scholarly journals Internal Curing Effect of Pre-Soaked Zeolite Sand on the Performance of Alkali-Activated Slag

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 718
Author(s):  
Guang-Zhu Zhang ◽  
Han-Seung Lee ◽  
Xiao-Yong Wang ◽  
Yi Han
Keyword(s):  
Compressive Strength ◽  
Electrical Resistivity ◽  
Natural Zeolite ◽  
Setting Time ◽  
Autogenous Shrinkage ◽  
Internal Curing ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Two Stages ◽  
Alkali Activated

This study clarifies the effects of pre-soaked zeolite sand as an internal curing material on the hydration, strength, autogenous shrinkage, and durability of alkali-activated slag (AAS) mortars. The liquid-to-binder ratio (L/b) of all of the AAS mortars was 0.55. Sodium hydroxide solution was used as an alkali activator and an internal curing liquid. Calcined zeolite and natural zeolite sand replaced the standard sand at 15% and 30%, respectively. The setting time, autogenous shrinkage, compressive strength, ultrasonic pulse velocity, and surface electrical resistivity were tested. The following conclusions were drawn: (1) The addition of zeolite significantly reduces the autogenous shrinkage of AAS mortar. Compared with the control group, 30% calcined zeolite reduced the autogenous shrinkage by 96.4%. Moreover, the autogenous shrinkage of the AAS mortars was noticed in two stages (a variable temperature stage and an ambient temperature stage), and the two stages split at one day of age. (2) The compressive strength of all of the specimens increased as the zeolite sand content increased, and the highest compressive strength was obtained for AAS combined with 30% natural zeolite sand. (3) Internal curing accelerated the formation of the second peak of heat flow and reduced the accumulated heat release. (4) Calcined zeolite sand delayed the setting time of the AAS mortars. (5) The addition of zeolite significantly reduced the surface electrical resistivity of the AAS mortars. In summary, zeolite sand is extremely useful as an internal curing agent to reduce autogenous shrinkage and to increase the compressive strength of AAS mortars.

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 The Effect of Different Types of Internal Curing Liquid on the Properties of Alkali-Activated Slag (AAS) Mortar

2021 ◽  
Vol 13 (4) ◽  
pp. 2407
Author(s):  
Guang-Zhu Zhang ◽  
Xiao-Yong Wang ◽  
Tae-Wan Kim ◽  
Jong-Yeon Lim ◽  
Yi Han
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Deionized Water ◽  
Internal Curing ◽  
Control Group ◽  
Alkali Activated Slag ◽  
Different Types ◽  
Naoh Solution ◽  
Activated Slag ◽  
Alkali Activated

This study shows the effect of different types of internal curing liquid on the properties of alkali-activated slag (AAS) mortar. NaOH solution and deionized water were used as the liquid internal curing agents and zeolite sand was the internal curing agent that replaced the standard sand at 15% and 30%, respectively. Experiments on the mechanical properties, hydration kinetics, autogenous shrinkage (AS), internal temperature, internal relative humidity, surface electrical resistivity, ultrasonic pulse velocity (UPV), and setting time were performed. The conclusions are as follows: (1) the setting times of AAS mortars with internal curing by water were longer than those of internal curing by NaOH solution. (2) NaOH solution more effectively reduces the AS of AAS mortars than water when used as an internal curing liquid. (3) The cumulative heat of the AAS mortar when using water for internal curing is substantially reduced compared to the control group. (4) For the AAS mortars with NaOH solution as an internal curing liquid, compared with the control specimen, the compressive strength results are increased. However, a decrease in compressive strength values occurs when water is used as an internal curing liquid in the AAS mortar. (5) The UPV decreases as the content of zeolite sand that replaces the standard sand increases. (6) When internal curing is carried out with water as the internal curing liquid, the surface resistivity values of the AAS mortar are higher than when the alkali solution is used as the internal curing liquid. To sum up, both NaOH and deionized water are effective as internal curing liquids, but the NaOH solution shows a better performance in terms of reducing shrinkage and improving mechanical properties than deionized water.

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.

scholarly journals Understanding the Role of Metakaolin towards Mitigating the Shrinkage Behavior of Alkali-Activated Slag

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6962
Author(s):  
Bo Fu ◽  
Zhenyun Cheng ◽  
Jingyun Han ◽  
Ning Li
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Activator Concentration ◽  
Reaction Products ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated ◽  
Shrinkage Behavior

This research investigates the mechanism of metakaolin for mitigating the autogenous and drying shrinkages of alkali-activated slag with regard to the activator parameters, including concentration and modulus. The results indicate that the incorporation of metakaolin can decrease the initial viscosity and setting time. Increasing activator concentration can promote the reaction process and shorten the setting time. An increase in the metakaolin content induces a decrease in compressive strength due to reduced formation of reaction products. However, increasing activator dosage and modulus can improve the compressive strength of alkali-activated slag containing 30% metakaolin. The inclusion of metakaolin can mitigate the autogenous and drying shrinkage of alkali-activated slag by coarsening the pore structure. On the other hand, increases in activator concentration and modulus result in an increase in magnitude of the autogenous and drying shrinkage of alkali-activated slag containing metakaolin. The influence of the activator modulus on the shrinkage behavior of alkali-activated slag-metakaolin binary system should be further investigated.

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 Influence of Cooking Oil on the Mitigation of Autogenous Shrinkage of Alkali-Activated Slag Concrete

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4907
Author(s):  
Jinguang Huang ◽  
Jiachuan Yan ◽  
Kaihua Liu ◽  
Bin Wei ◽  
Chaoying Zou
Keyword(s):  
Surface Tension ◽  
Setting Time ◽  
Autogenous Shrinkage ◽  
Carbonation Depth ◽  
Alkali Activated Slag ◽  
Cooking Oil ◽  
Carbonation Resistance ◽  
Activated Slag ◽  
Alkali Activated ◽  
Shrinkage Reducing Agent

This paper reports an investigation into the autogenous shrinkage, mechanical, and durability performances of alkali-activated slag concrete (AASC) with emulsified cooking oil (ECO). Properties of AASC including flowability, setting time, compressive strength, autogenous shrinkage, and carbonation depth are tested to clarify the effects of the ECO. Commercially available expansion agent (EA) and shrinkage reducing agent (SRA) are also applied on AASC to compare with ECO. Experimental results show that the utilization of ECO could significantly decrease the autogenous shrinkage of alkali-activated slag concrete owing to the reduction of surface tension and the denser internal structure. It also shows that cooking oil after emulsification could have better performances than that of plain cooking oil when applied on AASC. Setting time and carbonation resistance ability are also improved with the utilization of ECO. The application of ECO is considered a cheap and easy way to overcome the limitation of AASC.

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%.

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