Plastic Shrinkage Research Articles

Mitigation of plastic shrinkage cracking with natural fibers - kenaf, abaca, coir, jute and sisal

In this study, a number of different fibers - namely kenaf, jute, abaca, coir and sisal - were investigated as natural alternatives to polypropylene (PP) fibers for reducing plastic shrinkage cracking. The risk of plastic shrinkage cracking of mortars with water-to-cement ratio 0.5 containing either 0.6 or 0.9 kg/m3 of natural fibers was assessed according to the ASTM C1579-21 standard and compared with plain mortars and mortars with PP fibers. The water absorption of the natural fibers was low enough that (at the employed dosages) the effect on the workability and on other fresh properties was small. The natural fibers also had no measurable influence on cement hydration in the examined mortars, as revealed by isothermal calorimetry.The best performance in reducing the width of plastic shrinkage cracks was shown by kenaf and jute fibers at the dosage of 0.6 kg/m3, which outperformed even a higher dosage of PP fibers (0.9 kg/m3). Kenaf fibers in pellets, which are advantageous for dosing and mixing, performed similarly as loose fibers. The distribution of both loose and pelletized kenaf fibers in the mortars was studied by X-ray tomography, showing no substantial difference between the two ways of delivering the fibers.

A simplified but improved numerical approach to determine moisture balance for plastic shrinkage cracking in concrete

This paper introduces an improved numerical approach for evaluating moisture balance on concrete surface which can initiate plastic shrinkage cracking on the surface of fresh concrete in concrete slab. Because plastic shrinkage cracks occur when the tensile stress induced from the surface drying of concrete exceeds the tensile strength in the freshly placed concrete, moisture balance calculated by the introduced approach can be used as the primary indicator for plastic shrinkage cracking. The numerical approach introduced in this paper therefore emphasized an exact evaluation of bleeding and evaporation on the concrete surface. In determining bleeding, the approach introduced in the previous study was improved through the consideration of additional influencing factors of the accelerator and steel fiber and the supplementation of additional experimental data. For reliable prediction of evaporation, an empirical relation was newly introduced. The reduction of evaporation rate with time was taken into consideration, and the use of the weighed characteristic velocity rather than the direct application of the wind velocity was recommended. Determination of an exact distribution for the weighed characteristic wind velocity on the surface of a concrete slab was based on computational fluid dynamic (CFD) analyses. In particular, the effect of installing a windscreen along the sides of the concrete slab was intensively examined. Upon verification of the introduced numerical approach through correlation studies between experimental data and numerical results, additional parametric studies were also performed to numerically examine the relative contribution of each influencing factor in plastic shrinkage cracking. Moreover, the introduced approach can effectively be used for the on-site prediction of surface drying time of a concrete slab and for the preparation of a proper curing strategy to mitigate plastic shrinkage cracking.

An Experimental Investigation on Durability Properties of Fiber Reinforced Concrete for M25 Grade

In modern years Fibre reinforced concrete is cement based composite material has been developed. It has been successfully used in construction with its outstanding flexural tensile strength, resistance to splitting, impact resistance and outstanding permeability and frost resistance. It is a successful way to raise toughness, shock resistance and resistance to plastic shrinkage cracking of the mortar. Fibre is added as a reinforcing material possessing certain characteristic properties. Concrete is the most extensively used structural material in the world with an yearly production of over seven billion tons. For a multiplicity of reasons, much of this concrete is cracked. The reason for concrete to undergo cracking may be endorsed to structural, ecological or economic factors, but most of the cracks are formed due to the natural weakness of the material to resist tensile forces. Concrete normally shrinks and force crack when it is controlled. It is now well-known that steel fibre reinforcement offers a solution to the problem of cracking by making concrete tougher and more yielding. It has also been proved by wide investigation and field tests carried out over the past three decades. The present investigation focuses on introduction of steel, glass, carbon fibres, Polyvinyalcohol (PVA) fibres, of polypropylene fibres at the time of mixing and production improves a number of properties of concrete, particularly those related to strength, performance and durability. This review paper is an evaluative report of studies established in the recent years. It describes and gives an Experimental basis for the research.

Optimized mix design method of ultra-high performance concrete (UHPC) and effect of high steel fiber content: Mechanical performance and shrinkage properties

In this study, UHPC was successfully prepared based on the Modified Andreason and Andersen (MAA) model (distribution modulus m= 0.23 was confirmed) and Excel solver tool. Subsequently, the effect of steel fiber content (0%–6% by volume) on the mechanical properties and shrinkage properties was investigated. It was found that the compressive and flexural strengths increased significantly with the increase of steel fiber content from 0 % to 5 %, but decreased when it exceeded 5 %. The split tensile strength was always increased. In addition, the plastic shrinkage, autogenous shrinkage, and drying shrinkage of UHPC were reduced by 18.3%–67.4 %. It indicated that incorporating higher content of steel fiber into UHPC could enhance mechanical strength, but the mixing approach should be optimized when content of steel fiber exceeds 5%. In addition, the prevalence of steel fiber agglomeration was shown under X-CT, but the agglomeration of steel fiber still led to an increase in UHPC properties within a certain range. The air content of UHPC with 6 % fiber content is 3.5 %, which shows the reasonableness and good performance of the mix proportion calculated by the Excel solver demonstrated in the article. The article can lay a light on the industrial design and preparation of UHPC.

A Review on the Performance of Fibers on Restrained Plastic Shrinkage Cracks

Multiple studies have investigated the use of steel, synthetic fibers, and natural fibers to reduce plastic shrinkage cracks in concrete, which are mostly caused by water evaporation from the surface of the material. This review used original published research articles from the Web of Science and Scopus database to evaluate the performance and relationship between the fiber volume, aspect ratio, compressive strength, and plastic shrinkage cracking. This review also discussed the most widely used technique for evaluating plastic shrinkage cracking, the ASTM C 1579, with two bottom restraints and a central stress riser to induce cracking, and its modified version with additional reinforcement for further restraining the ASTM C 1579 mold. Longer fibers function better than shorter fibers because of their larger surface area, which allows them to bridge fissures. It was also observed that crack initiation time is delayed when fibers are added to concrete. In addition, as the volume proportion of the fibers increased, the plastic shrinkage cracks decreased, but the compressive strength declined. Furthermore, the volume fraction of the fibers had a greater effect on reducing cracking than the aspect ratio. It was also concluded that a fiber volume inclusion below 1% is best.

Role of self-curing mechanism in lightweight concrete: A state-of-the-art report

AbstractWorldwide, precast and hybrid construction methods are becoming increasingly popular in the construction industry. But many problems occur during the fabrication, such as segregation, bleeding, scaling, plastic shrinkage, dust formation, honeycombing, sintering, high sorptivity, and high permeability and transportation. This problem may be caused by an ineffective curing process that affects the quality of concrete and construction. In addition, it provides inadequate and incomplete cement hydration that has a 20% negative effect on the desired properties of the concrete. Various researchers have demonstrated the components of self-curing lightweight concrete that can enhance strength and physicochemical properties, and address the above-mentioned issues. In this review, the role of the self-curing mechanism in lightweight concrete based on the various self-curing chemical admixtures such as polyethylene glycol (PEG), superabsorbent polymer (SAP), polyvinyl alcohol (PVA), sodium lignosulfonate and calcium lignosulfonate as self-curing agents are discussed in detail. Also, this paper briefly reports on the scope, significance, mechanisms, and tests for self-curing lightweight concrete. Overall, this review analyzes the possibilities of future research perspectives on self-curing lightweight concrete with sustainable materials and fibres with comparative technical information.

Effect of Water to Cement Ratio on Properties of Calcium Sulfoaluminate Cement Mortars

Calcium sulfoaluminate (CSA) cements are a promising alternative to Portland clinker, however, a thorough understanding of their properties is needed for their broader use in the industry. One of the topics that requires a good understanding is the effect of the w/c ratio on the properties of CSA cements. To this end, the aim of this paper was to provide research into the effects of a w/c ratio in the range of 0.45–0.6 on the properties of fresh and hardened CSA pastes and mortars. For fresh mortars, consistency and setting time, as well as plastic shrinkage tests, were conducted, and were complemented by hydration heat tests, carried out on pastes. For hardened mortars, tests of compressive and flexural strength and dry shrinkage, as well as SEM photography, were conducted. It was found that, regardless of a higher hydration rate, the increase in w/c ratio decreased flexural and compressive strength, as well as shrinkage, while increasing consistency, setting time, and hydration heat. Also observed was a significant decrease in strength between 3 and 7 days of curing in mortars with a high w/c ratio. It can be concluded that, regardless of the hydration rate, low w/c ratios in CSA mortars provide better properties than high w/c ratios.

Improving the early-age behavior of concrete containing coarse recycled aggregate with raw-crushed wind-turbine blade

Recycled aggregate used in replacement of coarse natural aggregate can lower the quality of both fresh and hardened concrete properties. There are many methods to reduce the negative effects of recycled aggregate in the literature, although most involve unsustainable solutions that jeopardize any environmental benefits associated with their use. In this study, a novel approach is presented for mitigating the adverse impacts of coarse recycled aggregate used in concrete mixes. Furthermore, it allows solving the current issue of the recycling of wind-turbine blades at the same time. Raw-crushed wind-turbine blade, a waste from the crushing of decommissioned wind-turbine blades with a high proportion of glass fiber-reinforced polymer fibers, was added to concrete mixes containing coarse recycled aggregate. As a main outcome, additions of that waste were found to enhance the early-age properties of concrete containing that kind of aggregate. Plastic shrinkage was reduced, and flexural strength increased by as much as 47 % and 14 %, respectively, while compressive strength remained approximately constant.

Synergistic effects of pozzolan and carbon fibers on the performance of self-consolidating concrete under plastic shrinkage and dynamic loading

Synergistic effects of pozzolan and carbon fibers on the performance of self-consolidating concrete under plastic shrinkage and dynamic loading

Influence of recycled steel fiber on the properties of self-compacting concrete with high fly ash content


 
 
 The recycled steel fibers from waste steel cables have properties suitable for enhancing the load-bearing capacity, impact resistance, and shrinkage reduction of Self-Compacting Concrete (SCC). The use of a high content of fly ash in SCC reduces production costs and is environment friendly by minimizing the amount of cement in the mix. This article presents the experimental research results on the influence of the content of recycled steel fibers on the properties of high-fly-ash SCC. The research utilized recycled steel fibers from elevator steel cables with volume percentages of 0%, 0.5%, 1% and 1.5% respectively in SCC, with a fly ash content in the SCC mix of 50% by volume of powder. The evaluated properties included workability, plastic shrinkage, drying shrinkage compressive strength, and tensile strength. The results indicate that using recycled steel fibers with a maximum content of 1% enables the production of SCC that meets European standards for workability. In addition, when comparing SCC with 0.5% and 1% recycled steel fiber content to control SCC samples (without steel fibers), the compressive strength of SCC increased by 5.04% and 7.56% respectively, the tensile strength increased by 2.99% and 5.97% respectively, plastic shrinkage decreased by 27.34% and 30.47% respectively, and 28-day drying shrinkage decreased by 3.2% and 4.6% respectively. Using recycled steel fibers combined with high-volume fly ash is a reasonable solution to save production costs and be environmentally friendly. Additionally, this solution not only improves the compressive and tensile strength but also limits plastic and drying shrinkage deformations of SCC. As a result, the durability of SCC is enhanced.
 
 

Understanding and modeling the plastic deformation of 3D printed concrete based on viscoelastic creep behavior

3D printing concrete (3DPC) is susceptible to plastic deformation, for example, plastic shrinkage and plastic settlement, due to the absence of formwork. Monitoring and determining plastic deformation of 3DPC in large-scale construction remain challenging. In this study, we developed an analytical modeling method for predicting plastic deformation based on the creep behavior of 3DPC. A new creep model with high fitting accuracy was proposed for capturing creep characteristics over different resting time and applied stress level. Feasible acquisition of model parameters was achieved by correlating creep test results with UUCT (unconfined uniaxial compressive test) results. A multi-parameter modeling procedure based on superposition principle was then developed, and further validated by experimental results. This research may contribute to a better understanding and assessment of the plastic deformation of 3DPC in digital construction.

Evaluation of tensile properties and cracking potential evolution of fly ash-cement mortar at early age based on digital image correlation method

The early-age tensile properties and shrinkage behaviors of mortar are important to investigate its early-age cracking potential. This study employs the digital image correlation method to quantify the tensile properties and shrinkage behaviors of fly ash-cement mortars at early age, aiming to reveal the effect of fly ash on the mortar's cracking potential evolution. Fresh mortars with varying fly ash (FA) contents (0%, 10%, 20%, 30%) undergo comprehensive tests, encompassing tensile strength, ultimate tensile strain, plastic shrinkage, mass loss, and damage assessment within 90–180 mins after casting. The results show that FA could enhance early-age ultimate tensile strain and extend the time for the mortar to maintain plasticity while reducing early-age shrinkage strain and mass loss. The mortar's cracking risk is potentially linked to its setting time. The rheological state of mortar gradually changed from plastic to non-plastic after initial setting, and the ultimate tensile strain stabilized, but the shrinkage strain increased rapidly, which resulted in a greater risk of shrinkage-induced cracking. Furthermore, after 180 mins of curing, the damage index of the fly ash-cement mortar (10% FA) was 1.6 times that of pure Portland cement mortar, whereas the damage indexes of the fly ash-cement mortars with 20% and 30% FA contents are approximately equivalent to 82% of the pure Portland cement mortar's damage index. This indicates that incorporating more than 20% fly ash is beneficial in reducing the risk of plastic shrinkage-induced cracking in mortar.

Guar Gum, Gellan Gum Biopolymer Soil Stabilization

In civil engineering and construction, soil stabilization is an important aspect. There are diverse conventional techniques to improve soilproperties and for soil stabilization. This study explores the viability of twotypes of biopolymers, Guar gum and Gellan gum, as sustainable and ecofriendly additives for clayey soil stabilization. Compaction, unconfined compression test, permeability, consistency limit, consolidation tests were performed in the study. The sample for the test has been prepared that biopolymer has been mixed with soil in different proportions. These biopolymers forms hydrogels when they get activated, and it enhances the bonding between soil particles thereby increasing the strength. Treating soilwith biopolymer increases dry unit weight and decreases optimum moisturecontent (OMC).Addition of gum solution reduces friction between soil particles, leading to marginal increase in dry unit weight. Higher the biopolymer content lower is the OMC content and soil become more stiff. The compressive strength and load bearing capacity isfound increasing soilbiopolymerspecimen upon different days of curing. For every tested percentage of treatment the percentage reduction factor rises withbiopolymer concentration due to drop in void ratio that results in a drop in the soil's permeability. Guar Gum and Gellan Gum are used as stabilizers in soil treatment, increasing liquid and plastic limits, shrinkage limit, and viscosity. They activate hydrogels, strengthen bonding activity, and increaseshrinkage limit. The addition of Guar Gum and Gellan Gum improves soil biopolymer mix viscosity and adhesion. The findings of this study positivelyimply that adding this material to weak soil would improve the soil’s characteristics.

The Application of Neural Networks to Predict the Water Evaporation Percentage and the Plastic Shrinkage Size of Self-Compacting Concrete Structure

This article presents a solution using an artificial neural network and a neuro-fuzzy network to predict the rate of water evaporation and the size of the shrinkage of a self-compacting concrete mixture based on the concrete mixture parameters and the environment parameters. The concrete samples were mixed and measured at four different environmental conditions (i.e., humid, dry, hot with high humidity, and hot with low humidity), and two curing styles for the self-compacting concrete were measured. Data were collected for each sample at the time of mixing and pouring and every 60 minutes for the next ten hours to help create prediction models for the required parameters. A total of 528 samples were collected to create the training and testing data sets. The study proposed to use the classic Multi-Layer Perceptron and the modified Takaga-Sugeno-Kang neuro-fuzzy network to estimate the water evaporation rate and the shrinkage size of the concrete sample when using four inputs: the concrete water-to-binder ratio, environment temperature, relative humidity, and the time after pouring the concrete into the mold. Real-field experiments and numerical computations have shown that both of the models are good as parameter predictors, where low errors can be achieved. Both proposed networks achieved for testing results R2 bigger than 0.98, the mean of squared errors for water evaporation percentage was less than 1.43%, and the mean of squared errors for shrinkage sizes was less than 0.105 mm/m. The computation requirements of the two models in testing mode are also low, which can allow their easy use in practical applications. Doi: 10.28991/CEJ-2024-010-01-07 Full Text: PDF

Prediction of Plastic Shrinkage Cracking of Supplementary Cementitious Material-Modified Shotcrete Using Rheological and Mechanical Indicators.

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.

Shrinkage strains development in ultralight cementitious foams with embedded MPCM

An innovative material composed of cementitious foam and microencapsulated phase change materials (MPCMs) offers a promising alternative to commonly used insulation materials. The high shrinkage, which is the main drawback of this material is poorly recognized, although it may cause problems in the production process. This paper presents the findings of a comprehensive study on the shrinkage development in cementitious foams with a density range of 240–320 kg/m3, enriched by MPCMs. Through the measurements of shrinkage strains and water loss, an understanding of shrinkage behaviour was better recognized. The results confirmed no plastic shrinkage in the material and the expansion strains instead of typical autogenous contraction. It was also found that a substantial portion (approximately 60%) of the foam-based water is discharged without causing drying shrinkage but further water release induced high shrinkage strains. MPCM was found to reduce shrinkage strains as its content increases.

Early age and long‐term properties of mortars containing metakaolin and limestone powder as SCMs

AbstractIn this study we focus on the development of plastic shrinkage and capillary pore pressure on mortars containing metakaolin and limestone powder as cement replacement. Isothermal calorimetry was also used to compliment the early age properties of the investigated mortars. Strength development and phase assemblage using thermal analysis were also investigated. Five different replacement levels of metakaolin and LSP and two different amounts of SP were used. Our data show that the shrinkage strain values increased as the amount of SCMs increased, while capillary pressure showed a mixed trend. The hydration kinetics did not appear to be influenced much from the SCMs used. Strength development improved in general when metakaolin was used while decreasing when LSP was added, as already expected. The TGA data show an increase in the consumption of portlandite as the amount of SCMs was increased.

Effect of internal curing on shrinkage and cracking potential under autogenous and drying conditions

Autogenous shrinkage is a significant issue in ultra-high-performance concrete (UHPC). Internal curing has been effective in mitigating autogenous shrinkage, but its impact on drying shrinkage and crack-free concrete needs to be considered. This study investigates the controversial phenomenon of the effect of internal curing on shrinkage strains under drying conditions. A very specific steel fiber reinforced cementitious composite (Slurry infiltrated fiber concrete (SIFCON)) was examined to better understand the cumulative effects. Two additional internal curing water contents (36 kg/m3 and 60 kg/m3) and two superabsorbent polymers (SAP) with different particle sizes (D50: 215 µm and D50: 725 µm) were utilized. Shrinkage measurements were conducted on the SIFCON matrix for early (up to 7 days) and long-term (up to 90 days), under both autogenous and drying conditions. The SIFCON specimens were cured under autogenous and drying conditions for 90 days, then dried to simulate the field conditions, which was followed by crack mapping. The results indicate that SAP effectively mitigates shrinkage strains under both autogenous and drying conditions, attributed to its ability to reduce plastic shrinkage strains during the initial hours. However, crack mapping studies revealed increased cracked areas in specimens with SAP usage, higher internal curing water content, and larger SAP size. Additionally, specimens cured under autogenous conditions exhibited more cracks compared to those cured under drying conditions. This suggests that although shrinkage measurements demonstrate positive effects of internal curing in both conditions, the cumulative effect can vary.

Evolution of capillary pressure in 3D-printed concrete elements: numerical modelling and experimental validation

In the initial hours following extrusion, 3D-printed concrete elements undergo intensive water evaporation. This process leads to significant negative capillary pressure within the system. During the period before solidification, this capillary pressure induces volumetric contractions, commonly referred to as plastic shrinkage, in the 3D-printed concrete, and as a result, causes cracking. Therefore, managing and forecasting the negative capillary pressure in freshly deposited concrete filaments is crucial to mitigating the effects of plastic shrinkage. In this study, the progression of capillary pressure in 3D-printed elements, with filament thickness ranging from 37.5 mm to 150.0 mm, was experimentally evaluated and numerically simulated. The numerical simulations utilised the extended Richard's equation. Shrinkage strains were empirically measured using 3D digital image correlation and compared with numerical outcomes. Additionally, we examined various combinations of parameters to analyse their influence on the accuracy of the numerical results.

Behavior of drying and plastic shrinkage of Portland cement concrete prepared and cured under harsh field

The shrinkage of concrete is crucial under aggressive environmental conditions to avoid short and long-term deterioration. ACI committee for hot weather concreting specifies 35 °C as the maximum limit of fresh concrete to mitigate problems associated with that. This paper aims to investigate the plastic and drying shrinkage characteristics and compressive strength development of ordinary Portland cement (OPC) by varying w/c (0.3–0.45), casting temperatures (25–45 °C), and curing methods. The results demonstrated that the characteristics of concrete are significantly influenced by w/c, as well as the conditions at which they are cast and cured. In general, the plastic/drying shrinkage strains were observed to be minimum, while compressive strength was maximum when mixtures were cast at an ambient temperature of 32 °C. An increase in the w/c results in a corresponding rise in plastic/drying shrinkage strain, coupled with a decrease in the compressive strength of the mixtures. In addition, application of curing compound was found most effective in the field for enhancing the shrinkage characteristics whilst wet burlap practice was found beneficial in long-term compressive strength gain. These findings will enhance the optimization of mix designs for harsh conditions, improve construction efficiency, and support long-term concrete structure performance and sustainability.