Shrinkage Measurements Research Articles

Exploring the Possibility of Ionic Liquid as a Dimensional Stabilizer for Well-Preserved Waterlogged Archaeological Wood

Dehydration is the principal conservation process for waterlogged archaeological wood (WAW), with the aim of preventing shrinkage and cracking. For well-preserved WAW, shrinkage mainly takes place when the moisture content is below the fiber saturation point. Here, we conduct a new trial using ionic liquid as a dimensional stabilizer to maintain a stable swollen state of WAW. Molecular dynamics simulation (MD), shrinkage measurement, Fourier transform infrared spectroscopy (FTIR), and dynamic vapor sorption (DVS) were adopted to investigate the interactions and effects of 1-Butyl-3-methylimidazolium chloride ([Bmim][Cl]) on WAW (Dipterocarpaceae Dipterocarpus sp. with a maximum moisture content of 80.3%) in comparison with the conventional material polyethylene glycol (PEG). The results show that [Bmim][Cl] and its water mixtures have a comparable or slightly greater ability to swell amorphous cellulose than does water at room temperature, while crystalline cellulose is left intact. The samples treated with [Bmim][Cl] show less shrinkage than the PEG 300- and PEG 2000-treated samples at all tested concentrations after air-drying. The best dimension control was achieved by 40 wt% [Bmim][Cl], with volumetric shrinkage reduced from 5.03% to 0.47%. DVS analysis reveals that [Bmim][Cl] reduces moisture contents at moderate and low relative humidity (<80%) when the concentration is at or below 20 wt%, which suggests that good dimensional stability was not achieved by simply preserving the moisture content but possibly through the interaction of the ionic liquid with the wood polymers.

Assessment of waste eggshell powder as a limestone alternative in portland cement

The decarbonization of the concrete industry is an ongoing pursuit. One solution towards this goal is the use of limestone powder in portland cement. Waste eggshell has tremendous potential as an alternative calcite filler in cement due to its similarities with limestone. In this research, the feasibility of adding 15% and 35% ground eggshell in portland cement to make cement mortars was investigated. The hydration mechanism of eggshell and limestone blended cements was compared through the heat of hydration, phase assemblage, electrical resistivity, compressive strength, and shrinkage measurements. The experimental results showed that cement mortars with ground eggshell attained similar compressive strength as that with limestone. However, eggshell mixtures demand more mixing water to compensate the hydrophobicity of the eggshell membrane. The high calcite content in both eggshell and limestone accelerates the hydration of cement at 15% replacement, but ground eggshell retards cement hydration at 35% replacement due to the dominant influence of the membrane. Overall, eggshell waste is a feasible sustainable alternative to limestone powder at up to 15% portland cement replacement levels. Lifecycle assessment and cost analysis showed that adding 15% ground eggshell in cement concrete further reduces its embodied carbon and energy and cost compared to cement concrete containing limestone powder.

Evaluation of Clayey Raw Materials and Ceramic Masses from Ceramic Building Material Companies Located in Northeastern Brazil

The challenge of improving the quality of ceramic products is faced worldwide, especially in areas where artisanal production is common and the need for in-depth knowledge about raw materials, together with inefficient production processes, limits the advancement of the ceramic industry. Scientifically, detailed investigation of ceramic masses’ physical, chemical and mechanical properties can provide essential insights to optimize production, contribute to developing more advanced and sustainable techniques, and increase competitiveness. This study evaluated raw clay materials and ceramic masses obtained from northeastern Brazilian, focusing on their chemical composition, mineralogical phases, thermal behavior, and particle size distribution. Rectangular samples (80 mm × 20 mm × 7 mm) prepared using uniaxial pressing (25 MPa by 30 s) were fired at different temperatures (950 and 1050 °C) and linear shrinkage, flexural strength, water absorption, and apparent porosity measurements were taken. The results showed that the companies still need to improve the production process to meet the minimum strength requirement of 1.5 MPa according to the Brazilian standard NBR 15270.

Measuring shrinkage of expansive soils using a novel automated high‐frequency setup

AbstractSoil shrinkage characteristic curves are used to describe the shrinkage behavior and hydraulic properties of unsaturated soils. To construct soil shrinkage characteristic curves, a high‐data‐density measurement method is needed that relates water content to soil volume changes. We present a fully automated soil shrinkage measurement setup, based on the simplified evaporation method, to characterize the shrinkage behavior of undisturbed natural expansive clay soils. The high data density creates the opportunity to produce soil shrinkage characteristic curves without the need for a mathematical model. The technique allows for resaturation of the samples after drying, enabling differentiation between reversible and irreversible shrinkage. The setup consists of the commercialized HYPROP2 apparatus combined with optical distance sensors to measure the horizontal and vertical dimensions of the samples, yielding data on the sample volume, weight, and soil water suction. The measurement frequency is once per 10 min, and the measurement period is up to 4 weeks, providing a detailed time series of the drying and shrinkage characteristics. The setup can capture the different shrinkage phases and offers the opportunity to relate the soil shrinkage characteristic curve to soil water suction. The measurement data acquisition rate and accuracy enable detailed interpretation of soil water retention curves for nonrigid soils and are shown to be essential for understanding and quantifying the shrinkage potential of several types of deposits.

Effect of beeswax and coconut oil as natural coating agents on morphological, degradation behaviour, and water barrier properties of mycelium-based composite in modified controlled environment

Non-degradable coatings made of petroleum-based plastics hinder the degradation performance of products. This highlights the urgent need to develop biodegradable, bio-based coatings derived from renewable resources to create a more sustainable and greener world with a smaller environmental footprint. This study endeavours to examine the effects of beeswax and coconut oil additions on the morphological, degradation, and water-barrier properties of mycelium-based composite (MBC). Coconut oil is supplemented with varying amounts of beeswax, comprising 0, 20, 40, 60, 80, and 100 wt%. Dip coating is applied to prepare coated-MBC at 65 °C for 2 min. The coated-MBC is characterized by water absorption test, water loss measurement, density measurement, yeast and mould test, shrinkage measurement, weight loss measu rement, soil burial test, Scanning Electron Microscopy (SEM) and macroscopic appearance. Findings revealed that a higher composition of beeswax (80 BW) leads to lower water absorption ability (26.25 %) and no fungal growth for 36 days, in contrast to uncoated-MBC (0 BW), which are used as a reference sample.

Non-Uniform Drying Shrinkage in Robocasted Green Body Ceramic Products

The formation of defects, due to drying, in robocasted ceramic objects is an important issue arising from non-uniform shrinkage of the material during this step in the process. Common methods for shrinkage measurement are not well suited to the small size of robocasted cords or the complexity of robocasted objects. Innovative methods for shrinkage measurement were developed using non-destructive optical vision techniques with computer-controlled data acquisition, allowing measurement on millimetric cords and on specific zones of a product. The study of a single porcelain cord revealed an anisometric shrinkage related to the orientation of grains during extrusion. A differential shrinkage at the macroscopic scale was also measured on a robocasted object, indicating a moisture content gradient in the material. The methods presented in this paper are of particular relevance to real-time control of the drying process for robocasted objects.

Plastic-sleeve test method to measure autogenous and drying shrinkage in paste, mortar, and concrete: Test Results

The Plastic-Sleeve Test (PST) method of molding cylindrical specimens in plastic sleeves enables the measurement of autogenous and total shrinkage of pastes, mortars, and concretes. Photogrammetric tests confirmed that the linear support of the specimens with a temporary bottom support mold does not restrain deformation. Tests were performed to compare the PST versus corrugated tube methods and similar relative humidity and autogenous shrinkage results were obtained. The PST shows comparable CoV values to those of the corrugated tube test. The method presented provides solid circular cross-section samples, enabling control over entrapped air content, specimen shape, and bleeding effects, thereby ensuring the measurement method’s high repeatability. The PST showed a tighter seal than prismatic samples molded for total shrinkage testing according to EN 1367-4. Results indicate that the PST can effectively be used for molding samples intended for total shrinkage measurement. It is concluded that the PST method is an effective method to measure autogenous shrinkage and total shrinkage of cementitious materials.

Assessment of determination methods for time-zero of autogenous shrinkage in cement mortars

Determination of time-zero is crucial for standardizing autogenous shrinkage measurement, data processing and cracking risk calculation for cementitious materials. The main objective of this study is to assess mainstream methods of time-zero determination and to provide recommendations based on the underlying mechanism and data reliability. In total, nine kinds of determination methods for time-zero were conducted for mortars with different water-to-cement ratios (w/c) including a simplified measurement for the restraint stress generation. The method of combining penetration resistance and capillary pressure is suggested due to its clear mechanism and ease of operation in different cementitious systems. After classification and statistical evaluation, the final setting, the peak rate time of the temperature, the restraint stress generation time and the newly proposed combined method are considered more suitable among the assessed time-zero determination methods. The recommendation is applicable for cement mortars with the w/c 0.3–0.4 and also expected to be extended to more complex cementitious systems.

Morphological evaluation of adult domestic cat testicular biopsy after vitrification.

Testicular biopsies (9 mm3) from domestic cats (n = 10) submitted to orchiectomy were submitted to equilibrium vitrification in the presence of ethylene glycol (EG) alone or combined with dimethylsulfoxide (DMSO) as intracellular cryoprotectants, and sucrose or trehalose as extracellular cryoprotectants. The samples were vitrified with 40% EG or 20% EG + 20% DMSO, plus 0.1 M or 0.5 M of sucrose or trehalose. The study was divided into Step 1 and Step 2. In Step 1, intratubular cells (spermatogonia, spermatids, spermatocytes, and Sertoli cells) were quantified and classified as intact or degenerated (pyknotic and/or vacuolated cells). Cryodamage of seminiferous cords was determined by spermatogonia and Sertoli cell scoring of nuclei alterations, tubular basement membrane detachment, epithelium shrinkage, and tubular measures (total area, epithelium area, larger and smaller diameter, and height of the epithelium). In Step 2, Hoechst 33342 stain and propidium iodide (PI) fluorescent stain were used to assess the cell viability of the four best experimental groups in Step 1. The effect of treatments on all analyses was accessed using analysis of variance (ANOVA), and Fisher's post hoc test at P < 0.05 significance was considered. In Step 1, the mean percentage of spermatogonia and Sertoli cells morphological integrity did not show a difference when using both sugars at different concentrations, but their morphology was more affected when DMSO was used. EG use associated with 0.1 M of sucrose or trehalose positively affected spermatocyte and spermatid morphology, respectively. The larger diameter and epithelium height of seminiferous tubules were increased using DMSO plus 0.5 M sucrose and DMSO plus 0.1 M trehalose. The changes in spermatogonial/Sertoli nucleoli visualization were best scored in the EG groups, while the nuclei condensation was lower with sucrose. The basement membrane was satisfactorily preserved with 0.1 M sucrose. In Step 2, the percentage of cell viability was higher when EG plus 0.1 M sucrose was used. Therefore, DMSO's negative effect on the vitrification of testicular biopsies of adult domestic cats was evident. The EG plus 0.1 M of sucrose or trehalose associations are the most suitable CPAs to preserve the testicular histology structure of adult domestic cats in vitrification.

Assessments of polymerization shrinkage by optical coherence tomography-based digital image correlation analysis—Part I: Parameter identification

ObjectiveTo investigate the feasibility of optical coherence tomography (OCT)-based digital image correlation (DIC) analysis and to identify the experimental parameters for measurements of polymerization shrinkage. MethodsClass I cavities were prepared on bovine incisors and filled with Filtek Z350XT Flowable (Z350F). One OCT image of the polymerized restoration was processed to generate virtually displaced images. In addition, the tooth specimen was physically moved under OCT scanning. A DIC software analyzed these virtual and physical transformation sets and assessed the effects of subset sizes on accuracy. The refractive index of unpolymerized and polymerized Z350F was measured via OCT images. Finally, different particles (70–80 µm glass beads, 150–212 µm glass beads, and 75–150 µm zirconia powder) were added to Z350F to inspect the analyzing quality. ResultsThe analyses revealed a high correlation (>99.99%) for virtual movements within 131 pixels (639 µm) and low errors (<5.21%) within a 10-µm physical movement. A subset size of 51 × 51 pixels demonstrated the convergence of correlation coefficients and calculation time. The refractive index of Z350F did not change significantly after polymerization. Adding glass beads or zirconia particles caused light reflection or shielding in OCT images, whereas blank Z350F produced the best DIC analysis results. SignificanceThe OCT-based DIC analysis with the experimental conditions is feasible in measuring polymerization shrinkage of RBC restorations. The subset size in the DIC analysis should be identified to optimize the analysis conditions and results. Uses of hyper- or hypo-reflective particles is not recommended in this method.

Suitability and characterization of pumice, bauxite, and ferrochrome slag as alternative raw materials in vitrified ceramic industry

Since the natural raw materials used in the manufacture of clay-based ceramic products vary greatly in the sintering stage, the resulting products are quite heterogeneous. In addition, different types of waste could be used to make ceramic tiles and bricks. Therefore, this study aimed to investigate the effects of pumice, bauxite, and ferrochrome slag on the vitrified ceramic body. In this context, firstly, binary slip mixtures were prepared by composing 40% clay with 60% pumice, bauxite, and ferrochrome slag one by one, which was reduced to 150 µm in particle size. Then, the mixtures were shaped by slip casting method and sintered at 1000°C, 1100°C, 1200°C, and 1250°C. The qualitative XRD analysis was performed in order to see the phase variation, and physical properties were determined with shrinkage and water adsorption measurements. Since pumice transformed into a glassy phase after sintering at 1100°C, an amorphous phase was observed in all samples produced with pumice. In addition, the mullite development occurred in clay-pumice body composition with the temperature increment. However, tridymite and cristobalite phases were analysed in clay bauxite and ferrochrome body compositions. The shrinkage and water adsorption values, which were high in the samples sintered at 1000°C, began to reduce from 1100°C to 1250°C significantly. In particular, water adsorption reached 0% in the clay-pumice system which was suitable for a fully vitrified-high density standard (ISO13006-10545/98). Besides, the brighter colour was reached in the clay-pumice system while brown and black colour was seen in clay-bauxite and clay-ferrochrome bodies, respectively.

Rheology and printability of alumina-toughened zirconia pastes for high-density strong parts via direct ink writing

Direct ink writing (DIW) is a promising additive manufacturing technique for fabricating structural ceramics, including alumina-toughened zirconia (ATZ), heavily reliant on the rheological properties of the paste. The rheological properties of aqueous ATZ pastes with 25 wt% Pluronic® F127 hydrogel and solid loadings of 28–44 vol% were investigated, complemented by characterization of the parts, including relative density and shrinkage measurements, to assess the printability. The 42 vol% paste was identified as most suitable for producing high-density parts with minimal shrinkage. A controlled drying process gradually decreased humidity from 90% to 30% while raising temperature from 25 to 60°C over 4 days to prevent drying defects. Mechanical testing showed DIW-printed high-density (97.2±2.2%) parts with a mean flexural strength of 670±270 MPa, Vickers hardness of 13.6±2.8 GPa, and fracture resistance of 4.4±0.2 MPa, highlighting the potential for DIW to create high-density ATZ ceramic parts with favorable mechanical properties.

Adaptable intelligent filters based on nanotextured nonwoven membranes containing water-insoluble hydrogels

The work demonstrates, for the first time, thermo-responsive, water-insoluble, hydrogel-based, nano-fibrous filter media comprised of copolymers of N-isopropylacrylamide (NIPAM) and methyl methacrylate formed by electrospinning. Moreover, a comprehensive novel physical explanation of all aspects responsible for the physical mechanisms resulting in the thermo-responsive regulation of the water flow rate and an enhanced interception of nanoparticles by such filter membranes is given. They are the wettable-non-wettable transition, pore, and fiber-size changes, as well as a diminishing filter thickness at the lower critical solution temperature (LCST) of the copolymers developed here, which interplay with a significant reduction in the water viscosity with temperature. Poly(N-isopropylacrylamide) (PNIPAM) hydrogel is an attractive material because of its thermo-responsive properties. Its wettability changes with water temperature. This characteristic holds great promise for the development of advanced filter media and related responsive materials. In this study, PNIPAM hydrogels were designed and transformed into filter membranes for applications in water filtration in biomedical and other related systems. These thermo-responsive filter membranes offer the potential for enhanced filtration efficiency, selectivity, and the overall system performance. Here, two different procedures were adopted to form water-insoluble thermo-responsive filter media based on PNIPAM hydrogels. The PNIPAM-based hydrogels were electrospun, resulting in the formation of thermo-responsive water-insoluble nanofiber membranes. These membranes underwent a series of comprehensive experiments to assess their performance and characteristics, including mass loss, water droplets for the wettability assessment, filtration tests, shrinkage measurements, and microscopic observations. These diverse experiments yield a full understanding of the PNIPAM-based nanofiber membranes’ properties and their potential applications.

Experimental Study of Physical Properties of Laminated Veneer Lumber Made by Three Cameroonian Hardwoods with Two Adhesives

This work deals with the determination of some properties of laminated veneer lumber (LVL) made from tropical hardwoods, specifically focusing on Cameroonian woods. The LVL samples are manufactured using veneer from three tropical wood species: Ayous, Ilomba, and Bete. Two types of adhesives are used: a neoprene contact adhesive (Magpow) and a white vinyl adhesive (Nemo). The specimens have undergone multiple drying cycles, and hundreds of samples from each species have been selected with dimensions of 1 cm × 1 cm × 1 cm. These samples are then machined according to the specific wood grain of each species. The experiments conducted aim to determine properties such as moisture content, densities, volume swelling, shrinkage coefficients, and the hygroscopic point of equilibrium of the samples. Swelling and shrinkage measurements allow for the visualization of sample dimensions in relation to humidity levels, and the hysteresis of the adsorption phenomenon of the LVL is also obtained. The results show that regardless of the type of adhesive or veneer used, LVLs are denser than the wood they are made from. For each type of LVL, the ratio between the mass of a sample saturated in water and the mass of the dried sample remains constant. The rule of mixture is investigated, and the density properties of materials and the vacuum rates of LVL samples are compared with experimental data.

Multi-objective optimization of mix proportions for mass concrete with enhanced resistance to cracking and reduced temperature rise

The objective of this study is to investigate the influence of fly ash (FA), granulated blast furnace slag (GBFS), and a high-efficiency crack-resistant agent (HECRA) on the workability, mechanical properties, hydration heat (HH), adiabatic temperature rise (ATR), and volume stability of mass concrete (MC). Preliminary experiments determined that the total replacement of FA and GBFS in dual blending should be within 35% to 40%, with the GBFS content not exceeding 15%. A total of 16 concrete mix designs (MD) were formulated, including a control mix (comprising only cement (C)) and ternary blends (comprising C, FA, and GBFS), with the HECRA added at 0%, 4%, and 8% of the mass of cementitious materials. The workability of the MC was assessed through tests for air content (AC), bulk density (BD), slump, flow, and setting time. The mechanical strength, HH, ATR, and shrinkage rate of the MC were individually evaluated through compressive strength (CS) tests, HH experiments, ATR tests, and shrinkage measurements. A grey relational evaluation model was employed to establish correlations between C, FA, GBFS, and the HECRA concerning overall performance. Supported by the entropy value method, a comprehensive performance evaluation model was created. The results indicate that, compared to the control mix, the other groups exhibited reductions in mechanical performance, rates of HH, cumulative ATR, and increased self-volume deformation (SVD). These findings suggest that including FA, GBFS, and a HECRA can mitigate the HH and SVD of MC, albeit at the expense of its strength. According to the comprehensive performance evaluation model, when the C-to-FA-to-GBFS ratio is 6:3:1, and the HECRA constitutes 8% of the mass of cementitious materials, the specimens demonstrate the best overall performance. At 28d, the CS is 48.46 MPa, satisfying the design strength requirements for C35 concrete. The comprehensive performance of the large volume crack-resistant concrete with low temperature rise (LCCT) produced in this study meets engineering needs. It provides theoretical references for the mixed design of MC.

Utilizing porcelain tile polishing residue in eco-efficient high-strength geopolymers with steel microfibers

Geopolymers are an alternative that produces low environmental impact binders with satisfactory mechanical properties. This research evaluated the influence of adding steel microfibers to a binary geopolymer matrix composed of metakaolin and ceramic tile polishing residue. Three mortar compositions (1:2, 1:3 and 1:4 cement:sand mass ratios) were produced with three microfiber concentrations (vf = 0.45, vf = 0.90 and vf = 1.35 % of total volume). The mechanical properties were evaluated by testing compressive strength, dynamic modulus of elasticity, flexural strength, and toughness. For 1:3 mortar, autogenous shrinkage measurements were performed for the 3 microfiber concentrations. Equivalent carbon dioxide emissions and binder intensity were also quantified. The mechanical properties classify the geopolymer concrete as high strength, achieving up to 95 MPa (composition 1:3) of compressive strength at 28 days and low binder consumption (9.82 kg.m−3. MPa−1). An improvement in flexural tensile strength was observed as the concentration of steel microfibers increased, reaching 20 MPa with vf= 1.35 %. For the concentration vf= 0.90 %, there was a reduction of ∼38 % of the autogenous shrinkage measurements about the reference (vf=0.0 %) at 28 days. In addition, regarding the CO2 intensity index, the lowest values were obtained for the 1:3 compositions, being minimum for vf= 0.90 % (9.01 [kg. ECO2-eq /m³ of mortar]/MPa), producing geopolymeric composites with low CO2 emissions, allowing the production of construction materials with low environmental impact.

Long-Term Shrinkage Measurements on Large-Scale Specimens Exposed to Real Environmental Conditions

This article presents an experimental testing campaign on large-scale concrete specimens with cross-sectional areas of up to 1 m2 and a specimen length of 3 m. The primary goal of the testing campaign was to study the shrinkage behaviour of large-scale specimens exposed to real environmental conditions. Large-scale prismatic concrete specimens were equipped with vibrating wire strain gauges to monitor the strain evolution inside the specimens. To analyse the shrinkage behaviour of the specimens, the thermal strain had to be deducted from the measured strain. To study the influence of seasonal environmental conditions, different specimen production dates (in summer and winter) were examined. The measured shrinkage strains of the large-scale specimens are compared with the results of shrinkage models developed by two engineering entities (fib (Fédération Internationale du Béton) and RILEM (International Union of Laboratories and Experts in Construction, Materials, Systems and Structures)). The comparison shows a poor agreement of the measurements with the models, even though the results from the model for small specimens tested in the laboratory under constant environmental condition agree well with the experimental results. This leads to the conclusion that the poor agreement between the measurements and the shrinkage models must be due to the seasonally changing environmental conditions. The comparison of the results from specimens with different production dates shows that different shrinkage behaviour occurs, especially in the first year of measurements.

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.

Hydration behavior and strength development of supersulfated cement prepared by calcined phosphogypsum and slaked lime

The effect of the content of calcined phosphogypsum (CPG) and slaked lime (SL) on the fluidity, setting time, and compressive strength of supersulfated cement (SSC) were investigated. The hydration mechanism of the SSC containing CPG and SL was examined through electrical resistivity, hydration heat, and chemical shrinkage measurements and thermodynamic modelling was performed to predict the phase assemblages. The results indicate that SSC with CPG delayed the early age hydration and prolongs its induction period. The effect of CPG on delaying hydration was apparent in SSC with 5 % SL. CPG in SSC promotes the formation of ettringite (AFt), while excess SL inhibits it. With the increase of CPG, massive gypsum is produced, leading to the rapid setting and a decrease in fluidity. Excess AFt contributes to expansion and cracking, resulting in a decrease in compressive strength. With the incorporation of SL, the pH value of the pore solution increases, which is beneficial to the stabilization of AFt, thereby increasing the compressive strength. The compressive strength of SSC containing 10 % CPG and 10 % SL reached up to 35.2 MPa after 180 d. The study reveals the mechanism of the effect of CPG and SL on SSC hydration and provides theoretical guidance for preparing SSC for engineering applications.

In-situ shrinkage measurement of alkali-activated materials using focused ion beam combined with environmental scanning electron microscopy

Drying shrinkage of alkali-activated slag (AAS) has gained significant attention since the volumetric instability of this material can generate premature cracking and degrade the long-term durability of concrete structures. The unique shrinkage behavior of AAS originates mainly from the particular characteristics of its main hydrated products. However, few studies have even at-tempted to investigate the shrinkage behavior of hydrated products in AAS materials. This paper presented a new method of investigating drying shrinkage behavior of AAS using focused ion beam (FIB) combined with environmental scanning electron microscopy (ESEM). This innovative experimental method allowed the in-situ measurement of phase-specific shrinkage. The results showed FIB/ESEM technique can be successfully implemented to cementitious material to prepare phase-specific samples. Furthermore, object-oriented finite element method (OOF2) has been utilized to compute the shrinkage behavior of AAS concrete using a proposed multi-scale scheme. The computations can be made at multi-scales which highlight the effect of hydration products on shrinkage behaviors. OOF2 calculation at the micro-length scale predicted an increase in the shrinkage due to the well-dispersed hydration products inside the matrix. At larger scale, the decrease in the overall shrinkage is related to the extremely low shrinkage value by aggregates. The findings reveal OOF2 offers the capability to accurately measure local stress and strain distribution within heterogeneous materials, a feature notably absent in conventional numerical homogenization approaches. The importance of this benefit is highlighted particularly in the context of free-restrained shrinkage prediction, as conventional homogenization methods fail to account for stress.