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Pietro Lura - One of the best experts on this subject based on the ideXlab platform.
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On the mechanism of Plastic Shrinkage cracking in fresh cementitious materials
Cement and Concrete Research, 2018Co-Authors: Sadegh Ghourchian, Mateusz Wyrzykowski, Mathieu Plamondon, Pietro LuraAbstract:Abstract In this study, a continuum poromechanics approach is presented to model the Plastic Shrinkage cracking of fresh cementitious materials. The boundary conditions are according to the modified ASTM C1579–13 standard for mortars. The restrained deformations are linked to the restraint stresses according to the Cauchy-Navier equations of elasticity, assuming an incremental stress-strain relationship. The Bresler-Pister and Rankine failure criteria are utilized to model failure. The material parameters are adapted according to the Drucker-Prager and Griffith criteria. The crack initiation and propagation is verified experimentally by X-ray radiography. Eventually, the cracking mechanism is discussed and a safe capillary pressure limit is proposed. It is found that capillary pressure stiffening occurring before air entry, when deformations take place in the saturated state, is the predominant cause of Plastic Shrinkage cracking in the drying state.
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Performance of passive methods in Plastic Shrinkage cracking mitigation
Cement & Concrete Composites, 2018Co-Authors: Sadegh Ghourchian, Mateusz Wyrzykowski, Luis Baquerizo, Pietro LuraAbstract:Abstract The occurrence of Plastic Shrinkage cracking in fresh concrete may significantly compromise its service life. Therefore, it is essential to reduce the crack width with appropriate, efficient and effective methods. This study is dedicated to comparing the ability of passive mitigation methods including: Shrinkage Reducing Admixtures (SRA), accelerators based on Calcium Silicate Hydrate seeding agents and curing compounds, in controlling the Plastic Shrinkage cracking in the drying state. The performance of the different admixtures was evaluated according to the ASTM C1579-13 standard. Furthermore, a series of complementary test methods were utilized to study the mechanism of action of the different admixtures. Among the crack mitigation methods that were studied in this paper, SRA were the most effective.
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A poromechanics model for Plastic Shrinkage of fresh cementitious materials
Cement and Concrete Research, 2018Co-Authors: Sadegh Ghourchian, Mateusz Wyrzykowski, Pietro LuraAbstract:Abstract When fresh cementitious materials are exposed to evaporation, drying of the pore fluid leads to capillary pressure development and Plastic Shrinkage. Plastic Shrinkage occurring after the solid percolation threshold plays an important role in the initiation and propagation of Plastic Shrinkage cracks, which may compromise the durability and decrease the service life of concrete structures. In this study, a poromechanics approach to Plastic Shrinkage is developed. Novel experimental methods are utilized to quantify the material properties used as model input. An independent set of measurements is further used to validate the developed model. It is shown that the bulk modulus evolution plays a prominent role in controlling the Plastic Shrinkage of cementitious materials.
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Susceptibility of Portland cement and blended cement concretes to Plastic Shrinkage cracking
Cement & Concrete Composites, 2017Co-Authors: Sadegh Ghourchian, Mateusz Wyrzykowski, Luis Baquerizo, Pietro LuraAbstract:Abstract The market share of different types of blended cements is increasing year by year. Generally, blended cements are ground to higher fineness and exhibit a slower development of mechanical properties compared to Ordinary Portland Cement (OPC), which might affect the concrete performance in terms of Shrinkage cracking at early ages. In this paper, the performance of concretes made with different cement types is compared according to the ASTM C1579-13 standard for Plastic Shrinkage cracking. The cracking behavior was further correlated to the deformations of both unrestrained and restrained specimens measured by a 3D image correlation system. The main factors influencing the cracking behavior were discussed based on poromechanics. It is concluded that the bulk modulus evolution has a dominant effect on controlling the Plastic Shrinkage cracking. Concretes made of more reactive cements, in particular with higher clinker content, are less susceptible to Plastic Shrinkage cracking. For cements with the same clinker content, increasing the cement fineness reduces the risk of Plastic Shrinkage cracking.
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Impact of admixtures on the Plastic Shrinkage cracking of self-compacting concrete
Cement & Concrete Composites, 2014Co-Authors: Andreas Leemann, Peter Nygaard, Pietro LuraAbstract:Abstract Cracks accelerate the ingress of harmful fluids, impairing the durability of reinforced concrete structures. Plastic Shrinkage cracking poses a problem in particular for concrete components such as slabs, in which a high percentage of the surface area is exposed to drying. In this study, the impact of different admixtures on the occurrence and on the extent of Plastic Shrinkage cracking of SCC was investigated. Plastic Shrinkage cracking was measured according to ASTM C1579-06 in a climate chamber at a temperature of 30 °C and relative humidity of 60%. Starting directly after casting, the settlement, the capillary pressure and the mass loss were recorded. At the end of the test, the crack-width distribution was analyzed. A Shrinkage reducing admixture and a paraffin-based curing compound were effective in preventing cracking. Based on the observed evaporation, settlement, capillary pressure and cracking behavior, the mechanisms for crack prevention were identified.
Mohammed Maslehuddin - One of the best experts on this subject based on the ideXlab platform.
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effect of superPlasticizer on Plastic Shrinkage of plain and silica fume cement concretes
Construction and Building Materials, 2006Co-Authors: O S B Alamoudi, Taofiq O Abiola, Mohammed MaslehuddinAbstract:Abstract Four types of superPlasticizers were used in conjunction with three types of silica fume to prepare cement concrete slab specimens that were utilized to measure Plastic Shrinkage strain and time to attain maximum strain. The concrete slab specimens were cast and placed in an exposure chamber in which the relative humidity, temperature, and wind velocity were kept at 35 ± 5%, 45 ± 2 °C, and 15 ± 2 km/h, respectively. Results of this investigation indicate that the Plastic Shrinkage strain varied with the type of superPlasticizer and the type of silica fume. Maximum Plastic Shrinkage strain was measured in the undensified silica fume cement concrete with all superPlasticizers. Incompatibility was noted between polycarboxylic ether superPlasticizer and plain and two types of silica fume cement concretes.
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Effect of type and dosage of silica fume on Plastic Shrinkage in concrete exposed to hot weather
Construction and Building Materials, 2004Co-Authors: Omar Saeed Baghabra Al-amoudi, Mohammed Maslehuddin, Taofiq O AbiolaAbstract:Abstract The source and dosage of silica fume were varied to investigate their effect on the Plastic Shrinkage of concrete exposed to hot weather conditions. Highest Plastic Shrinkage was noted in the concrete specimens prepared with undensified silica fume. The physical properties of silica fume, such as fineness and bulk density, and microscopic properties, such as average pore radius and the total pore volume, were correlated with Plastic Shrinkage strains. No relationship was noted between the microscopic properties and the maximum Plastic Shrinkage strains. However, a good correlation was noted between the Plastic Shrinkage strain and the fineness and bulk density of the silica fume.
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Plastic Shrinkage cracking of blended cement concretes in hot environments
Magazine of Concrete Research, 1999Co-Authors: A. A. Almussalam, M. Abdul-waris, F. H. Dakhil, Mohammed Maslehuddin, Omar Saeed Baghabra Al-amoudiAbstract:This paper reports results of a study conducted to evaluate Plastic Shrinkage cracking of concrete made with varying dosages of several pozzolanic materials, such as fly ash (20, 30 and 40%), silica fume (5, 10 and 15%) and blastfurnace slag (50, 60 and 70%). These concrete specimens were exposed to hot—humid and hot—dry environments. The effect of these environmental conditions on Plastic Shrinkage cracking was evaluated. The rate of water evaporation in the blended cement concrete specimens was noted to be more than that in the plain cement concrete specimens. Further, bleeding in the blended cement concrete specimens was less than that in plain cement concrete specimens. The cumulative effect of these two parameters resulted in increased Plastic Shrinkage cracking of the blended cement concretes. Although cracks were observed earlier in the plain cement concrete specimens than in the blended cement concrete specimens, the total area of cracks in the latter cements was more than that in the former cemen...
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Effect of mix proportions on Plastic Shrinkage cracking of concrete in hot environments
Construction and Building Materials, 1998Co-Authors: A.a. Almusallam, M. Abdul-waris, Mohammed Maslehuddin, M M KhanAbstract:Abstract The effect of mix proportions, i.e. cement content and water–cement ratio, on Plastic Shrinkage cracking of concrete in hot and arid environments was investigated. The cumulative effect of these parameters on Plastic Shrinkage of concrete was assessed by measuring the rate of bleeding, water evaporation, and time and intensity of cracks. The results indicated that cement content and water–cement ratio significantly affect the parameters controlling Plastic Shrinkage of concrete. Lean-stiff concrete mixes cracked earlier than the rich-Plastic concrete mixes. The intensity of cracks in the former was, however, less than that in the latter. Plastic Shrinkage cracking occurred when the rate of evaporation was in the range of 0.2–0.7 kg m−2 h−1, as against a value of 1 kg m−2 h−1 suggested by ACI 305. The rate of evaporation and bleeding was the least in a lean-stiff concrete mix made with a cement content of 300 kg m−3 and a water–cement ratio of 0.40, indicating that this mix composition can be beneficially utilized in hot environments to minimize Plastic Shrinkage cracking.
Gregor Fischer - One of the best experts on this subject based on the ideXlab platform.
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influence of fibre characteristics on Plastic Shrinkage cracking in cement based materials a review
Construction and Building Materials, 2020Co-Authors: Ida Maria Gieysztor Bertelsen, Lisbeth M Ottosen, Gregor FischerAbstract:Abstract Plastic Shrinkage cracking in cement-based materials may occur at early age and the formation can negatively impact the long-term durability. A detailed review on existing research related to Plastic Shrinkage cracking is hereby presented including comparisons of laboratory-scale evaluation methods, crack measuring techniques and the influence of various types of fibres. The use of randomly distributed fibres for controlling Plastic Shrinkage cracking has shown good results and several fibres of different materials, mechanical properties, geometries, shapes, and volume fractions have been presented in the literature. These fibre characteristics were analysed on data from previous studies by descriptive statistics. From this analysis, many relevant fibre characteristics were discovered to have a positive influence on controlling crack formation. These positive effects were found for fibres with a finer fibre diameter, a higher aspect ratio, an increase in number of fibres per volume unit and specific fibre surface as well as the influence of chemical and mechanical interfacial fibre-to-matrix bonds. Also the increase in fibre volume fraction was found to have a positive effect when added to the mixture at an upper limit. No clear correlation was found between the fibre influence on the degree of surface cracking and the fibre length or the fibre modulus.
Ahmed Loukili - One of the best experts on this subject based on the ideXlab platform.
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Plastic Shrinkage and cracking risk of recycled aggregates concrete
Construction and Building Materials, 2016Co-Authors: Ahmed Z. Bendimerad, Emmanuel Roziere, Ahmed LoukiliAbstract:Abstract This paper presents the results of experimental research on recycled concrete at early age. The influence of recycled gravel and sand (RG and RS) and initial water saturation of RG on Plastic Shrinkage and cracking sensitivity was investigated. Four initial water saturations were studied: 30%, 70%, 100% and 120% of saturated surface dried (SSD). The total water was kept constant for all the mixtures, so the added water was adjusted to take into account the absorption of the aggregates during the mixing process. Other concrete mixtures were designed using 30% and 100% of recycled gravel, and 30% of recycled sand. The gravel/sand ratios were adjusted to keep the maximum paste thickness (MPT) constant. To understand the evolution of early age parameters, a timeline was established and the analyses showed correlations between the evolution of Plastic Shrinkage and other properties at early age. The initial water saturation did not significantly affect the evolution of Plastic Shrinkage. Recycled aggregates actually show a relatively high rate of absorption during the first hour after mixing, i.e. before the development of Plastic Shrinkage. A stress/strength approach based on experimentally assessed parameters was used to compare the cracking sensitivity of different concretes with recycled aggregates. A high rate of substitution of recycled gravel or sand affected the early age properties of the recycled concrete and the cracking sensitivity especially when natural sand was replaced by recycled concrete sand.
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Evaluation of Plastic Shrinkage Cracking of Self-Consolidating Concrete
Aci Materials Journal, 2006Co-Authors: Ph Turcry, Ahmed LoukiliAbstract:Self-consolidating concrete (SCC) is a fluid concrete, cast without vibration, that has a self-leveling ability that makes it appropriate for flat structures such as slabs or industrial floors. This article reports on a study that evaluated Plastic Shrinkage cracking of SCC. The authors compared five SCC mixtures with compressive strengths ranging from 30 to 50 MPa to five ordinary concrete (OC) mixtures. Free and restrained Plastic Shrinkage tests were performed in different drying conditions. When the evaporation rate is moderate (drying at 20 deg C and a relative humidity of 50%), Plastic Shrinkage occurs before and during setting. When the evaporation rate is high (windy condition), Plastic Shrinkage occurs only in the Plastic state, that is, before setting. In the presence of wind, SCC and OC mixtures have almost the same Plastic Shrinkage and restrained Shrinkage tests reveal that cracks of SCC tend to be less wide than cracks of OC. However, when the evaporation rate is low, SCC mixtures exhibit a higher Plastic Shrinkage than OC mixtures, due to their lack of bleeding. The authors conclude by recommending curing in order to protect SCC against evaporation at the fresh state.
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Evaluation of Plastic Shrinkage Cracking of self compacting concrete
Materials Journal, 2006Co-Authors: Ph Turcry, Ahmed LoukiliAbstract:This paper describes an experimental investigation of Plastic Shrinkage cracking of self-consolidating concrete (SCC). Five SCC mixtures with compressive strengths ranging from 30 to 50 MPa were compared to five ordinary concrete (OC) mixtures. Free and restrained Plastic Shrinkage tests were performed in drying conditions. Depending on evaporation rate, Plastic Shrinkage occurs before setting (wind), or before and during setting (no-wind). In the presence of wind, SCC and OC mixtures have almost the same Plastic Shrinkage. Moreover, restrained Shrinkage tests reveal that cracks of SCC tend to be less wide than cracks of OC. Nevertheless, when evaporation rate is low, SCC mixtures exhibit a higher Plastic Shrinkage than OC mixtures, due to their lack of bleeding. Consequently, SCC could be more vulnerable to Shrinkage cracking, especially during setting. Thus, curing is recommended to protect SCC against evaporation at the fresh state.
Ahmed Z. Bendimerad - One of the best experts on this subject based on the ideXlab platform.
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Plastic Shrinkage and cracking risk of recycled aggregates concrete
Construction and Building Materials, 2016Co-Authors: Ahmed Z. Bendimerad, Emmanuel Roziere, Ahmed LoukiliAbstract:Abstract This paper presents the results of experimental research on recycled concrete at early age. The influence of recycled gravel and sand (RG and RS) and initial water saturation of RG on Plastic Shrinkage and cracking sensitivity was investigated. Four initial water saturations were studied: 30%, 70%, 100% and 120% of saturated surface dried (SSD). The total water was kept constant for all the mixtures, so the added water was adjusted to take into account the absorption of the aggregates during the mixing process. Other concrete mixtures were designed using 30% and 100% of recycled gravel, and 30% of recycled sand. The gravel/sand ratios were adjusted to keep the maximum paste thickness (MPT) constant. To understand the evolution of early age parameters, a timeline was established and the analyses showed correlations between the evolution of Plastic Shrinkage and other properties at early age. The initial water saturation did not significantly affect the evolution of Plastic Shrinkage. Recycled aggregates actually show a relatively high rate of absorption during the first hour after mixing, i.e. before the development of Plastic Shrinkage. A stress/strength approach based on experimentally assessed parameters was used to compare the cracking sensitivity of different concretes with recycled aggregates. A high rate of substitution of recycled gravel or sand affected the early age properties of the recycled concrete and the cracking sensitivity especially when natural sand was replaced by recycled concrete sand.
