Table 3 - uploaded by Xavier Brunetaud
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Many studies have shown the effect of different parameters on the expansion induced by delayed ettringite formation (DEF),
but there is not yet a general agreement on their relative effects due to discrepancies on experimental results generally
attributed to different experimental conditions. The aim of this study is to assess the coupling effects...
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Citations
... The degree of DEF depends on various parameters, such as the chemical composition of cement, pore structure, and environmental conditions [14][15][16][17]. Early age temperature, whether during cement hydration in mass concrete as a result of cement-waste interaction or during thermal treatment conditions at elevated temperatures, is an important parameter that can promote DEF. ...
... ( and ) represents the alkali effect at high temperature during dissolution and hydrogarnet precipitation, respectively. These effects were empirically formulated from the results of [14,15,36]. Moreover, during storage, the alkali effect on the delayed ettringite precipitation rate ( ) was considered in the model as well, based on the experimental results of [16]. ...
... Finally, all blended samples used in this study are assumed to be fully saturated. (1) : [36] (2) : [14] (3) : [15]. Figure 4a presents the temperature evolution of OPC samples with different cement weights per cubic meter in concrete mix compositions. ...
This paper presents a numerical study to investigate delayed ettringite formation (DEF) that may pose a long-term durability risk by altering the microstructure with consequent swelling leading to cracking. A chemo–thermal model is used to predict the evolution and distribution of temperature and hydration phases in a wide range of blended cements. In particular, the influence of nuclear waste loading, waste package size, and the addition of supplementary cementitious materials (SCMs) on DEF is systematically and numerically investigated. The analyses show that higher amounts of ordinary Portland cement (OPC) and waste loadings result in higher hydration temperatures and consequently increased DEF potential by enhancing sulfoaluminate dissolution and hydrogarnet precipitation. Partial replacement of OPC with SCMs reduced hydration heat and mitigated DEF risks. The analysis indicated that the DEF evolution may be different for waste packages of different sizes due to a shift from sulfate-controlling to aluminate-controlling reactions at high temperatures. Interestingly, higher temperatures did not necessarily induce higher DEF potential due to the excessive precipitation of aluminates in the form of hydrogarnet. This research enriches our understanding of DEF’s complex behavior, providing valuable insights for engineering applications beyond civil engineering, such as nuclear waste conditioning.
... forced Concrete (UHPFRC). Several causes can be highlighted, including early-age or long-term shrinkage [1][2][3], chemical degradations [4,5] and the creep mechanism [6,7]. Since cracks in structures can be dangerous and considerably decrease their durability, developing techniques for crack detection and localization in concrete proves to be very important. ...
Crack imaging in highly heterogeneous materials, such as concrete, plays a great role in structural health monitoring and non-destructive evaluation and testing. Numerous works have shown that Nonlinear Coda Wave Interferometry is a robust tool to assess the overall level of nonlinearity caused by micro or macrocracks in heterogeneous media. This work presents a novel qualitative method for Imaging using NCWI (INCWI) based on the combination of Nonlinear Coda Wave Interferometry (NCWI) and a spatial averaging method. INCWI is used herein to locate cracks generated in a concrete beam subject to three-point bending. Measurements are performed after each loading level, in both pre-peak and post-peak phases, once the beam has been unloaded. The imaging algorithm is described and applied to each stage of beam damage. In the post-peak phase, crack size varies from 10 cm to 15 cm in length and from 25 μm to 200 μm in width. Also, the INCWI results are compared with acoustic emission measurements and microscopic observations.
... Cracks can be caused by various sources, e.g. fatigue loadings [1], chemical attacks [2,3] or shrinkage [4][5][6]. Therefore, it is important to know the characteristics of cracks in order to detect them either qualitatively or quantitatively and monitor their behaviours over time. ...
In civil engineering, an emerging ultrasonic approach based on Code Wave Interferometry (CWI), called Nonlinear Coda Wave Interferometry (NCWI) has been developed to detect microcracks in cementitious materials that cannot be detectedby conventional ultrasonic methods. NCWI uses a high amplitude low frequency (LF) nonlinear pump wave to generate a nonlinear clapping effect at microcracks that can be detected by a high frequency (HF) probe wave. The imaging of cracks inside heterougeneous materials using NCWI requires the inversion technique, which is constitued by model space and data space, in which conatains model parameters and data parameters respectively. In the frame of inversion with NCWI, the model parameter used is the scatetring cross section of a crack sigmaD, and the experimental parameter is the decorrelation coefficient Kd. Knowing that sigmaD depends on the pump wave amplitude. Therefore, in order to introduce NCWI in inversion, the relationship between the pump wave and sigmaD is needed, which is the goal of this study. The dynamic pump wave generates clapping effect at crack tips, the probe wave frequencies are higher than the pump waves’ by an order of magnitude, hence the effect of pump wave on the coda wave is rather averaged. Previous study showed that this clapping effect is equivalent to a single crack length change dL, dL can be related to an equivalent static stress sigma0 which produces the same dL in quasi-static regime, which is equivalent to the dynamic pump wave. Therefore, a relation can be established between sigma0 and sigmaD. This introduces NCWI into the inverison. Then, the theoretical estimation of Kd can be achieved by the simulation of NCWI using 2D Spectral Element Method (SEM2D), combining with the relationship between sigma0 and sigmaD, which can be used later on in the inversion for the crack imaging.
... The DEF chemical model was fitted using several experimental results. Fig. 13 shows the studies [58,59,60,61] that have been used by Sellier & Multon [18] to fit and validate the model assuming eq. (18). ...
This study investigates the development of delayed ettringite formation in concrete made of recycled concrete aggregates (RCA) and in mortars with a recycled concrete filler. Experimental results are compared to a chemical model of delayed ettringite formation by Sellier & Multon (2018). Three concretes were formulated, one with natural siliceous aggregates and two others with two different RCA. Concrete and mortar samples were screened for one year for DEF damage. Results show that RCA based concrete did not develop DEF damage, but concrete made of siliceous aggregate did. Recycled filler had a small negative effect on DEF but not as much as limestone filler. Comparison to chemical modelling, including six additional mortars from Yammine (2020), shows that the produced expansive volume cannot be directly linked to the measured expansion. The porosity of mortars and concrete plays an important role in controlling the expansion. All formulations that did exhibit large expansions had developed a maximum volume of expansive products higher than 30% of their porous volume. These results suggest a simple method to predict DEF related expansion in concrete with or without recycled concrete products.
... There have been numerous reports of structural damage due to DEF [1][2][3][4][5][6][7].To propose countermeasures for such problems, it is essential to understand and analyze the structures affected by durability issues like DEF. Although researchers have conducted experiments on DEF [8][9][10][11], very few studies have been able to describe the comprehensive understanding of DEF expansion. DEF depends on numerous parameters like chemical composition of cement, early age properties of concrete, environmental conditions, and physical conditions. ...
... However, they require rigorous calculations which are not ideal for FEM based analysis tools. Sellier and Multon [20] developed a comprehensive chemo-hygral thermal model for concrete expansion due to DEF based on numerous experimental and analytical studies [8,9,[21][22][23][24][25][26][27]. The model considers the chemical effects and environmental effects on DEF and is simple enough to be incorporated in the finite element simulations. ...
... When the heat treatment is applied, the ettringite and monosulfate start to dissolve into sulfates and aluminates if the temperature of the specimen (T) is greater than the threshold temperature of dissolution (T th,d ). Kchakech [29] proposed the value of threshold dissolution temperature (T th,d ) as a function of alkali content (Na) based on Brunetaud's experiments [8]. The threshold dissolution temperature can be defined as follows [8,20]: ...
This study investigates the effect of heat treatment on the kinetics of precipitation of the delayed ettringite in concrete structures and a chemical model for concrete expansion due to delayed ettringite formation (DEF). The expansion of concrete structures due to DEF majorly depends on the amount of sulfate, aluminate, and alkali content present in the cement. Apart from these parameters, environmental conditions like saturation, temperature, and duration of heat treatment also play a major role in the kinetics of the formation of delayed ettringite. The thermal energy, which is a function of concrete’s high temperature and its duration, can change the concrete’s microstructures affecting the kinetics of release of sulfate from the C-S-H gel. Such high temperature curing can also affect the leaching of alkali by modifying the pore structure. A comprehensive chemo-thermo-hygral model for DEF is discussed in this study based on study conducted by previous research. The previous model defines the kinetics of three major phenomenon related to DEF: dissolution of ettringite and monosulfate at high temperature; fixation of aluminate into hydrogarnet during the high-temperature curing; precipitation of delayed ettringite. In the current work, the model is integrated with a multi-component hydration heat model and a new thermal energy factor governing the precipitation kinetics which not only correlates well the final expansion with experimental values, but also closely simulates the kinetics of expansion. A multi-ionic transport model is considered for alkali equilibrium. Finally, the kinetics of DEF along with the chemical expansion is validated with the experimental results from literature.
... However, AFm solubility product solubility increases with increasing steam-curing temperature (Tosun, 2006;Zhuang and Sun, 2020;Katsioti et al., 2011). Brunetaud et al. (Brunetaud et al., 2007;Escadeillas et al., 2007;Escalante-Garcia and Sharp, 2001) reported that the delay of AFm in the re-formation of the AFt early after the completion of the steam treatment leads to the occurrence of delayed ettringite formation. In addition, resistance to AFt formation may occur in the solid paste due to the encapsulation and blocking effects of wetting products. ...
Steam curing at atmospheric pressure is a method used to raise concrete strength at early ages. The steam curing method is based on the application of hot water vapor at a temperature between 40°C and 100°C for a limited period. The highest temperatures and the longest curing period are determined based on the characteristics of the target concrete, the cost, and the production cycle. This study presents the effect of steam curing regime application on concrete properties. Steam curing has a negative effect on the microstructure of concrete, and this effect increases with higher temperatures. The curing period and the precuring period in addition to the cooling period influence the properties and the strength of concrete. This study summarizes the previous literature related to the effect of steam curing regime application on the properties of concrete. Previous studies confirm that concrete exposed to steam curing regime at low temperatures ranging between 45°C and 80°C and a longer period within a 24-hour cycle achieve better concrete properties. In addition, raising the steam curing temperatures above 80°C has a negative effect on concrete microstructure and other concrete properties in general. This study also concludes that adding pozzolanic or complementary cement materials contributes to reducing the damage resulting from the application of steam curing regime on concrete at later ages. Such verification is required to clarify the behavior of concrete under the influence of steam curing systems, understand their effect on the properties of concrete, and look for ways to reduce the damage from degrees of application of steam curing regime.
... -Drying (20 hours) in an oven at 60°. This temperature level was selected to avoid the superposition with the internal Sulfatic attack from the delayed formation of ettringite [35][36][37]. Daily, the mass of each sample is measured after the drying phase. The samples are tested with a compression test after 28 days of normal cure and at 5, 15, 30, and 60 cycles of immersion, to follow the evolution of their mechanical performance. ...
Recently, numerous plant fibers have been investigated as a means to reinforce concrete and replace synthetic fibers, thereby producing more eco-friendly concretes. The primary concern for these studies is the durability of the fibers in the external environment. For this purpose, the current paper presents a comparison study on the physical-mechanical behavior and durability against external sulfatic attack on Alfa and Hemp fiber-reinforced concrete. To assess the effects of sulfatic attack, different types of concrete underwent two aging protocols: 1) a complete immersion in 12.5 % Sodium Sulfate (Na2SO4) solution and, 2) an accelerated aging protocol which consisted of immersion/drying in the same sulfate solution at a temperature of 60°C. The results show that the optimal amount of 2 Sami ZIANE, Mohammed-Rissel KHELIFA, Samy MEZHOUD, Ahmed BEROUAL, Saber MEDAOUD plant fiber is variable, depending on several parameters such as the chemical composition, mechanical characteristics, and morphology of the fiber. In addition, the results show that the use of Alfa and hemp fibers could facilitate the production of green and durable structural concretes.
... -Cement composition: sulfates, aluminates and alkalis proportions and also the cement fineness influences DEF (Pavoine et al., 2012). -Aggregates mineralogical nature: (Monteiro et al., 1986) (Grattan-Bellew et al., 1998 (Brunetaud et al., 2007) (Al Shamaa et al., 2016) demonstrated that sand or aggregates petrographic nature and size can impact the DEF, in terms of kinetics but also amplitude. Here, the study takes an interest in quantifying the effects of aggregates nature. ...
... This fact is consistent with previous researches, which observed that an expansion of 0.1% corresponds to the first appearance of visible cracks in concrete elements affected by DEF. The decrease in the load capacity of the panel observed in a macroscopic level can, in fact, be microscopically explained by the separation between paste and aggregate, as commonly reported by several researchers (Brunetaud et al. 2007(Brunetaud et al. , 2008. Vertical strain (µε) ...
The paper discusses the structural behaviour of concrete struts deteriorated by internal swelling reactions due to delayed ettringite formation (DEF). To assess this behaviour, nonlinear finite elements analyses were performed using concrete damaged plasticity (CDP) model of ABAQUS, which was calibrated and validated. The effects of the internal swelling reactions were simulated numerically using a strategy of decreasing mechanical properties of concrete. MATLAB scripts were developed to automate the process of determining the CDP model parameters, especially those related to the damage in tension and compression with few input data. Decreases in the first crack and failure loads of 78% and 56% were observed which means that DEF expansions are an important issue in the load capacity of concrete structures. Besides, it was also observed a significant increase in cracks openings width, even for low expansion level, with values of 3.65 mm, and for high level of expansion with values of 4.51 mm. This is a relevant aspect for the durability of concrete structures that is severely affected by DEF expansions.
... The late formation of etringate to monosulfoaluminate (AFm) is caused by higher temperatures above 80 • C as the unstable etringate decomposes into AFm, (SO 4 ) 2-, Ca 2+ and Al(OH) 4 -, which are absorbed into the C-S-H gel. After completing a cycle of steam curing, lowering the temperature to the NCR may contribute to delayed ettringite formation phase, which increases the internal stress, resulting in damage to the delicate structures [58][59][60]. 2) Secondly, the addition of gels (C-S-H and C-A-S-H) at the later ages from the interaction of pozzolana with calcium hydroxide. This result is attributed to the relatively high degree of reaction of U-POFA from 28 to 360 days, because the consumption of Ca(OH) 2 in the pozzolanic reaction of U-POFA and the pore-filling by the reaction products, thus improving the microstructures, especially in the interfacial transition zone and micro-pore [61,62]. ...
This paper investigated the influence of steam curing regimes on the properties of high-strength green concrete (HSGC) containing varying quantities of ultra-fine palm oil fuel ash (U-POFA) from 0%, 20%, 40% and 60% from the mass of Portland cement. The HSGC specimens were steam cured at 50°C, 65°C, and 80°C for 16 hours in order to evaluate the effect of curing temperatures. Besides, the HSGC specimens were also cured at 80°C for 6, 11 and 16 hours in order to investigate the effect of curing period. The influence of different temperatures and periods of steam curing on the development of the compressive strength (CS) and microstructure of the HSGC was investigated at 1, 3, 7, 28, 90, 180 and 360 days. The results showed that replacing 20%, 40% and 60% of ordinary Portland cement (OPC) with U-POFA exhibited a decrease in the CS in early ages up to 7 days, whereas the long-term CS at 360 days improved by 5.4%, 10% and 9.2%, respectively in comparison to the control concrete mixture. It was also found that the application of steam curing regime at 80°C for 16 hours contributed towards increasing the strength of concrete by 193% at 1 day for HSGC containing 60% U-POFA when compared to normally cured specimen. The trends in CS development were complimented with microstructural analyses based on TGA, XRD and SEM/EDX. It was observed that steam curing has a significant influence on microstructures of matrix in early ages. However, it can be concluded that the partial replacement of U-POFA has positive impacts on the long-term properties of the HSGC at 360 days.
