Prediction Of Drying Shrinkage Research Articles

Influence of accelerator type on the volume stability of shotcrete and the establishment of shrinkage model

The characteristics of shotcrete can lead to significant shrinkage deformation, presenting potential threats to tunnel structure safety. To research this concern, in this study the effects of three accelerators on the volume stability of cement paste, cement mortar and concrete were investigated. The correlation equations of the shrinkage deformation of cement paste, cement mortar and concrete were established, and the drying shrinkage prediction model of cement mortar with accelerator was constructed by combining the ACI 209 model and the GL2000 model. Findings from this study show that the liquid alkali accelerator AR had the greatest autogenous shrinkage and drying shrinkage, with the highest mass loss under drying conditions. The study demonstrated that there exists a good linear relationship between the shrinkage deformation of cement paste, cement mortar and concrete with accelerator. Finally, the proposed prediction model for drying shrinkage of cement mortar exhibits strong predictive capabilities.

A numerical model for predicting the drying shrinkage behavior of concrete under ultra-low relative humidity

The drying shrinkage caused by rapid water loss will pose a great threat to the safety of concrete structures, especially for those serviced in an extremely dry environment. However, the majority of reported research primarily focuses on drying shrinkage behavior of concrete under relative humidity (RH) ranging from 50% to 100%, and the corresponding drying shrinkage prediction models have poor applicability, leading to an unclear understanding of it under ultra-low RH (RH<40%). In this study, a numerical model, finite element model with cohesive elements, was proposed to better predict the drying shrinkage behavior of concrete, even under the RH of 20%. Initially, geometric models of concrete with varying coarse aggregate size ranges and volume fractions were established. Subsequently, based on the relationship between RH and humidity diffusion coefficient of concrete with different water-cement ratio (w/c), a drying shrinkage model was proposed to examine the corresponding shrinkage strain of concrete even under ultra-low RH conditions, and its validity was verified through comparison with reported experimental research. Utilizing the developed model, the effects of size range and volume fraction of coarse aggregate, and the w/c, on the drying shrinkage of concrete across a wide range of RH levels were systematically investigated. The results indicated that increasing the aggregate size range can only slightly inhibit drying shrinkage, while there is a marked inhibition effect on it (decrease by about 45% at most) for increasing the aggregate vol% or reducing w/c, even under ultra-low RH of 20%. Finally, grey relation analysis was employed to assess the inhibition weight of each parameter on the drying shrinkage, following this sequence in order: RH > w/c > coarse aggregate vol% > coarse aggregate range size. We also envision that the proposed model could provide feasible guidelines for the inhibition of concrete in ultra-dry regions.

Effects and mechanisms of component ratio and cross-scale fibers on drying shrinkage of geopolymer mortar

This study initially examined the impact of varying component ratios on the drying shrinkage of geopolymer mortars. It further explored the drying shrinkage inhibition of cross-scale hybrid fibers, specifically carbon nanotubes (CNTs) and hooked steel fibers (HSFs). The findings indicate that increasing the content of granulated blast furnace slag (GBFS) or reducing the water-binder ratio and binder-sand ratio could effectively minimize the shrinkage of geopolymer mortar. The addition of fibers also had an inhibitory effect on shrinkage. Hybrid fibers exhibited better performance compared to steel fibers, and steel fibers performed better than CNTs. Finally, the mechanical mechanisms of fibers and aggregates on the shrinkage inhibition of geopolymer mortars was revealed and the drying shrinkage prediction models that suitable for fiber reinforced geopolymer mortars was proposed.

A Simplified Mesoscale Approach for the Prediction of Drying Shrinkage of Concrete

A Simplified Mesoscale Approach for the Prediction of Drying Shrinkage of Concrete

Development of drying shrinkage model for alkali-activated slag concrete

The current study aims to develop a drying shrinkage model for alkali-activated slag concrete (AASC). Three water-to-binder (W/B) ratios (0.44, 0.47 and 0.50), two fly ash contents (0 and 25%) and three silica fume contents (0, 5% and 15%) were studied. Slump, compressive strength and the drying shrinkage test lasting for over 300 d were performed. The results showed that: (1) Increasing both the W/B ratio and fly ash content increased the slump of the concrete, while a 5%-10% silica fume had little effect; (2) The compressive strength of the concrete was decreased with increasing both the W/B ratio and fly ash content, while it was improved with the addition of 5% silica fume; (3) Inclusions of fly ash and silica fume contributed to the reduction of the final drying shrinkage; (4) The current prediction models for drying shrinkage behavior of Portland cement-based concrete was not suitable for AASCs. Based on the results, a novel drying shrinkage prediction model with higher reliability for sodium silicate-activated slag-based concrete cured at the standard environment (20 ± 2 °C and RH of 60 ± 5 %) was developed, which is mainly derived from the model of ACI 209. The well-fitted results of this developed model fully indicated the relatively wide applicability of this model. However, given the complexity of the binder composition of AASC, this model still needs to be further upgraded in future.

Theoretical Prediction of Drying Shrinkage of Concretes Containing Fine Recycled Aggregate

Theoretical Prediction of Drying Shrinkage of Concretes Containing Fine Recycled Aggregate

Experimental studies and drying shrinkage prediction model for concrete containing waste foundry sand

Concrete being most extensively used construction material all over the globe has resulted in the over-exploitation of natural resources such as river-sand and gravels. Meanwhile, advancing industries and increasing population have also lead to an increased generation of waste materials. Many of these waste materials have the potential to be used in concrete. This study has investigated the effect of one such waste material referred to as Waste Foundry Sand (WFS) on the properties of concrete. Many researchers have studied the effect of WFS on the mechanical properties of concrete. However, no consensus has been reached yet and very contradictory results have been reported. Moreover, shrinkage of concrete containing WFS has not received much of the researchers’ attention and very limited literature is available related to this property. This study explores the workability, compressive strength, split tensile strength and drying shrinkage of such concretes. WFS was used as partial replacement of fine aggregate and the replacement levels were varied from 0 to 50% in equal increments of 10%. It was observed that the compressive strength and split tensile strength of concrete decreased with the addition of WFS. However, the mix WFS3 (30% WFS) showed the strength very similar to that of control concrete. A significant increase of 16.7%, 23.44%, 29.05%, 36.35% and 45.18% with respect to control concrete at the age of 28 days was observed in the magnitude of drying shrinkage when the amount of WFS in concrete was varied from 10 to 50%. Furthermore, it was seen that the available shrinkage prediction models could not be applied to the concrete containing waste foundry sand. Hence, a multivariable regression model inspired by ACI-209 model was developed for prediction of drying shrinkage in concrete. The proposed model included the parameters related to drying age and percentage of WFS in concrete and gave a high value of the coefficient of regression (R 2 ) indicating the effectiveness of the proposed model. • Incorporation of waste foundry sand (WFS) in concrete reduced the compressive strength and split tensile strength. • Least reduction in strength was observed in the mix containing 30% WFS as a replacement of river sand. • Drying shrinkage of concrete increased when WFS was added. • A multi-regression model with high regression coefficient was developed to predict the shrinkage in concrete containing WFS.

Effects of hybrid fibers on workability, mechanical, and time-dependent properties of high strength fiber-reinforced self-consolidating concrete

This paper aims to systematically investigate the impacts of hybrid fibers on properties of high strength fiber-reinforced self-consolidating concrete (FRSCC). In total, nine mixtures with different fiber types (Polyvinyl Alcohol/PVA, and hybrid fibers) and fiber factors (λ = 0 ~ 70) were fabricated with same basic mix proportioning. Workability tests include slump flow, T50 time, and J-ring tests were carried out to quantify the effects of fiber factor. The compressive strength, four-point bending tests, drying shrinkage, and compressive creep tests were performed on hardened concrete to reveal the intrinsic effects of single/hybrid fibers. Finally, a hyperbolic drying shrinkage prediction model with fiber factor was proposed. Experiment results indicated that single PVA fibers displayed identical influences on slump flow as steel fiber with similar fiber factor, however, can result in higher viscosity. Meanwhile, PVA fibers reduced the compressive strength and displayed limited restraining effects on the specific creep. However, the positive synergetic effects of hybrid fibers can reverse the reductions in compressive strength caused by the PVA fiber and increase flexural performances with multi-scale bridge effects. Moreover, hybrid fibers are more effective in inhibiting the time-dependent strains of FRSCC, followed by steel fiber and synthetic PVA fiber. The proposed hyperbolic drying shrinkage model is capable of predicting the drying shrinkage of FRSCC with a suitable shrinkage halftime.

Influence of coarse coal gangue aggregates on elastic modulus and drying shrinkage behaviour of concrete

The elastic modulus and drying shrinkage are the fundamental mechanical behaviour of concrete in structural design. To date, no model has been proposed for predicting the mechanical properties of concrete using coal gangue aggregates (CGAs), including rock coal gangue aggregate (RCGA) and spontaneous-combustion coal gangue aggregate (SCGA). The aim of this study is to investigate the influence of CGAs on the mechanical properties of concrete and to theoretically propose elastic modulus and drying shrinkage prediction models for coarse CGA concrete based on composite models. For this purpose, four groups of replacement ratios were selected to prepare concrete with coarse RCGA and coarse SCGA, and their elastic modulus at different curing days and time-dependent drying shrinkages were recorded. The secant modulus of the bulk aggregates was proposed and evaluated to estimate the corresponding elastic modulus. Elastic modulus and drying shrinkage models were theoretically derived based on two-phase composite models, accounting for the elastic modulus difference between the coarse CGAs (RCGA and SCGA) and coarse natural aggregate (NA) via the tested secant modulus difference. The results show that compared to the reference NA concrete, the coarse CGA concrete exhibited decreases of up to 23% and 32% in the 28-day elastic modulus and increases of 62%–92% in the 360-day drying shrinkage due to the lower modulus of the selected CGAs; additionally, the RCGA concrete exhibited a more favourable mechanical behaviour than that of the SCGA concrete. The models proposed in this study could accurately estimate the elastic behaviour of coarse CGA concrete, but further validation work could still be conducted.

Appropriate drying shrinkage prediction models for lightweight concrete containing coarse agro-waste aggregate

Oil palm shell (OPS) agro-waste aggregate was successfully employed to produce lightweight aggregate concretes. However, the high rate of drying shrinkage for this type of concrete can impair the intended functionality of the structures or reduce service life. In this study, drying shrinkage strain behaviour of normal-weight and lightweight aggregate concretes was compared with prediction models. Twelve different mix proportions were designed by using of crushed granite (NWA) and OPS aggregates as replacement of the NWA at increasing intervals of 20%. Actual drying shrinkage at early and long-term ages (275 days) was compared against theoretical results from drying shrinkage prediction models such as ACI209R, EN1992, GL2000, B3 and SAK. Comparison between the test results and predicted results indicated that the EN1992 was the most precise model at early-ages as well as GL2000 at long-term ages. In contrast, B3 was found the least precise model at both early and long-term ages.

Calculation of shrinkage stress in concrete structures with impact of internal curing

This paper presents recent advances in the calculation of shrinkage stress in concrete structures, especially focus on the effect of internal curing. In the modeling, an integrative model for autogenous and drying shrinkage predictions of concrete under drying environments is introduced first. Second, a model taking both cement hydration and moisture diffusion into account synchronously is used to calculate the distribution of internal relative humidity in concrete. Using the above two models, along with the shrinkage stress model for concrete pavement under nonlinear strain along the slab thickness, the development of shrinkage stress in concrete pavements since casting made by low, middle and high strength concrete respectively is calculated. In particular, the effects of internal curing with pre-wetted lightweight aggregates on the progress of shrinkage stress are investigated and discussed. Based on the present study, the following conclusions can be drawn: (1) the progress of shrinkage stress in concrete pavements obeys two-stage mode since concrete casting, a small stress stage (close to zero) in the moisture saturated period and a gradual increasing stage with the relative humidity gradually decreasing in the concrete; (2) the closer to the drying face, the higher the shrinkage stresses; (3) the shrinkage stress is greater in high strength slab than that in low or middle strength slab; (4) internal curing with pre-wetted lightweight aggregate can greatly reduce shrinkage stress in concrete pavement, either in low strength slab or high strength slab.

수축저감제를 사용한 콘크리트의 건조수축 예측에 관한 연구

수축저감제를 사용한 콘크리트의 건조수축 예측에 관한 연구

Drying shrinkage prediction of paste containing meta-kaolin and ultrafine fly ash for developing ultra-high performance concrete

The drying shrinkage development of the paste fraction of ultra-high performance concrete containing binary and ternary blends of meta-kaolin, fly ash and cement were investigated and predicted. The test results showed that, compared with the use of pure cement, the binary use of silica fume and cement or the binary use of fly ash and cement resulted in an increase in the drying shrinkage of paste, and the binary use of meta-kaolin and cement resulted in a decrease in the drying shrinkage of paste. The ternary use of meta-kaolin, fly ash and cement could produce paste with lower drying shrinkage than the binary use of silica fume and cement at the same supplementary cementitious materials content. Modified Gardner model and modified Bazant–Baweja B3 model were developed to predict the drying shrinkage development of the paste fraction of ultra-high performance concrete.

Evaluation of shrinkage induced cracking in early age concrete: From ring test to circular column

This article focuses on the modeling of shrinkage stress and evaluation of shrinkage induced cracking in early-age concrete. In the modeling, an integrative model for autogenous and drying shrinkage predictions of concrete at early-age is introduced first. Second, a model taking both cement hydration and moisture diffusion into account is used to calculate the distribution of internal humidity in concrete. Using above two models, the distribution of shrinkage stress in concrete ring and column at early-age from concrete cast are calculated. Meanwhile, the ring test is utilized to identify the time of shrinkage cracking of three kinds of concretes with compressive strength at 28 days around 30, 50, and 80 MPa. Based on model and ring test results, the shrinkage induced cracking tendency of concrete columns made of the three kinds of concretes is evaluated individually. The model results show that before drying, a uniform shrinkage strain along radial direction of a concrete column or ring is expected. After surface drying, shrinkage gradient along the radial direction is significant and the maximum and minimum shrinkage occur at the outer surface and the center of column or interior surface of the ring, respectively. The distribution of shrinkage stress along the radial direction of the ring or column is nonlinear and the nonlinearity is strong close to the drying surface. Due to the difference on restraint condition, lower shrinkage induced cracking tendency is expected in concrete column than that of steel restraint concrete ring, even both of them having the exact same outer diameter.

Shrinkage stress in concrete under dry–wet cycles: an example with concrete column

This paper focuses on the simulation of shrinkage stress in concrete structures under dry–wet environments. In the modeling, an integrative model for autogenous and drying shrinkage predictions of concrete under dry–wet cycles is introduced first. Second, a model taking both cement hydration and moisture diffusion into account synchronously is used to calculate the distribution of interior humidity in concrete. Using the above two models, the distributions of shrinkage strain and stress in concrete columns made by normal and high strength concrete respectively under dry–wet cycles are calculated. The model results show that shrinkage gradient along the radial direction of the column from the center to outer surface increases with age as the outer circumference suffers to dry. The maximum and minimum shrinkage occur at the outer surface and the center of the column, respectively, under drying condition. As wetting starts, the shrinkage strain decreases with increase of interior humidity. The closer to the wetting face, the higher the humidity and the lower the shrinkage strain, as well as the lower the shrinkage stress. As results of the dry–wet cycles acting on the outer circumference of the column, cyclic stress status is developed within the area close to the outer surface of the column. The depth of the influencing zone of dry–wet cyclic action is influenced by concrete strength and dry–wet regime. For low strength concrete, relatively deeper influencing zone is expected compared with that of high strength concrete. The models are verified by concrete-steel composite ring tests and a good agreement between model and test results is found.

Modeling on Shrinkage Stress in Early-Age Concrete Pavements

In this paper, an integrative model for autogenous and drying shrinkage predictions of concrete at early-age is introduced first. Second, a model taking both cement hydration and moisture diffusion into account synchronously is used to calculate the distribution of interior humidity in concrete. Using the two models, the distribution of shrinkage strain in early-age concrete pavements under the condition that the pavement surface suffers to dry is calculated. Afterwards, the shrinkage stress resulted from the nonlinear shrinkage strain is calculated by dividing the shrinkage strain into uniform strain, linear strain and nonlinear strain. The model results show that the gradient of shrinkage strain and stress along the slab depth is obvious under the condition that the slab top suffers to dry. The maximum and minimum shrinkage strain and stress occurs at slab top and bottom respectively. The distribution of shrinkage strain and stress along the pavement depth are nonlinear and the nonlinearity is strong close to the drying face and the rest is weak.

Calculation of Shrinkage Stress in Early-Age Concrete Pavements. I: Calculation of Shrinkage Strain

AbstractThis paper focuses on modeling of the distribution of shrinkage strain in early-age concrete pavements. In the modeling, an integrative model for autogenous and drying shrinkage predictions of concrete at an early age is introduced first. Second, a model taking both cement hydration and moisture diffusion into account synchronously is used to calculate the distribution of the interior humidity in concrete. The previous two models are experimentally verified independently by a series of shrinkage and interior humidity tests on three types of concretes with different compressive strengths. Using the models, the distribution of shrinkage strain in early-age concrete pavement (with respect to drying of the pavement surface) is calculated. The model results show the development of interior humidity inside of the pavement because the concrete cast obeys a two-stage mode, i.e., a vapor-saturated stage with 100% relative humidity (Stage 1) and a stage with the relative humidity gradually decreasing (Stage...

Recycled Aggregate Concretes for Structural Applications: From Investigation to Design

In this paper an investigation of mechanical behaviour and, in particular, elastic properties of recycled aggregate concrete (RAC) is presented. RACs were prepared by using a coarse aggregate made of old concrete particles coming from a recycling plant in which rubble from demolition of reinforced concrete structures is collected and suitably treated. Several concrete mixtures were prepared by using either the only virgin aggregates (as reference) or 30% recycled concrete aggregates replacing gravel, and by using two different kinds of cement. Different water to cement ratios were adopted ranging from 0.40 to 0.60, while concrete workability was always maintained at the same rate by adding different amounts of water-reducing admixture. Concrete compressive strength, elastic modulus and drying shrinkage were evaluated. Results obtained showed that structural concrete up to C32/40 strength class can be manufactured with RAC. Moreover, results obtained were discussed in order to obtain useful information for RAC structure design, particularly in terms of elastic modulus and drying shrinkage prediction.

Micromechanical modeling on autogenous and drying shrinkages of concrete

A micromechanical model for autogenous and drying shrinkage predictions of concrete at early-age is developed. The model is based on the capillary tension created in capillary pores in concrete and uses the interior humidity (RH) that can relate to the moisture loss in concrete directly as driving parameter for shrinkage predictions. The developed model can be used for shrinkage prediction of concrete, whatever the shrinkage is caused by self-desiccation or by dying. In addition, because the model can reflect the effect on moisture loss of age and position from one parameter, RH, the model can predict shrinkage strain in concrete structures not only for different time but also for different positions. To verify the model, a series shrinkage tests on three types of concrete with compressive strength around 30MPa, 50MPa and 80MPa respectively at 28days of moisture curing were carried out. The model predictions on the development of shrinkage strain are compared with experimental results and a good agreement between them is found.

Structural Concrete Prepared with Coarse Recycled Concrete Aggregate: From Investigation to Design

An investigation of mechanical behaviour and elastic properties of recycled aggregate concrete (RAC) is presented. RACs were prepared by using a coarse aggregate fraction made of recycled concrete coming from a recycling plant in which rubble from concrete structure demolition is collected and suitably treated. Several concrete mixtures were prepared by using either the only virgin aggregates (as reference) or 30% coarse recycled aggregate replacing gravel and by using two different kinds of cement. Different water-to-cement ratios were adopted ranging from 0.40 to 0.60. Concrete workability was always in the range 190–200 mm. Concrete compressive strength, elastic modulus, and drying shrinkage were evaluated. Results obtained showed that structural concrete up to C32/40 strength class can be manufactured with RAC. Moreover, results obtained from experimentation were discussed in order to obtain useful information for RAC structure design, particularly in terms of elastic modulus and drying shrinkage prediction.