scholarly journals Effect of Polypropylene Fiber on Properties of Alkali-Activated Slag Mortar

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Yangchen Xu ◽  
Haiming Chen ◽  
Pengju Wang
Keyword(s):  
Water Absorption ◽  
Setting Time ◽  
Impact Resistance ◽  
Polypropylene Fiber ◽  
Engineering Properties ◽  
Alkali Activated Slag ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Activated Slag ◽  
Alkali Activated

Alkali-activated slag (AAS) is becoming an increasingly popular building material due to its excellent engineering properties and low CO2 emissions, but its large shrinkage is an important reason to restrict its application and popularization. This work is aimed to study the possibility of inhibiting the shrinkage of AAS mortar by incorporating polypropylene fiber (PPF). For this, an experimental study was carried out to evaluate the effects of PPF content on setting time, fluidity, physical properties, mechanical properties, impact resistance, and microstructure of AAS mortar. The volume content of PPF is 0.05%, 0.1%, 0.15%, and 0.2%. The working, physical (porosity, water absorption, and bulk density), mechanical, shrinkage, and impact resistance properties of the AAS mortars were evaluated. The results show that incorporating PPF effectively reduces the shrinkage deformation of AAS mortar, significantly improves its impact resistance, enhances its toughness, and slightly improves its compressive strength in the later stage. At the same time, PPF delays the initial setting time of AAS mortar and reduces the fluidity, density, porosity, and water absorption of AAS mortar. SEM results show that the bridging effect of PPF between AAS mortars can inhibit the generation and propagation of cracks, improve the internal microstructure, and enhance the performance of AAS mortar.

scholarly journals Effect of Dosage of Alkaline Activator on the Properties of Alkali-Activated Slag Pastes

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Zhenzhen Jiao ◽  
Ying Wang ◽  
Wenzhong Zheng ◽  
Wenxuan Huang
Keyword(s):  
Compressive Strength ◽  
Room Temperature ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Engineering Properties ◽  
Alkali Activated Slag ◽  
Alkaline Activator ◽  
Activated Slag ◽  
Good Workability ◽  
Alkali Activated

This study focused on the engineering properties of alkali-activated slag (AAS) pastes prepared by mixing an activator consisting of sodium silicate and sodium hydroxide at room temperature. The water-to-slag ratio of AAS paste was kept constant at 0.35 by mass. AAS pastes were prepared using the activator with five different silicate moduli of 1, 1.2, 1.4, 1.6, and 1.8 and three different Na2O contents of 6%, 8%, and 10%. The results showed that both the silicate moduli and Na2O contents had significant effects on the engineering properties of AAS pastes. All the AAS pastes exhibited properties such as fast setting, good workability, and high early compressive strength. The final setting time varied from 9 to 36 min, and the fluidity was in the range of 147–226 mm. The 1 d compressive strength of all the AAS pastes, which could be easily achieved, had values above 55 MPa, whereas the highest strength obtained was 102 MPa with the silicate modulus of 1 and Na2O content of 8% at room temperature. The drying shrinkage increased as the silicate modulus increased. Furthermore, the hydration products and microstructures of AAS pastes were explained according to the microanalysis methods.

scholarly journals Effect of Internal Curing by Super Absorbent Polymer on the Autogenous Shrinkage of Alkali-Activated Slag Mortars

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4318
Author(s):  
Pengju Wang ◽  
Haiming Chen ◽  
Peiyuan Chen ◽  
Jin Pan ◽  
Yangchen Xu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Autogenous Shrinkage ◽  
Internal Curing ◽  
Engineering Properties ◽  
Super Absorbent Polymer ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Absorbent Polymer ◽  
Alkali Activated

Alkali activated slag (AAS) mortar is becoming an increasingly popular green building material because of its excellent engineering properties and low CO2 emissions, promising to replace ordinary Portland cement (OPC) mortar. However, AAS’s high shrinkage and short setting time are the important reasons to limit its wide application in engineering. This paper was conducted to investigate the effect of internal curing(IC) by super absorbent polymer (SAP) on the autogenous shrinkage of AAS mortars. For this, an experimental study was carried out to evaluate the effect of SAP dosage on the setting time, autogenous shrinkage, compressive strength, microstructure, and pore structure. The SAP were incorporated at different dosage of 0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 percent by weight of slag. The workability, physical (porosity), mechanical, and shrinkage properties of the mortars were evaluated, and a complementary study on microstructure was made. The results indicated that the setting time increased with an increase of SAP dosage due to the additional activator released by SAP. Autogenous shrinkage decreased with an increase of SAP dosage, and was mitigated completely when the dosage of SAP ≥ 0.2% wt of slag. Although IC by means of SAP reduced the compressive strength, this reduction (23% at 56 days for 0.2% SAP) was acceptable given the important role that it played on mitigating autogenous shrinkage. In the research, the 0.2% SAP dosage was the optimal content. The results can provide data and basis for practical application of AAS mortar.

scholarly journals Reuse of volcanic mud to controlled low-strength materials with cement and alkali-activated slag binders

2019 ◽  
Vol 107 ◽  
pp. 01008
Author(s):  
Chung-Ho Huang ◽  
Hao-Yu Fang
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Sodium Oxide ◽  
Engineering Properties ◽  
Fine Aggregate ◽  
Replacement Rate ◽  
Alkali Activated Slag ◽  
Low Strength ◽  
Activated Slag ◽  
Alkali Activated

This paper aims to evaluate the applicability of volcanic mud as the fine aggregate for controlled low-strength material (CLSM) by the experimental method. Two types of binder were selected, including cement and alkali-activated slag binders (without cement). The study mainly explored the effects of different addition rates of volcanic mud and different concentrations of alkaline agents (sodium hydroxide) on the engineering properties of CLSM. The test results show that the CLSMs with cement and volcanic mud have better workability and less water bleeding. However, the compressive strength of CLSM decreases as the replacement rate of volcanic mud increases, and the setting time also increases. The replacement rate of volcanic mud is recommended to be 20%. The volcanic mud mixed with the alkali-activated slag binder (without cement) can be successfully made into CLSM. When the concentration of sodium oxide in CLSM is 5%, although the compressive strength is highest at 7 days or 28 days, it cannot be hardened at the early age (before four days) and without compressive strength. CLSM with 20% sodium oxide concentration has poor workability. Its compressive strength is slightly lower than that of the 10% group. Therefore, the amount of calcium hydroxide recommended is 10%.

scholarly journals Effect of Ca(OH)2 Addition on the Engineering Properties of Sodium Sulfate Activated Slag

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4266
Author(s):  
Xiaodi Dai ◽  
Serdar Aydın ◽  
Mert Yücel Yardımcı ◽  
Karel Lesage ◽  
Geert De Schutter
Keyword(s):  
Sodium Sulfate ◽  
Setting Time ◽  
Engineering Properties ◽  
Main Reaction ◽  
Phase Identification ◽  
Reaction Products ◽  
Alkali Activated Slag ◽  
Setting Times ◽  
Activated Slag ◽  
Alkali Activated

Alkali-activated slag is considered as a sustainable construction material due to its environmentally friendly nature. To further promote the sustainable nature of alkali-activated slag, a sodium sulfate activator is suggested to be used since it can be obtained naturally and generates lower greenhouse gas emissions. However, the mixtures activated by sodium sulfate exhibit low early strength and very long setting times. This study investigates the effects of calcium hydroxide (Ca(OH)2) addition on some engineering properties such as rheology, setting time, mechanical properties, porosity, and microstructure of sodium sulfate activated ground granulated blast furnace slag (GGBFS). Furthermore, the changes of chemical groups in reaction products and phase identification have been evaluated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. Test results showed that Ca(OH)2 addition can substantially increase the reaction rate and the compressive strength at early ages. In addition, the very long setting times of the sodium sulfate-activated mixtures were shortened by the addition of Ca(OH)2. SEM analysis confirmed that the incorporation of excessive amounts of Ca(OH)2 could lead to a less well-packed microstructure although the reaction degree of GGBFS remained the same at later ages as compared to the sodium sulfate mixture. It was also revealed that in case of the Ca(OH)2 addition into sodium sulfate activator, the main reaction products are chain-structured C-A-S-H gels and ettringite.

scholarly journals Influence of Na2O Content and Ms (SiO2/Na2O) of Alkaline Activator on Workability and Setting of Alkali-Activated Slag Paste

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2072 ◽  
Author(s):  
Sung Choi ◽  
Kwang-Myong Lee
Keyword(s):  
Setting Time ◽  
High Strength ◽  
Abrupt Decrease ◽  
Na2o Content ◽  
Alkali Activated Slag ◽  
Granulated Blast Furnace Slag ◽  
Type Composition ◽  
Activated Slag ◽  
Binary Alkaline ◽  
Alkali Activated

The performance of alkali-activated slag (AAS) paste using activators of strong alkali components is affected by the type, composition, and dosage of the alkaline activators. Promoting the reaction of ground granulated blast furnace slag (GGBFS) by alkaline activators can produce high-strength AAS concrete, but the workability might be drastically reduced. This study is aimed to experimentally investigate the heat release, workability, and setting time of AAS pastes and the compressive strength of AAS mortars considering the Na2O content and the ratio of Na2O to SiO2 (Ms) of binary alkaline activators blended with sodium hydroxide and sodium silicate. The test results indicated that the AAS mortars exhibited a high strength of 25 MPa at 24 h, even at ambient temperature, even though the pastes with an Na2O content of ≥6% and an Ms of ≥1.0 exhibited an abrupt decrease in flowability and rapid setting.

Experimental Study on Alkali-Activated Slag-Lithium Slag-Fly Ash Environmental Concrete

2011 ◽  
Vol 287-290 ◽  
pp. 1237-1240
Author(s):  
Lan Fang Zhang ◽  
Rui Yan Wang
Keyword(s):  
Experimental Study ◽  
Compressive Strength ◽  
Fly Ash ◽  
Setting Time ◽  
Alkali Activated Slag ◽  
Percent Increase ◽  
Compressive Strength Of Concrete ◽  
Activated Slag ◽  
Lithium Slag ◽  
Alkali Activated

The aim of this paper is to study the influence of lithium-slag and fly ash on the workability , setting time and compressive strength of alkali-activated slag concrete. The results indicate that lithium-slag and fly-ash can ameliorate the workability, setting time and improve the compressive strength of alkali-activated slag concrete，and when 40% or 60% slag was replaced by lithium-slag or fly-ash, above 10 percent increase in 28-day compressive strength of concrete were obtained.

scholarly journals Effect of Sodium Aluminate Dosage as a Solid Alkaline Activator on the Properties of Alkali-Activated Slag Paste

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Bin Chen ◽  
Jun Wang ◽  
Jinyou Zhao
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Setting Time ◽  
Sodium Aluminate ◽  
Hydration Reaction ◽  
Hydration Products ◽  
Alkali Activated Slag ◽  
Alkaline Activator ◽  
Activated Slag ◽  
Alkali Activated

Extensive research into alkali-activated slag as a green gel material to substitute for cement has been done because of the advantages of low-carbon dioxide emissions and recycling of industrial solid waste. Alkali-activated slag usually has good mechanical properties, but the too fast setting time restricted its application and promotion. Changing the composition of alkaline activator could optimize setting time, usually making it by adding sodium carbonate or sodium sulfate but this would cause insufficient hydration reaction power and hinder compressive strength growth. In this paper, the effect of sodium aluminate dosage as an alkaline activator on the setting time, fluidity, compressive strength, hydration products, and microstructures was studied through experiments. It is fair to say that an appropriate amount of sodium aluminate could obtain a suitable setting time and better compressive strength. Sodium aluminate provided enough hydroxyl ions for the paste to promote the hydration reaction process that ensured obtaining high compressive strength and soluble aluminium formed precipitate wrapped on the surface of slag to inhibit the hydration reaction process in the early phase that prolonged setting time. The hydration mechanism research found that sodium aluminate played a key role in the formation of higher cross-linked gel hydration products in the late phase of the process. Preparing an alkali-activated slag with excellent mechanical properties and suitable setting time will significantly contribute to its application and promotion.

scholarly journals Effect of Cr6+ on the Properties of Alkali-Activated Slag Cement

2021 ◽  
Vol 8 ◽  
Author(s):  
Fu Bo ◽  
Cheng Zhenyun
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Cement Stone ◽  
Slag Cement ◽  
Hydration Kinetics ◽  
Alkali Activated Slag ◽  
Dual Beam ◽  
Press Method ◽  
Activated Slag ◽  
Alkali Activated

In order to investigate the effect of Cr6+ on the properties of alkali-activated slag cement (AAS), the effects of added dosage of Na2Cr2O4 on the setting time and compressive strength of AAS were measured. The leaching concentration of Cr6+ from AAS cement stone was measured using dual-beam UV-visible spectrophotometry. The effect of Na2Cr2O4 on the hydration kinetics of AAS cement was monitored by microcalorimetry and the corresponding kinetic parameters were analyzed. The pore solution from AAS was collected and analyzed using the high pressure press method. The effects of Na2Cr2O4 on the hydration products of AAS cement were observed and compared using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results showed that the AAS hydration process was markedly affected by Na2Cr2O4 dosage. The setting time of AAS pastes was increased and the compressive strength of cement stones was reduced with increasing dosage of Na2Cr2O4. With the development of AAS hydration, the leaching concentration of Na2Cr2O4 gradually decreased. Na2Cr2O4 did not affect the dissolution of slag particles, but impeded the formation of C-S-H gel. The Cr6+ was immobilized chemically in the form of needle-like CaCrO4 particles formed by the chemical reaction between Na2Cr2O4 and Ca2+ leaching from the slag.

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