Long-term (2 years) drying shrinkage evaluation of alkali-activated slag mortar: Experiments and partial factor analysis

Wang, Shunfeng; Wu, Kai; Yang, Zhenghong; Tang, Luping

doi:10.1016/j.cscm.2023.e01956

Cited by 6 publications

(4 citation statements)

References 61 publications

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“…Samples using a 5% concentration of the activator (Figure 5a-c) had lower compressive strength values at all measurement days compared to samples with 10% concentration (Figure 5d-f), regardless of the type and replacement rate of silica sand. This is because the lower the concentration of the alkaline activator in AASC, the slower the slag activation reaction, which prolongs the setting time and reduces the production of hydration reactants [15,17,99,100].…”

Section: Compressive Strengthmentioning

confidence: 99%

“…In Figure 9, regardless of the type and replacement rate of silica sand, 10% NaOH + 10% Na 2 SiO 3 specimens show lower porosity than the 5% NaOH + 5% Na 2 SiO 3 specimen. This means that when the concentration of the activator is high in AASC, the hydration reaction of the slag is promoted, the amount of hydration reactant formation is improved, and a dense matrix is formed [17,99,100].…”

Section: Total Porositymentioning

confidence: 99%

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Investigation of the Effect of Blended Aggregate on the Strength and Drying Shrinkage Characteristics of Alkali-Activated Slag Mortar

Kang,

Park,

Kim

2024

Materials

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To reduce drying shrinkage of AASC mortar (AASM), mixed aggregate mixed with river sand (RS) and silica sand in three sizes was used to investigate the effect of the physical properties of mixed aggregate on shrinkage reduction. A mixture of river sand (0.2–0.8 mm), S1 (2.5–5.0 mm), S2 (1.6–2.5 mm), and S3 (1.21–160 mm) had river sand–silica sand mean diameter ratios (dr) of 7.68 (S1/RS), 3.75 (S2/RS), and 3.02 (S3/RS). The compressive strength and drying shrinkage characteristics of mixed aggregates according to fineness modulus, surface area, bulk density, and pore space were investigated. It had the highest bulk density and lowest porosity at a substitution ratio of 50%, but the highest strength was measured at a substitution ratio of 50% or less. High mechanical properties were shown when the fineness modulus of the mixed aggregate was in the range of 2.25–3.75 and the surface area was in the range of 2.25–4.25 m2/kg. As the substitution rate of silica sand increased, drying shrinkage decreased. In particular, the drying shrinkage of RS + S1 mixed aggregate mixed with S1 silica sand, which had the largest particle size, was the smallest. When silica sand or river sand was used alone, the drying shrinkage of the sample manufactured only with S1, which has the largest particle size of silica sand, was the smallest among all mixes. Compared to RS, at a 5% activator concentration, drying shrinkage was reduced by approximately 40% for S1, 27% for S2, and 19% for S3. At a 10% concentration, S1 showed a reduction effect of 39%, S2 by 28%, and S3 by 13%. As a result of this study, it was confirmed that the drying shrinkage of AASM could be reduced simply by controlling the physical properties of the aggregate mixed with two types of aggregate. This is believed to have a synergistic effect in reducing drying shrinkage when combined with various reduction methods published in previous studies on AASM shrinkage reduction. However, additional research is needed to analyze the correlation and influencing factors between the strength, pore structure, and drying shrinkage of AASM using mixed aggregate.

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Section: Compressive Strengthmentioning

confidence: 99%

Section: Total Porositymentioning

confidence: 99%

Investigation of the Effect of Blended Aggregate on the Strength and Drying Shrinkage Characteristics of Alkali-Activated Slag Mortar

Kang,

Park,

Kim

2024

Materials

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“…The widely recognized mechanism of DS is that when the water gradually evaporates, surface tension is generated when the menisci are formed in the gel pores and capillary pores, thereby causing an equal compressive stress in the skeleton and causing volume shrinkage 14 , 15 . Current research primarily focuses on reducing the DS of AAMs by incorporating fibers 16 – 18 , chemical admixtures 4 , 19 , and mineral admixtures 20 , 21 , as well as changing the curing system 22 – 24 . Changing the curing system, while effectively reducing shrinkage, may also lead to a decrease in mechanical properties and issues of unstable internal curing humidity 24 .…”

Section: Introductionmentioning

confidence: 99%

Effect of borax-modified activator on mechanical properties and drying shrinkage of alkali-activated slag/metakaolin mortar

Chen,

Qin,

Chen

et al. 2024

Sci Rep

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Alkali-activated materials (AAMs) possess several advantages, such as high strengths and low carbon emissions. However, their application is hindered due to their significant shrinkage. This study explored the effect of borax-modified sodium silicate activator and metakaolin (MK) on the mechanical properties and drying shrinkage (DS) of alkali-activated slag (AAS) and AAS/MK (AASM) mortars. X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy were used to characterize the hydration products. The results showed that the DS reduction of the AAS mortar was related to decreased Na2O content, a reduction in the proportion of mesopores, and the formation of moisture-retaining borate compounds. The DS reduction of the AASM mortar was attributed to the ultra-fine differential effect induced by MK, reducing the connected pores. The modified activator combined with MK increased the chemically bound water content in the matrix. Additionally, the B–O bond and highly active MK improved compactness of the AASM mortar. The use of borax-modified activators and MK provides a new solution to address the significant shrinkage issue in AAMs. This sets the stage for AAMs to potentially replace OPC, contributing to low-carbon emissions and promoting environmental protection.

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“…The widely recognized mechanism of DS is that when the water gradually evaporates, surface tension is generated when the menisci are formed in the gel pores and capillary pores, thereby causing an equal compressive stress in the skeleton and causing volume shrinkage 14,15 . Current research primarily focuses on reducing the DS of AAMs by incorporating bers [16][17][18] , chemical admixtures 4,19 , and mineral admixtures 20,21 , as well as changing the curing system [22][23][24] . Changing the curing system, while effectively reducing shrinkage, may also lead to a decrease in mechanical properties and issues of unstable internal curing humidity 24 .…”

Section: Introductionmentioning

confidence: 99%

Effect of borax-modified activator on mechanical properties and drying shrinkage of alkali-activated slag/metakaolin mortar

Chen,

Qin,

Chen

et al. 2024

Preprint

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Alkali-activated materials (AAMs) possess several advantages, such as high strengths and low carbon emissions. However, their application is hindered due to their significant shrinkage. This study explored the effect of borax-modified sodium silicate activator and metakaolin (MK) on the mechanical properties and drying shrinkage (DS) of alkali-activated slag (AAS) and AAS/MK (AASM) mortars. X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy were used to characterize the hydration products. The results show that the DS reduction of the AAS mortar is related to decreased Na2O content, a reduction in the proportion of mesopores, and the formation of moisture-retaining borate compounds. The DS reduction of the AASM mortar is attributed to the ultra-fine differential effect induced by MK, reducing the connected pores. The modified activator combined with MK increased the chemically bound water content in the matrix. Additionally, the B-O bond and highly active MK improved compactness of the AASM mortar.

show abstract

Long-term (2 years) drying shrinkage evaluation of alkali-activated slag mortar: Experiments and partial factor analysis

Cited by 6 publications

References 61 publications

Investigation of the Effect of Blended Aggregate on the Strength and Drying Shrinkage Characteristics of Alkali-Activated Slag Mortar

Investigation of the Effect of Blended Aggregate on the Strength and Drying Shrinkage Characteristics of Alkali-Activated Slag Mortar

Effect of borax-modified activator on mechanical properties and drying shrinkage of alkali-activated slag/metakaolin mortar

Effect of borax-modified activator on mechanical properties and drying shrinkage of alkali-activated slag/metakaolin mortar

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