Autogenous Shrinkage Behavior Research Articles

Effect of MgO-based expansive agent on strengths, volume stability, and microstructures of C80 SCC in steel tube arch

In order to meet the requirements of concrete filling, vibration, and pumping during the construction of the concrete-filled steel tube (CFST) arch bridge, the C80 expansive self-compacting concrete (SCC) is prepared using the absolute volume method. This research investigates the effects of MgO-based expansive agent (EA) and water-to-binder ratio (w/b) on the fresh properties, mechanical properties, autogenous shrinkage, and creep behaviors of expansive SCC. The microstructure of expansive SCC is analyzed by scanning electronic microscopy (SEM) and nuclear magnetic resonance (NMR). Results show that, as the MgO-based EA content increases from 5 % to 10 %, its effect on fresh properties of SCC is negligible. The addition of EA retards the hydration reaction of cement at early ages, thus delaying the strength development. However, the long-term mechanical strengths of the SCC are enhanced, due to the expansion product refines the microstructure at later ages. Moreover, the 14-day autogenous shrinkage of SCC with 10 % EA content is eliminated and shows the micro expansion (155.3 με). The microstructural analysis shows that the porosity of SCC with 10 % EA content is 1.8 % while the pore throat below 0.1 μm accounting for 55 % and the pore size above 30 μm is negligible. This research reveals the mechanism of the effects of MgO-based EA and w/b on the volume stability of the SCC, facilitating the application of expansive SCC in CFST composite structures.

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

Regulation of oxidation degree for graphene oxide on hydration process and engineering properties of natural hydraulic lime pastes for grout strengthening of stone cultural relics

The stone cultural relics represented by grottoes carry precious historical and cultural information and are important representations of the mutual learning of civilizations. Fissures are the main threat to stone cultural relics. The development of grout strengthening materials for fissure repair is of great significance to restrain or delay other threats, such as instability, water seepage, and surface weathering. In this work, based on the improved Hummers’ method, graphene oxide (GO) with different oxidation degrees was prepared by adjusting the amount of added KMnO4, which was then added to natural hydraulic lime (NHL2) pastes to explore the effect of the GO oxidation degree on the hydration process and engineering properties of NHL2 pastes. The results indicated that the addition of GO significantly promoted the hydration rate of the NHL2 pastes and resulted in the formation of more regular and ordered flower-like hydration products and aggregates. Compared with the reference sample, the engineering properties of the modified NHL2 pastes, including the mechanical properties and the autogenous shrinkage behavior, were significantly improved. The simulated grouting experiment also indicated that NHL2 pastes had good groutability and interface combination statuses. In the hydration process of NHL2, GO provided nucleation sites. The hydration reactions were preferentially carried out on the GO sheets, and regular aggregates formed to fill the cracks and holes in the NHL2 pastes, which improved the mechanical properties of the strengthened material. This work provides an effective strategy for the grout strengthening of stone cultural relics fissures.

Mechanical and shrinkage performance of steel fiber reinforced high strength self-compacting lightweight concrete

This study investigated the effects of mixture proportion on the mechanical and shrinkage behaviors of steel fiber reinforced high strength self-compacting lightweight concrete (SHSLC) mixtures incorporating bottom ash aggregates for internal curing. In this study, different types of fine aggregates, fine aggregate ratios, supplementary materials such as silica fume (SF) and colloidal nano-silica (CNS), and four types of steel fibers were considered to develop SHSLC. The self-compacting characteristics of concrete were evaluated by means of slump flow, J-ring flow, and V-funnel tests. The test results indicate that incorporation of SF and CNS had a positive effect on the mechanical properties, but 4% incorporation of CNS decreased workability and strength due to the agglomeration of mixture. The addition of steel fibers improved compressive strength, and flexural toughness of SHSLC, but reduced the flowability and passing ability with increased fiber contents. Due to the internal curing from coarse bottom ash, significant reduction of autogenous shrinkage up to 33% was observed, whereas 7% for drying shrinkage. The incorporation of fibers reduced the autogenous and drying shrinkage up to 31% and 22% compared with non-fiber reinforced concrete, respectively. Finally, the autogenous shrinkage behavior was simulated with several models in the literature, and a model for high strength self-compacting lightweight concrete with and without fibers considering equivalent age was proposed.

Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent polymers

Superabsorbent Polymer (SAP) has emerged as a topic of considerable interest in recent years. The present study systematically and quantitively investigated the effect of SAP on hydration, autogenous shrinkage, mechanical properties, and microstructure of cement mortars. Influences of SAP on hydration heat and autogenous shrinkage were studied by utilizing TAM AIR technology and a non-contact autogenous shrinkage test method. Scanning Electron Microscope (SEM) was employed to assess the microstructure evolution. Although SAP decreased the peak rate of hydration heat and retarded the hydration, it significantly increased the cumulative heat, indicating SAP helps promote the hydration. Hydration promotion caused by SAP mainly occurred in the deceleration period and attenuation period. SAP can significantly mitigate the autogenous shrinkage when the content ranged from 0 to 0.5%. Microstructure characteristics showed that pores and gaps were introduced when SAP was added. The microstructure difference caused by SAP contributed to the inferior mechanical behaviors of cement mortars treated by SAP.

A mechanistic model for the time-dependent autogenous shrinkage of high performance concrete

An accurate prediction of time-dependent autogenous shrinkage behaviors of concrete, especially for high performance concrete (HPC) at an early age, is of great significance to assess and control the cracking risks of restrained structural elements. In this study, based on the capillary tension theory, a mechanistic model for evaluating the time-dependent autogenous shrinkage behaviors of high performance concrete is proposed. A total of 416 data points including the concrete composition, curing condition, age of concrete, water-to-cement (binder) ratio, internal relative humidity, elastic modulus, and measured autogenous shrinkage are selectively collected for the model establishment. The effects of silica fume on the development of autogenous shrinkage are also considered. Upon the sound physical basis, the model requires only a few parameter inputs related to the mixture proportion and physicochemical properties of constituents. The reasonable agreements between the analytical predictions and independent experimental results, as well as common used formulas from different codes (i.e., ACI 209, Eurocode 2, and Model Code 2010), demonstrate that the time-dependent evolution of autogenous shrinkage of HPC can be reasonably predicted by the model proposed in this study.

Autogenous Shrinkage, Pozzolanic Activity and Mechanical Properties of Metakaolin Blended Cementitious Materials

In the literature, there are some conflicting results regarding the influence of metakaolin (MK) addition on autogenous shrinkage behavior of cementitious materials. In this study, with the aim of identifying how the use of MK changes the properties of cementitious materials, cement was partially replaced by MK in different proportions (8%, 16%, and 24%) in pastes produced with variable water/binder ratios (w/b; 0.28, 0.35 and 0.42). The temperature development and calcium hydroxide consumption by thermogravimetric analysis were observed to better characterize the effects of MK on the autogenous shrinkage behavior. The mechanical properties such as compressive strength and flexural strength were experimentally investigated. The results show that the addition of MK has contrasting effects on autogenous shrinkage during early ages depending on the w/b ratio. Thermogravimetric analysis showed that the amount of stratlingite was smaller in pastes with low w/b ratios than in pastes with high w/b ratio. The calcium hydroxide consumption with the pozzolanic reaction of MK was significant even at 2 days, but consumption ratios with respect to the reference paste slowed down at 7 to 28 days.

Experimental study on autogenous shrinkage behaviors of different Portland blast furnace slag cements

In this study, the differences in autogenous shrinkage behaviors among the Portland blast furnace slag (BFS) cements were investigated experimentally. Portland BFS cements that contain 40–45% BFS were collected from eight different plants in Japan and their autogenous shrinkage at early ages were measured with mortar specimens. After the proper thermal dilation correction of the experimental results, it is indicated that several Portland BFS cements could exhibit significantly different autogenous shrinkage behaviors, even if they are in the same class for the products. The laser diffraction test was conducted to compare fineness of cement particles, but the fineness property of Portland BFS cements was inconsistent with the measured autogenous shrinkages. Subsequently, the chemical composition of each powder and the reaction progress of cement paste specimens were measured by thermal gravimetric analysis and X-ray diffraction Rietveld analysis (XRD). It was realized that the crystallized slag mineral contents through the heat treatment process are consistent with the autogenous shrinkage measurement results and well correlated with hydration level of slag. The crystallized slag mineral contents through the heating process can be an indicator to assess the degree of autogenous shrinkage. The differences in the composition of BFS can be identified through the heat treatment process and this can result in different reaction progresses and autogenous shrinkage behaviors among Portland BFS cements.

Autogenous shrinkage behavior of ultra-high performance concrete

This study presents experimental results on the shrinkage behavior of ultra-high performance concrete (UHPC), including the shrinkage development pattern, the calculation of autogenous shrinkage strain and the steel fiber restraining effect. UHPC is found to exhibit a multi-stage shrinkage characteristic. During the first two dormant stages, shrinkage is mainly composed of thermal contraction when limited hydration reaction occurs. Rapid shrinkage development commences once hydration is accelerated, leading to pore moisture depletion and pore refinement. In the later stage, shrinkage gradually levels off due to the decreasing hydration reactivity and the stiffening matrix. Autogenous shrinkage is separated by the removal of thermal strain based on the knowledge of coefficient of thermal deformation (CTD). This leads to the appearance of a transient swelling segment which may be attributed to the formation of Ca(OH)2 and ettringite crystals generating expansive stresses. Addition of steel fibers is found to reduce the shrinkage strain significantly. Its shrinkage restraining effect is a result of the matrix-fiber interfacing bonding and is numerically characterized by a mathematical model with the volume fraction and geometrical features of steel fibers as the major variables.

Numerical simulation of early age expansion and autogenous shrinkage behavior of blast furnace slag concrete with expansive additive

Numerical simulation of early age expansion and autogenous shrinkage behavior of blast furnace slag concrete with expansive additive

Effect of temperature rising inhibitor on autogenous shrinkage of cement pastes

This study examines autogenous shrinkage behavior of cement pastes affected by temperature rising inhibitor (TRI). Dynamic elastic modulus, hydration kinetics, mineral phase compositions, pore solution and microstructure development were investigated by ultrasonic method, isothermal calorimetry, quantitative X-ray diffraction, inductively coupled plasma-optical spectroscopy and electrical resistivity, respectively. The results of the investigation indicate that reduction in surface tension of the pore solution is not due to the impact of TRI. Conversely, it is shown that growth process of ettringite crystals in pore solution the inhibition is delayed which results from the decreased growth rate of ettringite in pore solution and the slow dissolution rate of aluminum from clinkers affected by TRI. This is used to explain the derivation trend of mineral phases of clinkers, chemical compositions of pore solution, and decreases in the autogenous shrinkage of cement pastes. Experiments involving TRI and pure calcium sulfate aluminum clinker indicate expansion stress generation for a longer period when compared to that in the cement pastes only containing TRI, thereby confirming delayed ettringite growth mechanism.

Investigation of mechanical properties and shrinkage of ultra-high performance concrete: Influence of steel fiber content and shape

Use of steel fibers in ultra-high performance concrete (UHPC) plays a significant role in enhancing strength and toughness and restraining shrinkage. This paper investigates the effect of steel fiber content and shape on mechanical strength, toughness, and autogenous and drying shrinkage of UHPC. Three steel fiber shapes, including straight, corrugated, and hooked fibers, with volume fraction ranging from 0 to 3% were employed. Compressive, flexural, and fiber-matrix bond strengths were evaluated. A statistical quadratic model and the Composite Theory were employed to predict the flexural strength of UHPC. Test results indicated that the increase in fiber volume can enhance the compressive and flexural strengths of UHPC and reduce shrinkage. The optimum fiber content for strength and shrinkage was found at 2%, beyond which the strength was slightly increased and the shrinkage was slightly decreased. For a given fiber content, the use of hooked fibers was most efficient in improving fiber-matrix bond and flexural strengths and reducing shrinkage. The flexural strengths of UHPC made with various fiber contents and shapes can be predicted using the proposed quadratic model and the Composite Theory. The latter considers the primary parameters affecting performance, including bond strength, matrix properties, and fiber characteristics. Finally, several models were used to simulate autogenous shrinkage behavior of UHPC and optimal models were found.

Utilization of miscanthus combustion ash as internal curing agent in cement-based materials: Effect on autogenous shrinkage

Abstract The present study aims to evaluate the characterization of combustion ash of miscanthus and its possible application for self-desiccation and autogenous shrinkage mitigation in cement-based materials. Comprehensive tests were performed on the sealed samples to evaluate the behavior of self-desiccation and autogenous shrinkage of low water/binder ratio (0.25) cement pastes blended with miscanthus ash (MA). The lab-generated MA is featured by high content of amorphous silica and porous structure. Its porous structure with pore size distribution mainly within the range of 30–50 nm in diameter makes it a potential internal curing agent for self-desiccation and autogenous shrinkage mitigation. Incorporation of 20% by weight MA into cement paste shows high efficiency in self-desiccation mitigation, contributing to the significantly reduced autogenous shrinkage. Decreasing the mean particle size from 20.43 µm to 6.67 µm lowers the self-desiccation mitigation efficiency of biomass ash MA in the blended cement pastes.

Synergistic Benefits of Using Expansive and Shrinkage Reducing Admixture on High-Performance Concrete.

High-performance concrete (HPC) is widely used in construction according to great mechanical properties, but it has a high risk of shrinkage cracking due to autogenous shrinkage stress. Therefore, the aim of this research was to investigate the effect of a combination of expansive admixture (EA) and shrinkage reducing admixture (SA) on the autogenous shrinkage of high-performance concrete without heat treatment. Two different EA to cement weight ratios of 0.0, 5.0%, and two different SA to cement weight ratios of 0.0, and 1.0% were combined and considered. To investigate the differences in the time-zero conditions effect on the autogenous shrinkage behaviors, four different initial points were compared. The test results indicate that the EA and/or SA content was conductive to a little bite increase compressive strength (22.6–37.9%) and tensile strength (<4.8%). According to the synergistic effect of the EA and SA on the HPC, the autogenous shrinkage significantly decreased (<50%), as compared to those specimens with only one type of admixture (EA or SA). Furthermore, all the specimens incurred restrained autogenous shrinkage cracks at an early age, except the specimen using the combined EA and SA. Therefore, it can be concluded that the combination of EA and SA is effective for improving the properties of HPC.

Effects of mix proportion and curing condition on shrinkage behavior of HPFRCCs with silica fume and blast furnace slag

This study investigated the effects of mixture proportion and curing condition on the mechanical and shrinkage behaviors of high-performance fiber-reinforced cementitious composites (HPFRCCs). Different water-to-binder (W/B) ratios and amounts of mineral admixtures, such as zirconium silica fume (Zr SF) and blast furnace slag were evaluated. The test results indicate that initial steam-heat curing accelerated the strength development and was sufficient to develop its full strength. The ultimate autogenous shrinkage was insignificantly affected by the curing conditions, but the heat curing accelerated the development of autogenous shrinkage. HPFRCC with a lower W/B ratio and greater amount of Zr SF exhibited higher autogenous shrinkage but lower drying shrinkage. In addition, the amount of total shrinkage of HPFRCC was more effectively reduced by providing heat curing when a higher W/B ratio and a smaller amount of Zr SF were used. There were no increases in the autogenous and drying shrinkage for HPFRCC immediately after finishing the initial heat curing, meaning that there is no possibility of shrinkage cracks forming in HPFRCC elements after the heat curing process. Finally, the autogenous shrinkage behaviors of HPFRCC were simulated with several prediction models from literature and an optimized model, considering equivalent age, was suggested.

Experimental investigation on the autogenous shrinkage of steam cured ultra-high performance concrete

The ultra-high performance concrete (UHPC) has the potential to be widely used for its excellent mechanical properties and durability. However, characteristics such as high superfine particles content, free of coarse aggregate and extremely low water to binder ratio lead to high autogenous shrinkage in UHPC that could even cause cracking. In this work, the mixture parameters on the autogenous shrinkage behavior of steam cured UHPC were investigated. High performance liquid chromatography was employed to determine the sulfate concentration at different ages. The development of microstructure and hydration products were investigated by a range of analytical techniques such as X-ray diffraction analysis, scanning electron microscopy and nuclear magnetic resonance spectroscopy etc. The results showed that key factors that affected autogenous shrinkage of UHPC were steel fiber, silica fume and aggregate to cement ratio. The autogenous shrinkage mainly occurred during steam curing, and a slight expansion behavior was observed after steam curing. The microstructure observation showed that the hydration was significantly promoted by steam curing and Ca(OH)2 can be rarely observed. A very dense microstructure and closely bonded interface between aggregate and the matrix was observed. The decrease of sulfate concentration and appearance of a weak shoulder at about 13 ppm in the 27Al MAS NMR spectra of sample at 60 d indicated that ettringite formation was responsible for slight expansion after steam curing.

Influence of Autogenous Shrinkage and early Anti-Cracking Behavior of USHC with Pretreatment RHA

The effect of calcinations time on carbon content and grinding time on fineness of rice husk ash (RHA) has studied. The influence of workability, compressive strength, autogenous shrinkage and early anti-cracking behavior of pretreatment RHA with calcined 30min-grinded 30min-pre-wet as admixture to UHSC has researched, the result shows that, when the content of cement replaced by RHA is 10%, the workability and compressive strength change little, while the autogenous shrinkage of UHSC reduce by 28.3%, and early anti-cracking grade increase from III to IV.

유지류를 중심으로 한 수축저감제 종류 변화가 고강도 콘크리트의 기초물성 및 자기수축에 미치는 영향

In this research, the fundamental properties and autogenous shrinkage behaviors of high strength concrete of 0.30 water-to-binder ratio was evaluated depending on the various shrinkage compensating admixtures such as soybean oil (BO), wasted cooking oil (WO), and emulsified refined cooking oil (ERCO) comparing to commercial shrinkage reducing admixture (SR), and expanding admixture (EA). According to the experiment results, the workability of the concrete mixture showed decreased when it contained BO, and WO rather than Plain. In the case of ERCO, due to the water dispersing effect caused by emulsification, similar workability was obtained to Plain. For compressive strength, the concrete mixtures with BO, and WO decreased compressive strength rather than Plain concrete mixture, while the concrete mixture with ERCO showed decreased compressive strength at early age and recovered strength at later age. Regarding the autogenous shrinakge reducing performance, the oil-based admixtures of BO, WO, and ERCO showed better performance than SR and EA; it is considered that the saponification, the hydrolyzed reaction of fatty-acid from oils by calcium hydroxide, the hydration product of cement paste, contributes on filling the capillary pores of the concrete matrix, and thus it decreases the shrinkage. eventually, workability, strength, autogenous shrinkage reducing of 30~40 %, and economical aspects, it can be state that using ERCO may be an efficient solution for autogenous shrinkage of high strength concrete.

Effectiveness of shrinkage-reducing admixture in reducing autogenous shrinkage stress of ultra-high-performance fiber-reinforced concrete

This study describes the effect of shrinkage-reducing admixture (SRA) on free and restrained autogenous shrinkage behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC). To investigate the cracking potential, tensile strength development was experimentally obtained and predicted on the basis of the degree of hydration model. Three different SRA to cement weight ratios of 0, 1, and 2% and three different reinforcement ratios of 1.3, 2.9, and 8.0% were considered. A higher SRA content contributed to a slightly higher tensile strength and a lower autogenous shrinkage. In addition, a higher SRA content and a lower reinforcement ratio resulted in better restrained autogenous shrinkage behaviors, such as lower autogenous shrinkage stress and cracking potential. Therefore, it can be concluded that the use of SRA or a lower reinforcement ratio is favorable for improving the restrained shrinkage behaviors of UHPFRC.

초기재령에서 열팽창계수를 고려한 고성능 섬유보강 시멘트 복합체의 자기수축 특성에 관한 실험적 연구

HPFRCC is characterized by a very low water-to-binder ratio which induce extremely large autogenous shrinkage at early age. The restriction of such autogenous shrinkage through the use of forms and reinforcing bars will increase substantially the risk of excessive residual stresses and shrinkage cracking. The exact understanding of the shrinkage behavior and studies on solutions to reduce shrinkage should be imperatively undertaken for further application of HPFRCC to real structures. Therefore, this paper investigated the mechanical properties of HPFRCC with respect to the eventual introduction of expansive admixture(EA) and shrinkage reducing agent (SRA) in the mixture. Autogenous shrinkage test was conducted considering the coefficient of thermal expansion (CTE) measured at early age so as to examine the effects of EA and SRA on the autogenous shrinkage behavior of HPFRCC.