An Innovative Admixture to Enhance the Fresh Properties of Slag Pastes

2013 ◽  
Vol 477-478 ◽  
pp. 915-919
Author(s):  
Qun Pan ◽  
Shuang Zhao ◽  
Han Ying Zheng ◽  
Bin Zhu
Keyword(s):  
Setting Time ◽  
Heat Of Hydration ◽  
Fresh Properties ◽  
Slag Cement ◽  
Setting Times ◽  
Initial Setting ◽  
New Type ◽  
Activated Slag ◽  
Alkali Activated ◽  
Initial Peak

This study reports a new type compound admixture YP developed for slag cement activated by water glass. The effect of the compound admixture on properties of slag pastes, including mini slump, setting time and heat of hydration was examined. It is found that the slump of slag paste was increased from 60 mm to 120 mm by using the admixture. Furthermore, the initial and final setting times of paste with the admixture were 96 min and 132 min, while it only took 18 min and 23 min to achieve initial setting and final setting for the paste without using the admixture. In addition, the results also indicate that the initial peak was delayed for nearly 7 hours and the heat flow of hydration was reduced from 5864 μw/g to 461μw/g, when the admixture was added. It can be concluded that the new admixture is capable of imparting a significant improvement of workability of alkali-activated slag cement with a suitable setting behavior.

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.

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.

The Effect of Surfactant and Alkali on the Surface Tension of Simulated Solutions of Alkali Activated Slag Cement System

2011 ◽  
Vol 399-401 ◽  
pp. 1246-1250
Author(s):  
Xian Feng Liu ◽  
Jia Hui Peng ◽  
Chang Hui Yang ◽  
Yu Yan Shu ◽  
Da Chang Wu
Keyword(s):  
Surface Tension ◽  
Water Glass ◽  
High Viscosity ◽  
Heat Of Hydration ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Cement System ◽  
Cement And Concrete ◽  
Activated Slag ◽  
Alkali Activated

Alkali activated slag cement and concrete are high strength, rapid hardening, low heat of hydration, good durability and so on. Whereas, too high viscosity and bad workability of the fresh mixture is the crux of the matter to embarrass application of alkali-activated slag cement and concrete. Development of special superplasticizer for alkali activated slag cement and concrete is a worth exploring way to solve the problem, and the study on the surface tension of simulated solutions of alkali activated slag cement system is one of the basic researches about the special superplasticizer. In this paper, the surface tension of surfactant-alkali-water was studied by Wilhelmy method. The results showed, first, water-glass had the best efficacity of several alkali activators, when the modulus of water-glass was 1.5 and dosage of water-glass by Na2O was 8%, the surface tension was reduced by 33 mN/m and reduced to 39.9mN/m; second, [CH3(CH2)9]2N(CH3)2Cl had the best efficacity of several surfactants, when the concentration of [CH3(CH2)9]2N(CH3)2Cl was 50g/L, the surface tension was reduced by 35.3 mN/m and reduced to 32.5 mN/m; finally, the effect of surfactant and alkali together on the surface tension of water was complex, surfactants had hardly effective in water glass.

scholarly journals Development and Characteristics of Aerated Alkali-Activated Slag Cement Mixed with Zinc Powder

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6293
Author(s):  
Taewan Kim ◽  
Choonghyun Kang ◽  
Kiyoung Seo
Keyword(s):  
Pore Size ◽  
Setting Time ◽  
Curing Temperature ◽  
Clear Correlation ◽  
Slag Cement ◽  
Water Binding ◽  
Alkali Activated Slag ◽  
Aerated Concrete ◽  
Activated Slag ◽  
Alkali Activated

Experiments on the development and properties of aerated concrete based on alkali-activated slag cement (AASC) and using Zn powder (ZP) as a gas agent were carried out. The experiments were designed for water-binding material (w/b) ratios of 0.35 and 0.45, curing temperatures of 23 ± 2 °C and 40 ± 2 °C, and ZP of 0.25%, 0.50%, 0.75%, and 1.0%. ZP generates hydrogen (H2) gas in AASC to form pores. At a w/b of 0.35, the curing temperature had little effect on the pore size by ZP. However, a w/b of 0.45 showed a clear correlation that the pore diameter increased as the curing temperature increased. The low w/b of 0.35 showed a small change in the pore size according to the curing temperature due to the faster setting time than 0.45 and the increased viscosity of the paste. Therefore, at a termination time exceeding at least 60 min and a w/b of 0.45 or more, it was possible to increase the size and expansion force of the pores formed by the ZP through the change of the curing temperature. ZP showed applicability to the manufacture of AASC-based aerated concrete, and the characteristics of foaming according to the curing temperature, w/b ratio, and ZP concentration were confirmed.

Influence of New Type Water Reducer Agent YC on Properties of Alkali-Activated Slag Cement Mortar

2011 ◽  
Vol 374-377 ◽  
pp. 1357-1360
Author(s):  
Ke Chen ◽  
Chang Hui Yang ◽  
Ze Dong Yu ◽  
Qun Pan ◽  
Shuang Zhao
Keyword(s):  
Cement Mortar ◽  
Reduction Rate ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Cement System ◽  
Influence Of Water ◽  
New Type ◽  
Type Water ◽  
Activated Slag ◽  
Alkali Activated

Through test on influence of water reducer agent YC on properties of alkali activated slag cement mortar, it is shown that water reducer agent YC has favorable plasticizing effect on alkali activated slag cement. When the alkali component is NaOH, the water reducer agent YC gives a water reduction rate of 22.0% to the alkali activated slag cement mortar and the flow ability loss with time is small. The water reducer agent can be adsorbed on the surface of slag and enhance theξpotential of the alkali activated slag cement system.

Research on Set Retarder of High and Super High Strength Alkali -Activated Slag Cement and Concrete

2011 ◽  
Vol 477 ◽  
pp. 164-169 ◽  
Author(s):  
Chang Hui Yang ◽  
Fang Wu ◽  
Ke Chen
Keyword(s):  
Setting Time ◽  
High Strength ◽  
Heat Evolution ◽  
Strength Development ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Negative Effect ◽  
Cement And Concrete ◽  
Activated Slag ◽  
Alkali Activated

The set of alkali-activated slag cement (AASC) and concrete and the measures for set-retarding were reviewed. Due to the fast set of high and super high strength alkali-activated slag cement and concrete, an inorganic compound set retarder YP-3 was developed. The effect of the retarder on setting time and strength as well as heat evolution of AASC were tested, and the mechanism of the retarder was analysed. Results show that the retarder can regulate the initial set of high strength AASC in the range of 29hrs with little negative effect on its strength development. The retarder could react with silicate ions from liquid to rapidly form a compact film in early age of hydration of AASC, the film covered the surface of slag and obstructed R+ and OH- in contact with slag particle directly. Consequently the set of AAC was delayed.

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.

Influence of hydrated lime on mechanical and shrinkage properties of alkali-activated slag cement

2021 ◽  
Vol 289 ◽  
pp. 123201
Author(s):  
Juan He ◽  
Wenbin Bai ◽  
Weihao Zheng ◽  
Junhong He ◽  
Guochen Sang
Keyword(s):  
Hydrated Lime ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

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.

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