Shrinkage Of Paste Research Articles

Chemical shrinkage, autogenous shrinkage, drying shrinkage, and expansion stability of interfacial transition zone material using alkali-treated banana fiber for concrete

ABSTRACT It might be of interest for authors to learn more that in the early 1900s, fibers were used in cement-based material, as cement-based materials exhibit shrinkage cracking over time, which can be controlled by adding fibers. The main aim of the inserting natural fiber into cement-based material is to decrease the shrinkage of cement-based material, prevent the rising of shrinkage cracks, and develop low-cracking cement-based material. In the research, the same aim aforementioned was kept same way. For carrying out the aim, agricultural waste, known as banana fiber (BF), can be considered a shrinkage reducer, expansion stabilization, a renewable material and has potential to make cement-based material transformed into a green construction material. This research investigated the effect of BF incorporation on cement paste shrinkage. Thus, five mixes were developed with different BF additions based on the total volume of cement paste (0, 0.5, 1, 1.5 and 2%). For each mixture, four tests were carried out to assess the impact of BF addition on the paste’s volume stability: chemical, autogenous, drying shrinkage and expansion. Testing was conducted for up to 90 days. Compared to the control mix, the addition of 2% BF reduced chemical shrinkage, autogenous shrinkage, drying shrinkage, and expansion by 27%, 57%, 47%, and 66%, respectively. Furthermore, a positive correlation was observed between chemical shrinkage and both autogenous and drying shrinkage and the percentage of BF content. Conversely, there was an inverse relationship between chemical shrinkage and expansion. The most significant conclusion to emerge from this study is that the incorporation of banana fiber (BF) into alkali-treated concrete results in a reduction in chemical shrinkage, autogenous shrinkage, drying shrinkage, and expansion. This is attributed to the molecular structure of BF, which is characterized by uninterrupted glycosidic linkages, leading to alkaline breakdown within the alkaline environment. Consequently, the alkali-treated BF can be described as a volume stability admixture in concrete technology.

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.

Improvement on engineering properties and volumetric stability of alkali-activated slag-based composite cementitious material with rice husk ash and magnesium oxide

This study used rice husk ash (RHA) and magnesium oxide (MgO) to improve the engineering properties and volumetric stability of alkali-activated slag-based cementitious material. Experimental results found that when the amount of slag substituted by RHA increased from 0% to 20%, the initial setting time was extended from 15 to 20 min, and the final setting time was shortened from 35 to 30 min for the paste without MgO. The optimal substitution amount of RHA was 10%, which had the maximum compressive strengths at ages of 28 and 56 days to achieve 104.44 and 102.43 MPa for the paste without MgO, respectively. The drying shrinkage of paste without MgO increased with both the increase of RHA from 0% to 20% and ages from 3 to 56 days. With RHA, the drying shrinkage substantially decreased with the substitutions of MgO from 0% to 2.0% and almost remained steady after ages of 7 or 14 days. The optimal amount of RHA to replace slag was less than 10% and the optimal content of MgO was less than 1%, which can effectively improve the volumetric stability and reduce the heat of hydration of paste.

Investigating volume stability Performance of paste with Phragmites Australis (PA) Fibers

Environmental sustainability is a critical concern in the construction industry due to its substantial energy consumption and carbon dioxide emissions. This study addresses the sustainability of building materials by exploring the volume stability of cementitious system by adding natural fibers, specifically those derived from the Phragmites Australis (PA) plant. Natural fibers exhibit high strength and stiffness, making them suitable for structural applications. In this experimental study, four paste mixes were prepared, incorporating varying percentages (0%, 0.5%, 1%, and 2%) of PA fibers. Testing included drying shrinkage, autogenous shrinkage, and expansion. Results showed a notable reduction in paste shrinkage, with percentages of 12.7%, 19%, and 29% observed at 7 days with the addition of 0.5%, 1%, and 2% PA fibers, respectively, at an elevated temperature of 45°C. These findings suggest the potential for PA fibers to mitigate shrinkage in building materials, thus contributing to the overall environmental sustainability of construction practices.

Study on the mitigation of drying shrinkage and crack of limestone powder cement paste and its mechanism

To investigate the reasons for the mitigation of drying shrinkage but earlier cracking in limestone powder cement paste, various admixtures such as fly ash, metakaolin, super-absorbent polymer, and expansion agent were selected for the above-mentioned experiments. The effects of mixing two admixtures on the drying shrinkage deformation and crack resistance performance of the limestone powder-cement paste was studied. Additionally, hydration exotherm, hydration products, microscopic morphology of samples were analyzed to understand the underlying mechanisms. Based on the hydration process, the addition of fly ash and metakaolin can promote the formation of carbon aluminate in the reaction system, thereby reducing the porosity. Fly ash is more beneficial for the hydration heat peak value of cement paste, effectively eliminating temperature strain. The results indicate that effects of mixing two admixtures on the improvement of drying shrinkage and crack resistance of limestone powder cement paste are much better than using a single admixture. Among them, the combination of metakaolin and expansion agent shows the best overall mitigating effect on the drying shrinkage and crack resistance of limestone powder cement paste. This compound admixtures reduces the drying shrinkage of the paste by approximately 30% and delays the cracking time of the specimens by 34.4 h.

Shrinkage performance and modelling of concretes incorporating crushed limestone sand with a high content of fillers for pavement slabs

Because of the gradual depletion of gravel and river sand resources and restrictions on quarrying activities to maintain the ecological balance, limestone crushed sand with a high content of limestone fillers is being explored to be used, as an alternative source of supply, in Portland cement concrete (PCC) for rigid pavement. This paper aims to first present mechanical test results carried out on three types of PCC formulated with crushed limestone sand as fine aggregates, devoid of superplasticizers. Since shrinkage cracking is an important problem for rigid pavement, the shrinkage behaviour of these concretes is then experimentally investigated. Furthermore, three existing models (ACI-209, Eurocode2, and triple-sphere models) and a novel-developed model are used to estimate the mixtures’ shrinkage. Results showed that the designed mixtures exhibited normal shrinkage values. The shrinkage modelling revealed that the proposed model well fitted the experimental data. Besides, Eurocode2 and ACI-209 models may be adapted for the case of limestone concretes containing a high content of limestone fillers and then used to accurately estimate their shrinkage strains. However, the triple-sphere model was unsuitable for these concretes and overestimated their ultimate shrinkage since it does not take into account their high filler content. Nevertheless, by adjusting the paste shrinkage expression, the ultimate shrinkage strain values of the tested mixtures were improved.

Benchmarking Standard and Micromechanical Models for Creep and Shrinkage of Concrete Relevant for Nuclear Power Plants.

The creep and shrinkage of concrete play important roles for many nuclear power plant (NPP) and engineering structures. This paper benchmarks the standard and micromechanical models using a revamped and appended Northwestern University database of laboratory creep and shrinkage data with 4663 data sets. The benchmarking takes into account relevant concretes and conditions for NPPs using 781 plausible data sets and 1417 problematic data sets, which cover together 47% of the experimental data sets in the database. The B3, B4, and EC2 models were compared using the coefficient of variation of error (CoV) adjusted for the same significance for short-term and long-term measurements. The B4 model shows the lowest variations for autogenous shrinkage and basic and total creep, while the EC2 model performs slightly better for drying and total shrinkage. In addition, confidence levels at 5, 10, 90, and 95% are quantified in every decade. Two micromechanical models, Vi(CA)2T and SCK CEN, use continuum micromechanics for the mean field homogenization and thermodynamics of the water-pore structure interaction. Validations are carried out for the 28-day Young's modulus of concrete, basic creep compliance, and drying shrinkage of paste and concrete. The Vi(CA)2T model is the second best model for the 28-day Young's modulus and the basic creep problematic data sets. The SCK CEN micromechanical model provides good prediction for drying shrinkage.

Role of limestone powder in alkali-activated slag paste with superabsorbent polymer

Superabsorbent polymer (SAP) has been commonly used to mitigate the shrinkage of alkali-activated slag (AAS) pastes through internal curing. However, the effectiveness of internal curing might be affected by the microstructure of the pastes. Therefore, the effects of incorporating limestone powder (LP) on the microstructure and shrinkage of AAS pastes containing SAP are studied. The results reveal that incorporating LP mitigates the autogenous shrinkage of the pastes with SAP. This is because the incorporation of LP reduces the fraction of mesopores in the pastes containing SAP, while adding SAP maintains the internal relative humidity and increases the size of minimum pores that can drive autogenous shrinkage. In contrast, adding LP tends to enhance the driving force of autogenous shrinkage in the pastes without SAP due to the conversion of mesopores to gel pores. Furthermore, incorporating LP simultaneously enhances the reaction and generates more macropores in the pastes, causing a negligible influence on their mechanical properties and an increase of drying shrinkage. Overall, incorporating LP promotes the internal curing effectiveness in decreasing the autogenous shrinkage of the pastes.

Effects of construction waste powder on micro–macro properties of green high-strength cement paste with low water-to-binder ratio

The replacement of cement with ground construction waste powder is considered a sustainable strategy for the production of high-strength cement-based materials. This study investigated the influences of construction waste powder types and replacements on the micro–macro characterizations of green high-strength cement paste with low water-to-binder (w/b) ratio. The results highlighted that paste with 0.2 w/b ratio contained abundant hydration products and un-hydrated cement, and construction waste powder exerted good nucleation sites and filling effects in paste. The mix of construction waste powder did not change the hydration product types but reduced calcium hydroxide content in paste. Mixing appropriate ground brick powder up to 50% declined paste drying shrinkage, but the paste drying shrinkage continuously increased as ground paste/mortar/concrete powder content increases. The maximum drying shrinkage of paste with 50% ground brick powder and 50% ground concrete powder was 3.3% lower and 32.4% higher than the plain paste. When ground brick powder content was below 50% or ground paste/mortar/concrete powder content was below 30%, construction waste powder blended paste had similar or better compressive strength than plain paste, but incorporating 70% construction waste powder reduced the paste compressive strength. When construction waste powder content was identical, ground brick powder blended paste had higher compressive strength than paste containing ground paste/mortar/concrete powder. Incorporating appropriate dosage of ground brick powder reduced the transport properties and total porosity of paste, whereas the transport properties and total porosity both increased with ground paste/mortar/concrete powder incorporation. Optimizing construction waste powder types and contents can prepare green paste owning high-strength and low transport properties.

Preliminarily evaluation of poly (AA-co-AMPS) on the properties of sulphoaluminate cement

• Comparing the effect of structural parameters on the rheology and hydration of SAC. • Stronger effect of degree of polymerization on its properties. • Long-term strength reduction of SAC caused by poly (AA- co -AMPS). • Changes in hydration rates leading the paste shrinkage and strength reduction. The previous article reported the effect of poly (AA- co -AMPS) on the rheology of sulphoaluminate cement (SAC), but the effect of structural parameters of the copolymer on the properties, especially the mechanical properties, would decide the value for SAC as a superplasticizer. To further evaluate their effect on SAC, a series of copolymers were synthesized, and their effects on the rheology, hydration, and mechanical properties were tested. Copolymers could control the fluidity and the setting as reported, but the degree of polymerization would be a stronger factor than the ratio of carboxyl to sulfonyl groups. Meanwhile, flocculation structure destruction and particle dispersion are the main reasons for rheology properties changing, while inhibiting the formation of AFt would significantly retard the hydration. However, the polycarboxylic acid segments in this copolymer might cause or enhance the inherent shrinkage of SAC leading to the compressive strength of 28 d decreasing.

Effect of limestone in General Purpose cement on autogenous shrinkage of high strength GGBFS concrete and pastes

This work investigates the autogenous shrinkage of pastes and concretes prepared using General Purpose cement and GGBFS (40% and 60%) up to 100 days. To determine the underlying factors influencing autogenous shrinkage, hydration progression and evolution of microstructure were investigated. Results showed that autogenous shrinkage of GGBFS blends continuously increased after 28 days (until 100 days) whereas the control samples reached a plateau after about 28 days. Late reaction between limestone from the General Purpose cement and alumina from GGBFS progressed untill 90 days forming a high amount of monocarboaluminates. General Purpose cement blends with high GGBFS content can behave as ternary blends and not as binary blends due to the small amount of limestone usually added to General Purpose cements. These long term reactions lead to a significant refinement of the pore structure which is responsible of the late autogenous shrinkage in GGBFS blends.

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.

Effect of using limestone fines on the chemical shrinkage of pastes and mortars.

The main aim of this study is to examine the effect of incorporating limestone fine (LF) on chemical shrinkage of pastes and mortars. For this purpose, five paste and five mortar mixes were prepared with 0, 5, 10, 15, and 20% (by weight) LF as a replacement of cement. The water-to-binder (w/b) ratio was 0.45 for all mixes. The sand-to-binder (s/b) ratio in the mortar mixes was 2. Testing included chemical shrinkage, compressive strength, density, and ultrasonic pulse velocity (UPV). Chemical shrinkage was tested each hour for the first 24h, and thereafter each 2days until a total period of 90days. Furthermore, compressive strength and UPV tests were conducted at 1 day, 7, 28, and 90 days of curing. The results show that the long-term chemical shrinkage of pastes was found to increase with the increase in LF content up to 15%. Beyond this level of replacement, the chemical shrinkage started to decrease. However, the chemical shrinkage for mortars increased with the increase in LF content up to 10% LF and a decrease was observed beyond this level. It was also noticed that compressive strength for pastes and mortars attained the highest value for mixes containing 10 and 15% LF. The trend in the UPV results is somewhat similar to those of strength. Density for pastes and mortars increased up to 15% LF followed by a decrease at 20% replacement level. Correlations between the various properties were conducted. It was found that an increase in chemical shrinkage led to an increase in compressive strength.

Chemical shrinkage of paste and mortar containing limestone fines

The effect of including limestone fine (LF) on the chemical shrinkage of cement paste and mortar is investigated. The cement was partially replaced with 0 to 20% (by weight) with LF. The water to cementitious material (CM) ratio was maintained at 0.45. In the mortar mixes, the proportion of sand (S) to CM was 1:2. In addition to the chemical shrinkage test, compressive strength and density of specimens were determined. The chemical shrinkage data were collected up to 28 days. However, for compressive strength and density, testing continued up to 90 days of water curing. There appears to be an increase in chemical shrinkage between 10 and 15% limestone for both paste and mortar mixes. The trend appears to be similar for the compressive and density results.

Early‐age behavior and mechanical properties of cement‐based materials with various types and fineness of recycled powder

AbstractRecycled powder (RP) that includes recycled paste powder (RPP), recycled mortar powder (RMP), and recycled concrete powder (RCP) is an eco‐friendly alternative binder. This work investigated the influence of RP types and fineness on early‐age behavior and mechanical strength of cement‐based materials. The results show that substituting RP for cement causes the reduction of new hydration products in cement‐based materials. The blended RP decreases the fluidity of paste mixture, and the fluidity of paste including fine RPP is lower than that of paste including fine RMP and RCP; moreover, the fluidity increases following the growth of RP particle size. Incorporating fine RPP shortens the setting time of cement‐based materials, while the setting time is prolonged as RMP and RCP incorporate; in addition, the enlarged particle size of RP prolongs the setting time. The drying shrinkage increases following the increasing replacement ratio of RPP. Incorporating less proportion of fine RMP and RCP lessens the drying shrinkage of paste, while the drying shrinkage increases after coarse or high‐volume RMP and RCP substituting. The maximum shrinkage of paste including 30% fine and coarse RCP is 3.4% and 7.3% higher than that of plain paste. Substituting fine RP for less dosage of cement has less impact on the mechanical strength of its newmade mortar, while the mechanical strength markedly decreases after high‐volume or coarse RP substituting. The compression strength of mortar including 30% fine and coarse RCP is 22.2% and 35.1% lower than that of plain mortar.

Shrinkage compensation design and mechanism of geopolymer pastes

Geopolymers (GI) possess excellent seawater erosion resistance because of stable hydration products and compact microstructures, and therefore, they have broad application prospects in marine engineering if their large volume shrinkage behavior can be mitigated. In this study, active MgO was used to compensate for different GI shrinkage stages and a scheme was proposed for staged compensation. Autogenous shrinkage was controlled by adjusting the content, activity, and combinations of active MgO with particle sizes of 1–100 µm. Based on the effects of MgO on shrinkage, GI paste composition and microstructure, the GI reaction process and mechanism of MgO-compensated volume shrinkage were examined and summarized. The results showed that the GI paste shrinkage decreased with MgO addition, and the higher the MgO activity, the smaller was the paste shrinkage in the early stages of hardening. Late-stage shrinkage of hardened paste was improved with the addition of low-activity MgO. Combining low and high activity MgO addition effectively ameliorated the paste hardening shrinkage at different stages. In the high-alkalinity environment of the liquid-phase GI reaction, the Mg(OH)2 product presented microcrystalline structures, and it was dispersed in the cement matrix, which resulted in uniform volume expansion. Meanwhile, other reaction products containing magnesium were produced, filling pores in the hardened paste and effectively compensating for volume shrinkage during the hardening process. Based on the effects of MgO on the composition structure, reaction process, and volume shrinkage performance of GI slurries, this study proposes a mechanism for MgO to compensate for the volume shrinkage of GI.

Effect of nano-silica on chemical and volume shrinkage of cement-based composites

Nano-materials modified cement-based materials have attracted wide attention due to their advantages of improving early strength and durability. However, few studies have been conducted on influence of nano-materials on chemical shrinkage of paste and volume shrinkage of concrete. Therein, the influence rules of nano-silica on chemical shrinkage of paste and volume shrinkage of concrete and its action mechanism have been explored and discussed. The result indicated that added nano-silica aggravated the chemical shrinkage of paste and volume shrinkage of the concrete. The paste chemical shrinkage and concrete volume shrinkage increased with the amount of nano-silica in particular as presented in early stage. The chemical shrinkage of cement at 3d and 28d increased by 93.7% and 57.5% respectively, when adding 1.2% nano-silica. Correspondingly, the 1d, 7d and 60d volume shrinkage of concrete increased by 82.1%, 66.7% and 16.7% respectively. The action mechanism of shrinkage intensification is mainly the pozzolanic effect, nucleation effect and acceleration hydration effect of nano-silica, which accelerated the cement hydration.

Mechanisms behind radiation-induced deterioration of concrete

This paper describes the mechanism of radiation-induced deterioration of concrete and its components based on the literature review. The deterioration mechanism in different levels starting from the interaction between neutron and nucleus through the mineral metamictization and cement paste shrinkage up to the reduction of mechanical properties of concrete is explained in detail. All basic dependencies and patterns of volumetric change of minerals, aggregates, cement paste and finally concrete are also described in order to create a base for the future development of numerical models. Finally, the reduction of concrete mechanical properties is in correlation with its volumetric expansion. The radiation-induced volumetric expansion of concrete is affected by irradiation conditions (neutron fluence, neutron spectrum and temperature) and concrete composition (the amount, the proportion, the type and the structure of the minerals in the aggregate composition and the amount, the composition, the age and the structure of the cement paste).

Influence of concrete additives on cement paste shrinkage

The paper deals with the analysis of the effect of chosen latent hydraulic additives on concrete drying shrinkage. Variant dosage of latent hydraulic additives in cement paste was examined. Measuring of shrinkage in time was accompanied by testing of compressive strength and tensile strength at the age 28 days and 280 days. Results of investigations are summarized and compared.

Mechanical properties, microstructure and drying shrinkage of hybrid fly ash-basalt fiber geopolymer paste

This paper evaluates the mechanical properties, microstructure and drying shrinkage of hybrid fly ash-basalt fiber geopolymer paste. Fly ash was replaced with basalt fiber at the replacement levels of 0, 10, 20, 30, 40 and 100%. Na2SiO3/NaOH ratio of 1.0 and liquid to binder (L/B) ratio of 0.60 were used for making geopolymer pastes. Setting time, strength and drying shrinkage of geopolymer pastes were tested. The results showed that the replacement of fly ash with basalt fibers in geopolymer pastes resulted in increased setting times and strength and reduced drying shrinkage of paste. The basalt fiber acted as small reinforcing fibers and enhanced the development of CSH, CASH and NASH which further enhanced the properties of paste. In addition, the total porosity and critical pore size of fly ash geopolymer paste reduce with increasing replacement content in fly ash which makes the paste more homogeneous and dense compared to fly ash geopolymer.