Figura 18 - uploaded by Victor C Pandolfelli
Content may be subject to copyright.
![Evolução do módulo de elasticidade dinâmico dos concretos ao longo do tempo. [Figure 18: Evolution of the concretes' dynamic Young's modulus with the time.]](profile/Victor-Pandolfelli/publication/262445295/figure/fig3/AS:392473802231812@1470584454211/Figura-18-Evolucao-do-modulo-de-elasticidade-dinamico-dos-concretos-ao-longo-do-tempo.png)
Evolução do módulo de elasticidade dinâmico dos concretos ao longo do tempo. [Figure 18: Evolution of the concretes' dynamic Young's modulus with the time.]
Source publication
When a concrete is produced, especially a high performance one, the first concern is the cement type to be used, making this binder an essential compound. The rheological properties of high performance concretes are related to the hydration of cement aluminates phase, whereas the development of mechanical strength depends on the hydrated silicates...
Similar publications
This paper aims to realize a study of the influence of cement type used in realizing a plastering monolayer mortar, which have the same characteristic as a multilayer system, the last layer defined as a final layer and having a decorative role. The experimental program implies studies made by using latest methods. The physic-mechanical characterist...
Citations
... well as sintered silicon carbide [26] and cementitious composites reinforced with particles like silica and silicon carbide [27][28][29][30][31][32], along with carbon nanotubes [9], and carbon microfibres [30]. ...
Aerostatic thrust bearings utilise air as a lubricant to support loads while minimising friction and wear. The airflow within these bearings is controlled by a restrictor, which can be constructed from various materials, including porous substances. The selection of a porous material for the restrictor is particularly influenced by factors such as permeability, stiffness, and homogeneity. This work proposes a microstructural design for air restrictors based on compacted cementitious composites. A novel cementitious composite, consisting of silicon carbide (SiC) particles and Portland cement, is fabricated through cold pressing at 10 MPa and a low water-to-cement ratio of 0.30. To evaluate the effects of SiC particle size and weight fraction on the physical and mechanical properties of the composites, a statistical design approach is employed. The response variables include apparent density, apparent porosity, oxygen permeability coefficient, compressive strength, flexural strength, and dynamic modulus. In general, a significant reduction in density, compressive strength, flexural strength, and dynamic modulus, along with an increase in porosity and oxygen permeability, is achieved by composites made with smaller SiC particles. A higher weight fraction of SiC reduces bulk density and compressive strength, while increasing porosity and oxygen permeability. Finally, composites made with 67 wt% of fine SiC particles exhibit promising characteristics for aerostatic bearings, particularly in terms of porosity and permeability.
... to CP V-ARI and CP V-ARI-RS. For both evaluated traces, CP V-ARI-RS requires higher amounts of water consumption. CP IV cement have a lower percentage of clinker and gypsum compared to CP V cement (ABNT 2014). CP V-ARI cement also has finer particles which is directly related to the w=c, as smaller particles require more water (Betioli et al. 2020). De Castro et al. (2011 analyzed water consumption with various types of cement in concrete production. They found that CP V-ARI requires more water for the desired consistency compared to other cement types. When analyzing the chitosan dosage in mortars, it was found that increasing chitosan required an increase in the w=c to maintain consistency. This findin ...
... À1 ) is close to that of Portland cement (170 m 2 .kg À1 ) that also justifies the water absorption decrease by soil-cement-waste bricks, which, being a pozzolanic material, allows a good interaction of the hydration reactions of cement composite [55]. ...
Soil-cement brick is a composite obtained by mixing soil, cement, and water in previously established proportions. This material is an alternative for urban or rural construction, as it offers several advantages for its use in masonry, such as the addition of waste. For the addition of waste into cement materials the waste from iron ore extraction process has been highlighted Thousands of tons of this waste are generated on a daily basis large mining companies, leading to air pollution and the occupation of large physical spaces. Thus, the aim of this work was to evaluate the effect of replacing different percentages (0, 10, 20, 30, and 40%) of soil by this mining waste on the properties of soil-cement bricks. The raw materials used were: soil (A-4 classification), CPV-ARI cement, and solid mining waste, which were characterized by physicochemical analysis. The mix ratio used for bricks production was 1:9 (cement:soil), where soil was replaced by different waste percentages. Technological properties such as: dry density, water absorption, immersion mass loss, compressive strength, thermal conductivity, and microstructure were determined. The results indicated that the added mining waste positively influenced the density of cement bricks in the soil. In addition, up to 40% of the waste could be incorporated into the brick, considering the current characterisation standards.
... The manufacturers propose that dentinal fluid in the roots is responsible for the intra-channel polymerization of cement, but this fluid is not only composed of water and bioceramics require water for polymerization. 34,35 The procedure recommended in this study (PBS HP CIMMO® bioceramic cement monobloc filling) does not require additional devices to perform. There is also no indication for the use of intraoperative radiographs, since extravasation of the material beyond the apical foramen is not a concern due to the bioactive and regenerative properties of bioceramics. ...
Statement of the Problem: The bioceramic cements have properties that provide periradicular and root regeneration. Attributes that determine regenerative dentistry. Purpose: the objective of this study was to evaluate endodontic treatments of necrotic teeth performed with PBS HP CIMMO® cement (without gutta-percha), compared to conventional treatments, filled with gutta-percha. Materials and Method: A two-arm, double-blind, single-center, randomized, and prospective clinical trial was designed (NCT03514264). CONSORT guidelines were followed. Eighty-six patients aged 18-60 years were enrolled; only one tooth per patient was treated. Patients were treated in two sessions in Group A (gutta-percha thermoplasticization and vertical hydraulic compresssion and AH Plus® n=43) and one session in Group B (PBS HP CIMMO® n=43). The evaluation was performed one year after the treatment. Two examiners performed clinical examinations and evaluated CT images for the presence or absence of periradicular lesion. Intention-to-treat analysis was used. Results: Tomographic analyzes showed differences between the groups: group B (PBS HP CIMMO®) presented a higher number of cases with periradicular regeneration (p=0.0004). Conclusion: The results of the present study indicated the possibility of rehabilitation of necrotic teeth through endodontic filling with bioceramic (PBS HP CIMMO®), without gutta-percha, in a single session.
... It is observed that the tailing consists mainly of Hematite and Quartz. Ref. [19], states that quartz found in very fine particles can assume three functions when incorporated into cement mixtures: improve packing, serve as nucleation points, facilitating the cement hydration, or aid in strength as a reactivity material depending on the stage in which it is found. In this way, the IOT presents potential to improve the mechanical behavior of cementitious compounds. ...
... Through the BET, a surface area of 7.790 m²/g was obtained for the IOT. As verified by [19] Portland cement CPV-ARI has 1.70 m²/g of surface area, obtained by the same method. Therefore, the residue is more than 350% thinner than the binder. ...
The iron ore market is one of the main responsible for the iron demand in the steel industry and it also represents great importance in the Brazilian economy. The growing development of the sector has led to an increase in the generation of iron ore tailings (IOT). Due to the large amount produced and the form of conditioning, the IOT is related to several environmental impacts. This is especially evident when accidents occur, such as dam breaks. In this context, the iron ore tailing has been the object of studies for use with different purposes. This study aims to evaluate the prospects for reuse of the IOT as a partial substitute for Portland cement. The collected tailing, after drying and homogenization, was submitted to the comminution process, reducing its granulometry. With the powdered IOT, characterization tests were carried out in relation to its chemical and mineralogical composition, particle size distribution, specific mass and surface area. Subsequently, specimens of reference cement pastes were molded and the binder was replaced by 50% by the tailing and the water/fine factor (w/f) was varied. The physical and mechanical properties of the pastes were evaluated in the fresh and hardened state, with respect to their consistency and compressive strength. The superficial physical structure of the pastes was analyzed through digital microscope image. In the fresh state, cement pastes with 50% replacement of hydraulic binder by IOT generated higher fluidity of up to 22,19% in relation to the reference for the same water / fines (w/f) factor. In the mechanical characterization, it was observed a gain of strength in the paste made with IOT replacement when reducing the w/f factor, indicating the possibility of filler effect or pozzolanic reaction. In addition, the use of IOT reduces the consumption of non-renewable natural resources for civil construction, as well as contributes to the reduction of environmental impacts generated by the extraction of iron ore.
Composites based on silicon carbide (SiC) and Portland cement manufactured by uniaxial compaction with a low water-to-cement ratio (0.25) are designed and characterised to obtain a promising porous microstructure to be used as an air restrictor for aerostatic bearings. A 3141 full factorial design is used to investigate the effects of SiC amount (10, 20, 30 and 40 wt.%) and compacting pressure (10, 20 and 30 MPa) on bulk density, apparent porosity, flexural strength and modulus. A second statistical design (22) is carried out to verify the effects of SiC and pressure levels on oxygen permeability, compressive strength and modulus. Higher porosity levels (upper than 20%) are obtained by adding 40 wt.% of SiC for all pressures, but also by adding 30 wt.% of SiC and 10 MPa of compaction. In contrast, reduced flexural strength is obtained under these conditions. Cement-based composites reinforced with 30 wt.% SiC at 20 MPa achieve high mechanical performance combined with 15% of porosity and high permeability, being a promising material for aerostatic bearings.
This article evaluated the effect of using mining waste on the mechanical, physical, thermal, and microstructural properties of cement-wood panels. The percentages of 10, 20, 30, and 40% were evaluated as replacing cement with mining waste. The wood particles of Pinus oocarpa were evaluated for their chemical, anatomical, and physical characteristics, and the mining waste was evaluated for its granulometry, chemical composition, and inhibition index. The composites were evaluated for their physical-mechanical properties, X-ray diffraction and infrared spectroscopy analysis, microstructural, thermal, and durability. All evaluated treatments met the requirements of the Bison standard for MOR and MOE for static bending and internal bonding, even after accelerated aging. It was possible to conclude that it is feasible to replace 40% of cement with mining waste for the production of cement-wood panels in industrial scale.
Abstract Self-compacting concretes (SCCs) are considered promising materials in the civil engineering field. Their main characteristic is the ability to compact only through gravitational force. Mineral additions such as rice husk ash (RHA) and fly ash (FA) are recommended to be used in SCCs during their mix designing, in order to increase fluidity and mechanical strength. These materials are also considered wastes from industry, without a certain destination, which contributes to environmental pollution. In this study, four mixtures of SCC were tested using RHA and FA with two different types of Portland cement, CEM CP IV and white CEM. For the fresh state tests, all of the SCCs mixtures showed satisfactory results. The SCCs with white CEM showed higher mechanical strength at 7 days than CEM CP IV. Analyzing the mineral additions, their use improved the mechanical strength of SCCs at 28 days, there is also observed a higher pozzolanic effect to RHA.
The mining industry produces large amounts of waste during the iron ore processing. This material is usually discarded into tailing dams, posing high maintenance and monitoring costs as well as causing serious environmental disruptions, such as air contamination and leaching of substances. The reuse of such waste as alternative materials in the construction industry is an alternative to its disposal. Therefore, this study aimed at evaluating the effect of using iron ore tailing (IOT) on the physical, mechanical, thermal and durability properties of concrete roof tiles obtained by the extrusion process. The base trace in mass consisted of 1 : 3 : 0.56 (cement : medium grade natural sand : limestone powder). The treatments were based on 25, 50, 75, and 100% mass replacement of limestone powder by iron ore tailing. After shaping, the concrete roof tiles were taken to a saturated humidity chamber at room temperature for 28 days. Concrete roof tiles were evaluated for water absorption, dry weight, transverse breaking strength, bulk density, apparent porosity properties and microstructure at 28 curing days and after accelerated aging. Thermal conductivity, wettability, XRD, permeability and impact resistance analyses of roof tiles were also performed. There were significant transverse breaking strength and porosity values improvements as a result of using greater amount of IOT compared to traditional concrete roof tiles. The technological properties were improved by increasing the amount of waste, meeting international marketing standards. The use of iron ore tailing as total LP replacement showed great potential for use as raw material for concrete roof tiles production, allowing the correct disposal and development of new, more sustainable products, as well as the improvement of roof tiles physical and mechanical properties.
