Papers by Keyword: Cement Composite

Abstract: Wastes from various industrial processes are used in the construction industry in the production of cement composites, for example as a replacement for part of the cement. In addition to contributing to promoting circularity and reducing the carbon footprint, several waste materials have properties that promote improved durability of the resulting composites due to their pozzolanic properties. This paper deals with testing of the pozzolanic activity of selected wastes from local manufacturing processes such as slag, zeolite, microsilica and fly ash using the thermal analysis method (TG/DSC). The highest pozzolanic activity after 2 days was observed for blast furnace slag, however, after 56 days it was recorded for fly ash and ladle slag. Blas furnace slag and microsilica showed very similar pozzolanic activities evaluated by a comparable amount of unreacted calcium oxide of about 35%.

Abstract: The current view on the determination of the abrasion resistance of a cement composite is mainly focused on the resistance of the composite to the effects of mechanical abrasion. However, many concrete structures are exposed to the abrasive effects of flowing liquids. One of the test procedures simulating this principle of abrasion is based on the creation of a very fast flow of liquids, often including abrasive media. Based on worldwide published research on the given topic, the use of the action of ultrasonic waves in a liquid, leading to the simulation of the cavitation stress of a composite, which is a very dangerous phenomenon, is considered a suitable method for creating the mentioned abrasion effects. The following article discusses new possibilities for simulating and evaluating the abrasive effects of cavitation on cement composites using the action of ultrasonic waves in a liquid. These effects will be monitored on cement pastes, which will be modified with several types of commonly used admixtures. Furthermore, the connection between the effects of the mentioned abrasive action and several physical-mechanical parameters will be monitored.

Abstract: The high-strength concrete is a cement composite reaching high compressive strength, namely, pursuant to the legislation, higher than 60 MPa in the terms of cube compressive strength. The development of high-strength concretes exceeding 100 MPa is still an up-to-date issue and the production of these concretes is still limited only to a prefabrication. Contemporary construction industry and projecting activity have begun to focus on a construction of statically demanding buildings, which can include e.g. high-rise buildings. Such projecting often requires using of the state-of-the-art materials like cement composites with high mechanical parameters for construction of more subtle buildings. Within this article, the procedure of ready-mixed concretes development with the compressive strength around 100 MPa designed according to a project documentation for actual construction of high-rise building with the height up to 160 meters and 46 floors is described, together with the influence of the aggregate on the resulting composite strength.

Abstract: Development of new material is focused on modification of properties of materials with silicate binder so that these could be used for renovation of horizontal structures of high-temperature devices and at the same time contribute to reduction of heat transportation of constructions with higher surface temperature (in this case 200 and 500 °C). Main requirements for this material is low volume weight and low coefficient of thermal conductivity. This paper assesses influence of exposition to higher temperatures on microstructure.

Abstract: Utilizing coconut coir fiber can offer an alternative method of adding value to agricultural wastes and help to conserve the environment with green products. The aim of this research was to investigate the potential use of coconut coir fiber as an eco-friendly material for cement composites. The properties of these cement composites mixed with varying proportions of paper waste were compared to ordinary white Portland cement. In addition, the surface structure and chemical characteristics of the samples were examined with a scanning electron microscope (SEM) and an energy-dispersive x-ray spectrometer (EDS). The results showed that the cement composites consisted mainly of the elements carbon (C), oxygen (O), and calcium (Ca) in the range of 34-44%, 42-49%, and 11-19% by weight, respectively. The density of OPC, 0%, 50%, 100% of coconut coir fiber cement composite at 28 days curing time were found 1.85±0.03 g/cm³,1.72±0.02 g/cm³, 1.66±0.05 g/cm³, 1.56±0.02 g/cm³, respectively. Moreover, the compressive and flexural strength of the cement composites decreased with an increase in the coconut coir fiber volume fraction.

Abstract: The paper deals with the possibilities of using secondary raw materials in the development of new advanced lightweight plasters. It was about fibers from recycled waste materials (waste paper, PET bottles, tyres) and recycled insulation (stone wool). The aim of adding fibers to these lightweight building materials was improvement of mechanical properties, improvement thermal insulation properties and reduction of crack sensitivity. It can be stated, based on the evaluation of the selected measurements, that both types of cellulose fibers and fibers from recycled tyres had positive influence on the mechanical properties, namely in the case of compressive strength. From the point of view of thermal insulating properties, it can be said that only 2 types of fibers have reduced the value of the thermal conductivity. They were mixtures with stone fibers and with recycled tyres fibers. Both of these mixtures also showed the lowest average values of bulk density. Based on the carried out research works can be it concluded that the use of recycled tyres fibers show as optimal.

Abstract: This paper deals with the possibilities of experimental determination of the dynamic and static modulus of elasticity of fine-grained cement composites in the early stage of setting and hardening - up to 72 hours. Several cement pastes and cement mortars were produced for the purpose of this experiment. The measurement of the modulus of elasticity on the manufactured cement-based composites was carried out in the first 24 hours, each time only by the ultrasonic pulse velocity test using the innovative Vikasonic instrument. In the following 48 hours, the resonance method and the static load test were employed. The results of the pilot measurement and particularly the assessment of the possibilities of determination of the moduli of elasticity are presented in this paper.

Abstract: In this study Glass fibre reinforced fly ash -cement roofing tiles were fabricated using three different forms of coal fly ash (CFA) such as CFA as it is, CFA particle sizes below 75μm and below 45μm.The separated CFA was used to replace cement 30% by the weight and those matrices were reinforced by Alkali Resistant (AR) glass fibres adding 1% and 2% by weight.The corrugated roof tiles have dimensions of 490×250×8mm and they were hand cast using ordinary vibration. Physical and mechanical tests were performed after 28 days of aging. The tiles were tested in accordance with SLS 1189. Transverse strength increased with increasing fibre percentage. Further, the transverse strength decreased with decreasing CFA particle size. Highest characteristic transverse strength was observed in the CFA as it is sample which is 1650N and the lowest from CFA below 45µm particle size sample which is 1240N. However, all the samples satisfy the strength requirement which is 230N. High water absorption was observed in all the samples which is around 20%.The dry density was ranged in between 1.62-1.68g/cm³ .The lowest average dry density was observed in CFA as it is samples whereas CFA below 75μm particle size and CFA below 45μm particle size samples showed similar density values. The dry density of tile samples is in comparable with the dry density of asbestos cement sheets (≈1.63g/cm³) and the characteristic transverse strength is in comparable with Calicut clay tiles (1000-2000N) in Sri Lanka. Therefore, glass fibre reinforced fly ash-cement roofing tiles are promising substitute for asbestos roofing sheets.

Abstract: The article deals with the shrinkage of a cement composite with various contents of waste micronized limestone powder with a fraction size of 0-63 μm and crushed limestone with a fraction size of 0-2 mm. Waste micronized powder is produced by high-speed grinding of marble sludge. The difference in shrinkage of various mixtures has been described by means of structural analysis. Electron microscopy has been used for this analysis. Mixtures with 10 wt. % of cement and various ratios of micronized marble powder to crushed limestone (1: 1; 1: 2; 2: 1; 1: 0) were investigated. The increasing amount of waste micronized powder adversely affects the shrinkage of the cement composite. This effect is caused by the increasing water–cement ratio for the purpose of achieving the same workability of the mixture.

Abstract: In this article, we consider a method of producing biostable innovative materials in order to improve the biological resistance and durability of buildings and structures based on them. We present the results of the research work focused on the study of the cement composites bioresistance. Powders of milled quartz sand and dolomite were the fillers for the composites. Mathematical methods of experiments design allowed us to derive the dependences describing how the bioresistance coefficient, the elastic modulus and the water demand depend on the granulometric composition after 3 and 9 months of aging in the environment of filamentous fungi. We have found that the multifractional compositions have a higher bioresistance coefficient. We determined that dolomite significantly enhances bioresistance of the samples and Portland cement composites, filled with quartz sand and dolomite, are fungal resist.