixture, whether linear, binary, or ternary, leads to a significant improvement in compressive strength. Furthermore, better strength is observed in the ternary mixture at 28 days, with a strength of 43 MPa, with the following proportions (FC 70%, PB 20%, PC 10%). Finally, the result at 180 days of 48 MPa confirms the following proportions (PC 60 %, FC 30 %, PB 10 %) The compliance of some SCSC compositions was tested according to the recommendations of the French Association of Civil Engineering.

4

Optimizing high-performance concrete properties containing blast furnace slag and marble powder

Edeb Belkacem, Allout Naas, Benkhelil Mahmoud, Guettala Salim

Advances in Materials Science

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2024

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Vol. 24, nr 3(81)

89--110

EN

Building and industrialization-related environmental harm is becoming an increasingly serious concern. In an effort to create an eco-friendly high-performance concrete (HPC), this paper addresses the idea of partially replacing cement with recyclable industrial waste. The current study will experimentally examine the slump, the strengths of compressive (SC) and porosity (P) of fifteen HPC mixtures manufactured from locally available resources. Hence, the effects of utilizing marble powder (MP) as a mineral additive in binary mixes and ternary with cement (PC) and granulated ground blast furnace slag (GGBFS) on the HPCs properties were studied in order to develop statistical models based on mixture design. Highly accurate prediction graphs and models were created for HPC workability, P at 28-day, SC at 7 and 28-day. All responses have satisfactory coefficients of correlation (R2 ≥ 0.76). Replacing cement with GGBFS causes a rise in slump in mixtures. Nevertheless, that only remains relevant when the mixtures have a small MP percentage (≤ 25%). A minor decrease in SC can be attributed by an increase of GGBFS. After 28-day, using GGBFS alone caused a little drop in SC; however, when GGBFS and PC were mixed, SC increased, in comparison with reference composition, and the porosity was reduced. Conversely, SC is superior with lower porosity when a small amount of MP is utilized. The best combination is HPC14, containing 5% GGBFS; it offers an optimal equilibrium among the three qualities; with HPC4's (15%GGBFS+5%MP) qualities, being almost identical to those of reference HPC15, a lower amount of cement may also be utilized. Findings encourage the use of MP and GGBFS to partially replace cement to produce eco-friendly and cost-effective HPC. An extremely high correlation coefficient indicated a strong relationship between P and SC.

5

Evaluation of the feasibility of incorporating higher RAP materials content in asphalt concrete with the use of additives that improve the workability of asphalt mixtures

Liphardt Adam, Radziszewski Piotr, Sarnowski Michał

Roads and Bridges - Drogi i Mosty

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2023

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Vol. 22, no. 4

515--526

EN

The material recycling due to the environmental protection and sustainable development is playing an increasingly important role in the road pavement construction. This is especially true for the use of reclaimed asphalt pavement (RAP) materials for the pavement construction layers. One of the problems encountered in the use of larger quantities of the RAP in asphalt mixtures is the deterioration of their workability and homogeneity especially in the case of cold dosing of RAP. The paper reports the results of a study on the use of additives to improve the workability of asphalt concrete for the subbase layer with an increase of up to 40% in crushed RAP content, dosed in the cold technology. In the study, additives of the F-T waxes, plant-derived liquefiers and zeolites were used to improve homogeneity and compactability of the mixtures using reduced paving temperatures. An evaluation of the compactability of mixtures with different contents of the RAP, using 3 types of additives to improve workability, was carried out. Compactability was evaluated by the compaction analysis in a gyratory compactor, determining, among other things, the required number of cycles to achieve the required compaction, as well as the shear stress and compaction index as a function of the number of compaction cycles. Subsequently, the asphalt mixtures were tested to verify their resistance to permanent deformation and resistance to water. Based on the results of the research and analysis, it was shown that it is possible to use increased RAP materials content in asphalt concrete base layers at both standard and reduced paving temperatures, through the use of additives that improve the workability and compactability of the mixtures.

PL

Recykling materiałowy ze względu na ochronę środowiska, zrównoważony rozwój odgrywa coraz większe znaczenie w budowie nawierzchni drogowych. Szczególnie dotyczy to zastosowania destruktu asfaltowego do warstw konstrukcyjnych nawierzchni. Jednym z problemów występujących przy stosowaniu większych ilości destruktu asfaltowego w mieszankach mineralno-asfaltowych jest pogorszenie ich urabialności i jednorodności szczególnie w przypadku dozowania granulatu asfaltowego na zimno. Artykuł zawiera wyniki badań nad zastosowaniem dodatków poprawiających urabialność betonu asfaltowego do warstwy podbudowy ze zwiększonym do 40% dodatkiem granulatu asfaltowego dozowanym w technologii na zimno. W badaniach zastosowano dodatki parafin F-T, upłynniaczy pochodzenia roślinnego oraz zeolitów, które miały na celu poprawę homogeniczności i zagęszczalności mieszanek przy zastosowaniu obniżonych temperatur wbudowania. Przeprowadzono ocenę zagęszczalności mieszanek z różną zawartością granulatu asfaltowego przy zastosowaniu 3 rodzajów dodatków poprawiających urabialność. Zagęszczalność oceniano na podstawie analizy przebiegu zagęszczania w prasie żyratorowej, określając m.in. wymaganą ilość cykli do uzyskania wymaganego zagęszczenia, a także naprężenia ścinające oraz wskaźnik zagęszczenia w funkcji ilości cykli zagęszczania. W dalszej kolejności mieszanki mineralno-asfaltowe poddano badaniom w celu weryfikacji ich odporności na deformacje trwałe oraz działanie wody. Na podstawie wyników badań i analiz wykazano, że istnieje możliwość stosowania zwiększonej zawartości granulatu asfaltowego w warstwach podbudowy z betonu asfaltowego zarówno w standardowych, jak i obniżonych temperaturach wbudowania dzięki zastosowaniu dodatków poprawiających urabialność i zagęszczalność mieszanek.

6

Effects of incorporating granite powder in the mechanical properties of concrete

Muñoz Pérez Socrates Pedro, Atoche Zamora Jorge Jr.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2023

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Vol. 32, No. 1

18--33

EN

This study analyzes the effects of the incorporation of the granite powder (GP) as a partial replacement of the sand in the concrete in percentages of 10%, 15%, 20% and 30% to carry out a mix design of 210 kg·cm–2. Seeking to find an optimal proportion to increase its mechanical properties where the geotechnical characteristics of the aggregates were identified, workability, temperature, beams and concrete specimens were elaborated. The results of bending and compression tests were compared after 7, 14 and 28 days from setting between the standard concrete and the concrete incorporated with the GP. It is concluded that the optimal result was at 20% GP with 268.6 kg·cm–2, where the compressive strength increases by 13%, while its flexural property rupture modulus of 35 kg·cm–2 and workability are in an optimal range according to the stipulated parameters, thus allowing an important application for this waste in the construction industry, therefore contributing to recycling, environmental quality and the development of the usage of new materials.

7

Diagnostic methods and ways of testing the workability of coal - a review

Biały Witold, Bozek Pavol, Bołoz Łukasz

Production Engineering Archives

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2023

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Vol. 29, Iss. 4

401-412

EN

The need to classify rocks in terms of workability stems primarily from the need to choose the appropriate, most effective diagnostic method (DM) and way of mining the given rock. Studying and measuring the workability of rocks is extremely difficult due to the fact that workability depends on many various factors. There are many DM for determining the workability of rocks, but none of them take into account the influence of all factors, hence the obtained results are only indicative. In the article, many DM and ways of determining the cutting resistance with the use of various devices are presented and characterized. The principles of their operations are presented, as well as the DM of measuring the cutting resistance and its utilitarian usefulness in forecasting the selection of mining machines on the basis of cutting for specific mining and geological conditions. The core of the problem is confirmed by the number of covered DM and tools in various research centers around the world. In the article, new tools measuring and evaluating the mechanical properties of the coal solid, all created in Poland, are presented. Their structure, principles of their operation, as well as the innovation of these solutions, are all presented. In this article, their ad-vantages and disadvantages are highlighted, as well as showing the DM which best represents the way of work of the winning machine. Therefore, the results achieved through the aforementioned DM can be understood as representative values.

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Performance study of alkali-activated phosphate slag-granulated blast furnace slag composites: effect of the granulated blast furnace slag content

Zhang Yannian, Yang Daokui, Wang Qingjie

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e181, 2023

EN

Alkali-activated materials (AAMs) are a kind of hardened slurry produced by an alkali activation reaction between a silicate precursor and an alkali activator that is treated as an environmentally friendly cementitious material that can be used in place of ordinary Portland cement (OPC). However, some studies point out that the AAMs with a single precursor had some defects. To realize the high value-added utilization of phosphorus slag (PS), this paper mixed PS with granulated blast furnace slag (GBFS) to prepare alkali-activated composite cementitious materials. The workability, mechanical properties, and hydration of alkali-activated phosphorus slag—granulated blast furnace slag (AAPG) were characterized using fluidity, setting time, compressive strength, flexural strength, hydration heat, XRD, FTIR, TG-DSC, and SEM + EDS. The results show that GBFS can improve the fluidity of AAPG, but the slurry will flash set after exceeding 20% GBFS content. GBFS can rapidly hydrate to generate C-S–H to improve its early strength, but the later stage results in larger pores due to the uneven distribution of matrix products. The hydration generation products of AAPG are C-S–H and C-(N)-A-S–H dominated by the Q2 unit, with some hydrotalcite by-products generated.

9

Investigation of the workability and surface roughness of thin brass wires in various dieless drawing technologies

Milenin Andrij, Wróbel Mirosław, Kustra Piotr

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e10, 2022

EN

Possibilities of improving the workability of the CuZn37 brass thin wire in a diameter of 0.14–0.18 mm produced by the dieless drawing processes were explored. The workability was defined as the maximum final longitudinal strain of the wire up to its fracture, achievable in the dieless drawing process. Two technologies of dieless drawing were developed and their workability was compared. The first one is the classical one-pass process; the second, a multi-pass one. For both developed technologies, it was possible to obtain a good-quality product but more than two times higher workability has been demonstrated for the multi-pass technology. No evident effect of the deformation temperature from the window of technologically accepted parameters on the workability was found but an increase in the temperature significantly increased the roughness of the product surface. For the same deformation temperature, the roughness of the wire obtained from the multi-pass process appeared to be significantly lower than for the one of the classical one-pass technologies.

10

Effect and mechanism analysis of hydroxylated nano‑boron nitride on workability and multi‑scale mechanical properties of cement paste

Liu Jianglin, Li Yue, Jin Caiyun, Lin Hui, Li Hongwen

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e122

EN

Nano-boron nitride (h-BN) has excellent physical and mechanical properties. Due to its stable chemical performance, the improvement effect on the properties of cement-based materials was limited. Therefore, the chemical modification method was used to prepare functional h-BN to improve its application potential in cement-based materials in this paper. The hydroxylated nano-boron nitride (h-BN-OH) was prepared by modified pristine h-BN with saturated sodium hydroxide (NaOH). The effects of h-BN-OH after ultrasonic dispersion for 10 min, 20 min, 30 min and 40 min on the setting time, fluidity, resistivity, mascroscopic strength and microscopic Young’s modulus of hydration products of ordinary Portland cement were investigated. Fourier transform infrared spectroscopy (FTIR) test results showed that h-BN-OH had obvious hydroxyl infrared characteristic peaks. After adding h-BN-OH into cement paste, the initial and final setting time of cement paste was shortened 6.44-15.34% and 5.05-13.00%, respectively; the fluidity was reduced 9.86-22.79%, and the resistivity was increased 7.14-25.96%. Meanwhile, the compressive strength of cement paste and the microscopic Young’s modulus of hydration products were significantly improved 10.82-40.85% and 9.90-31.01%, respectively. The main reasons were as follows: (1) The dispersion effect and stability of h-BN-OH in cement pore solution were better than that of pristine h-BN, and the hydroxyl group grafted on the h-BN-OH provided nucleation sites for the growth of calcium-silicate hydrate (C-S-H) gel. (2) The hydroxyl groups grafted on the h-BN-OH can absorb Ca2+, resulting the polymerization degree (nc) and medium chain length (MCL) of C-S-H gel increased. The formation of C-S-H gel network structure was accelerated by the increasing proportion of Q3. (3) The pore structure of cement hydration products was significantly optimized.

11

Effect of using rice husk ash as partial replacement of cement on properties of fresh and hardened concrete

Ajwad Ali, Ahmad Sameel, Abdullah, Jaffar Syed Taseer Abbas, Ilyas Usman, Adnan Muhammad Ahmad

Architecture Civil Engineering Environment

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2022

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Vol. 15, no. 2

85--94

EN

Rice husk disposal has become a great challenge for Pakistan being one of the largest rice producer across the globe. Rice Husk Ash (RHA) contains sufficient pozzolanic properties which opens up opportunities for its usage as cementitious material as partial replacement of Ordinary Portland Cement (OPC). In this research RHA was added as cement replacement in different percentages by weight of cement i.e. 0%, 6%, 12%, 18% and 24% at constant mix ratio of 1:2:4 and water-cement ratio of 0.6 that is M15 grade concrete with a target strength of 15-20 MPa. The properties of concrete like workability, compressive strength, tensile strength, flexure strength, and water permeability were investigated by casting standard concrete samples in the form of cubes, cylinders and beams in addition to cost comparison study The outcomes show that workability of fresh concrete increases with an increase in RHA content and almost all concrete properties studied in this research gave more favorable results at 6% replacement level compared with the control mix.

12

Physical and mechanical properties of dune sand mortar reinforced with recycled pet fiber: an experimental study

Ghrieb Abderrahmane, Abadou Yacine

Advances in Materials Science

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2022

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Vol. 22, nr 4(74)

41--56

EN

Polyethylene terephthalate is a synthetic material known as PET. PET strapping bands is a material commonly used in all industries for packaging and bundling. The excessive use of this material has led to the pollution of the urban environment, which necessitated the search for effective solutions to dispose of this waste. The treatment and reuse of these materials is among the best solutions that contribute to reducing environmental pollution on the one hand and enabling the obtaining of economical products on the other hand. The main purpose of this experimental study is to valorize dune sand mortar and PET waste in the manufacture of cement mortar. It also aims to investigate the impact of the inclusion of recycled PET fibers on the physical and mechanical properties of the reinforced mortar. The study was carried out in several phases; after a physical and chemical characterization of the materials used, a method for the composition of mixtures was proposed, which is based on the progressive substitution of dune sand by recycled PET fibers. The quantity of cement added to each mixture is fixed at 450 g, and that of dune sand and fibers is taken as equal to 1350 g. In order to properly examine the influence of the incorporation of fibers on the properties of the reinforced mortar, the substitution rate of dune sand by the fibers varied from 0% to 2.5% with a step of 0.5%. For each mixture, many characteristics of the mortar were tested, such as consistency, bulk density, compressive strength, and flexural strength. The results obtained show that the incorporation of PET fibers has a significant effect on the fresh and hardened properties of the treated mortar.

13

Determination of Coal Cutting Forces Using the Cutting Head of POU-BW/01-WAP Device

Biały Witold, Fries Jiri, Galecki Greg

Multidisciplinary Aspects of Production Engineering

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2021

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Vol. 4, Iss. 1

281--289

EN

The paper presents a method for measuring and recording the forces involved in the coal cutting process. Moreover, a method for visualization of all forces involved in the cutting process was described. In the following part, the construction and principle of operation of a device for determination of forces involved in the cutting process (coal mining), referred to by the author as POU-BW/01-WAP, are presented. Resistance extensometry was used to measure the forces. This is the only device in the world that determines two of three force components that take part in the cutting process. For this purpose, two independent measuring blocks were used, which are strain gauges of force: cutting (Fs) and knife pressure (Fd). In order to register these forces, a real mining knife used in longwall shearer drums was applied – i.e. tangential-rotary. The equipment has the ATEX certificate allowing for operation in real conditions as a device intended for use in potentially explosive atmospheres – in accordance with the directive 94/9/EC. It has received many awards at world fairs for inventions and innovative solutions.

14

The effect of varied types of steel fibers on the performance of self-compacting concrete modified with volcanic pumice powder

Magbool Hassan M., Zeyad Abdullah M.

Materials Science Poland

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2021

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Vol. 39, No. 2

172--187

EN

The aim of this work involves studying the impact of varied types of steel fibers (SF) on the performance of self-compacting concrete (SCC), containing volcanic pumice powder (VPP). In this study, five types of steel fiber, which had a hooked end with two lengths of (SF1) and (SF3), flat end of length (SF2), in addition to the pointed end of (SF4) and (SF5) by 1% of volume fraction, were used. In addition, hybrid steel fiber (a mixture of all the steel fiber types) by 0.2% of volume fraction of concrete volume was used. Moreover, VPP was utilized by 30% cement mass as a substitute material for producing SCC. The impact of steel fiber properties in the shape of SF on the fresh concrete properties as slump flow and segregation were investigated. In addition to their influence on the compressive strength, split tensile strength, flexural strength, toughness, porosity, water absorption, and bulk density were examined. The results showed that SF led to decreasing the SCC fresh properties. Utilizing SF, on the other hand, improved the SCC hardened properties, as well as the toughness indices.

15

Experimental study on the working and mechanical properties of high performance cementitious structural grouts

Zhang Lu, Liu Mengmeng

Ecological Chemistry and Engineering. S

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2021

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Vol. 28, nr 4

487--498

EN

By using the experimental study method, the working properties and mechanical properties of grouting materials were determined by changing the cement-sand ratio, water-cement ratio, and cement admixtures. The main factors affecting the properties of grouting materials and the mutual influence rules of various factors are analysed and determined, and the best value range is obtained. Finally, the compressive strength of 28-day ordinary Portland cement structure grouting is optimised to 50-80 MPa. Based on the grouting ratio of ordinary Portland cement, an experimental study on the early strength structure paste of sulphate aluminate cement was carried out. The paste with one day strength as high as 70 MPa and good compatibility was prepared, and the early strength change law of the optimum ratio was deduced.

16

Badania rozmieszczenia cząstek dodatków mineralnych w cementach dwuskładnikowych

Marchetti Guillermina, Di Salvo Barsi Antonela, Rahhal Viviana, Irassar Edgardo F.

Cement Wapno Beton

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2021

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R. 26, nr 5

366--378

PL

Zbadano wpływ dodatku wapiennego [DW], dolomitowego [DD], metaillitu [MI] i prażonej gliny illitowej [GP] na gęstość mikrostruktury zaczynów z cementów dwuskładnikowych, pod względem grubości warstwy wody [GWW] i optymalnego zapotrzebowania na wodę [OZW]. Przeanalizowano wpływ tych uzupełniających materiałów cementowych [UMC] na rozpływ zaczynów i zapraw cementowych oraz omówiono wytrzymałość zapraw na ściskanie. Wyniki wykazują, że wpływ dodatków UMC na gęstość mikrostruktury zaczynów jest ściśle związany z rozkładem wielkości ziaren. Optymalna zawartość UMC zapewnia wieloskładnikowym cementom maksymalną gęstość mikrostruktury zaczynów. Wpływ na rozpływ zaczynów zależy nie tylko od gęstości mikrostruktury, ale także od powierzchni ziaren, a zastosowanie wymienionych UMC zwiększa wytrzymałość zapraw na ściskanie.

EN

The effect of limestone filler [LF], dolomite filler [DF], metakaolin [MK], and metaillite [MI] additives on the packing density of the binary blended cements were studied using of the water film thickness [WFT] and the optimal water demand [OWD]. The influence of these supplementary cementitious materials [SCM] on the flowability of cement pastes and mortars was analyzed and the compressive strength of mortars was discussed. The results indicate that the incorporation of these SCM on the packing density is highly related to the particle size distribution and the optimal addition of SCM to the blended cements, assures maximum packing density. The effects on flowability not only depend on packing density but of the surface area of particles and the addition of SCM enhance the compressive strength of the mortars.

17

The Cutting Resistance of Rock Salt in Function of Temperature

Kotwica Krzysztof, Stopka Grzegorz

New Trends in Production Engineering

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2020

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Vol. 3, Iss. 1

211--220

EN

Currently over then 16 percent of the total worldwide salt production is excavated in underground mines. Salt deposits often lie at great depths up to 1000 m, where the temperature of the surrounding rocks reaches 50°C and even exceeds it. A large part of it is exploited using mechanical methods, mainly with the use of road headers and continuous miners. When excavating salt rock, the cutters of the road header mining head come into contact with the rock. This generate friction and in consequence a rise in temperature. In AGH University of Science and Technology the laboratory tests were carried out to determine the effect of temperature on cutting resistance and selected mechanical properties of rock salt. On the special laboratory test stand the rock salt sample was cutted at three different temperatures - 20, 50 and 80°C. The cuttability index and the side chipping angle were measured for each temperature. Additionally the same tests were performed in the case of salt sample after cooling to room temperature. The selected mechanical parameters of rock salt - compressive, tensile and shear strength were also measured for the same temperature values. The obtained results were compared and described in the paper.

18

Effects of steel fibres on fresh and hardened properties of cement concrete

Ali Saqib, Kumar Haresh, Rizvi Samar Hussain, Raza Muhammad Saleem, Ansari Jawaid Kamal

Civil and Environmental Engineering Reports

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2020

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Vol. 30, no. 3

186--199

EN

Concrete possesses distinct features that make it widely acceptable for use across the globe; however, along with its obvious benefits, it has numerous drawbacks i.e., it is brittle in nature and its production causes an adverse impact on the environment. To counter such problems, researchers around the world have introduced sustainable measures. Fibre addition is foremost among these solutions in that it prevents crack propagation and increases the overall strength of concrete. In the present age, civil engineering structures have their own structural and durability requirements and so, modification in traditional concrete has become a necessity. This research is targeted at steel fibre reinforced concrete (SFRC), which is a superior quality concrete because of its enhanced strength. The steel fibres are obtained from binding wire that is used to tie the steel reinforcement. By referring to past research, steel fibres with an aspect ratio (length to diameter ratio) of 30 were considered favourable. The controlled, mixed design of the concrete was prepared with a targeted strength of 4000 psi and, while mixing the concrete ingredients, fibres were added to allow uniform dispersion. The fresh and hardened properties of workability, compressive, and tensile strength were tested and the results of fibres at 0%, 1%, 2% and 3% concrete mass were compared and analysed. The results indicated that highest compressive and tensile strength values were achieved with 3% fibre addition. However, with further addition, it was observed that concrete loses its workability. Therefore, it is suggested that 1% addition of steel fibres produces good strength with sufficient workability.

19

Właściwości materiałów cementowych wzmacnianych odpornymi na środowisko zasadowe włóknami szklanymi, jako odpowiedniego materiału do zastosowań naprawczych

Arabi Nourredine

Cement Wapno Beton

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2020

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R. 25, nr 6

457--468

PL

Zbadano matrycę cementową, wzmocnioną włóknami szklanymi, jako odpowiedniego materiału do naprawy uszkodzonych konstrukcji. Zastosowano dwa podejścia do projektowania mieszanek: w pierwszym z nich stosowano konwencjonalną zaprawę, w drugim różne proporcje cementu i piasku, w celu wyboru najlepszej mieszanki. Osiągnięto korzystny stosunek urabialności z zawartością włókien. Stwierdzono, że stosunek cementu do piasku jest kluczowy dla urabialności mieszanki i powinien zawierać się w zakresie od 0,4 do 0,5. W doświadczeniach stosowano trzy długości włókien – 3, 6 i 12 mm. Przeprowadzono próby ściskania i zginania oraz zbadano zmiany skurczu, dla różnych zawartości i długości włókien. Stwierdzono poprawę wytrzymałości na zginanie zapraw cementowych wzmocnionych włóknami szklanymi, zwłaszcza gdy długość włókien zwiększono do 12 mm, w przypadku ich zawartości wynoszącej 2%. Wytrzymałość na ściskanie zmniejszyła się wraz z większą zawartością włókien.

EN

The cement matrix reinforced with glass fibres was studied as a suitable material for the repair of damaged structures. Two approaches to mixture designs were tested: the first used a conventional mortar and the second with various cement-sand ratios to optimise the mixture. A compromise between the workability and high fibre ratio was achieved. Cement/sand ratio was found to be crucial for the workability of the mixes, with optimal values within the range 0.4-0.5. Three fibre lengths: 3, 6, and 12 mm were tested. Compression and flexural tests were carried out as well as the measurements of shrinkage evolution, which is a critical factor. Improvement was observed in the flexural behaviour of glass fibres reinforced cement mortars when the fibre length was increased to 12 mm with a glass fibre content of 2%. However, the compressive strength decreased with higher fibre content.

20

Prediction of fracture onset in flashless warm forging Mg alloy AZ61

Skubisz Piotr, Lisiecki Łukasz

Computer Methods in Materials Science

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2019

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Vol. 19, No. 3

100--106

EN

The paper presents an innovative precision forging process, highlighting the use of advanced simulation of net forging process in multiple-tool die set with consideration of counter-pressure and interaction of components so as to control speed and displacement of metal flow. In addition to the use of finite element method in optimization of process conditions, damage criteria have been formulated to investigate the effect on plasticity and tendency of formation of defects and define process conditions which contribute to cracking occurrence in warm forging of magnesium alloy AZ61. Both forged samples and numerical simulation prediction indicate minimization of cracking hazard in lower work-temperature range at relatively high strain rate by employing counter-pressure imposing hydrostatic component into state of stress.

PL

Praca dotyczy analizy wpływu zastosowania przeciwnacisku w procesie kucia dokładnego przy zastosowaniu bezwypływkowej metody opartej na równowadze ciśnień. Przedstawiona koncepcja narzędzi do kucia dokładnego metodą bezwypływkową jest innowacyjnym rozwiązaniem, które nie jest jeszcze dobrze rozeznane, zwłaszcza w zakresie optymalnego doboru parametrów kinematycznych procesu. Odpowiednia konstrukcja matryc z ruchomymi wkładkami oraz dobór prędkości poszczególnych narzędzi, jak również wartości przeciwnacisków wywieranych przez elementy matryc składanych zapewniają zwiększenie plastyczności materiału, umożliwiając kucie bezwypływkowe w jednej operacji kucia. Pozwala to wytwarzać odkuwki porównywalne do kształtów uzyskiwanych na urządzeniach wielooperacyjnych typu Hatebur, eliminując obróbkę skrawaniem do niezbędnego minimum. Zapewniając poprawę plastyczności, umożliwia również kształtowanie materiałów trudnoodkształcalnych, takich jak stopy magnezu. Przedstawione wyniki kucia stopu magnezu potwierdzają możliwości wykorzystania tej techniki do kucia odkuwki cienkościennej ze stopu AZ61 w zakresie temperatur przeróbki na ciepło oraz jednoczesnych dużych prędkościach odkształcania. Powodzenie kucia bezwypływkowego w układzie wielonarzędziowym, w przeciwieństwie do typowych procesów kucia bezwypływkowego nie zależy tylko od dokładnego doboru masy wsadu do kucia. Aby zapewnić optymalny schemat płynięcia metalu, prędkości narzędzi, wartość nacisków i przeciwnacisków kompensatora oraz jego położenie muszą być ściśle określone i kontrolowane w całym cyklu odkształcania. Stąd przedstawiona technika kucia, wymaga dokładnego sterowania parametrami procesu kucia. Z uwagi na obiektywne trudności kontrolno-pomiarowe, optymalizacja procesu w oparciu o próby fizyczne jest trudna. Zastosowanie technik komputerowych umożliwia analizę powiązań ciśnienia podtrzymującego kompensator ze zmianami plastyczności oraz zapewnia informacje poznawcze dotyczące wpływu przeciwnacisku na rozkład naprężeń i stanu naprężeń, pozwalając tym samym na parametryzację zmiennych procesowych. Jednocześnie, analiza numeryczna w programie QFormVX, umożliwiła powiązanie warunków procesowych z prognozowaniem ryzyka powstawania pęknięć w oparciu o kryteria Cockcrofta-Lathama i Freudenthala, które potwierdziły zasadność założeń konstrukcyjnych, wskazując zakresy najkorzystniejszych wartości przeciwnacisków.