scholarly journals Study of Mechanical Properties and Durability of Alkali-Activated Coal Gangue-Slag Concrete

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5576
Author(s):  
Hongguang Zhu ◽  
Sen Yang ◽  
Weijian Li ◽  
Zonghui Li ◽  
Jingchong Fan ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Damage Mechanics ◽  
Ordinary Portland Cement ◽  
Coal Gangue ◽  
Function Model ◽  
Freeze Thaw ◽  
Activated Coal ◽  
Activated Coal Gangue ◽  
Alkali Activated

Herein, a new geopolymer is recognized as a potential alternative cementing material of ordinary Portland cement (OPC), which is used for reducing carbon emissions and efficiently recycling the waste. Therefore this paper mainly studied the alkali-activated coal gangue-slag concrete (ACSC) was prepared by using the coal gangue-slag and Na2SiO3 and NaOH complex activator. The ratio of coal gangue (calcined and uncalcined) coarse aggregate replacing the gravel was 0%, 30%, 50%, 70%, and 100%. The water and salt freeze-thaw resistance, compressive strength, chloride permeation, microstructure, performance mechanism, inner freeze-thaw damage distribution, and mechanics models of ACSC were investigated. Results show that ACSC displayed excellent early age compressive strength, and the compact degree and uniformity of structure were better compared with the ordinary Portland cement (OPC) when the coal gangue replacement rate was less than 50%. The ACSC demonstrated the best chloride penetration resistance under 30% uncalcined coal gangue content, which was less than 27.75% lower than that of using OPC. At the same number cycles, especially in the salt freezing, the calcined coal gangue had lowered advantages of improving resistance freeze-thaw damage resistance. Water and salt accumulative freeze-thaw damage mechanics models of ACSC were established by using the relative dynamic elasticity modulus. The exponential function model was superior to the power function model with better precision and relativity, and the models accurately reflected the freeze-thaw damage effect.

Effects of Kiln Dust-Activated Coal Gangue on the Properties of High-Content Slag Cement

2013 ◽  
Vol 753-755 ◽  
pp. 525-528
Author(s):  
Chun Mei Wang ◽  
Jing Wang ◽  
Li Rong Yang ◽  
Guang Dong Cao ◽  
Dan Yang Dong
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Setting Time ◽  
Coal Gangue ◽  
Slag Cement ◽  
Activated Coal ◽  
Kiln Dust ◽  
Activated Coal Gangue

The effects of amounts of the kiln dust-activated coal gangue on the setting time and compressive strength of high-content slag cement were investigated. The performance of sulphate resistance of cement with 30 wt.% kiln dust-activated coal gangue was evaluated. The results reveal that the setting time of high-content slag cement is prolonged. Appropriate kiln dust-activated coal gangue amounts can increase the compressive strength, while too much activated coal gangue (>30 wt.%) leads to the decrease in compressive strength. Cement with 10 wt.% kiln dust-activated coal gangue exhibits a good compressive strength. The performance of sulphate resistance of Portland cement with 30 wt.% kiln dust-activated coal gangue is distinctly enhanced, while that of high-content slag cement is improved to some extent.

Study on compressive strength and durability of alkali-activated coal gangue-slag concrete and its mechanism

2020 ◽  
Vol 368 ◽  
pp. 112-124 ◽  
Author(s):  
Hongqiang Ma ◽  
Hongguang Zhu ◽  
Chao Wu ◽  
Hongyu Chen ◽  
Jianwei Sun ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Coal Gangue ◽  
Activated Coal ◽  
Strength And Durability ◽  
Activated Coal Gangue ◽  
Alkali Activated

scholarly journals Experimental Study of the Mechanical and Microstructure Characteristics of Coal Gangue Road Stabilization Materials Based on Alkali Slag Cementation

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3601
Author(s):  
Changbai Wang ◽  
Junxin Yang ◽  
Shuzhan Xu
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Coal Gangue ◽  
Hydration Time ◽  
Alkali Activated Slag ◽  
Microstructure Characteristics ◽  
Activated Coal ◽  
Activated Slag ◽  
Activated Coal Gangue ◽  
Alkali Activated

To accelerate the resource utilization of coal gangue and meet the strategic requirements of carbon neutralization, alkali-activated, slag-cemented coal gangue is applied in the preparation of solid waste-based road stabilization materials. Here, the cementation characteristics and microstructure characteristics of alkali-activated, slag-cemented coal gangue road stabilization materials are studied using the alkali equivalent and coal gangue aggregate ratio as experimental variables. The results show that with the increase in alkali equivalent from 1% to 7%, the unconfined compressive strength of the alkali-activated coal gangue road stabilization material initially increases and then decreases, with 3% being the optimal group in terms of stabilization, the aggregate ratio of coal gangue increases from 70% to 85%, and the 7-day unconfined compressive strength of the stabilized material decreases approximately linearly from 8.16 to 1.68 MPa. At the same time, the porosity gradually increases but still meets the requirements of the specification. With the increase in hydration time, a large number of hydration products are formed in the alkali slag cementation system, and they are closely attached to the surface of and interweave with the coal gangue to fill the pores, resulting in the alkali slag slurry and coal gangue being brought closer together.

Shrinkage-reducing measures and mechanisms analysis for alkali-activated coal gangue-slag mortar at room temperature

2020 ◽  
Vol 252 ◽  
pp. 119001 ◽  
Author(s):  
Hongqiang Ma ◽  
Hongguang Zhu ◽  
Hongyu Chen ◽  
Yadong Ni ◽  
Xiaonan Xu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Coal Gangue ◽  
Activated Coal ◽  
Activated Coal Gangue ◽  
Alkali Activated

A Review of Alkali-Activated Slag as Cement Replacement

2019 ◽  
Vol 803 ◽  
pp. 262-266
Author(s):  
Osama Ahmed Mohamed ◽  
Maadoum M. Mustafa
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Construction Industry ◽  
Ordinary Portland Cement ◽  
Environmental Footprint ◽  
Alkali Activated Slag ◽  
Cement Replacement ◽  
Activated Slag ◽  
Alkali Activated

Alkali activated slag (AAS) offers opportunities to the construction industry as an alternative to ordinary Portland cement (OPC). The production of OPC and its use contributes significantly to release of CO2 into the atmosphere while AAS is an industrial by-product that contributes much less to the environmental footprint that needs to be recycled if not landfilled. This paper outlines some of the key properties, merits and demerits of AAS when used as alternative to OPC. Competitive compressive strength of AAS concrete is amongst of the advantages of replacing cement with AAS while high shrinkage and carbonation levels are potential disadvantages.

scholarly journals Effect of Elevated Temperature on Alkali Activated Slag and Fly Ash based Geopolymer Concrete

2020 ◽  
Vol 9 (4) ◽  
pp. 1241-1250
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Flexural Strength ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Geopolymer Concrete ◽  
Base Materials ◽  
Activated Slag ◽  
Alkali Activated

Activated Slag (AAS) and Fly Ash (FA) based geopolymer concrete a new blended alkali-activated concrete that has been progressively studied over the past years because of its environmental benefits superior engineering properties. Geopolymer has many favorable characteristics in comparison to Ordinary Portland Cement. Many base materials could be utilized to make geopolymer with the convenient concentration of activator solution. In this study, the experimental program composed of two phases; phase on divided into four groups; Group one deliberated the effect of sodium hydroxide molarity and different curing condition on compressive strength. Group two studied the effect of alkali activated solution (NaOH and Na2SiO3) content on compressive strength and workability. The effect of sand replacement with slag on compressive strength and workability was explained in group three. Group four studied the effect of slag replacement with several base materials Fly Ash (FA), Ordinary Portland Cement (OPC), pulverized Red Brick (PRB), and Meta Kaolin (MK). Phase two contains three mixtures from phase one which had the highest compressive strength. For each mixture, the fresh concrete test was air content. In addition the hardened concrete tests were the compressive strength at 3, 7, 28, 90, 180, and 365 days, the flexural strength at 28, 90, and 365 days, and the young's modulus at 28, 90, and 365 days. Moreover; the three mixtures were exposed to elevated temperature at 100oC, 300oC, and 600oC to study the effect of elevated temperature on compressive and flexural strength.

scholarly journals Alkali-Activated Hybrid Cements Based on Fly Ash and Construction and Demolition Wastes Using Sodium Sulfate and Sodium Carbonate

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7572
Author(s):  
William Valencia-Saavedra ◽  
Rafael Robayo-Salazar ◽  
Ruby Mejía de Gutiérrez
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
Sodium Carbonate ◽  
Sodium Sulfate ◽  
Room Temperature ◽  
Ordinary Portland Cement ◽  
Mechanical Performance ◽  
Construction And Demolition Wastes ◽  
Alkali Activated

This article demonstrates the possibility of producing alkali-activated hybrid cements based on fly ash (FA), and construction and demolition wastes (concrete waste, COW; ceramic waste, CEW; and masonry waste, MAW) using sodium sulfate (Na2SO4) (2–6%) and sodium carbonate (Na2CO3) (5–10%) as activators. From a mixture of COW, CEW, and MAW in equal proportions (33.33%), a new precursor called CDW was generated. The precursors were mixed with ordinary Portland cement (OPC) (10–30%). Curing of the materials was performed at room temperature (25 °C). The hybrid cements activated with Na2SO4 reached compressive strengths of up to 31 MPa at 28 days of curing, and the hybrid cements activated with Na2CO3 yielded compressive strengths of up to 22 MPa. Based on their mechanical performance, the optimal mixtures were selected: FA/30OPC-4%Na2SO4, CDW/30OPC-4%Na2SO4, FA/30OPC-10%Na2CO3, and CDW/30OPC-10%Na2CO3. At prolonged ages (180 days), these mixtures reached compressive strength values similar to those reported for pastes based on 100% OPC. A notable advantage is the reduction of the heat of the reaction, which can be reduced by up to 10 times relative to that reported for the hydration of Portland cement. These results show the feasibility of manufacturing alkaline-activated hybrid cements using alternative activators with a lower environmental impact.

scholarly journals Effect of Ordinary Portland Cement and Water Glass on the Properties of Alkali Activated Fly Ash Concrete

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 40 ◽  
Author(s):  
Vytautas Bocullo ◽  
Danutė Vaičiukynienė ◽  
Ramūnas Gečys ◽  
Mindaugas Daukšys
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
Water Glass ◽  
Ordinary Portland Cement ◽  
Reference Sample ◽  
Freeze And Thaw ◽  
Naoh Solution ◽  
Increased Strength ◽  
Alkali Activated

This research presents the influence of ordinary Portland cement (OPC) and/or water glass addition on fly ash alkali-activated mortar and concrete. The results show that fly ash (FA) concrete activated with a NaOH solution and water glass mixture had better resistance to freeze and thaw, carbonation, alkali-silica reaction (ASR) and developed higher compressive strength and static elastic modulus compared with the FA concrete activated only with an NaOH solution. The addition of OPC contributes to the development of a denser microstructure of alkali activated concrete (AAC) samples. In the presence of water glass and OPC, the compressive strength (52.60 MPa) of the samples increased more than two times as compared with the reference sample (21.36 MPa) without OPC and water glass. The combination of OPC and water glass showed the increased strength and enhanced durability of AAC. The samples were more resistant to freeze and thaw, ASR, and carbonation.

Effect of Activated Coal Gangue in North China on the Compressive Strength and Hydration Process of Cement

2019 ◽  
Vol 31 (4) ◽  
pp. 04019022
Author(s):  
Shuangxi Zhou ◽  
Jingliang Dong ◽  
Lehua Yu ◽  
Changjie Xu ◽  
Xiangke Jiao ◽  
...  
Keyword(s):  
Compressive Strength ◽  
North China ◽  
Coal Gangue ◽  
Hydration Process ◽  
Activated Coal ◽  
Activated Coal Gangue

Influence of Calcination Temperature on Activity of Hydration Properties of Gangue

2011 ◽  
Vol 415-417 ◽  
pp. 1466-1469
Author(s):  
Jian Ping Zhu ◽  
Jian Wu Zhang ◽  
Song Hai Zhao ◽  
Dong Xu Li
Keyword(s):  
Compressive Strength ◽  
Thermal Activation ◽  
Amorphous Material ◽  
Coal Gangue ◽  
Process Conditions ◽  
Gangue Mineral ◽  
Activation Process ◽  
Activated Coal ◽  
Oxygen Bond ◽  
Activated Coal Gangue

The mineral structure and hydration activity changes of the Jiyuan gangue calcined at different temperatures were studied in the paper. Differential scanning calorimeter (DSC), X-ray diffraction (XRD) testing, strength testing of cement and Microhardness analysis methods were used to study the thermal activation of coal gangue mineral composition, and macroscopic characterization of the activity of heat-activated coal gangue. The results showed that after heat activation, the destruction of the gangue can be effective in the silicon-oxygen bond, aluminum-oxygen bond, forming amorphous material, and thereby enhanced the activity of coal gangue. Best thermal activation process conditions of Jiyuan gangue is calcined at 800°C for 2h. Adding 40% of the heat-activated coal gangue Activated at this condition to cement, the compressive strength than the same dosage as is the compressive strength of coal gangue increased 106%.

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