THE EFFECT OF FLUID CATALYTIC CRACKING CATALYST WASTE ON REFRACTORY CASTABLE PROPERTIES

The fluid catalytic cracking (FCC) catalyst waste (CW) is eroded catalyst debris from the cracking unit, which is collected by an electrostatic precipitator. CW is zeolite material, which unique properties are underused in refractory castable production technology. This work deals with untreated CW and thermally treated - CWt. The hydration and structure development of cementitous compositions with CW and CWt were investigated. In comparison with CW, CWt is a considerably softer accelerating additive of cement hydration and a certain amount of this additive (10 - 20 %) markedly increases the compressive strength of cementitious stone. The impact of CWt additive on refractory castable properties was investigated. It was established that the increase of CWt additive content causes the increase of castable compressive strength and decrease of shrinkage, ensures a more compact structure of castable and best thermal durability versus analogical castable without the additive

THE EFFECT OF POZZOLANIC WASTE OF DIFFERENT NATURE ON THE HYDRATION PRODUCTS, STRUCTURE AND PROPERTIES OF HARDENED CEMENT PASTE

The paper analyses the effect of different pozzolanic waste - ground waste glass, metakaolin and addition made of ground waste glass and metakaolin, on cement hydration and physical-mechanical properties of hardened cement paste. Four batches of specimens were made for the tests. Cement (C) in the cement matrix was replaced with 5% of ground waste glass (5S), 15 % of metakaolin and mixed pozzolanic was addition (MIX 20) made of 5% of ground waste glass and 15 % of metakaolin. The best improvement of mechanical properties after 90 days of curing was observed in the specimens modified with the mixed pozzolanic addition. X-ray, TGA tests and microstructure analysis revealed that the improvement of mechanical properties is caused by the higher content of hydration products and a strong contact zone between glass particles and foam glass splinters present in metakaolin waste addition. The formation of C-S-H hydrates on the surface of glass foam splinters and in the pores was also observed. This kind of microstructure formation has a positive effect on cement matrix microstructure and physical-mechanical properties of hardened cement paste

Hemp Shive-Based Bio-Composites Bounded by Potato Starch Binder: The Roles of Aggregate Particle Size and Aspect Ratio

According to European regulations, the construction industry supports and strives to save non-renewable natural resources, increases the share of reusable resources in production and attempts to use renewable natural resources as much as possible by creating alternative building materials, such as bio-composites. Various building materials containing hemp shives (HS) are relatively popular and are often used in practice. The properties of these materials vary widely due to the usage of significantly different binders and because the parameters of the HS can significantly affect the properties of the bio-composite. Potato starch (PS), the properties of which have not been studied extensively in the past, was used as a binder in this study. Depending on the type of manufacturing process and technology employed for hemp fibre production, the HS particle shape and size can vary widely, which leads to the following statement: the properties of bio-composites produced by using the same method, but with different HS, may differ significantly. In order to investigate the effects of HS on the properties of bio-composites, including the hydro-thermal properties, an in-depth study was conducted to examine the structure, the physical properties and the particle size of HS. It was discovered that in order to obtain a material of higher compressive strength, the HS with smaller dimensions should be used; however, if enhanced thermal properties are required, the HS with longer particles should be used

THE EFFECT OF CRYSTALLIZING ADMIXTURE ON THE PROPERTIES AND SHRINKAGE OF CONCRETE

This study investigates the effect of the amount (from 0.6 % to 1.4 %) of crystallizing admixture (CA) on the shrinkage, density, porosity and mechanical properties of concrete specimens. A higher content of CA increased the total porosity of concrete from 10.6 % to 11.15 %. In contrast to the specimens containing 0.8- 1.0% of CA, the lowest amount of closed pores and highest total porosity was observed in the specimens containing 1.2 %-1.4 % of the CA. Compared to the control specimen, concrete specimens containing 1.4 % of CA showed a 5.4 % decrease in flexural strength and a 13.6 % decrease in compressive strength after 28 days of curing. The specimens containing 0.9 %-1.0 % of CA demonstrated the lowest shrinkage in the period of 190 days. The shrinkage of these specimens reduced 4.8 %-4.9 % compared to the control specimen. Higher content of CA had an opposite effect on the shrinkage, a short-term expansion of specimens was observed after 28-56 days. Taking into account all the properties of the concrete specimen, the optimum amount of CA, which could prevent cracks in the structures is 1.0% of the cement mass

Development of Cordierite Ceramics from Natural Raw Materials

Cordierite ceramics are known for their low CTE and high compressive strength values which affords them place in fields where demanding thermal and mechanical properties are required. Development of such ceramics is greatly dependent on materials used. If raw materials are used formation of additional phases and pore/glass formation is expected. The purpose of this research is to examine the process of cordierite development from mixed compositions formed from precursors of the natural raw materials as illite clay, dolomite and quartz sand and synthetic additives – MgO, γ-Al2O3 and their influence on thermal and mechanical properties. It is verified that the addition of 10 wt.% of illite clay and about 20-21 wt.% dolomite in staring compositions at the sintering temperature of 1200 °C results in the development of dense ceramic material with perfect-shaped crystalline cordierite phase and secondary anorthite phase. Sintered cordierite ceramics have been tested, among other properties, for their compressive strength, coefficient of thermal expansion and modulus of elasticity after 20 cycles of thermal shock treatment

A Study of Metal-Cement Composites with Additives

The application of small-sized metal fillers (SMF) provides a combination of high bulk density, increased durability and ferromagnetic properties of composite materials on the cement basis. However, the total strength of the composite can be compromised by poor adhesion of metal particles with the cement matrix. The use of versatile additives like microsilica and metakaolin is able to improve the structural integrity and mechanical properties of heavy concretes. The paper considers the results of a study using specimens of heavy concretes with SMF aiming to estimate its strength, structural features and ultrasonic parameters. It was found that the contact of SMF particles with the cement was not perfect, since the voids appeared between them and the cement matrix during the cement hydration process (exothermal reaction). Due to the border porosity, the specimens with the metal fillers have lower compressive strength, lower ultrasound velocity and increased frequency slope of attenuation. Microsilica and metakaolin additives facilitate better contact zone between the cement matrix and metal fillers

Исследование порового пространства в металлоцементных композитах

Введение. Металлоцементные композиты (МЦК), в частно-сти тяжелые бетоны (ТБ) с плотностью 4 т/м3 и выше, использу¬ются для изготовления балластов и пригрузов в портовом стро¬ительстве, для плавучих нефтегазовых платформ, элементов за¬щиты подводных трубопроводов, стабилизации грунта, защиты от электромагнитного воздействия и т. д. [1]. В качестве метал¬лических заполнителей могут использоваться отходы металло-обработки. Такие материалы имеют повышенную плотность и вы¬сокую износостойкость. Высокие защитные свойства от действия электромагнитных полей МЦК получают при использовании специальных заполнителей с высоким (35-70 %) содержанием железа, среди них - барит, илменит, магнетит и гематит [2]. Особо тяжелые МЦК с плотностью более 5,0 т/м' для защиты от радио¬активных и электромагнитных воздействий [3] содержат метал¬лические шлаки с хромом и свинцом, а также феррохром, фер¬росилиций, феррофосфор и боросодержащие материалы. В связи с высокой стоимостью производства изделий из МЦК с природными заполнителями все больший интерес пред¬ставляет использование металлических отходов. Их рациональ¬ное использование - важное направление в защите окружающей среды. Исследования в области новых строительных материалов с железосодержащими отходами, в частности, перфорирован¬ной стальной ленты, пистонов, пылевидных отходов от фильтро- агрегатов и металлических порошков [4-7], показали перспек¬тивность их применения в МЦК. В качестве связующего ис¬пользуются портландцемент, пуццолановый, шлаковый и алю- минатиый цементы [8]. Положительными факторами являются низкая цена, возможность эффективной утилизации, а также получение изделий с новыми свойствами. Однако использование отходов в ряде случаев приводит к ухудшению качества мате¬риала. В связи с этим необходимо разрабатывать оптимальные составы МЦК и контролировать их свойства различными совре¬менными методами. Металлоцементные композиты с малоразмерными метал-лическими заполнителями (ММЗ) имеют высокую износостой-кость, высокую термостойкость и низкую усадку. Однако пол-ностью исключить усадку и растрескивание на границе цемента и металлического заполнителя является трудной задачей [8]. Кроме того, с ММЗ сложно работать из-за трудностей с переме¬шиванием и укладкой, а также из-за проблем расслоения бетон¬ной смеси. Различные виды ММЗ описаны в работе [9]. Рассмотрены также различные виды ММЗ, например железо¬содержащих опилок, и возможность использования их в бетон¬ных смесях, частично заменяя ими песок [9-10]. ММЗ позволяют эффективно увеличить плотность МЦК. Однако установлено [7], что увеличение ММЗ снижает прочность материала и показа¬тель осадки конуса бетонной смеси. При использовании ММЗ общая прочность композита может снижаться из-за их плохо¬го сцепления металла с цементом. Для повышения прочности путем улучшения контактной зоны (заполнитель - цементная матрица) часто используют специальные добавки, в том числе наноразмерные, такие как суперпластификаторы, микрокремне¬зем, метакаолин, нано-микрокремнезем [6]. С помощью неразрушающих методов контроля, в частности, ультразвукового, возможно оценивать прочностные свойства МЦК, наличие пор и дефектов, однородность состава изделий по объ¬ему. Однако практически нет таких данных по бетонам с ММЗ. Целью данной работы было оценить влияние ММЗ и доба-вок на прочность образцов МЦК, а также возможность исполь-зования ультразвуковых измерений для их контроля неразру-шающим способом. Изображения, полученные при помощи оп¬тической микроскопии, отображали характерные особенности поверхностей разрушения образцов разных составов и особен¬ности сцепленения металлического заполнителя с цементной матрицей

THE EFFECT OF A COMPLEX POZZOLANIC ADDITIVE CONSISTING OF MILLED GLASS AND METAKAOLIN ON THE DEGRADATION OF A CEMENTITIOUS COMPOSITE WITH GROUND WASTE GLASS CAUSED BY ALKALI-SILICA REACTION

This paper investigates the effect of partial replacement of cement by milled glass (MS), metakaolin (MK), and their mixture and partial replacement of sand by crushed glass (TS) on the physical and mechanical properties of a cementitious composite, as well as on the resistance of the composite to degradation caused by alkali-silica reaction (ASR). After 28 and 56 days of curing, the highest improvement in the mechanical properties was observed in the batches of specimens with the MS, MK and their mixture. The physical and mechanical properties of specimens with partially replaced sand to TS also deteriorated the least (the lowest expansion 0.02 %) with the application of the MS and MK mixture after 56 days of exposure to alkaline attack. XRD and microstructural analyses have shown that the reduction in expansion is due to the higher content of hydration products, as well as to the denser contact zone between the aggregate and the cementitious matrix

Investigation of Hydration Features of the Special Concrete with Aggregates of Various Metal Particles

This study presents an analysis of various size metal particle waste (MP) influences on Portland cement (PC) paste hydration course, concrete sample structure densification during hardening and physical-mechanical properties. Investigations have shown that MP filler accelerates maximum heat release rate in PC pastes. MP intensifies structure development in the early phase, but slows it down in later PC hydration period. After 28-days of hardening the compressive strength of the concrete samples without MP filler is about 20% higher than of samples with MP. When in concrete composition microsilica and MP fillers are used together, compressive strength of concrete sample composition is up to 50% higher than of samples with MP filler only