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In this paper, the effect of water-binder ratio, sand ratio and high-range water reducer (HRWR) content on the rheological behavior of mortar formulated from concrete mixture was investigated by using a RheoCAD rheometer. The segregation of fresh concrete and hardened concrete was, respectively, measured by two different modified methods, coarse ag...
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... This is particularly relevant in concrete slabs, where excessive bleeding leads to cracking, delamination, and damage of the structure of subsurface concrete. 5,19 It is known that bleeding depends on the cement type, 18 admixtures, 20,21 w/c ratio, 20,22 aggregate size and type, 23 and the scale of the used cementitious mixes (i.e., concrete, mortar, or paste). 17,24 Concrete subjected to uncontrolled bleeding may need expensive repair, or even replacement of the entire concrete element. ...
Bleeding is a common problem in concrete slabs, and may lead to serious damage. The goal of this article is to understand the impact of alternative binders and their properties on the bleeding of concrete. Therefore, the impact of the type of binder on the bleeding process is investigated. The results show that the addition of granite powder or fly ash allows for the increased control of the bleeding process. It was found that a finer particle size distribution (PSD), an increased specific surface area (SSA), and a higher bulk density may reduce the amount of dispensed water in the concrete mix. Furthermore, the use of additives with an increased SSA leads to even a 30% reduction of the bleeding rate of mixes. The utilization of additives with a finer PSD than cement enables a 37% reduction of the bleeding rate of mixes. The influence of bleeding on compressive strength was assessed using destructive and non‐destructive tests: Replacing 30% of cement with granite powder leads to a 30% reduction of concrete strength after 28 days of curing; on the other hand, replacing 30% of cement with siliceous fly ash leads to an 18% reduction of strength. Importantly, bleeding was also found to lead to the heterogeneity of the physical and mechanical properties across the concrete section. Consequently, the proper control of the bleeding process leads to more homogeneous properties of concrete across its cross‐section.
... For example, crack detection is used for structural health monitoring [17,18], computer vision is used to assess fires [19], bughole concrete detection is used [20], and the mixing concrete evolution is monitored [21]. There are several methods for measuring or identifying the segregation in hardened LWAC and conventional concretes [22][23][24][25], and the most extended method is using image-processing-based techniques [25][26][27]; furthermore, determining densities of different sections of a concrete specimen is also used [28] for evaluating the segregation [29]. The main goal of these techniques is to confirm well-graded, homogenously distributed, and randomly oriented coarse aggregate to improve the concrete mechanical and durability properties. ...
... There are several methods for measuring or identifying the segregation in concretes using image analysis techniques [22][23][24][25]. In this research, two different methods were selected based on studies that have been carried out by the authors. ...
Due to the low density of the aggregates and the longer mixing times, lightweight aggregate concrete (LWAC) is susceptible to segregation of the aggregates. Several studies have proposed different methods to estimate the segregation of concrete because segregation affects strength and durability in structures. Image analysis techniques have become very popular for quickly analysing different materials and, together with the widespread use of mobile applications, can make it much easier for engineers to obtain parameters that identify concrete segregation. The aim of this work was the development of a mobile application to photograph the section of a concrete specimen and indicate the segregation values. A simple, fast, and effective application was implemented, and the results were validated with other previously published results, which can facilitate the task of engineers and researchers to determine the segregation of concrete.
... It was also proposed that the increase in sand ratio tends to decrease the bleeding pressure of concrete. Low slump mixture (with less w/c ratio) influence towards less bleeding (Pan et al. 2021). But the bleeding from the concrete cannot be eliminated (Moccia et al. 2021). ...
Natural fibers like banana, rice-husk and yarn fibers are used in concrete to enhance the strength properties as well as the toughness of concrete. Freshly prepared flow able concretes tend to segregate. When the concrete is compacted, due to vibration the water rises on the surface of the freshly placed concrete which is termed as bleeding. The purpose of this study is to analyze the behavior of natural fibers in terms bleeding of freshly prepared concrete with natural fibers and its compressive strength. The specific aim of the research is to explore the effect of banana, rice-husk and yarn fiber on the bleeding of fresh concrete; remedial measures and to analyze the compressive strengths. Because higher value of bleeding affects compressive strength of concrete. For this purpose, banana, rice-husk and yarn fiber reinforced concretes are prepared with fiber lengths of 50 mm, 50 mm and 5-10mm respectively. These natural fibers is taken as 2.5 % by mass of cement and mix design ratio is kept as 1:2:4 respectively. The plain concrete (PC) is taken as reference and values of bleeding and compressive strength for each fiber reinforced concrete (FRC) are compared with PC. Results indicated that PC shows 3.6 ml bleeding and banana fiber reinforced concrete (BFRC) shows zero (0 ml) bleeding. Whereas rice rusk fiber reinforced concrete (RHFRC) and yarn fiber reinforced concrete (YFRC) show 2 ml and 1.70 ml bleeding. PC, BFRC, RHFRC and YFRC show 4.62, 4.42, 5.13, 5.89 Mpa compressive strengths respectively.
... In order to measure the segregation degree of concrete and evaluate the segregation resistance of fresh concrete, many measurement methods have been proposed [3,[5][6][7][8]. Using these test methods, the segregation resistance of fresh concretes has been successfully evaluated [5,[9][10][11][12]. ...
... In order to measure the segregation degree of concrete and evaluate the segregation resistance of fresh concrete, many measurement methods have been proposed [3,[5][6][7][8]. Using these test methods, the segregation resistance of fresh concretes has been successfully evaluated [5,[9][10][11][12]. Nevertheless, the current researches on the segregation of fresh concrete are almost experimental approach. ...
Current meshless particle methods are able to simulate the flow of fresh concrete, but fail to predict the segregation since fresh concrete is regarded as homogeneous fluid. This study aims to develop a numerical approach to predict the segregation of coarse aggregate (CA) in fresh concrete together with the flow behavior. A double-phase & multi-particle (DPMP) model was proposed to describe fresh concrete, which treats fresh concrete as a double-phase fluid composed of matrix mortar and the CA particles that had random shapes, size distribution, and different density from matrix mortar. Each CA particle was formed by the element particles, of which number was dependent on the size and shape of described CA particle. Three types of inter-particle interaction, including CA-CA particles, CA-mortar particles, and two mortar particles, were investigated, respectively. Then, based on the complete implicit MPS (I-MPS) method and the DPMP model, the L-box flow of two series of high fluidity concrete were simulated. The ability of the proposed numerical approach to simultaneously simulate the flow and segregation behaviors of fresh concrete was confirmed. Moreover, this numerical method can analyze the changes of localized rheological parameters of segregated concrete.
... Bleeding is a process also related to the rheological properties of pastes [12,21]. The preparation of the ingredients and the mixing procedure influences the bleeding process [22,23]. Figure 3 shows the volume of the bleeding water V b that is dispensed from the cement pastes overtime of the bleeding process. ...
The article presents the results of bleeding tests for cement pastes modified with the addition of granite powder. Bleeding is the process of dispensing the water from the inside of the mixture towards the top. Bleeding in cementitious mixes is an important process related to early-age properties of composites (like cracking of concrete slabs). There are known examples of damage to horizontally formed concrete structures due to the uncontrolled bleeding process. The research was performed for four series of modified cement slurries of the addition of granite powder. The test was carried out with the use of a method allowing to obtain high accuracy of measurement (ASTM C243-95 Standard Test Method for Bleeding of Cement Pastes and Mortars (Withdrawn 2001), [1]) of the released water over time, with particular emphasis on the first 30 min of the process. Three phases of the bleeding process were observed during the investigation (initial bleeding, accelerated bleeding, stable bleeding) into cement pastes. An additional division of the first phase on three phases (start of the process, components ordering, appropriate bleeding) was also proposed. The results of the research also present that thanks to the addition of granite powder, it is possible to reduce the volume of dispensed water in the bleeding process. The main issues were recognized and directions of future research area are indicated.
The mortar attached to recycled concrete aggregate (RCA) surface significantly influences the resulting concrete properties due to the high porosity, low strength, and high water absorption. In this study, the physical and mechanical characteristics of RCA and their effects on the fresh, mechanical, and durability properties of the resulting concrete were reviewed with respect to bonded mortar. Owing to the high disparity in the quality of RCA obtained from various sources, a high degree of performance heterogeneity was observed. Concrete produced with RCA is less resistant to crushing, impact, and abrasion than concrete incorporating normal aggregate, because RCA exhibits a lower specific gravity, lower bulk density, and increased porosity. The mechanical properties of concrete also deteriorated with increasing RCA content, indicating that lower values associated with the physical and mechanical properties influenced the hardened concrete properties. This is because of the presence of porous mortar adhered to the surface and higher water absorption, which makes the acid and salt attack by the ingression of sulfate and chloride solution higher than that of the control sample with NA only. In this article, a comprehensive literature review and analysis of the effects of bonded mortar on RCA and the resulting concrete properties were conducted, and prediction equations for the mechanical and durability properties of such concrete were also presented.
In the process of pumping, the segregation of concrete mixture will lead to the difficulty of construction, and even the possibility of pipe blocking. There is a lack of a quickly evaluation for on-site construction. In order to solve this problem, a rapid wet-sieved test was proposed in this study and then its feasibility was evaluated based on concrete mixes with different water-cement ratios. Subsequently, the influence of sand ratio on the segregation degree of concrete was investigated. The test results show that a combination of 2.36 mm screen size and 20 s vibrating time did the best. The wet-sieved mortar content and stratification degree were increased by 4.6%-25.2% and 0.3%-17.9% by pumping, respectively. With the sand ratio increasing from 0.40 to 0.60, the pumping pressure decreased by 51.9%. The linear fitting correlation between pumping pressure and wet-sieved mortar content (0.96) is better than that between pumping pressure and stratification degree (0.85), which indicates that the proposed test method can reliably characterize the degree of segregation during the pumping of ready-mixed concrete.
