Tensile strength development for concrete mixes with 194 kg/m³ water content (in the legend, the numbers after WC and SL denote the w/c ratio and the intended slump in inches, respectively), from Abel and Hover (1998)

Tensile strength development for concrete mixes with 194 kg/m³ water content (in the legend, the numbers after WC and SL denote the w/c ratio and the intended slump in inches, respectively), from Abel and Hover (1998)

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Plastic shrinkage cracking in concrete is mainly a physical process, in which chemical reactions between cement and water do not play a decisive role. It is commonly believed that rapid and excessive moisture loss due to evaporation is the primary cause of the phenomenon. This paper presents a new model to estimate the severity of plastic shrinkage...

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... Concrete shrinkage processes can be classified into three main types: including plastic, autogenous, and drying shrinkage, as indicated in Fig. 1 [9][10][11][12][13]. Plastic and drying shrinkage occurs when concrete is in its plastic and hardened phases, respectively, within approximately the first 6 h and after 24 h of concrete age [14][15][16][17][18]. However, autogenous shrinkage commences shortly after the dormant period, also continuing in the hardened concrete [12,19,20]. ...
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Early-age shrinkage of concrete can initiate premature cracking, which can compromise the durability of concrete structures. Monitoring capillary pressure, the leading cause of concrete shrinkage, and understanding its evolution is crucial for the performance-based design of concrete, particularly at early-stages when it is more prone to cracking. This study deploys an innovative multi-scale experimental program using high-capacity tensiometers to monitor the capillary pressure up to 2000 kPa. This allowed investigating the effects of key design parameters, including the water-to-cement ratio, GGBS, SRA, and measurement depth, on the capillary pressure evolution in concrete. A new robust deep neural network model was developed to conduct extensive numerical experiments to predict the capillary pressure evolution of diverse mixtures. The net effect of multi-parameters on the capillary pressure can be investigated with this model, providing insights into the optimum design of more durable concrete mixtures with the lowest capillary pressure evolution, and guiding the implementation of appropriate cost-effective shrinkage-mitigating strategies.
... Hydration of cement is also subject to weather and temperature, under high weather conditions above 38 o C early hydration occurs in cement [1], consequential to this, high strength is gained in concrete at the early stages but reduces considerably at the latter stages. Plastic shrinkage is caused due to the quick evaporation of water [2], and as a result, the cooling causes cracking and tensile stresses within the concrete [3]. More so, this issue affects greatly and negatively practically globally, as concrete might lose its plasticity under severe weather conditions while being transported to the site where it is needed, this can be economically draining. ...
Article
This study was carried out with the fundamental aim of conducting experimental investigations into the influence of sugar as an admixture on both the setting time of cement and the compressive strength of concrete. The research involved the variation of the proportion of cement replaced by sugar at specific weight percentages, including 0.0%, 0.06%, 0.08%, 1%, 2%, and 3%. The aim of this experiment was to determine the effect of sugar as an admixture on the setting time of cement paste and the determination of the compressive strength of the obtained concrete. On a global scale, this research addresses the pressing issue of the substantial demand for cement and its profound environmental implications. The study explores innovative approaches to partially substitute cement in concrete mix, thereby fostering sustainability within the construction sector. The experiment of this study have yielded noteworthy outcomes. Particularly, at the admixture levels of 0.06% and 0.08% sugar by weight of cement, the compressive strength results not only met but exceeded the expectations, surpassing even the performance of the control concrete M15 sample, while retarding the setting time of cement paste. These findings present a compelling argument for the potential utilization of sugar as an admixture in cementitious materials, offering promising prospects for sustainable and environmentally responsible construction practices. This research adds to the broader discourse on sustainable construction and emphasizes the potential benefits of sugar admixture in enhancing concrete properties while cushioning the environmental effect attached with conventional cement usage.
... Thus, the results indicated that rheological characteristics, compressive strength, and water-reducer content can be used to control the plastic shrinkage cracking of shotcrete. the formation of plastic cracks are many, which are most intensely manifested at different stages of concrete solidification [6][7][8]. ...
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Plastic shrinkage cracking is a complex and multifaceted process that occurs in the period between placement and the final setting. During this period, the mixture is viscoplastic in nature and therefore possesses rheological properties. The investigation of the relationship between rheological behavior and its propensity to undergo cracking during the plastic phase presents an intriguing subject of study. However, many factors influence plastic cracking, and the corresponding interaction of its effects is complex in nature. This study aimed to evaluate the impact of rheological and physicomechanical properties on the occurrence of plastic cracking in high-performance shotcrete containing various supplementary cementitious materials. To achieve this, plastic cracking was evaluated employing the ASTM C 1579 standard and a smart crack viewer FCV-30, and the rheological parameters were controlled using an ICAR rheometer. In addition, a study was conducted to assess the strength development and fresh properties. Further, a relationship was established via statistical evaluation, and the best predicting models were selected. According to the study results, it can be concluded that high-yield stress and low plastic viscosity for colloidal silica mixtures are indicators of plastic cracking resistance owing to improved fresh microstructure and accelerated hydration reaction. However, earlier strength development and the presence of a water-reducing admixture allowed mixtures containing silica fume to achieve crack reduction. A higher indicator of yield stress is an indicator of the capillary pressure development of these mixtures. In addition, a series containing ultrafine fly ash (having high flow resistance and torque viscosity) exhibited a risk of early capillary pressure build-up and a decrease in strength characteristics, which could be stabilized with the addition of colloidal silica. Consequently, the mixture containing both silica fume and colloidal silica exhibited the best performance. Thus, the results indicated that rheological characteristics, compressive strength, and water-reducer content can be used to control the plastic shrinkage cracking of shotcrete.
... where P c is the capillary pressure (Pa), γ is the surface tension of pore solution (N/m), R 1 and R 2 are the minimum and maximum of water curvature (m). Given that the capillary pressure is the main mechanism for all types of shrinkage at an early age [1], monitoring its evolution in concrete can provide a deeper insight into the poromechanical behaviour of concrete along with a prediction of early age shrinkage [5,[15][16][17]. Furthermore, new shrinkage mitigating strategies can be developed from understanding the evolution of capillary pressure [18][19][20][21][22][23][24]. ...
Chapter
Owing to their high surface-to-volume ratio, concrete pavements and slabs are more prone to shrinkage, leading to premature cracking and, as a result, loss of serviceability. Capillary pressure in concrete, identified as the main contributor to shrinkage, needs to be frequently monitored to evaluate the shrinkage behaviour of concrete. However, capillary pressure measurement is currently limited to 100 kPa, covering only the initial few hours of age due to the low capacity of existing capillary pressure sensors. This results in very limited record of capillary pressure during the processes occurring within concrete after casting and has prevented a better understanding of the influence of capillary pressure on concrete durability. In this study, high capacity tensiometers (HCTs) were used for the first time to investigate the evolution of capillary pressure in early age concrete over longer periods and at higher capillary pressure values. The results showed that HCTs can quantify the evolution of capillary pressure up to 2000 kPa, a twenty fold increase in comparison to existing methods. This new transformative technology is a major step forward in concrete research and can provide new insights into the shrinkage behaviour of early age concrete. Furthermore, this novel technique can be used in situ in construction projects to monitor the real-time development of capillary pressure of concrete at an early age, aiding practitioners in the decision-making for the employment of effective mitigation strategies to reduce shrinkage and, in turn, increase the durability of infrastructures.KeywordsCapillary PressureHigh Capacity TensiometerEarly Age ShrinkageSelf-Consolidating Concrete
... After the placement of mass concrete, the cementitious material hydrates and exothermic and starts to cool down slowly after the temperature peak, forming large tensile stresses and highly susceptible to the formation of temperature cracks [1][2]. The tropical coastal region of Malaysia has a hot climatic environment, high average annual temperatures, varying quality of local raw materials, and lack of mineral admixtures [3][4]. ...
Article
The tropical coastal region of Malaysia has a hot climate, high average annual temperature, and varying quality of local raw materials, making it challenging and difficult to carry out large volume concrete projects in this region. In this paper, we developed a special admixture for bulk concrete in subtropical coastal environment by modifying the basis of acrylic acid-based polycarboxylic acid admixture. The concrete prepared with this admixture has good ease, no water secretion, excellent mechanical properties and greatly improved exothermic characteristics. The C50 mass concrete prepared with this admixture has an initial slump/extension of 220/585mm, a 2h slump/extension of 210/570mm, and a crack resistance class I.
... Plastic shrinkage cracking mainly occurs in concrete elements that are larger in surface area and smaller in depth. The principal phenomenon behind plastic shrinkage cracking is the rapid evaporation of accumulated water as a result of bleeding [19]. Bleeding usually takes place when aggregate particles settle due to gravity, which enables an upward movement of water towards the surface through the particle pores [19,20]. ...
... The principal phenomenon behind plastic shrinkage cracking is the rapid evaporation of accumulated water as a result of bleeding [19]. Bleeding usually takes place when aggregate particles settle due to gravity, which enables an upward movement of water towards the surface through the particle pores [19,20]. Climate conditions, such as excessive heat and wind, may also accelerate the rate of water evaporation on the concrete surfaces. ...
... This behaviour was influenced by the amount of water available in the mix required for stiffening. Bleeding was halted when concrete reached the initial setting [19,22]. At 160 minutes, it was observed that the coarser MH considerably increased the cumulative bleeding of concrete compared to MC due to its quicker particle settlement A similar behaviour was also observed in Figs. 9 and 10 for the M-and C-series concrete, respectively. ...
Article
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Construction industries have started to utilize manufactured sand (MS) as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain MS, which also produces a considerable amount of microfine aggregate (MFA). The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying MFA levels, specifically 0%, 3%, 6%, 9%, and 12% (by weight) as the partial replacements of MS on bleeding and plastic shrinkage cracking of concrete. In addition to the varying MFA levels, some concrete mixes also included fly ash (FA) and superplasticizer to investigate the effect of free-water content in the mixes. The bleeding test data were taken as on-site measurements, while the cracks from the plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life gradually decreased, while a progressive increase was observed for crack width, crack length, and crack area.
... [56,57] explains this phenomenon. Shrinkage includes autogenous shrinkage, caused by the volume of hydration products, namely C-S-H gel and Ca(OH) 2 crystals, being less than the total volume of cement and water before the reaction, and drying shrinkage due to the evaporation of water during the hardening process [58,59]. The drying process is a diffusion process, so caused deceleration of the shrinkage rate. ...
Article
The present experimental and analytical study conducted a 710-day creep experiment on high-performance concrete(HPC) with a loading period of 45–260 days. The effects of the loading period on the shrinkage, elastic modulus, and creep of HPC, as well as the deviation from the prediction results of the ordinary concrete model, were examined. The results show that admixtures delay the hydration and hardening process of HPC compared with ordinary concrete. The influence of the loading period on the creep of the aged HPC is mainly reflected in the first day of creep development. The creep of concrete declines with the loading age following a hyperbolic function, fC(τ), so a creep model based on fC(τ) is established and validated by the test results. Moreover, we take fψ́(τ) to characterize the influence coefficient of the loading period for the creep coefficient. fψ́(τ) is first proposed based on the literature on the experiments with ordinary concrete with a loading age in the range of 1–5000 days and then modified based on the experimental results to predict the creep of HPC. Finally, the broad applicability of fψ́(τ) was confirmed by applying it to six studies. The present study can provide a basis for establishing the creep model for high-performance concrete.
... Capillary pressure in the concrete has been directly measured by the capillary pressure sensors [11,12,19,20,26,40]. However, because of the low capacity of these sensors, capillary pressure measurements have been limited to 100 kPa, a value that is typically reached within the initial few hours after concrete casting. ...
... Furthermore, these sensors cease to operate if air entry of the porous filter is reached and cavitation occurs within the water reservoir or there is a blockage of the sensing face by cement paste [6,19,26,41,42]. Given these shortcomings, models developed to predict the capillary pressure value and plastic shrinkage cracking risks based on the evaporation rate, bleeding and settlement, have been limited to concrete ages of about 6 h and have not been validated for longer periods or higher capillary pressures [6,11,14,19,20,40,42]. This is an important limitation because the hydration rate and self-desiccation of cement occurring after 6 h of concrete age are at their highest, causing higher capillary pressures due to the self-desiccation, a process demonstrated by Lura et al. [43] and Poole [44]. ...
... In this period, because of the low hydration degree, α (t=5) = 2.6%, evaporation is the dominant factor for the change in capillary pressure. A similar trend was observed in this timeframe in previous studies [11,14,19,40,41,60]. ...
Article
Capillary pressure is frequently measured to evaluate the shrinkage performance of concrete but has been limited to pressures <100 kPa preventing a better understanding of the early age factors affecting concrete durability. In this study, high capacity tensiometers (HCTs) were employed for the first time to investigate the behavior of early age concrete. The evolution of capillary pressure in Self-Consolidating Concrete (SCC) with and without shrinkage reducing admixture was evaluated. The results demonstrate that HCTs are capable of measuring capillary pressure beyond 1500 kPa. This transformative new record of capillary pressure behavior has enabled the development of a model for the capillary pressure in early age concrete correlated to water evaporation, self-desiccation, setting time, temperature, and hydration processes. This ability to quantify real-time capillary pressure change in concrete generates important implications for optimizing the commercial durability of SCC and for understanding the link between early age concrete processes and resultant mechanical performance.
... Bleeding usually takes place when aggregate particles tend to settle due to gravity, which enables an upward movement of free water to the surface through channels. 16,17 This property shall be related to the plastic shrinkage cracking of concrete as the amount of bleed water determines the cracking rate at the surface. The shrinkage cracking is initiated when the bleed water is evaporated from the concrete surface due to the excessive heat and wind speed. ...
... The principal phenomenon for the cracking is the creation of negative tensile pressure at the surface, which pulls the particles and propagates the hairline cracks at the surface. [17][18][19] From the concise review of literature, effects of varying cement properties, [20][21][22] addition of fibers [23][24][25][26] and inclusion of shrinkage reducing admixtures 27,28 were proposed as the factors for bleeding and plastic shrinkage induced cracking of concrete. The presence of MFA could be also considered as a key factor, which is not appeared in any literature. ...
... The crack areas of various concrete specimens with different fiber volumes were compared to the calculated PSC severity values and the model was predicted based on these results. Moreover, Sayahi et al. 17 derived a model to estimate the severity of PSC of concrete even prior to the casting based on the tensile-stress relationship. This model can be able to predict the PSC severity level based on the evaporationbleeding ratio or accelerating the initial setting time of concrete. ...
Article
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Manufactured sand (MS) has been started utilizing as an alternative in constructions due to the escalated demand for river sand (RS). The microfine aggregate (MFA) is a salient constituent in manufactured sand, which is a crushed reactive form of parent rocks having particles less than 0.075 mm. This paper presents the effects of varying microfine aggregate levels on bleeding , plastic shrinkage cracking (PSC) and compressive strength of MS made concrete. Two types of MS were utilized: MS from Hornblende-Gneiss rock (MH) and MS from Charnockite rock (MC) and the MFA level was ranged from 0% to 12% at 3% increments and the reference concrete was prepared with RS alone. With the MFA levels, the bleeding of MS concretes was reduced where, at 0% MFA level the maximum bleeding rates were observed for MC (1.63 kg/m 2) and MH (0.84 kg/m 2) concretes. PSC results were analyzed from an image processing technique, which revealed an increasing trend of mean and maximum crack widths, crack length and crack area with the MFA levels. At 0% MFA, the mean crack width of MC (0.19 mm) and MH (0.17 mm) con-cretes manifested marginally similar to RS concrete (0.17 mm). The decreasing bleeding with the MFA levels can be attributed to the increasing severity to PSC. Moreover, the optimum 28 days compressive strength of MC (57.5 MPa) and MH (56.1 MPa) concretes was achieved at 3% MFA level which are higher than RS concrete (51.5 MPa). Consequently, the MFA level should be limited to 3% for better plastic and hardened performance of MS made concrete.
... It seems that the existing models sometimes are unable to explain some cases of plastic shrinkage cracking (e.g., why sometimes lower evaporation causes more cracking than another concrete exposed to higher evaporation) [2]. This paper reports test results to evaluate the precision of a novel model, proposed by the authors [16], to anticipate/compare the risk of plastic shrinkage cracking in different concrete mixtures. The new model is distinct from the other available methods by relating the tensile stress-strength ratio of cementitious materials to the amount of the evaporated and bleed water, in addition to the initial setting time. ...
... Tensile strength evolution of concretes with 194 kg/m 3 water content (in the legend, the numbers after WC and SL denote the w/c ratio and the intended slump in inches, respectively), from [19]. Accordingly, Eq. (1) is proposed to estimate the plastic shrinkage cracking severity in cementitious materials (For further details regarding the model's theoretical background the reader is referred to [16]). ...
... This comparison shows that while the model can precisely predict the crack reduction trend, the estimated PRCS is larger in contrast to the test outcomes. This difference may be attributed, among others, to the restrain degree of the specimens, since it is not considered in the model, see [16]. ...
Article
Plastic shrinkage cracking in cementitious materials is caused mainly by rapid and excessive moisture loss during mixture’s early ages, before sufficient tensile strength is gained. A novel model has been previously developed by the authors to estimate the severity of plastic shrinkage cracking in concrete. This paper presents findings of a series of full-scale experiments carried out to validate the accuracy of the proposed model. The experiments included investigating the impact of cement type, water-cement ratio (w/c), and admixtures (i.e., accelerator, retarder, and superplasticizer). The tests were performed in three rounds under similar ambient conditions using 3 slabs (3 m × 2 m) and 3 ring test moulds at each round. The results confirm the accuracy of the model in anticipating/comparing the cracking severity of the tested concretes.