Deformation of Alkali-Activated Materials at an Early Age Under Different Curing Conditions

The production of alkali-activated materials (AAMs) is known for its environmentally friendly processing method, where several amorphous-rich aluminosilicate material sources combine with an alkali media solution to form solid, ceramic-like materials. In terms of the Si:Al, Na(K):Al, and Na(K):H2O ratios, the theory of AAM formation is quite well developed, but some open questions in the technology process remain, especially with regards to the means of curing, where the generation of defects can be persistent. Knowing that deformation is extremely high in the early ages, this study investigates the effects of temperature and moisture on shrinkage behavior within the first 72 h of AA pastes made from ladle (LS) and electric arc furnace (EAF) slag and activated by sodium silicate (Na2SiO3). The method to determine the deformation of alkali-activated slag-based materials, in terms of both autogenous and drying shrinkage, was based on the modified ASTM C1698-19 standard for the measurement of autogenous shrinkage in cement pastes. Autogenous deformation and strain were measured in four samples, using the standard procedure at room temperature, 40 and 60°C. Furthermore, using an adjusted method, nine samples were characterized for strain and partial surface pressure, while drying at room temperature, 40, or 60°C at a relative humidity of 30 or 90%. The results show that the highest rate of autogenous shrinkage occurred at a temperature of 60°C, followed by drying shrinkage at 60°C and 30% relative humidity, owing to the fact that the rate of evaporation was highest at this moisture content. The study aimed to provide guidance regarding selection of the optimal curing set in order to minimize deformations in slag-based alkali-activated materials. In the present case, curing at a temperature of around 40°C under lower moisture conditions for the first 24 h provided optimal mechanical properties for the slags investigated. The methodology might also be of use for other aluminosilicate sources such as metakaolin, fly ash, and mineral wool–based alkali-activated materials.

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Synthesis of a New Polycarboxylate at Room Temperature and Its Influence on the Properties of Cement Pastes with Different Supplementary Cementitious Materials

Advances in Civil Engineering ◽

10.1155/2020/8854422 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Shuncheng Xiang ◽

Yingli Gao ◽

Caijun Shi

Keyword(s):

Room Temperature ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Cementitious Materials ◽

Heat Evolution ◽

Hydration Heat ◽

Supplementary Cementitious Materials ◽

Cement Pastes ◽

Binder Ratio ◽

Water Binder Ratio

Three polycarboxylates with different comb structures (i.e., the same degree of polymerization in side chains but different main chains) were synthesized via radical polymerization reaction at room temperature. The effect of polycarboxylates on the surface tension and the flowability in cement pastes was determined. The best product was selected to study its effects on the hydration heat evolution, compressive strength, autogenous shrinkage, and drying shrinkage of cement pastes with different kinds and contents of supplementary cementitious materials. The results showed that with the increase of molar ratio between AA and TPEG to 6 : 1, we could synthesis the best product. When the water-binder ratio was 0.4, with the increase of polycarboxylates, the cement hydration heat evolution had been slowed down, and the more the dosage was, the more obvious the effect was. Adding supplementary cementitious materials to cement under the same experimental conditions also played a mitigation role in slowing down the hydration heat. When the water-binder ratio was 0.3, supplementary cementitious materials could increase the strength of cement by 24.5% in maximum; its autogenous shrinkage and drying shrinkage could be decreased, respectively, by 60.1% and 21.9% in the lowest.

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Shrinkage Behavior of Alkali-Activated Slag Cement Pastes

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.761.45 ◽

2018 ◽

Vol 761 ◽

pp. 45-48 ◽

Cited By ~ 10

Author(s):

Vladyslav Omelchuk ◽

Guang Ye ◽

Rayisa Runova ◽

Igor I. Rudenko

Keyword(s):

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Chemical Shrinkage ◽

Slag Cement ◽

Cement Pastes ◽

Alkali Activated Slag ◽

Activated Slag ◽

Mineral Additives ◽

Alkali Activated ◽

Shrinkage Behavior

Nowadays, alkali-activated cements (AACs) are the most promising alternatives to ordinary portland cement (OPC). Such cements characterized by better strength and corrosion resistance that determine improved durability of materials based on them. However, the shrinkage of AAC systems is noticeably higher compared with OPC. The purpose of this work was to study the shrinkage behavior of alkali-activated slag cement (AASC) pastes. To improve early age performance of AASCs – OPC and Ca(OH)2, as mineral additives, were added to the designed cement mixtures. The properties, like, flexural and compressive strength of cement mortars, chemical shrinkage, autogenous shrinkage and drying shrinkage of cement pastes were studied. The results showed that the chemical shrinkage, autogenous shrinkage and drying shrinkage at 28 days were between 0.064 – 0.074 ml/g, 4.5 – 7.9 mm/m and 3.3 – 4.9 mm/m, respectively. The relationship between the nature of alkaline components, the type of mineral additives and the shrinkage behavior of cements were discussed.

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The Modeling Research on the Early-Age Shrinkage of UHPFRC in Different Curing Conditions

Advances in Civil Engineering ◽

10.1155/2018/9291725 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8

Author(s):

Song Han ◽

Yazhou Liu ◽

Dan Liu ◽

Mingzhe An ◽

Ziruo Yu

Keyword(s):

Relative Humidity ◽

Pore Structure ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Calculation Model ◽

Fiber Reinforced Concrete ◽

Early Age ◽

Chemical Shrinkage ◽

Hydration Degree ◽

Curing Conditions

The early-age shrinkage of ultra-high performance fiber reinforced concrete (UHPFRC) in dry, sealed, and soaked curing was systematically measured. The calculation model of early-age shrinkage was established based on the theory of shrinkage of cementitious materials. According to the results of the relative humidity, hydration degree, pore structure, and elastic modulus of hardened slurry, the shrinkage calculation model in different curing conditions was calibrated. The results show that the early-age shrinkage of UHPFRC can be divided into three parts: chemical shrinkage, autogenous shrinkage caused by self-drying, and drying shrinkage caused by external drying. Based on the degree of hydration, the chemical shrinkage model was established. Based on the pore structure, the hydration degree, and the relative humidity of hardened slurry, the autogenous shrinkage model was established by introducing the effective pore coefficient. The drying shrinkage model was established based on the internal humidity. According to the shrinkage of soaked samples, the calculated value of chemical shrinkage in sealed and drying conditions was calibrated. This research provides theoretical support for the structural design and engineering application of UHPFRC.

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Drying shrinkage of alkali activated binders cured at room temperature

Construction and Building Materials ◽

10.1016/j.conbuildmat.2018.12.223 ◽

2019 ◽

Vol 201 ◽

pp. 563-570 ◽

Cited By ~ 14

Author(s):

Faris Matalkah ◽

Talal Salem ◽

Mamoon Shaafaey ◽

Parviz Soroushian

Keyword(s):

Room Temperature ◽

Drying Shrinkage ◽

Alkali Activated Binders ◽

Alkali Activated

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Mitigating the Drying Shrinkage and Autogenous Shrinkage of Alkali-Activated Slag by NaAlO2

Materials ◽

10.3390/ma13163499 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3499

Author(s):

Bin Chen ◽

Jun Wang ◽

Jinyou Zhao

Keyword(s):

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Nitrogen Adsorption ◽

Partial Substitution ◽

Hydration Reaction ◽

X Ray Diffraction ◽

Na2o Content ◽

Alkali Activated Slag ◽

Activated Slag ◽

Alkali Activated

The shrinkage of alkali-activated slag (AAS) is obviously higher than ordinary Portland cement, which limited its application in engineering. In this study, the effects of NaAlO2 in mitigating drying shrinkage and autogenous shrinkage of AAS were studied. To further understand the shrinkage mechanism, the hydration products and microstructures were studied by X-ray diffraction, scanning electron microscopy and nitrogen adsorption approaches. As the partial substitution rate of NaAlO2 for Na2SiO3 increased, the drying shrinkage and autogenous shrinkage reduced significantly. The addition of NaAlO2 could slow down the rate of hydration reaction and reduce the porosity, change the pore diameter and the composition of generated paste and cause more hydrotalcite and tetranatrolite generated—which contributed to reduced shrinkage. Additionally, raising the Na2O content rate caused obvious differences in drying shrinkage and autogenous shrinkage. As the Na2O content elevated, the drying shrinkage decreased and autogenous shrinkage increased. A high Na2O content would cause complete hydration reactions and provoke high autogenous shrinkage. However, incomplete hydration reactions left more water in the paste, and the evaporated water dramatically influenced drying shrinkage. The results indicate that addition of NaAlO2 could greatly mitigate the drying shrinkage and autogenous shrinkage of AAS.

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Autogenous Shrinkage, Strength, and Hydration Heat of Ultra-High-Strength Paste Incorporating Nano-Zirconium Dioxide

Sustainability ◽

10.3390/su12229372 ◽

2020 ◽

Vol 12 (22) ◽

pp. 9372

Author(s):

Guang-Zhu Zhang ◽

Han-Seung Lee ◽

Xiao-Yong Wang

Keyword(s):

Relative Humidity ◽

Room Temperature ◽

Autogenous Shrinkage ◽

High Strength ◽

Hydration Heat ◽

Experimental Device ◽

Hydration Reaction ◽

Hydration Products ◽

Internal Relative Humidity ◽

Two Stages

Ultra-high-strength paste (UHSP) combined with nanomaterials has been extensively studied. However, the research on nano-ZrO2 is limited. In this study, UHSP with various nano-ZrO2 contents is analyzed. The motivation of this study is to clarify the effects of nano-ZrO2 on the hydration products, strength, autogenous shrinkage, and hydration heat of UHSPs. The water-to-binder ratio (w/b) of the specimens is 0.2. The nano-ZrO2 content is 0, 1.5, and 3 wt.%. The strength is measured at the age of 3, 7, and 28 days. The hydration heat is measured from the mixing stage to 3 days. The hydration products are analyzed by X-ray diffraction (XRD) and thermogravimetric analysis (TG). The autogenous shrinkage is measured from the mixing stage for 7 days using a new experimental device. The new experimental device can measure autogenous shrinkage, internal relative humidity, and internal temperature simultaneously. The following conclusions can be drawn based on the experimental studies: (1) Two stages were noticed in the autogenous shrinkage of UHSPs: a variable-temperature stage and a room-temperature stage. The cut-off point of these two stages occurred in roughly 1.5 days. Furthermore, in the room-temperature stage, there was a straight-line relationship between the autogenous shrinkage and internal relative humidity. (2) With the increase of the nano-ZrO2 amount, the compressive strength at 3 days, 7 days, and 4 weeks increased. (3) With the nano-ZrO2 increasing, the flow decreased. (4) With the nano-ZrO2 increasing, the hydration heat increased due to the physical nucleation effect of the nano-ZrO2. Furthermore, the nano-ZrO2 used in this study was chemically inert and did not take part in the cement hydration reaction based on the XRD, differential thermal, and TG data. This paper is of great significance for the development of high-strength cementitious materials doped with nano-ZrO2.

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Alkali-Activated Fly Ashes: Influence of Curing Conditions on Mechanical Strength

U Porto Journal of Engineering ◽

10.24840/2183-6493_003.002_0006 ◽

2018 ◽

Vol 3 (2) ◽

pp. 57-67

Author(s):

Filipe Almeida ◽

Nuno Cristelo ◽

Tiago Miranda ◽

Castorina S. Vieira ◽

Maria De Lurdes Lopes ◽

...

Keyword(s):

Compressive Strength ◽

Relative Humidity ◽

Mechanical Strength ◽

Research Groups ◽

Fly Ashes ◽

Curing Conditions ◽

Alkaline Activation ◽

Strength Tests ◽

Higher Temperature ◽

Alkali Activated

Alkaline activation of fly ashes is a procedure that enables an alternative binder which has been receiving much interest by several research groups particularly on the manufacturing of mortars and concretes. The properties of the materials that are developed during the alkaline activation are influenced by the curing conditions (temperature and relative humidity). Another relevant facet related to the curing procedures is the possibility of carbonation occur, which may have an impact on the mechanical strength of the alkaline cements. In this research, several sets of curing conditions were tested to understand which one results in a higher strength and reveals carbonation. Uniaxial compressive strength tests were conducted to assess mechanical behavior. The outcome suggests that higher temperature and low relative humidity yields higher mechanical strength.

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Novel Alkali-Activated Materials with Photocatalytic and Bactericidal Properties Based on Ceramic Tile Waste

Coatings ◽

10.3390/coatings12010035 ◽

2021 ◽

Vol 12 (1) ◽

pp. 35

Author(s):

Ashley Bonilla ◽

Mónica A. Villaquirán-Caicedo ◽

Ruby Mejía de Gutiérrez

Keyword(s):

Pseudomonas Aeruginosa ◽

Photocatalytic Activity ◽

Klebsiella Pneumoniae ◽

Room Temperature ◽

Bacterial Strains ◽

Cement Pastes ◽

Molar Ratios ◽

Bactericidal Properties ◽

Mechanical And Physical Properties ◽

Alkali Activated

Ceramics tile wastes (CWs) were mechanically conditioned for the preparation of alkali-activated hybrid-cements from CW (90 wt.%) and Portland cement (10 wt.%) mixtures using sodium silicate (SS) + NaOH as alkaline activators. Molar ratios of SiO2/Al2O3 (6.3 to 7.7) and Na2O/SiO2 (0.07 to 0.16) were used. The cements were prepared at room temperature (25 °C) and characterized by mechanical and physical properties and microstructure. The optimized cement was used for the preparation of novel photoactivated composite materials by incorporating 5 and 10 wt.% TiO2 (Ti) and ZnO (Z) nanoparticles, and its self-cleaning and bactericidal properties were evaluated by means of the degradation of rhodamine-B (Rh-B) and the growth inhibition of Klebsiella pneumoniae and Pseudomonas aeruginosa bacteria. The results of this study showed that the 100SS-5Z and 50SS:50G-10Ti cements have an effective photocatalytic activity for Rh-B degradation of 98.4% and 76.4%, respectively, after 24 h. Additionally, the 100SS-5Z and 50SS:50G-10Ti cement pastes and their respective mortars were effective in inhibiting the growth of Pseudomonas Aeruginosa and Klebsiella pneumoniae bacterial strains, evidenced by the formation of bacterial inhibition halos around the sample discs. Finally, these results are novel, and open the possibility of using constructions and demolition tile waste in high proportions for the elaboration of new rendering mortar with innovative properties.

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Effect of Steel Slag on Shrinkage Characteristics of Calcium Sulfoaluminate Cement

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1036.263 ◽

2021 ◽

Vol 1036 ◽

pp. 263-276

Author(s):

Hao Ran Huang ◽

Yi Shun Liao ◽

Siraj Ai Qunaynah ◽

Guo Xi Jiang ◽

Da Wei Guo ◽

...

Keyword(s):

Compressive Strength ◽

Relative Humidity ◽

Cement Paste ◽

Steel Slag ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Chemical Shrinkage ◽

Calcium Sulfoaluminate Cement ◽

Calcium Sulfoaluminate ◽

Slag Content

The effects of steel slag with 0, 10%, 20 % and 40% content on the chemical shrinkage, autogenous shrinkage, internal relative humidity, and drying shrinkage of calcium sulfoaluminate cement paste were studied. The results show that the compressive strength of calcium sulfoaluminate cement paste at an early stage decreases gradually when the content of steel slag increases. When the steel slag content is 0 and 10%, the compressive strength of hardened cement pastes gradually decreases at 90 and 180 days, but the samples with steel slag content of 20% and 40% maintain the compressive strength growth within 180 d. With the extension of curing period, the gap of compressive strength is gradually narrowed. The autogenous shrinkage decreases with the increase of steel slag content and has a good linear relationship with the relative humidity inside the paste. The proportion of autogenous shrinkage to chemical shrinkage is deficient, and most chemical shrinkage occurs in the form of the pore volume. Although the trends of drying shrinkage and autogenous are consistent, the former is more severe than the latter.

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Effect of Nano-Silica on the Autogenous Shrinkage, Strength, and Hydration Heat of Ultra-High Strength Concrete

Applied Sciences ◽

10.3390/app10155202 ◽

2020 ◽

Vol 10 (15) ◽

pp. 5202 ◽

Cited By ~ 1

Author(s):

Guang-Zhu Zhang ◽

Hyeong-Kyu Cho ◽

Xiao-Yong Wang

Keyword(s):

Compressive Strength ◽

Relative Humidity ◽

High Strength Concrete ◽

Room Temperature ◽

Autogenous Shrinkage ◽

High Strength ◽

Silica Content ◽

Nano Silica ◽

Internal Relative Humidity ◽

Two Stages

In this paper, the effect of nano-silica on the autogenous shrinkage, hydration heat, compressive strength hydration products of Ultra-High Strength Concrete (UHSC) is studied. The water/binder ratio (w/b) of UHSC is 0.2. The nano-silica replaces 2% and 4% of the mass fraction of the cement in UHSCs, respectively. A new instrument was developed to simultaneously measure the autogenous shrinkage, internal relative humidity, and internal temperature of UHSC. The following results were obtained from the analysis of the experimental data: (1) The trends in the autogenous shrinking of UHSC can be divided into two stages, which are the variable temperature stage and the room temperature stage. The dividing point between the two stages occurs at the age of approximately 2 days. During the room temperature stage, the internal relative humidity and autogenous shrinkage showed a good linear relationship. (2) The compressive strength of UHSC increased significantly with the increase of nano-silica content at 3 days, 7 days, and 28 days. (3) The total accumulated heat of UHSC increased during the 72 h, with the increasing of nano-silica content. (4) The XRD data at the age of 28 days showed that the Ca(OH)2 peaks of nS2 and nS4 have a tendency to weaken due to the pozzolanic reaction, compared with the peak of nS0.

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