Study of the NaOH concentration and aluminium compound on the ettringite formation in fluidized bed combustion (FBC) fly ash geopolymer

AbstractFluidized bed combustion (FBC) fly ash contains high amount of calcium sulfate (CaSO4) due to feeding of lime into the combustion process to capture the SOx gases. The CaSO4 can be formed and react with alumina in the FBC fly ash under base condition resulted in calcium sulfoaluminate (ettringite). Therefore, effect of sodium hydroxide (NaOH) concentration on ettringite formation in FBC fly ash geopolymer was studied. In addition, the properties of geopolymer was improved by the addition of aluminium compound. The geopolymer was prepared from FBC fly ash mixed with aluminum hydroxide (Al(OH)3),sodium silicate and sodium hydroxide solution which Al(OH)3 could convert the calcium compound in FBC fly ash to calcium aluminate hydrate and aluminosilicate. It exhibited the strength gain of geopolymer. It was found that there is no sign of ettringite formation when 15 M NaOH was used. Use of Al(OH)3 not exceed 2.5% by weight of FBC fly ash in geopolymer preparation gave the compressive strength of 35 MPa at 90 days, while that of Al(OH)3 at 5% by weight resulted in sodium aluminateformation and strength reduction

Strength behavior of fly ash geopolymer with microwave pre-radiation curing

AbstractThis research studied on the effect of microwave energy on the compressive strength of geopolymer and comparedwith that of geopolymer curing with the conventional heat system. Geopolymer was produced by the reaction between a pozzolan and the highly concentrated alkali and sodium silicate solutions, and then cured at the temperature of 65oC. Pre–radiation of microwave energy was applied before heat curing. Microwave energy helped the geopolymerization reaction resulting in the increase in leaching of silica and alumina on the fly ash surfaces and development of compressive strength. System with 90 watt microwave pre – radiation for 5 min plus 6 h heat curing gave a compressive strength of 34 MPa, which was higher than that of system with 65oC heat curing for 24 h (31 MPa). Therefore, the microwave energy could reduce the curing time and save energy obtaining the higher strength of geopolymer

ผลของซิลิกาฟูมต่อสมบัติของวัสดุจีโอโพลิเมอร์จากเถ้าลอยกระบวนการเผา แบบฟลูอิดไดซ์เบด Effect of Silica Fume on the Properties of Fluidized Bed Combustion (FBC) Fly Ash Geopolymer

บทคัดย่อเถ้าลอยที่ได้จากการเผาแบบฟลูอิดไดซ์เบด (Fluidized bed combustion, FBC) มีรูปร่างที่ไม่แน่นอน มีรูพรุน และความเป็นผลึกค่อนข้างสูง เนื่องจากอุณหภูมิในการเผาถ่านหินไม่สูง (ประมาณ 900oC) นอกจากนี้ยังมีแคลเซียมเป็นส่วนผสมปริมาณมากจึงไม่นิยมนำเถ้าลอย FBC เป็นสารปอซโซลาน ผสมกับปูนซีเมนต์ผลิตคอนกรีต งานวิจัยนี้จึงเสนอแนวทางใช้เถ้าลอย FBC ในการผลิตเป็นวัสดุจีโอโพลิเมอร์และเพิ่มความเป็นอสัณฐานและความว่องไวของเถ้าลอย FBC โดยผสมซิลิกาฟูมในอัตราส่วนต่างๆ เพื่อเปลี่ยนปริมาณแคลเซียมที่มากเกินพอในเถ้าลอย FBC เป็นสารประกอบแคลเซียมซิลิเกตไฮเดรตที่ให้กำลังอัดแก่จีโอโพลิเมอร์  ซึ่งพบว่าอัตราส่วนผสมที่เหมาะสมระหว่างเถ้าลอย FBC กับซิลิกาฟูม (SF) คือ การแทนที่เถ้าลอย FBC ด้วยซิลิกาฟูมร้อยละ 3.75 โดยน้ำหนัก ทำให้ได้วัสดุจีโอโพลิเมอร์มีค่ากำลังอัดเพิ่มขึ้น โดยค่ากำลังอัดที่อายุ 90 วัน มีค่าเท่ากับ 21.4 เมกกะปาสคาลAbstractFluidized bed combustion (FBC) fly ash has the irregular shape, high porosity and crystalline owing to low combustion temperature (~900oC). In addition, it contains high amount of calcium compound resulted in low use as pozzolan for concrete production. Therefore, this research proposed the utilization of FBC fly ash in geopolymer. Increase in morphological property and reactivity of FBC fly ash was performed by blending with silica fume and grinding.  Silica fume reacted with excess calcium in FBC fly ash resulted in calcium silicate compound which enhanced the strength of geopolymer. It was found that the replacement of FBC fly ash with silica fume at 3.75% by weight increased the strength of geopolymer to 21.4 MPa at 90-day curing age

Calcium wastes as an additive for a low calcium fly ash geopolymer

Abstract A geopolymer is a low-carbon cement based on the utilization of waste ash in alkali-activated conditions. Coal fly ash is widely used as a source material for geopolymer synthesis since it contains a sufficient amount of reactive alumina and silica for geopolymerization. Geopolymer products are known to have beneficial fire resistance and mechanical properties. Class F or low-calcium fly ash (LCFA) is generally used as a primary aluminosilicate source; however, heat curing is required to complete the reaction and hardening process and achieve a strong composite. Furthermore, calcium additives are often required to improve the strength of LCFA geopolymers. This paper presents the potential of reusing calcium waste for this purpose. Three calcium wastes, namely calcium carbide residue (CCR), limestone waste, and waste cement (WC) slurry in powder form were used as additives and compared with the use of ordinary Portland cement (OPC). LCFA was replaced with the calcium additives at 20%. However, 20% CCR resulted in flash setting, hence 5% CCR was used instead. A durability test using 3% HCl solution was also performed. The results showed that the reactivity of calcium additives played an important role in strength development. In the calcium–aluminosilicate–alkali system, calcium silicate hydrate (CSH) and calcium aluminosilicate hydrate (CASH) were formed. The maximum strength of 21.9 MPa was obtained from the OPC/LCFA geopolymer, and 3% HCl solution had a deleterious effect on the strength. OPC and CCR were favorable reactive sources of calcium compounds to blend with LCFA. From the thermogravimetric results, lower thermal weight changes with higher strength gains were achieved. Low CaCO3 decomposition at 750 °C according to the TGA curves indicated the more formation of thermally stable CSH and high compressive strength of Ca/LCFA geopolymers

ผลของปริมาณเกาลินต่อสมบัติของโฟมชีวภาพ ที่มีแป้งข้าวโพดผสมแป้งข้าวเหนียวเป็นองค์ประกอบEffects of Kaolin Content on Properties of Biofoam Based on Corn Starch/Glutinous Rice Flour Blend

บทคัดย่อเพื่อลดปริมาณการใช้โฟมพอลิสไตรีนซึ่งก่อให้เกิดปัญหาขยะพลาสติกในสิ่งแวดล้อม งานวิจัยนี้ได้พัฒนาโฟมชีวภาพจากแป้งข้าวโพดผสมกับแป้งข้าวเหนียว เพื่อเป็นทางเลือกหนึ่งในการใช้ทดแทนโฟมพอลิสไตรีน โดยใช้สารเติมแต่ง ได้แก่ กัวร์กัม ไขผึ้ง แมกเนเซียมสเตียเรท และกลีเซอรอล และเสริมแรงด้วยเกาลิน ได้ศึกษาผลของเกาลิน (5  10 และ 15 phr) ต่อสมบัติทางกายภาพ สมบัติเชิงกล และสมบัติทางความร้อนของโฟม การศึกษาพบว่าการเสริมแรงด้วยเกาลินมีผลให้ความหนาแน่นของโฟมมีค่าสูงขึ้น ขนาดและสัดส่วนของเซลล์เปิดมีค่ามากขึ้น ในขณะที่เซลล์ปิดมีขนาดใกล้เคียงกันแต่มีผนังเซลล์หนาขึ้น และมีสัดส่วนน้อยลง นอกจากนี้ปริมาณเกาลินที่มากขึ้นยังส่งผลให้โฟมแป้งมีการดูดซับความชื้นน้อยลงและคงรูปร่างได้ดีขึ้นหลังการแช่น้ำเป็นเวลา 30 นาที ถึงแม้ว่าการเติมเกาลินจะมีผลให้ค่าระยะยืด ณ จุดขาดของโฟมลดลง 44% แต่พบว่าโฟมมีค่าโมดูลัสเพิ่มขึ้นถึง 87% เมื่อเติมเกาลิน 15 phr นอกจากนี้ยังพบว่าการเติมเกาลินส่งผลให้จุดหลอมเหลวของโฟมเพิ่มขึ้นด้วยAbstractIn order to reduce the use of expanded polystyrene (EPS) foam that is a source of solid wastes in the environment, biofoam made of corn starch/glutinous rice flour blend was developed with an aim to replace EPS foam. Some additives such as guar gum, beewax, magnesium stearate and glycerol were also added and kaolin was used as a reinforcing agent. Effects of kaolin content (5, 10, and 15 phr) on physical, mechanical, and thermal properties of the foam were investigated. It was found that with the addition of kaolin, the foam density, the size and fraction of opened cells increased, accordingly. In contrast, the closed cells showed no change in size, while the thickness of cell wall increased. Furthermore, with increasing in kaolin content, the foam exhibited the reduction in moisture content as well as water absorption capacity, resulting in good dimensional stability after soaking in water for 30 min. Although the addition of 15 phr kaolin brought about the 44% reduction in elongation at break, Young’s modulus of the foam increased by 87%. Besides, it was also found that melting temperature of the foam can be increased with increasing kaolin content

Investigations on electrostatic dissipative materials derived from Poly(vinyl alcohol)/ferrofluid composites

Biodegradable polymer composites based on polyvinyl alcohol (PVA) and ferrofluid (FF) were prepared by solutioncasting method. Such composites were characterized by various methods in order to evaluate their potential for use as elec-trostatic dissipative (ESD) materials. Effects of ferrofluid content on mechanical, thermal, and electrical properties of thecomposites were investigated. The morphology of the composites was examined by SEM and the water contact angle on thecomposite surface was also measured. Experimental results showed that surface resistivity of the composites can be reducedby the addition of FF. The abrupt transition of such resistivity occurred in the concentration range 20-30 wt.% FF. Theconductive mechanism of the proposed composites is a complex manner, including contact conduction and tunnelingconduction

Alkali-activated material synthesized from palm oil fuel ash for Cu/Zn ion removal from aqueous solutions

Heavy-metal-contaminated wastewater is harmful to human beings as well as to the environment. Heavy metals are easily soluble in acidic conditions; thus, chemical treatment is necessary for this type of wastewater. Hydroxide precipitation of heavy metals is a simple and low-cost process that was used in this research. Palm oil fuel ash (POFA) was used to synthesize an alkali-activated material (AAM) for use as a pH modifier and hydroxide (OH− ion) releasing agent in Cu and Zn contaminated solutions. The released hydroxide reacts with Cu2+ and Zn2+ ions and forms metal hydroxide, which was removed from the wastewater by precipitation. The final concentrations of Cu2+ and Zn2+ ions in the solution were lower than the standard allowances of 5 and 2 ppm, respectively. The retention time and pH value of the solution played an important role in the final concentration of metal ions. The hydroxide precipitate was removed from the solution by a simple filtration process. Tests also showed that the POFA alkali-activated material could be reused. The precipitation method using POFA alkali-activated material is, therefore, a simple and cost-effective method for wastewater treatment. Heavy-metal-contaminated agricultural wastes can be converted into useful composite, leading to green and sustainable products

Effect of surfactants on the distribution of natural rubber latex in cement and geopolymer composites based on X-ray computed tomography

The production of natural rubber latex (NRL) has increased significantly and its use, particularly in construction materials, has been promoted and studied. The presence of NRL in cement composites reduces crack formation and improves ductility. However, the incorporation of NRL in cement composites leads to coagulation of the NRL and fast setting; the use of a surfactant is recommended to avoid these problems. This study investigated two types of surfactant, an anionic surfactant (sodium dodecyl sulfate, SDS) and a nonionic surfactant (Tween 20). An NRL-fly ash geopolymers was also studied for comparison. The three-dimensional microstructure, including the pore and rubber distribution in the NRL composite, was investigated by X-ray micro-computed tomography (micro-CT). The test results show that both surfactants generate pores in the composites. The fine pore formation in the NRL geopolymer composite was found to be better than in the NRL-cement composite. In the NRL cement, Tween 20 generated 2.72% of pores by volume, which was slightly lower than the 3.05% generated by SDS. In the geopolymer system, fast setting of the geopolymer took place with Tween 20. A low pore percentage of 1.67% was obtained for SDS. The agglomerated NRL appeared in various shapes and sizes, particularly at the surface and corners of both NRL composites. A high level of agglomeration of NRL with a plate shape was found in the cement composite with SDS (anionic surfactant). A smaller NRL particle size and better distribution of NRL was found in the geopolymer compared with the cement composite. The results thus confirm that the surfactants can be used to disperse NRL in the cement and geopolymer composites

Characteristics of Waste Iron Powder as a Fine Filler in a High-Calcium Fly Ash Geopolymer

Geopolymer (GP) has been applied as an environmentally-friendly construction material in recent years. Many pozzolanic wastes, such as fly ash (FA) and bottom ash, are commonly used as source materials for synthesizing geopolymer. Nonetheless, many non-pozzolanic wastes are often applied in the field of civil engineering, including waste iron powder (WIP). WIPs are massively produced as by-products from iron and steel industries, and the production rate increases every year. As an iron-based material, WIP has properties of heat induction and restoration, which can enhance the heat curing process of GP. Therefore, this study aimed to utilize WIP in high-calcium FA geopolymer to develop a new type of geopolymer and examine its properties compared to the conventional geopolymer. Scanning electron microscopy and X-ray diffraction were performed on the geopolymers. Mechanical properties, including compressive strength and flexural strength, were also determined. In addition, setting time and temperature monitoring during the heat curing process were carried out. The results indicated that the addition of WIP in FA geopolymer decreased the compressive strength, owing to the formation of tetrahydroxoferrate (II) sodium or Na2[Fe(OH)4]. However, a significant increase in the flexural strength of GP with WIP addition was detected. A flexural strength of 8.5 MPa was achieved by a 28-day sample with 20% of WIP addition, nearly three times higher than that of control