Autogenous Shrinkage Research Articles

Using superabsorbent polymer to mitigate the fast setting and high autogenous shrinkage of carbide slag and sodium silicate activated ultrafine GGBS based composites

Alkali-activated GGBS based composite is a low carbon engineering material, but limited by some unavoidable disadvantages, such as fast setting and high autogenous shrinkage. In present work, superabsorbent polymer (SAP), which was synthesized by copolymerizing acrylic acid and acrylamide, was used to control the setting time and autogenous shrinkage of carbide slag and sodium silicate activated ultrafine GGBS based composites (CSGC). Results indicated that the fast setting of CSGC was effectively controlled by the addition of SAP. The initial and final setting time were delayed by more than 30 min and 60 min respectively, which provides the possibility to ensure the on-site construction operation. Although SAP mitigated the fast setting of CSGC, it had a negligible effect on the heat release during hydration. Autogenous shrinkage was reduced by 27% when only 0.1% SAP was added, and the compensation of autogenous shrinkage became more pronounced with the increased SAP dosage. The amount of large capillary pores above 100 nm was significantly increased in CSGC incorporating high SAP dosage, which leads to a decline in compressive strength. However, the compressive strength of CSGC with low SAP dosage can match that of reference group at 28 d, due to the internal curing effect of released water from SAP.

An eco-friendly and low-cost superhydrophobic alkali-activated Portland slag cement mortar

Alkali-activated slag cement (AASC) has shown immense potential for application as a low-carbon and eco-friendly cementitious material. It’s crucial to modify the AASC with superhydrophobic property to obtain excellent durability performance. In this paper, low-cost and non-toxic stearic acid (SA) is selected as a hydrophobic agent to impart integral hydrophobic property to the alkali-activated Portland slag cement mortar (AAPSCM). The SA-modified AAPSCM (M-AAPSCM) shows superhydrophobicity with a contact angle of 150.6° and a sliding angle of 9.5°, even when hammered to reveal its broken inner structure. The characterization analysis indicates that stearic acid not only successfully grafts onto the mortar surface but also forms calcium stearate, which successfully reduces the surface energy of the material. Combined with the porous rough structure constructed by medium sand and ethanol volatilization, the originally hydrophilic material achieves hydrophobic modification under the dual synergistic effect. The M-AAPSCM reached a compressive strength of 20.8 MPa after 28 days of curing, satisfying the requirements for hydraulic engineering applications. And the M-AAPSCM not only exhibits an excellent self-cleaning ability against contaminants like sand particles and chalk powder, but also demonstrates remarkable mechanical robustness, even after being subjected to blade scratching or mechanical fracture. Concurrently, the initial and final setting times of M-AAPSCM were determined to be 32 minutes and 41 minutes respectively, demonstrating its rapid-setting characteristic. Additionally, following the hydrophobic modification, AAPSCM effectively overcomes its inherent issues of severe autogenous shrinkage and poor carbonation resistance. Furthermore, when compared with the ordinary AAPSCM (O-AAPSCM), the durability of the M-AAPSCM against dry-wet cycles, icing, and freeze-thaw cycles is significantly enhanced.

Influence of Glass Microfibers on the Control of Autogenous Shrinkage in Very High Strength Self-Compacting Concretes (VHSSCC)

High-performance concrete (HPC) is widely used in infrastructure for its durability and sustainability benefits. However, it faces challenges like autogenous shrinkage, leading to potential cracking and reduced durability. Fiber reinforcement offers a solution by mitigating shrinkage-induced stresses and enhancing concrete durability. In this sense, this study investigates the use of glass microfibers to mitigate autogenous shrinkage and early-age cracking in high-strength self-compacting concrete. Samples were prepared with two water-to-binder ratios (w/b): 0.25 and 0.32; and three glass microfiber contents: 0.20%, 0.25%, and 0.30 vol.%. The concrete mixtures were characterized in the fresh state for slump flow and in the hardened state for compressive strength, static, and dynamic Young’s modulus. Unrestrained and restrained shrinkage tests were also conducted in the seven days-age. The findings revealed that glass microfibers reduced the workability in mixtures with lower slump flow values (w/b of 0.25), while less viscous mixtures (w/b of 0.32) exhibited a slight improvement. Compressive strength showed a proportional enhancement with increasing fiber contents in concretes with a w/b ratio of 0.32. A contrasting trend emerged in concretes with a w/b ratio of 0.25, wherein strength diminished as fiber additions increased. The modulus of elasticity improved with fiber additions only in the matrix with a w/b ratio of 0.25, showing no correlation with compressive strength results. In shrinkage tests, the addition of glass microfibers up to specific limits (0.20% for a w/b ratio of 0.25 and 0.25% for w/b of 0.32) demonstrated improvements in controlling concrete deformation in unrestrained shrinkage analyses. Concerning cracking reduction in restrained concrete specimens, the mixtures did not exhibit significant improvements in crack prevention.

Impact of ettringite seeding on hydration, strength and shrinkage of Na2SO4 activated slag

Na2SO4 activated slag (NSAS) is accepted as one of the most promising low carbon cementitious materials, while its slow strength development seemed the most prominent defect. In this study, nanoscale ettringite (NE) was prepared, and used as nucleation seed to stimulate the hydration of NSAS, thereby promoting the strength development. Compressive strength, hydration process, pore structure, and shrinkage were studied, and the underlying mechanism was revealed. Results indicated that 5% NE enhanced the compressive strength of NSAS paste by 74% at 7 d and by 98% at 28 d, and the reason was that NE significantly facilitated the hydration of slag and the formation of hydrates, including ettringite and C-(A)-S-H gel, especially in the early stage. Furthermore, the presence of NE hastened the dissolution of aluminum phases, and these aluminum phases were inclined to precipitate as ettringite rather than C-(A)-S-H gel. Meanwhile, NE caused the size miniaturization of ettringite crystal formed in hydration. The reason might be that NE provided more nucleation sites, which led to the dispersed growth of ettringite. The small ettringite was harmless to pore structure, and compensated for autogenous shrinkage. In the presence of 1% NE, the porosity and autogenous shrinkage at 28 d decreased from 9.62% to 8.24% and 5209 μm/m to 3992 μm/m, respectively. In addition, NE-NSAS showed great potential in low-carbon cementitious materials.

Impact of Superabsorbent Polymer on Shrinkage and Compressive Strength of Mortar and Concrete

This article aims to study the effects of mixtures with superabsorbent polymers (SAPs) when using different mixing methods. The mixing methods used in this study are the dry mixing method and wet mixing method. Autogenous shrinkage, total shrinkage, drying shrinkage, compressive strength, and curing sensitivity index values are investigated. The results show that mixtures with SAPs have reduced autogenous shrinkage and total shrinkage. Shrinkage is more effectively reduced by the dry SAP mixing method than the wet SAP mixing method. The compressive strength derived by the dry SAP mixing method is higher than that derived by the wet SAP mixing method.

A novel foaming-sintering technique for developing eco-friendly lightweight aggregates for high strength lightweight aggregate concrete

To address the scarcity of natural aggregates and reduce energy consumption in the concrete industry, a sustainable lightweight aggregate (LWA) was prepared with a self-foaming and sintering method by utilizing waste glass powder as the primary precursor and incineration bottom ash as a foaming agent. The effect of NaOH content (0 M, 2 M, and 8 M) on the physical properties of LWA was investigated. Replacing manufactured sand with sintered LWA (0 M-LWA and 2 M-LWA) by 50 vol% and 100 vol% to investigate their impact on the physical properties, mechanical properties, shrinkage, and alkali-silica reaction of high strength LWA concrete. The high strength LWA concrete prepared with 0 M-LWA possessed a density of 2127 kg/m3 and compressive strength of 108.7 MPa, which were slightly lower than that with manufactured sand. Due to the porous and lightweight nature of 2 M-LWA, the density and compressive strength of LWA concrete significantly decreased with the increased 2 M-LWA volume. Nevertheless, 100%-2M showed satisfying density of 1835 kg/m3 and compressive strength of 50 MPa. The internal curing effect of 2 M-LWA effectively mitigated the autogenous shrinkage of LWA concrete. The alkali-silica reaction expansion of all LWA was innocuous.

Effect of CaO on the shrinkage and microstructure of alkali-activated slag/fly ash microsphere

Alkali-activated materials (AAMs) are regarded as promising alternatives to Portland cement. However, the significant high shrinkage of AAMs, particularly in alkali-activated slag system, is a critical issue that hinders their wide application. This study investigated the effect of expansive admixture, i.e. CaO on the autogenous shrinkage and drying shrinkage of alkali-activated slag/ fly ash microsphere (AASFAM). The effect of CaO content on heat evolution, reaction products, microstructure development and compressive strength was systematically investigated. The results revealed that the addition of CaO can effectively reduce both the autogenous and drying shrinkage of AASFAM. Mixture with 3% and 5% CaO exhibited expansion within the first 24 hours after casting, while the drying shrinkage was reduced by 72% and 82%, respectively. The addition of CaO promoted the formation of crystalline phases including Ca(OH)2, hydrotalcite and calcite, leading to a lower free water content and coarser pore structure, which in turn reduced the capillary stress during the drying process. The results demonstrated the promising potential of CaO in effectively mitigating the high autogenous shrinkage and drying shrinkage of AAMs without compromising its mechanical properties.

Enhancing and comparing shrinkage prediction models for High-Strength Concrete with and without admixtures

This study aimed to improve and compare the parameterization of three prominent shrinkage prediction models—RILEM B4, MC 2010, and WITS—tailored specifically for High-Strength Concrete (HSC), both with and without the inclusion of admixtures. The dataset used for refining model parameters consisted of 220 experiments related to drying shrinkage and 342 experiments concerning autogenous shrinkage. Model performance evaluation involved various statistical metrics applied to the entire HSC dataset, subdatasets, and distinct time periods of shrinkage (0–99 days, 100–199 days, 200–499 days, and ≥500 days). The statistical indicators included Root Mean Square Error (RMSE), R-squared adjusted (R2 adj), Akaike’s Information Criterion (AIC), and the overall coefficient of variation (C.o.Vall). Modified models exhibited significantly improved predictions compared to the original models, with most predictions falling within ±20% of the measured shrinkages. For HSC drying shrinkage, the original model accuracy ranked as WITS, RILEM B4, and MC 2010. However, after parameter adjustments, WITS, MC 2010, and RILEM B4 were the best-performing models. Conversely, for HSC autogenous shrinkage predictions, the RILEM B4 model surpassed the MC 2010 model, demonstrating superior accuracy and reliability in forecasting this specific type of shrinkage behaviour within High-Strength Concrete.

Improvement of shrinkage resistance and mechanical property of cement-fly ash-slag ternary blends by shrinkage-reducing polycarboxylate superplasticizer

Fly ash and slag are two commonly used supplementary cementitious materials (SCMs) in modern concrete, which can significantly enhance the long-term durability of concrete. However, their application is somewhat limited due to the negative impact on early strength development and shrinkage cracking. This study proposed using a recently developed shrinkage-reducing polycarboxylate admixture (SR-PCA) to alleviate the above problems. The effect of SR-PCA on compressive strength, drying shrinkage, autogenous shrinkage, mass loss, pore structure and hydration process were also investigated. The results showed that SR-PCA enhanced the 28d compressive strength due to the refinement of pore structure and improved hydration degree. With the addition of SR-PCA, the drying shrinkage and autogenous shrinkage were significantly reduced, particularly in the mixture blended with 50% fly ash, while showing a slight impact in the sample with 50% slag. SR-PCA decreased the drying shrinkage by lowering the hydrous compressibility factor (CF) value and mesopore volumetric percentage. The incorporation of SR-PCA retarded cement hydration at an early age, thereby reducing the early-age autogenous shrinkage, while the long-term autogenous shrinkage was mitigated due to the enhancement effect on the hydration degree at 28 days. Therefore, SR-PCA is a practical approach for enhancing shrinkage resistance and compressive strength in cement-fly ash-slag blends, thereby contributing to the broader application of these industrial by-products.

Effect of Fly Ash Replacement Content on the Autogenous Shrinkage of Self-Compacting Concrete.

Based on an experimental program, autogenous shrinkage of self-compacting concrete (SCC) has been investigated by varied factors such as partial replacement by fly ash content, the unit quantity of binder, and water-binder ratio of mixture design, The results indicate that the autogenous shrinkage of self-compacting concrete decreases with increasing fly ash content and water-binder ratio and that when the unit quantity of binder is 550 kg/m3, the autogenous shrinkage of self-compacting concrete is smaller than that with unit binder quantity of 500 kg/m3 or 600 kg/m3. These observations suggest that a good correlation exists between the autogenous shrinkage and the mineral mixture design.

Enhancing Volumetric Stability of Metakaolin-Based Geopolymer Composites with Organic Modifiers WER and SCA

Shrinkage during hardening and curing is one of the largest challenges for the widespread application of metakaolin-based geopolymers (MKGs). To solve this problem, a silane coupling agent (SCA) and waterborne epoxy resin (WER) were used to synthesize MKG composites. The individual and synergistic effects of the SCA and WER on chemical, autogenous, and drying shrinkage were assessed, the modification mechanisms were investigated by microstructural characterization, and shrinkage resistance was evaluated by the chloride ion permeability of MKG composite coatings. The results showed that the SCA and WER significantly decreased the chemical shrinkage, autogenous shrinkage, and drying shrinkage of the MKG, with the highest reductions of 46.4%, 131.2%, and 25.2% obtained by the combination of 20 wt% WER and 1 wt% SCA. The incorporation of the organic modifiers densified the microstructure. Compared with the MKG, the total volume of mesopores and macropores in MKG-WER, MKG-SCA, and MKG-WER-SCA decreased by 11.5%, 8.7%, and 3.8%, respectively. In particular, the silanol hydrolyzed from the SCA can react with the opened epoxy ring of the WER and the aluminosilicate oligomers simultaneously to form a compact network and resist shrinkage during the hardening and continuous reaction of the geopolymer. Furthermore, the apparently lowered chloride ion diffusion coefficient of concrete (i.e., reduction of 51.4% to 59.5%) by the WER- and SCA-modified MKG coatings verified their improved shrinkage resistance. The findings in this study provide promising methods to essentially solve the shrinkage problem of MKGs at the microscale and shed light on the modification mechanism by WERs and SCAs, and they also suggest the applicability of MKG composites in protective coatings for marine concrete.

Multiscale analysis of shrinkage-induced performance degradation of shear wall and application to structural analysis

Shrinkage-induced cracks reduce the stiffness of concrete structures. Shear walls are more sensitive to drying shrinkage than other members because of their fully restricted condition and large surface areas exposed to air. This study examines how concrete structural performance is affected by shrinkage due to moisture loss via hydration or dissipation by applying multiscale integrated finite element analysis. First, a cyclic shear loading test on shear wall specimens subjected to drying in a previous study was reproduced. Based on the reproduction analysis model, parametric analysis was conducted, focusing on the member scale, mix proportion, and surface treatment of concrete. Shrinkage-induced cracks reduced member stiffness, and the effects of the member scale on drying speed were shown. The dominance of autogenous shrinkage in the case of high-strength concrete was also observed. The sealing of the concrete surface effectively prevented moisture dissipation, but moisture supply from ambient air was also blocked when the humidity inside the concrete was low. Thus, a proper surface protection method should be selected considering water consumption via hydration. Finally, the use of equivalent material properties for considering initial damage due to shrinkage was proposed as a simple way to account for drying effects in structural analyses.

Shrinkage Reduction in Nanopore-Rich Cement Paste Based on Facile Organic Modification of Montmorillonite.

The organic modification of montmorillonite was successfully achieved using cetyltrimethyl ammonium bromide under facile conditions. The modified montmorillonite was subsequently used for the fabrication of montmorillonite-induced nanopore-rich cement paste (MNCP), and the shrinkage behavior and fundamental performance of MNCP were also investigated. The results indicate that alkali cations on a montmorillonite layer surface were exchanged by using CTAB under 80 °C, successfully achieving the organic modification of montmorillonite. As a pore-forming agent, the modified montmorillonite caused a reduction in shrinkage: the 28-day autogenous shrinkage at a design density of 400 kg/m3 and 800 kg/m3 was reduced to 2.05 mm/m and 0.24 mm/m, and the highest reduction percentages during the 28-day drying shrinkage were 68.1% and 62.2%, respectively. The enlarged interlamellar pores and hydrophobic effects caused by the organic modification of montmorillonite aided this process. Organic-modified montmorillonite had a minor influence on dry density and thermal conductivity and could contribute to an enhancement of strength in MNCP.

Optimizing pore structure of perforated cenospheres for effective internal curing of alkali-activated slag mortars

Based on the controllability of the pore structure of perforated cenospheres (PCs), this study utilized PCs with different etching concentrations for the internal curing of alkali-activated slag (AAS), aiming to achieve the optimal etching parameters for efficient internal curing. Three etching concentrations (0.3 M, 0.7 M, 1.0 M) were set to investigate the effects of water-filled PCs on the performance of internal curing of AAS mortars. The results indicated that the water released from the PCs delayed the hydration of AAS and maintained high internal relative humidity. The chemical shrinkage of AAS could be reduced. Water-filled PCs internal curing promoted the generation of hydration products around the PCs and increased their packing density, leading to a reduction in mesopores and a 12.7—27.7% increase in elastic modulus at 28 d. With the optimal etching concentration of 0.7 M, water-filled PCs significantly mitigate the autogenous shrinkage by 75.8% while enhancing the compressive strength of AAS mortars.

Cohesive element-based chemo-thermo-mechanical multi-field coupled cracking simulation of early-age concrete

Due to the intense exothermic hydration process, early-age concrete undergoes restrained shrinkage deformation, which can easily lead to cracks in concrete structures during construction. In order to accurately predict the adverse effects of early-age concrete cracking behavior, a cohesive element-based chemo-thermo-mechanical multi-field coupled cracking model of early-age concrete is proposed in this study. Parametric analysis shows that by selecting appropriate gap conductance, constitutive thickness, mesh size, and viscosity coefficient for the cohesive elements, the multi-field coupled cracking model can successfully simulate the entire cracking process of early-age concrete, and it has the ability to obtain crack development behavior based on the real displacement field jumps, coordinates, and damage of cohesive elements. The validation of the numerical examples reveals the competing mechanisms between thermal expansion and autogenous shrinkage in early-age concrete and accurately predicts the cracking strain, region, time, and width (within an order of magnitude) as reported in the literature.

Effect of Poly(ethylene glycol)–Poly(propylene glycol) Triblock Copolymers on Autogenous Shrinkage and Properties of Cement Pastes

This study investigates the hydration, microstructure, autogenous shrinkage, electrical resistivity, and mechanical properties of Portland cement pastes modified with PEG-PPG triblock copolymers with varied molecular weights. The early age properties including setting time and hydration heat were examined using the Vicat test and isothermal calorimetry. The hydration products and pore size distribution were analyzed using thermogravimetric analysis (TGA) and nitrogen adsorption, respectively. Mechanical properties and electrical resistivity were evaluated using the compressive strength test and electrochemical impedance spectroscopy (EIS). It was shown that the addition of the copolymers reduced the surface tension of the cement paste pore solution due to the presence of a hydrophobic block (PPG) in the molecular structure of the copolymers. The setting time and hydration heat were relatively similar in the control paste as well as the pastes modified with the copolymers. The results showed that copolymers were able to reduce the autogenous shrinkage in the paste due primarily to a reduction in pore solution surface tension. TGA showed a slight increase in the hydration degree of the paste modified with the copolymers. The compressive strength was reduced in the pastes modified with the copolymers that showed an increased volume of air voids. The addition of copolymers did not affect the electrical resistivity of the pastes except in the case where there was a large volume of air voids, which acted as electrical insulators.

Development and evaluation of basaltic volcanic ash based high performance concrete incorporating metakaolin, micro and nano-silica

High-performance concrete is an excellent choice for modern engineering structures due to its superior performance, low maintenance costs, and long service life. Therefore, this study was aimed to produce high-performance concrete by incorporating a high volume of basaltic volcanic ash along with metakaolin (MK), micro-silica (MS), and nano-silica (NS). An investigation was performed in regard to the mechanical and durability properties, autogenous and drying shrinkage, and microstructural and pore-structure properties. A control mix, binary mixes, and ternary mixes were examined. The binary mixes contained fine (VA) and ultra-fine (VAF) volcanic ashes, and the ternary mixes contained combinations of VA with MK, MS, and NS. Test results show that ternary mixes with 30% and 40% cement substitution demonstrated better strength development and higher resistance to chloride penetration and water absorption. All binary and ternary mixes displayed lower autogenous shrinkage, as well as lower or comparable drying shrinkage than the control mix. Moreover, the combination of VA with MK, MS, and NS up to 40% resulted in micro and pore structure refinement by forming high-density gels. The findings indicate that VA in combination with MK, MS, and NS, can effectively substitute cement at up to 40% for the production of sustainable high-performance concrete.

Investigation on the compressive strength and durability properties of alkali-activated slag mortar: Effect of superabsorbent polymer dosage and water content

This paper presents the properties of alkali-activated slag (AAS) mortar additivated with a superabsorbent polymer (SAP) to improve its mechanical and durability properties. The effect of different dosages of SAP (0.0–0.3% with respect to the blast furnace slag weight) and different extra water additions on setting time, autogenous shrinkage, compressive strength, water permeability, frost resistance, heat of hydration, and porosity is presented and discussed. The results highlight the beneficial effect of adding SAP on the mechanical and durability properties of the proposed mixtures. Only at higher percentages of SAP and additional water occur performance drops due to excessive macro-porosity of the system. It is interesting to point out that, in contrast, shrinkage always decreases as the percentages of SAP addition and additional water increase, although it cannot be completely eliminated. Experimental evidence also highlights that significant benefits can be gained from using this material in harsh environments.

A Review on Chemical and Autogenous Shrinkage of Cementitious Systems.

Chemical shrinkage (CS) is an intrinsic parameter that may affect the early age cracking of paste, mortar and concrete. It is well known as the driving force of self-desiccation, autogenous shrinkage (AGS) and drying shrinkage. During the first stage of cement hydration (at the initial setting time), the CS and AGS are equal. In the hardened stages, there is a difference in values between the two shrinkage parameters. This paper is a comprehensive review on CS and AGS, measurement techniques, modeling and prediction of different cementitious systems. Based on the various experimental studies, chemical shrinkage depends on the water to binder ratio (w/b) and is proportional to the degree of hydration. A low w/b ratio leads to high CS and AGS. The composition of cement has an effect on both CS and AGS. Also, incorporating supplementary cementitious materials (SCMs) affects both shrinkage parameters. It is concluded that adding fly ash (FA) to concrete contributes to CS and AGS reductions. However, this is not the case when concrete contains slag. More than 170 references were consulted including 35 which were published after 2020. According to the authors knowledge, there is no published work on the effect of fibers, especially bio-fibers, on the chemical shrinkage of cement-based composites. Therefore, in addition to traditional chemical shrinkage of cementitious systems, this review includes a section on recent papers conducted by the authors on the effect of bio-fibers on the chemical shrinkage of cement composites.

Evaluation of Autogenous Shrinkage and Thermal Behavior of Cellulose Fiber and Synthetic Fiber Reinforced High-strength Concrete

Evaluation of Autogenous Shrinkage and Thermal Behavior of Cellulose Fiber and Synthetic Fiber Reinforced High-strength Concrete