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Ilustração dos mecanismos de estabilização de suspensões: (a) estabilização eletrostática, (b) estabilização estérica e (c) estabilização eletroestérica [5]. [Figure 6: Illustration of suspensions stabilization mechanisms: (a) electrostatic stabilization, (b) steric and (c) electrosteric one [5].]
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Concrete, the most widely used construction material, is constantly developing. During the recent years, several researches have been carried out and the search for materials with higher mechanical and durability performance has been the objective of the concrete technology area. These materials allow designers and the architects to use them effici...
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... o termo estabilização eletroestérica é usado para descrever o mecanismo de dispersão imposto pelos aditivos superplastificantes (Fig. 6). A estabilização eletroestérica é uma combinação da repulsão eletrostática da dupla camada elétrica e da repulsão estérica, onde a variação e a magnitude de cada contribuição depende de diversos parâmetros, tais como a quantidade de aditivo adsorvido, o grau de dissociação do polieletrólito, a densidade do conjunto de cargas na ...
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The main disadvantage of using concrete, which is accepted to be irreplaceable building material, is the formation of micro cracks. This is due to the fact that concrete is weak in tension. To arrest the microcracks developed in the concrete and to eliminate the drawbacks due to microcracks, the recent trend in the innovation of the concrete is the...
Citations
... In this way, to improve the efficiency of milling processes, producing greater fineness with lower energy consumption and consequently lower carbon dioxide emissions (Prziwara;Kwade, 2020;Zan;Ishak, 2023), the forces of repulsion between the particles must outweigh the forces of attraction (De Castro;Pandolfelli, 2009). Grinding aids may be used during this process, the most common being amines, glycols, alcohols, and phenols (Engelsen, 2009;Katsioti et al., 2009;Toprak;Altun;Benzer, 2018). ...
... In this way, to improve the efficiency of milling processes, producing greater fineness with lower energy consumption and consequently lower carbon dioxide emissions (Prziwara;Kwade, 2020;Zan;Ishak, 2023), the forces of repulsion between the particles must outweigh the forces of attraction (De Castro;Pandolfelli, 2009). Grinding aids may be used during this process, the most common being amines, glycols, alcohols, and phenols (Engelsen, 2009;Katsioti et al., 2009;Toprak;Altun;Benzer, 2018). ...
This study aimed to evaluate the effect of mechanoactivation with and without grinding aids (GAs) on the physical characteristics of recycled concrete powder (RCP) for use as supplementary cementitious material (MCS). RCP was subjected to the comminution process in a planetary ball mill for 30, 60, 120, 180, and 240 minutes, using three types of grinding aids (propylene glycol (PG), sodium hexametaphosphate (SHMP) and triethanolamine (TEA)), at different levels (0, 0.05, 0.1, 0.5 and 1%). The powders’ performance as SCM (10% substitution) was evaluated in pastes on consistency and compressive strength at 7 days. Considering the shortest milling time and the lowest content of milling aid, mechanoactivation for 30 minutes with 0.5% propylene glycol (PG) additive reduced the d50 from 20.99 to 8.85 µm and increased the BET from 6.23 to 7.50 m²/g, without altering crystallinity. The results in pastes indicated that the use of grinding aids favored the use of recycled concrete powder as MSC, with a statistically significant score in particularity resistance.
... In addition, the water/cement factor must always be as low as possible, within the required characteristics of the block and the quality of the materials available for its composition. The higher the water content in the mixture, the greater the tendency for exudation to occur, which causes the water to reach the surface of the block, creating a greater number of voids inside and, consequently, reducing the resistance, increasing the permeability, and impairing the block's durability (Castro and Pandolfelli, 2009). ...
This study aimed to analyze potential industrial solid waste that can be added to soil-cement blocks. A narrative literature review was conducted in the Scopus academic database, using as the search criteria keywords related to the topic, such as soil-cement, building materials, soil-cement blocks, soil-cement bricks, physical and mechanical properties, solid waste, life cycle analysis, and civil construction. A variety of industrial solid waste that can be incorporated into soil-cement blocks was observed, such as waste rock, sludge from water treatment plants, wood sawdust, polyethylene terephthalate fibers (PET), vegetable fibers from loofah, hemp fibers, rice husks, brachiaria grass, poultry eggshells, sugar cane bagasse, wheat and barley straw, welding slag, foundry sand, waste from quartzite mining, construction, and demolition, mechanical turning, pulp industry grains, and steel mill co-products. Among the investigated wastes, those that improved the physical and mechanical properties of the soil-cement blocks were grains from the cellulose industry, rice husks, Brachiaria grass, steel by-products with granulated soil-cement blocks and blast furnace slag. The waste that produced no satisfactory results was sludge from a water treatment plant, sugarcane bagasse, and vegetable loofah. Through this research, it was possible to verify that the behavior of soil-cement blocks is influenced by several factors in their manufacture, mainly regarding the type and percentage of incorporated waste. However, it is important to be concerned with its application in waste blocks so as not to increase the environmental impacts in the long term.
... where CPFT is the cumulative percentage finer than particles with diameter D, D L represents larger particle diameter, and q is the distribution coefficient. It does not consider a minimum particle size, but assumes a sequence of decreasing particles, allowing the CPFT to be equal to zero without substantial interference on the material density [17,18]. ...
... Therefore, the changes introduced in the Alfred method reinforce the idea that the absence of a fixed minimum particle size can lead to discrepancies in the particle packaging method. Consequently, literature reports that Alfred method is the most realistic [17,18,20]. The EMMA mix analyser software [21] was used to obtain the theoretical curve (with D L , D S and q values as input) and, as shown in Fig. 2, adjusting the granules amount with the different granulometry available allowed the system optimization. ...
... particle size distribution -PSD). It has been found that the use of particle packing models (PPMs) could lead to a significant reduction in the cement content of concrete by improving its aggregate's skeleton [7][8][9]. PPMs approach is based on the idea of optimizing the PSD or grading of the aggregates skeleton in concrete mixtures [2][3][4]10]. One of the first PPM proposed was Fuller-Thompson's model in 1907 [7]. ...
Pressure is mounting in the construction industry to adopt more environmentally sustainable methods to reduce CO2 emissions. One of the most efficient methods in this regard is the use of low cement systems, the so-called low cement concrete (LCC). Although eco-efficient, the use of structural LCC is somewhat new and its performance and long-term behaviour are still relatively unknown. This project aims to mix-proportion concrete mixtures with reduced amount of cement through particle packing models (PPMs). Fresh and hardened state evaluations are performed on mixtures with distinct carbon footprint while gaps, recommendations, and further needs are highlighted. Results indicate that PPMs enable the development of LCC systems with suitable performance in the hardened state while presenting reasonably small environmental impact. Otherwise, particular attention should be taken in the fresh state properties of highly packed granular systems, which might be improved through the use of admixtures, fillers and supplementary cementing materials.
... Therefore, recent studies demonstrated that IF might be used to reduce PC content, hence enhancing concrete eco-efficiency [6][7][8]. Another novel technique used to reduce the amount of PC in concrete is through the use of advanced mixdesign techniques that aim to increase the material's packing density, lowering its porosity and amount of cement paste required [9,10]. Yet, although the above strategies are widely known, low-CO 2 concrete mixtures with reduced porosity (and low PC content) is currently not used for important structural applications since concerns regarding their fresh state performance were raised by the technical society. ...
... Literature suggests that the lower the IPS, the lower the flowability of granular systems (i.e. the higher the viscosity and particles collisions). Conversely, high IPS yields less viscous, more flowable mixes [9,14]. ...
... Moreover, some SCMs types are depleting over the years due to the closure of industries responsible for producing these residues [15,16]. Limestone-based fillers have also been used in concrete as a partial PC replacement to increase eco-efficiency and physical properties such as overall porosity [17][18][19][20]. These fillers are generally called inert materials and are commonly used due to their physical features, the socalled filler effect [19][20][21]. ...
... Another strategy to decrease PC usage is adopting advanced mix-design techniques, such as particle packing models (PPMs). PPMs may enhance the granular system of the material, reducing its porosity and consequently minimizing the amount of cementitious materials required to fill the voids amongst the aggregate particles [15,17,18]. Although different PPM approaches are found in the literature able to improve ecoefficiency of concrete, there is currently little to almost no discussion regarding the interaction between ''packing", ''rheological behaviour", and ''mechanical performance" of concrete mixtures presenting reduced amounts of PC, the so-called low cement concrete (LCC) systems. ...
... In order to understand the fresh properties of high packing density systems, there is a need for studying the mobility among the particles throughout the whole PSD. Previous research shows that the Interparticle Separation (IPS) distance and Maximum Paste Thickness (MPT) are two mobility parameters (MP) that are essential to understanding the concrete behaviour in the fresh state [17,26,35,[38][39][40]. IPS is considered the average distance of two adjacent fines particles (smaller than 100-125 mm), assuming non-agglomerated particles [35]. ...
Concrete, the major construction material used in the construction industry worldwide, presents a huge environmental impact producing about 7% of the global carbon dioxide. Given the concerns related to global warming, studies have been focusing on distinct approaches aiming to reduce the amount of
Portland cement (PC), which is the least sustainable ingredient of the mixture, by adopting alternative mix-design strategies such as the use of particle packing models (PPMs). However, there is currently a lack of data on the efficiency of the use of continuous PPMs to reduce PC while maintaining or improving concrete fresh and/or hardened properties. This work aims to investigate the impact of current and modified
versions of continuous PPMs on the fresh (rheological behaviour) and hardened (compressive strength, modulus of elasticity, porosity, and permeability) state of mixtures designed with low and moderate amounts of PC. Results demonstrate that eco-efficient concrete may be produced through current and modified continuous PPMs without compromising the fresh and hardened properties of the material. Nevertheless, further durability and long-term investigations must be performed on systems with
reduced PC contents.
... It achieves its extraordinary strength characteristics through optimization of the particle packing density of its cementitious matrix [Holschemacher, 2005]. This high particle packing density also leads to high durability [Castro, 2009, de Larrard, 1994. When properly reinforced with discontinuous fibers, UHPC can develop other beneficial properties, including pseudoductile tensile behavior and toughness. ...
... It achieves its extraordinary strength characteristics through optimization of the particle packing density of its cementitious matrix [2]. This high particle packing density also leads to high durability [3,4]. When properly reinforced with discontinuous fibers, UHPC can develop other beneficial properties, including pseudo-ductile tensile behavior [5] and toughness [6]. ...
... The various types of existing interactions (interparticle attractive forces, or Van der Waals forces, electrostatic forces between oppositely charged sites and strong bonds involving water molecules) are responsible for promoting this process of agglomeration. [9][10] For the purpose of dispersing these micro/nanoparticles, it is common to use a surfactant, also known as a dispersant. ...
... Surfactants can be classified according to the chemical structure of their hydrophilic groups, which can be anionic, cationic or nonionic. [9,11] Rheology is a very important tool to study the behavior of emulsions during processing. Among the rheological properties, viscosity is particularly important, especially when working with polymer composites. ...
Dispersions of 10% wt hydrotalcite were prepared by mixing using an ultrasound probe and then incorporated into NBR latex for the purpose of evaluating the influence of the surfactant presence and dispersion stability of the hydrotalcite, both in water and in latex. The surfactant used was Pluronic F-127 and its influence was determined on the size of the agglomerates, the degree of sedimentation and the viscosity of water/LDH dispersions and latex/LDH suspensions. Preliminary results showed the efficiency of the surfactant in promoting dispersion of water/LDH, presenting lower agglomerate diameter values and increased stability of the dispersion. For the latex/LDH suspension, the viscosity of the system containing surfactant was significantly greater due to a better dispersion of LDH. After coagulation, the systems were examined in detail using X-ray diffraction (XRD) and the results did not show differences in the degree of intercalation, but XRD pattern of LDH was not observed, indicating the breakdown of crystallinity and ordering of the clay crystallites. The ash content showed that the presence of surfactant was an important factor to optimize the incorporation of the clay during coagulation. The estimation of Payne effect from shear modulus indicated a better filler dispersion in NBR matrix when using Pluronic F-127, this behavior was also confirmed by FESEM micrographs.
... (2)] is the fact that it does not consider the existence of a minimum particle diameter. It assumes a sequence of decreasing particles, enabling the CPFT to equal zero without significant interference on the material density (Castro and Pandolfelli 2009). ...
... Using the equation, if D S equals zero, the equation is exactly the Andreasen equation, which is the only distinction between both methods. Some authors (Ortega et al. 1997;Castro and Pandolfelli 2009) believe that the Alfred method is more realistic. In practice, both are commonly used. ...
... Computing simulations have shown that the value of q ¼ 0.37 provides higher particle packing density for materials (Castro and Pandolfelli 2009). Lower values usually keep the particle packing to a maximum, whereas higher q values exhibit certain residual porosity (Ortega et al. 1997;Castro and Pandolfelli 2009). ...
Alkali-activated binders (AAB) or geopolymers are new ceramic materials with the potential to replace portland cement in a wide range of applications, from immobilization of heavy metals to concretes for civil engineering. They rely on the alkaline activation of aluminosilicates, such as blast furnace slag (BFS), pulverized fly ash (PFA), and metakaolin (MK). Despite their high mechanical strength and chemical durability, geopolymer concretes are in many cases marked with high porosity and permeability, which could negatively affect the performance or long-term durability of concretes. This paper employs the Andreasen particle packing method, commonly used for ceramic materials, to improve the geopolymer formulations studied on the development of micro-concretes. Three parameters were inves-tigated: (1) the Andreasen packing factor q, 0.21, 0.235, and 0.26, which alter particle size distribution of aggregates; (2) the solution to solids rate, 1.3, 1.4, and 1.5; and (3) the type of aggregates, either glass or quartz. The influence of these parameters on mechanical strength, in addition to porosity and apparent density, were determined. Results have shown that the Andreasen method may be used to change the rheology and, therefore, develop different geopolymer mixes. In the particular case of the development of geopolymer floor tiles, the best formulation is the one with a solution to solid rate of 1.4, Andreasen packing factor of 0.235, and quartz aggregate.
