Autogenous Shrinkage Of Cement Paste Research Articles

Synthesis of a chitosan-based superabsorbent polymer and its influence on cement paste

To address the challenge of adaptability between cement-based materials and conventional superabsorbent polymers (sodium polyacrylate, Na-PA), a chitosan-based superabsorbent polymer (CSP) with high salt and alkaline resistance was synthesized, and the optimal synthesis process was determined by a single-factor method. The macroscopic performance and microstructure of CSP and Na-PA were compared, and their influences on cement paste were studied. The results show that CSP exhibits a gradual swelling process during water absorption, which is independent of the solution environment. The poriferous structure of CSP allows it to form a network composed of gel membranes. The introduction of amide group enhances the resistance of CSP to salt and alkaline conditions. The autogenous shrinkage of cement paste is mitigated by CSP, with a superior effect compared to Na-PA. The longer desorption time of CSP allows it to promote cement hydration for a longer period, reducing the loss of compressive strength. The heat release, chemically bound water and hydration products (portlandite and amorphous substances) of CSP pastes are higher than those of Na-PA pastes. The water desorption from CSP fills some middle capillary pores and mesopores, leading to the pores in the hardened cement paste being more concentrated in smaller sizes.

Influence of type and particle size of superabsorbent polymer on early water distribution and internal curing zone properties of cement paste

The types of commercial superabsorbent polymer (SAP) mainly include ionic-SAP acrylic acid (AA) and nonionic-SAP acrylamide-acrylic acid copolymer (AM), which have different particle sizes due to the limited preparation methods. This study used 1H low-field NMR to clarify the influence of type and particle size of SAP on the water distribution of cement paste. Backscattering electrons and nanoindentation were used to quantitatively analyze the area, porosity, and micromechanical properties of internal curing zone. Finally, void system analysis, compressive strength, and autogenous shrinking were systematically studied. The results indicate that the water absorption and retention capacity of AM in cement paste increase with the increase of particle size, and the area of internal curing zone also increased. As the area of internal curing area increases, the autogenous shrinkage of cement paste significantly decreases. The internal curing effect reduces the unhydrated cement content and increases the high-density C–S–H content of internal curing zone, thereby improving the micromechanical properties and to some extent offsetting the decrease in mechanical properties caused by voids. However, larger particle size AM forms larger void and higher air content, leading to a further decrease in strength. Ionic-SAP AA releases a large amount of water before final setting, weakening internal curing effect and reducing the area of internal curing zone. In addition, the early release of water leads to an increase in the local water-cement ratio, which increases the porosity and low-density C–S–H content of internal curing zone, thereby reducing the micromechanical properties.

The role of carbon nanotubes to reduce autogenous shrinkage of cement paste at different ages

The effects of carbon nanotubes (CNTs) on autogenous shrinkage of cement paste were explored. The additions of CNTs were 0.025%–0.125% of cement by mass. Results showed that the autogenous shrinkage of cement paste with 0.05% CNTs was lowest, 22.1% lower than PC. The autogenous shrinkages of CNTs blended cements were predicted based on the poroelastic model and poroviscoelastic model, respectively. The root mean square error (RMSE) of autogenous shrinkage prediction based on poroelastic model was 3 times higher than that of poroviscoelastic model, which indicated that poroviscoelastic model was more appropriate for predicting the autogenous shrinkage of CNTs-cement paste. The role of CNTs on shrinkage mitigation were analyzed by combination with microscopic tests and prediction results. Results indicated that CNTs possess distinctive mitigation effects at different curing ages, which were related to the CNTs contents.

Comprehensive study on the hydration kinetics, mechanical properties and autogenous shrinkage of cement pastes during steam curing

Steam curing is a crucial stage for the strength development of steam-cured concrete. This study comprehensively investigated the hydration kinetics, mechanical properties, and autogenous shrinkage (AS) of cement pastes during steam curing. A hydration-dependent analytical method was proposed to analyze the mechanisms governing the development of mechanical properties and AS of steam-cured cement pastes (SCPs). Results revealed that in this investigated curing regimes, the peak hydration rate of SCPs was approximately 7 times higher than that of standard-cured pastes (NCPs). SCPs exhibited faster time-dependent mechanical property development but slower hydration-dependent mechanical property development than NCPs. This difference was primarily attributed to variations in initial structure establishment and free water content. Moreover, an elevated curing temperature reduced the growth rate of hydration-dependent AS due to large capillary pores and low surface tension, which suggested that AS should not be considered as a cause of heat damage to SCPs.

Early age hydration and autogenous shrinkage of blended cement containing brick powder

Early age hydration and autogenous shrinkage of blended cement containing brick powder (BP) was investigated using hydration heat, internal relative humidity (IRH) and 1H NMR methods. The results show that BP can promoting the early nucleation and growth process of cement. The unique porous structure of BP gives it water absorption property, which plays a role in internal curing. The internal curing effect of BP reduced the rate of decrease of IRH in cement paste and effectively reduced the autogenous shrinkage of cement paste. These findings suggest that moderate adjustment of the dosage of BP can effectively promote the hydration and control the autogenous shrinkage of cement-based materials.

Numerical study of the autogenous shrinkage of cement pastes with supplementary cementitious materials based on solidification theory

The addition of supplementary cementitious materials (SCMs), which is an effective method to reduce the CO2 emission during the cement production, will change the autogenous shrinkage of early-age hydrating cementitious systems. In this paper the effect of different SCMs, i.e., silica fume and fly ash, on the physical properties and autogenous shrinkage of cement paste is studied, both experimentally and numerically. The experiment results show that autogenous shrinkages of cement pastes reduce significantly with the increase of water-binder ratio. The addition of fly ash will lead to smaller autogenous shrinkage while the influence of the dry densified silica fume on the autogenous shrinkage is not pronounced. A numerical simulation model, in which autogenous shrinkage is split up into an elastic part and a time-dependent part is proposed in this paper. The two parts are calculated separately. The simulation of the visco-elastic response of the cement paste to the internal driving force was performed by using a solidification theory model that takes the aging into consideration. The physical properties of different kinds of cement paste are experimentally investigated and the measured results are taken as input parameters of the simulation model. The simulated autogenous shrinkage of different kinds of cement pastes are compared with the measured results to verify the prediction of the proposed model.

Analysis of the development of autogenous shrinkage of CEM I 42.5R and CEM III/A 42.5N cement pastes with different water to cement ratios

In concrete technology, cements with a high content of Portland clinker are increasingly being replaced by blended binders with a lower carbon footprint. Such binders include blastfurnace cements, which are successfully used in concretes designed for large-scale elements, self-compacting concretes, as well as for the precast concrete industry. Blast furnace cements exhibit lower strength gain relative to Portland cements and a lower heat of hydration. Composites that incorporate them are significantly more resistant to the occurrence of thermal stresses at the early stages of curing of concrete. This paper provides a comparative study of the development of autogenous shrinkage of cement pastes made from CEM I 42.5R and CEM III/A 42.5N with a variable w/c ratio using the dilatometric method on a proprietary instrument covered by the patent PL241667. Furthermore, tests on consistency, setting times and compressive strength were performed after 2, 7 and 28 days of curing. From the analyses carried out, it was found that cement pastes containing blast furnace cement show greater autogenous shrinkage over a period of 28 days compared to pastes containing Portland cement. The pozzolanic reaction of granulated blast furnace slag contributes to the increase in recorded autogenous shrinkage. An increase in the water-cement ratio has an impact on the decreased strength gain, and the value of autogenous shrinkage. The research results indicate the need to take autogenous shrinkage into account when designing high-performance concretes containing blast furnace cement due to the increased susceptibility to shrinkage microcracks and for the durability of the material.

Autogenous shrinkage and hydration property of cement pastes containing rice husk ash

In this paper, the rice hush ash (RHA) with different particle size were applied to explore its effect on the autogenous shrinkage and hydration property of cement pastes. The water absorption/release behavior of RHA in cement pastes were characterized by using 1H nuclear magnetic resonance. Additionally, the microstructure and compressive strength of cement pastes containing RHA were also measured. Experimental results showed that water absorption capacity of raw RHA in cement pastes reached 0.89 g/g due to its porous structure, but reduced with the decrease of RHA particle size. The addition of RHA could mitigate the development of self-desiccation, being ascribed to the release of water from RHA after about 12 h which decreased the consumption of capillary water. The autogenous shrinkage of cement pastes containing RHA was reduced by about 41.6 %, 35.6 % and 23.8 %, respectively when the mean particle size of RHA decreased from 43.6 µm to 8.5 µm. Furthermore, the addition of RHA could shorten the dormant period and greatly enhance early-age compressive strength of cement pastes due to its water absorption effect. At later ages, the hydration degree of cement was continuously increased under the double effect of internal curing and pozzolanic reaction of RHA, resulting in the formation of the dense interfacial transition zone (ITZ) between matrix and RHA particles, ultimately improved long-term strength.

Early-Age Properties Development of Recycled Glass Powder Blended Cement Paste: Strengths, Shrinkage, Nanoscale Characteristics, and Environmental Analysis

Recycling solid waste in cement-based materials cannot only ease its load on the natural environment but also reduce the carbon emissions of building materials. This study aims to investigate the effect of recycled glass powder (RGP) on the early-age mechanical properties and autogenous shrinkage of cement pastes, where cement is replaced by 10%, 20% and 30% of RGP. In addition, the microstructure and nano-mechanical properties of cement paste with different RGP content and water to binder (W/B) ratio were also evaluated using SEM, MIP and nanoindentation techniques. The results indicate that the early-age autogenous shrinkage decreases with the increase of RGP content and W/B ratio. While the mechanical strength deteriorates due to the addition of RGP, it can be compensated by reducing the W/B ratio. Although the addition of RGP increases the total porosity of the hardened paste, it reduces the small size porosity (

Mitigating autogenous shrinkage of cement paste with novel shrinkage-reducing polycarboxylate superplasticizer

Mitigating autogenous shrinkage of cement paste with novel shrinkage-reducing polycarboxylate superplasticizer

Incorporating elastic and creep deformations in modelling the three-dimensional autogenous shrinkage of cement paste

A structure-based modelling framework was established to simulate the three-dimensional autogenous shrinkage of cement paste. A cement hydration model, HYMOSTRUC3D-E, was used to obtain the microstructures and ionic concentrations of the cement paste. A lattice fracture model based on the effective stress and effective modulus was used to consider the elastic and creep parts of autogenous shrinkage. For Portland cement pastes with water-to-cement ratios of 0.3 and 0.4 (where the time zero of autogenous shrinkage was set as the time of the drop in internal relative humidity), the simulated linear elastic autogenous shrinkage was respectively −188 and −79 μm/m at 160 h. The obtained linear total autogenous shrinkage including elastic and creep deformations was respectively −501 and −236 μm/m at 160 h. These values of the elastic autogenous shrinkage and total autogenous shrinkage are close to the predications of poromechanical models and experimental data obtained using a corrugated tube.

The Numerical Analysis of Replenishment of Hydrogel Void Space Concrete Using Hydrogels Containing Nano-Silica Particles through ELM-ANFIS.

Currently, Nano-materials are gaining popularity in the building industry due to their high performance in terms of sustainability and smart functionality. In order to reduce cement production and CO2 emissions, nano-silica (NS) has been frequently utilized as a cement alternative and concrete addition. The influence of Nano-silica-containing hydrogels on the mechanical strength, electrical resistivity, and autogenous shrinkage of cement pastes was investigated. The goal of this study was to identify the main structure–property relationships of water-swollen polymer hydrogel particles used as internal curing agents in cementitious admixtures, as well as to report a unique synthesis process to combine pozzolanic materials with hydrogel particles and determine the replenishment of hydrogel void space. Experiments were designed to measure the absorption capacity and kinetics of hydrogel particles immersed in pure water and cementitious pore solution, as well as to precisely analyze the data derived from the tests using hybridized soft computing models such as Extreme learning machine (ELM) and Adaptive neuro-fuzzy inference system (ANFIS). The models were developed, and the findings were measured using regression indices (RMSE and R2). The findings indicated that combining nano-silica with polymeric hydrogel particles creates a favorable environment for the pozzolanic reaction to occur, and that nano-silica assists in the refilling of hydrogel void space with hydrated cement phases.

Clarifying the deformation restriction of unhydrated phase in cement paste to its autogenous shrinkage

Autogenous shrinkage of cement paste depends on the competition between bulk stress (driving force) and deformation restriction (intrinsic modulus). Since the bulk stress can be calculated according to capillary theory, the deformation restriction contributed by unhydrated phase should be paid more attention due to its higher proportion and modulus. However, it is hard to trace the development of unhydrated particles distribution and time-dependent modulus in real time. To clarify the deformation restriction of unhydrated phase, cement pastes consist of nearly fully-hydrated matrix and inert fillers with targeted size and volume were prepared in the present study. Based on the bulk stress calculated by saturation degree and the modulus obtained by upscaling calculation, an empirical function was proposed to link autogenous shrinkage, internal stress, and deformation restriction of cement paste directly. Moreover, the deformation restriction mechanism of unhydrated particles was explained by the effective volume of restricted region around the unhydrated particle, and the deformation restriction can be maximized by rationally arranging unhydrated phase with volume content of 30–40% and particle size of 5–10 μm. The results provide a new sight in understanding the deformation restriction of unhydrated phase, and then lay a solid foundation to minimize the shrinkage of cement-based materials by microstructurally design of cement paste.

A practical model for predicting the autogenous shrinkage of cementitious materials

In this study, the prism method was used to test the autogenous shrinkage of cement paste, mortar, and gravel concrete (cement paste with gravel) in order to analyze the effect of aggregate on autogenous shrinkage. A concise shrinkage model considering the aggregate volume fraction and the average size of aggregate is proposed. The results of the prism method show that the autogenous shrinkage of paste with a high w/c ratio and large volume fraction of aggregate is small. Under the same w/c ratio, the autogenous shrinkage ratios of mortar or concrete to pure cement paste tend to be constants, which do not vary with time. To determine the specific effect of the aggregate on shrinkage, the finite element method is used to calculate the autogenous shrinkage of pure cement paste and mortar. The simulation results show that high aggregate content and smaller particle size are beneficial in decreasing the autogenous shrinkage of mortar and concrete. A power function model considering the volume fraction and the average size of aggregate is developed to describe the effect of aggregate on the paste’s shrinkage based on the experimental and simulation results. The one of application of the model is that the shrinkage of mortar and concrete can be calculated by the shrinkage of the pure cement paste, the volume fraction, and the average particle size of the aggregate.

Investigation of the early-age performance and microstructure of nano-C–S–H blended cement-based materials

Abstract Nano calcium silicate hydrate (nano-C–S–H) has become a novel additive for advanced cement-based materials. In this paper, the effect of nano-C–S–H on the early-age performance of cement paste has been studied, and some micro-characterization methods were used to measure the microstructure of nano-C–S–H-modified cement-based material. The results showed that the initial fluidity of cement paste was improved after addition of nano-C–S–H, but the fluidity gradual loss increased with the dosage of nano-C–S–H. The autogenous shrinkage of cement paste can be reduced by up to 42% maximum at an appropriate addition of nano-C–S–H. The mechanical property of cement paste was enhanced noticeably after adding nano-C–S–H, namely, the compressive strengths were improved by 52% and 47.74% at age of 1 day and 7 days, respectively. More hydration products were observed and pore diameter of cement matrix was refined after adding nano-C–S–H, indicating that the early hydration process of cement was accelerated by nano-C–S–H. This was mainly attributed to seed effect of nano-C–S–H. The detailed relationship between microstructure and early-age performance was also discussed.

Water to Cement Ratio Effect on Cement Paste Microstructural Development by Electrical Resistivity Measurements and Computer Illustration

The effect of the water-to-cement ratio on cement paste microstructural development was investigated using electrical resistivity measurements and computer modelling. Three cement pastes with 0.3, 0.35, and 0.4 w/c ratios were used in this study. The electrical resistivity measurements curve as a function of time for the three pastes shows that the lower the w/c ratio the higher the electrical resistivity through the whole time. The effect of overall porosity and initial distances between particles significantly influence the measurements. Although low w/c ratio paste has low liquid electrical resistivity comparing to other samples, still has high bulk electrical at all ages. The influence of particles proximity due to lower water amount was interpreted through monitoring the electrical resistivity development and computer illustration. The demonstration provides more explanation about the importance of water-to-cement ratio. Through the conducted experiments, empirical correlations were developed regard predicting compressive strength and autogenous shrinkage of cement pastes when all parameters are related to porosity. Setting time was also predicted by monitoring the critical points on the electrical resistivity curve. Scanning electron microscopy (SEM) was employed to elucidate the effect of the w/c ratio on the morphology of hydration products, and it was observed that high w/c ratio paste has more fibers per unite area comparing to lower w/c ratio pastes due to the long distances between hydrates for expanding.

Mechanisms of internal curing water release from retentive and non-retentive superabsorbent polymers in cement paste

This paper examines the mechanisms of desorption within cement pastes for superabsorbent polymers (SAP) with different sorption kinetics: retentive and non-retentive (self-releasing). Despite the different behavior in solution, both SAP types mitigated the autogenous shrinkage of cement pastes. 1H NMR and X-ray tomography showed that the cavities formed by both SAP types were saturated until 9–11 h after mixing, while the entrained water in the cavities redistributed to the cement matrix afterwards. In particular, the non-retentive SAP might have rapidly released the absorbed water, but the released water stayed in the original cavities. Therefore, the behavior of the SAP in the pore solution may not completely determine their internal curing performance in cement pastes. In particular, the initial absorption that forms the solution-filled cavities might be more important than whether the SAP are able to retain the solution for extended periods of time or not.

Mitigating autogenous shrinkage using a combination of superabsorbent polymer and magnesia-based expansive additive

Various strategies have been developed to mitigate the autogenous shrinkage of cement-based materials (CBMs), including internal curing and shrinkage compensation. However, the sole use of internal curing or shrinkage compensation is insufficient in many cases. In this study, magnesia-based expansive additives (MEAs) coupled with a superabsorbent polymer (SAP) were investigated as internal curing agents to mitigate the autogenous shrinkage of cement pastes. The internal relative humidity (RH), autogenous deformation and compressive strength of cement pastes containing two different types of MEAs and SAP were examined. The results showed that, with the incorporation of SAP, the RH in the cement paste was maintained at a higher level than that in cement pastes without SAP, and hence autogenous shrinkage was reduced. The combination of SAP and MEA provided very effective compensation for the autogenous shrinkage of cement paste. Moreover, the cement paste containing 8 wt% MEA and 0.2 wt% SAP produced a gentle expansion of 111 microstrain rather than shrinkage. This was attributed to the increased hydration degree of magnesia owing to the additional water supply provided by the SAP. This study provides a novel and efficient way to mitigate the autogenous shrinkage of CBMs.

Effect of Supplementary Materials on the Autogenous Shrinkage of Cement Paste.

In recent years more and more attention has been given to autogenous shrinkage due to the increasing use of high-performance concrete, which always contains supplementary materials. With the addition of supplementary materials—e.g., fly ash and blast furnace slag—internal relative humidity, chemical shrinkage and mechanical properties of cement paste will be affected. These properties significantly influence the autogenous shrinkage of cement paste. In this study, three supplementary materials—i.e., silica fume, fly ash and blast furnace slag—are investigated. Measurements of final setting time, internal relative humidity, chemical shrinkage, compressive strength and autogenous deformation of the cement pastes with and without supplementary materials are presented. Two water-binder ratios, 0.3 and 0.4, are considered. The effects of different supplementary materials on autogenous shrinkage of cement paste are discussed.

Modeling autogenous shrinkage of hydrating cement paste by estimating the meniscus radius

In this study, a model for predicting the autogenous shrinkage of hydrating cement paste was developed by estimating the radius of meniscus, which varies with age. The meniscus radius was estimated by considering the pore structure that varies with age, and the amount of water consumed by the hydration reaction. The proposed model was verified through a comparison with test data, with respect to the self-desiccation estimated from the meniscus radius and autogenous shrinkage of cement paste with different water-to-cement ratios. While considering poroelastic behavior, the proposed model predicted autogenous shrinkage of cement paste with reasonable accuracy. It was shown that the amount of water consumed by the hydration reaction increases the autogenous shrinkage; however, the pore structure has a greater effect on the magnitude of autogenous shrinkage. The proposed model is expected to be useful in predicting autogenous shrinkage of concrete without measuring the internal relative humidity.