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Post by SteveStuff on Mar 8, 2017 18:15:25 GMT -8
www.youtube.com/watch?v=dLoedeB9GU8&sns=emCorrect me if this has already been addressed elsewhere. I'm a pretty long-time and regular quiet snoop around here and have not seen this... Anyone have any negative vibes or data about this method and/or resulting material? With any luck, im about to blow you all away with some new ideas!!!...... haha. Or get proven wrong in an epic way but that is what all of you are here for too, right! Thanks to everyone here that takes the time to provide input and data for the rest of us, you are what makes me love this tiny niche of humans!
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Post by coisinger on Mar 9, 2017 10:33:09 GMT -8
Waiting for Peter to come in with his standard, "Use commercial refractory materials for the best results", which I tend to agree with.
Can you make a refractory that will work? Certainly.
Do you want a refractory that will work for a year or two? Not really.
Do you want a refractory that will last decades? Stick with the commercial refractory materials for best results.
Peter you see how I worked that?
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Post by Vortex on Mar 9, 2017 11:22:25 GMT -8
I would tend to agree, but not everyone has access to commercial refractories. It's good to know what can be used in an emergency, or where people have nothing else available, but it's also good to make them aware that they might be wasting their time.
Steve: I'm sure I've seen that video linked off a thread here before but I cant seem to find it now.
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Post by SteveStuff on Mar 9, 2017 16:19:16 GMT -8
Thanks guys.
I actually already agree that the commercial stuff is the way to go... I plan to use Kastolite for any final works of mine which is what I have found easily shipped here. Haven't really had time to look up any other kind that may be locally available as I work A LOT but have remote internet so any free mental time I have I immediately go back to this passion online.
Just curious from the pros if this is a decent DIY method?...
Thanks again!
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Post by coisinger on Mar 9, 2017 16:44:11 GMT -8
I have not personally tried castable. My prefered methods is insulated fire brick.
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Post by SteveStuff on Mar 9, 2017 17:10:08 GMT -8
Any reason? Cost seems to be close depending on the area/source. Just curious. Thx for the input!
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Post by coisinger on Mar 13, 2017 3:43:31 GMT -8
Fire brick just lasts.
It may be slightly more costly up front but you will not have to replace it (caveat: as often). With homebrew castings, you 'may' need to replace failed formulations much more often. You could get lucky and hit he magic formulation right off the bat, but it's likely you will have to do rework.
IF you are testing, this is not an issue. If you are constructing a long term project, stick with proven materials.
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Post by jkirk3279 on Mar 15, 2017 13:41:10 GMT -8
go.galegroup.com/ps/i.do?v=2.1&u=lom_accessmich&it=r&id=GALE%7CA458679892&p=AONE&sw=w&authCount=1Hopefully this link will work. It details how to make a Waterglass based mortar that can be cast, then hardened at moderate heat, 200C. It becomes water insoluble at that point. You wouldn't even need a kiln, you could harden these bricks in your oven or bbq grill. Does the idea of using professional materials sound preferable? Sure. For the final version. For prototypes and testing new ideas, cheaper is better. Lye can even be made in a rain barrel with hardwood ash. If anyone has a chemical engineering background, it would be great to get an English translation of the above link. The recipe makes a very hard firebrick that can be cast into shape. I know the reaction calls for aluminum but at first glance I don't see where it comes from. If this stuff could make for a castable riser good to 2000F it would be a boon,
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Post by Vortex on Mar 15, 2017 14:47:57 GMT -8
The link asks you to login to access the file.
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Post by jkirk3279 on Mar 16, 2017 13:31:50 GMT -8
The link asks you to login to access the file. The full file with charts, yes. But there's a "full text" button that lets you read the paper. I hope someone can help me decode the recipe. For example, a chemist would know how many liters "14 moles" of Na2OH is. i know the reaction requires aluminum but I don't see where it's added. i know the reaction uses baking soda--sodium bicarbonate. This mortar doesn't even require clay. Although of of course Kaolin powder could be added. After reading the recipe, I think it makes very hard, flame resistant Waterglass bricks. The quoted compression modulus was unsurprising, but the Young's modulus made my eyes bug out. I'm starting to think this stuff might make castable cylinders. As in, put a cardboard tube inside a barrel, toss in shredded stainless steel scrubbies and pour. |
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Post by Vortex on Mar 16, 2017 15:45:33 GMT -8
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Post by jkirk3279 on Mar 16, 2017 17:41:05 GMT -8
ABSTRACT This research is focused on sodium silicate bonded silica aggregates for making sustainable construction materials such as bricks and precast products. Different compositions are investigated to produce castable mortars. The mortars are cured at temperatures ranging from 150 to 300[degrees]C and characterized, in particular microstructural and mechanical properties are investigated. Very high compressive strength of 100 MPa and elastic modulus of 5 GPa are obtained for samples with optimized compositions and heat treatments. Solubility and degradation study of the samples in water demonstrate that alkali silicates are prone to be soluble if not treated at 200[degrees]C or above. Transformation of Si-OH to Si-O-Si not only increases the strength but also makes it insoluble in water. It is concluded that sodium silicate bonded bricks and blocks are very promising and affordable materials for construction. They represent an alternative to Portland cement concrete bricks and to sintered clay bricks, providing higher strength and representing an eco-friendly material. Keywords: Silica aggregates Bricks Silicates Mechanical strength Water insoluble 1. Introduction Currently infrastructure and housing sector make use of huge amounts of cement concrete and clay bricks. Both the production of cement and ceramic construction materials require extensive energy and result in C[O.sub.2] emissions. Therefore environmental activists and government regulations are continuously forcing scientists and engineers in development of new alternatives to cement and sintered ceramics which could be able to fulfil the desired requirements [1,2]. The earth crust is mostly composed of aluminosilicates, and most of the researches are trying to mimic the natural stone formation processes in the labs which can be viable for commercial production. Among the various processes available, the ones using alkali silicate binders are particularly interesting. When an aluminosilicate material and an activating agent like sodium hydroxide are combined, a partially crystalline solid is obtained. The class of these materials is designated as geopolymers. The aluminosilicate sources can be naturally occurring or industrial wastes like fly ash, clays tailing, kaolin and pozzolans [3,4]. Geopolymerization reaction also occurs without aluminum, forming Si-O-Si type network. This Si-O-Si bonding gives much higher strength but the drawback of these kinds of materials is that they are water soluble [1]. These types of bonds (Si-O-Si) can be stabilized by carbonation from atmospheric C[O.sub.2] which is a wellknown process to harden the inorganic silicate paints [5]. If a similar process is achieved in-situ by the use of sodium carbonates and mild thermal treatments (above 200[degrees]C), the mortar may be hardened and stabilized to water. This in-situ carbonation has already been successively used for the hardening process of geopolymers [6]. It is also known that the higher the amorphous silica content, the higher is the geopolymerization reaction due to higher dissolution of the silica and other contents [7,8]. To initiate the chemical reaction between silica aggregates and alkali, three components are necessary namingly, a critical amount of reactive mineral phase in the aggregates, pH of the alkali solution and moisture [9]. For the chemical reaction to take place, the alkali concentration should be high; pH should be higher than 11. For that purpose usually a 14 M solution of sodium silicate is used for the dissolution of the aggregates [10,11]. Higher pH of activating solution results in higher geopolymerization and strength [7]. In this research, we have studied the binding effect of sodium silicate on naturally occurring silica aggregates rather than aluminosilicate minerals as it is done for geopolymers. The investigated binding process is similar to geopolymerization but with lower amount of aluminum hence without true geopolymerization reaction. We have used compositions as reported by Temuujin et al. and Sarkar for the fly ash geopolymers to make the silica inorganic geopolymer bricks by using silica sand aggregates instead of fly ash or any other aluminosilicate [10]. With respect to geopolymerization reaction more emphasis is given to Si--0--Si polymerization rather than Si-O-Al (geopolymerization) hence named differently as an inorganic polymerization. We also study the effects on the silica inorganic polymerization by increasing amounts of sand aggregates and in-situ carbonation using sodium bicarbonate. The physical and mechanical properties of as prepared silica inorganic polymer samples are carefully reported. 2. Experimental 2.1. Materials and preparation Silica sand aggregates by Norman sand (Beckum/Germany CEN Standard Sand EN 196-1, ISO-679) were used as silica source for which the chemical composition (measured by X-ray fluorescence spectrometer (Bruker M4 Tornado)), is given in the Table 1. Sodium bicarbonate (CRUCIANI DAB E500/italy) was used as in-situ C[O.sub.2] source. Water glass with 9% [Na.sub.2]O, 30% Si[O.sub.2] and 61% [H.sub.2]O (Prochin, Italy) and specific gravity of 1.35 g/[cm.sup.3], was used in the formulation. 14 M sodium hydroxide solution was used as an activator solution. A dense homogenized slurry was prepared by milling the sand aggregates together with sodium hydroxide solution, water glass and sodium bicarbonate (for in-situ carbonation formulation), for 10 min using a planetary ball mill and alumina balls as grinding media. Table 2 indicates sample codes and compositions utilized for sampling and testing. Water may also be added later to enhance plasticity of the mortar but with much care as it may be detrimental to uniform properties. After mixing, grinding and adjusting water contents, the mortars were cast in to polyethylene plastic molds with a height to diameter ratio more than 2 (0.9 cm diameter and 2.5 cm height). After forming, the samples were demoulded from the cylindrical vessels and cured at different temperatures (150, 200 and 300[degrees]C) for 2 h in muffle furnace and characterized further. 2.2. Analysis of samples Calorimetric properties (Differential thermal analysis) of the prepared mortar samples were measured from 25 to 700[degrees]C by Mettler Toledo instrument. X-ray diffraction patterns were obtained by Rigaku diffractometer with Cu K[alpha] radiation generated at 40 kV and 20 mA. FTIR analysis was performed on ATR (Attenuated Total Reflectance; Perkin Elmer) with diamond crystal as a probe. Thermal conductivities were measured by C-Therm thermal conductivity analyser. Micrographic analysis was performed using electron microscope (Model: Zeiss, Jena, Germany). Bulk density was calculated by measuring the dimensions and weight of each samples. Mechanical properties of the samples after curing were measured using Lloyd LR5 K instrument in compression mode by applying ASTM C109 standard protocol. 3. Results and discussion 3.1. XRD analysis The XRD spectra of sand aggregates and prepared samples after curing is shown in Fig. 1. In general, all the spectra indicate the absence of amorphous phases, as there is no hump or broaden peaks visible and the most abundant phase is quartz in aggregates as well as in hardened samples. In pure sand aggregates, the peaks are more intense compared to their silicate mortars, because the percentage of silica was reduced by the addition of sodium hydroxide from alkali activator and water glass. All the compositions made for this work show similar trends. There are no peaks appearing after polymerization as the samples and aggregates were mostly quartz silica. But a very small peak present in aggregates at 27.94 (Anorthite; Ca[Al.sub.2][Si.sub.2][O.sub.8], JCPDS 89-1462) is diminished after hardening where as another similar small peak reappeared in mortars without NaHC[O.sub.3] treated, at 27.50 corresponding to CAH10 (CaO x [Al.sub.2][O.sub.4] 10[H.sub.2]O). Anorthite is a zeolitic compound where Al+ is present in the four fold symmetry and its presence gives the insight of the aggregates where this was formed due to weathering and erosion and remained in contact with water for longer times. [12]. Due to dissolution of anorthite, calcium and aluminum react to form CAH10 which is cementing compound formed by calcium. In IGBC, calcium and aluminum didn't form CAH10 due to higher affinity of calcium oxide toward C[O.sub.2] to form CaC[O.sub.3], hence CAH10 peak is absent in the samples treated with sodium bicarbonate. A very small peak for CaC[O.sub.3] was appeared at 29.33 (JCPDS card number 72-1652) as shown in Fig. 1. The amounts of these minerals were very less hence very tiny peaks were able to be visible in the XRD graphs while other smaller peaks were able to be seen in the data of XRD [13,14]. [FIGURE 1 OMITTED] [Ca.sub.3][Si.sub.2][O.sub.7] x 2[H.sub.2]O + 3C[O.sub.2] 2Si[O.sub.2(gel)] + 3CaC[O.sub.3] + 2[H.sub.2]O Newly born silica will form an inorganic binder which enhance the strength by fixation of other compounds making network more stable. 3.2. Water solubility The samples treated at different temperatures underwent a solubility test by immersing in water for 24 h (only representative samples treated above and below 200[degrees]C as the behavior of all the compositions was same). Fig. 2(b) shows a sample cured at 150[degrees]C which after the solubility test looks deteriorated. On the contrary samples treated at 200[degrees]C are insoluble in water as shown in Fig. 2. This property of stability against water is acquired due to removal of the larger fraction of -OH groups from silicates making the mass insoluble as will be explained with different tests [1,15]. 3.3. Thermal calorimetry Fig. 3 depicts the differential thermal calorimetry of the three compositions. The samples treated at 150[degrees]C were chosen to record the changes occurring at 220[degrees]C while thermal scanning up to 700[degrees]C which actually make these samples insoluble. Up to 100[degrees]C the physically absorbed water was evaporated and an endothermic small peak is observed. The small size of the curve indicates that there was very minute amount of water; absorbed from atmosphere or remained during heat treatment at 150[degrees]C. This peak is little more intense in case of IG where water remained as such because of its hardest structure. All the samples treated below 200[degrees]C were water soluble and this curve justified the reason. For all the samples there is a kink in the pattern at around 220[degrees]C. This kink is attributed to the loss of hydroxyl groups attached to Ca, Si and other radicals [16,17]. Dehydration occurred as follows. 2(Si[O.sup.2-.sub.3] x 2M+) - OH [(Si[O.sup.2-.sub.3] x 2M+).sub.2] x O + [H.sub.2]O [up arrow]
IG150 and IGBC150 both have similar curves as compared to IGC150 where it shows a continuous sign of heat evolution after 450[degrees]C. IGC150 samples were having more relative amounts of sodium silicates and sodium hydroxides as well and that's how these were with lower degree of inorganic polymerization hence network continued to grow by heating compared to other compositions [6], In IGBC the broader peak from 300 to 600[degrees]C is due to decomposition of sodium bicarbonate used in its processing. Another peak at around 300[degrees]C is due to small amount of hydrated aluminosilicates present formed due to small amount of aluminum [18]. At 220[degrees]C, the dehydroxylation of Si-OH bonds was occurred. After dehydroxylation of Si-OH it converts to Si-O-Si type network which is stable and not soluble in water. When the mortar in the rigid dry form was treated at 200[degrees]C for two hours, thermal agitations were sufficiently high to remove or dehydrate it although DTA of IG150 shows that at 220 [degrees]C the temperature corresponds at maximum dehydration rate.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
3.4. SEM analysis
The microstructural details were evaluated using SEM micrographs as shown in Fig. 4. Fig. 4(a) and (b) shows the micrographs of IG200 and IG300 respectively. Fig. 4(a) shows a quite uniform structure compared to Fig. 4(b). The uniform microstructure of IG200 indicates that the sand particles were uniformly ground by the activating solution creating a uniform mass. The uniformity depicts the hard nature of the mortar which is also confirmed later in mechanical testing. The samples at 300[degrees]C reveal a porous structure due to evolution of chemically bonded water molecules through the network at 300[degrees]C (dehydroxylation of small amount of aluminosilicates formed due to presence of aluminum). The effect of carbonation can be seen in the microstructure of IGBC200 and IGBC300 (Fig. 4(c) and (d) respectively) with more densely packed structure with very less porosity for IGBC200 while relatively more for IGBC300 as aluminosilicate formed dehydroxylated at 300 [degrees]C and also decomposition of carbonates starts at that temperature. More dense structure for IGBC200 was due to higher degree of polymerization of silica particles initiated by the C[O.sub.2] derived by the decomposition of sodium bicarbonate [19]. In contrast to previous two cases, the microstructure of IGC200 and IGC300 shows porous structures as shown in Fig. 4(e) and (f). IGC200 is more porous because more water was added for processing which increases the amount of physically absorbed water. IGC300 seems dense and uniform compared to IGC200 due to contraction and reduction in volume after treated at 300 [degrees]C; evaporation and dehydroxylation created strong capillary action, which resulted in shrinkage [20].
[FIGURE 4 OMITTED]
3.5. Density, porosity and thermal conductivity
The porosity of samples with different composition and heat treatment is determined by measuring the bulk and the apparent densities of the samples and is given in Table 3. It is noted as soon as the curing temperature is increased the porosity is also increasing because of the removal of volatile components out of the samples. The highest porosity is found in IGBC treated at 300[degrees]C although there is minor difference from IGBC200 because the large amount of bicarbonate is dissociated between 150 and 200[degrees]C. The higher porosity is attributed to the removal of water and sodium bicarbonate dissociation. The least porosity is calculated for the stable (insoluble in water) sample IG200, due to least amount of water utilized while processing. For IGC, the porosity is similar to IG although prepared with higher amount of water; due to the contraction because of capillary forces while curing [20]. Thermal conductivities range from 0.11 to 0.18 W/mK which are not only lower than ordinary Portland cement mortars but also from conventional geopolymers [6].
3.6. Compressive strength
Mechanical strength of the different samples is measured through mechanical compression tests and the behavior is shown in Fig. 5, given in Table 3. The compressive strength and Young's modulus for IGC are comparatively more than the previously ever achieved for the geopolymer mortars [21,22]. The uniform structure in SEM micrographs also predicts higher strength levels as the structure is uniform and intact. But the strength is decreased for IG300 due to the evolution of chemically held water from the structure at 300[degrees]C creating porosity, which weakens the structure. IG samples were having less amount of water compared to other compositions that's how the strength was higher compared to other samples cured at same temperature.
[FIGURE 5 OMITTED]
IGBC samples also showed better strength (compared to IGC but still their strength was low when we compare with IG due to higher amount of sodium silicate used in processing of IGBC.) as a result of C[O.sub.2] produced from sodium bicarbonate, which is helpful in mobilization of aluminum ions and fast hardening of silica network. As the aluminum amount was very less, this effect was due to reaction between silica particles by making networking between silica tetrahedra from sodium silicate and particles by carbonation. Not only the compressive strength but also a higher Young's modulus for IGBC200 is observed. The strength of IGBC300 is least amongst all compositions because not only chemically held water is evolved but also C[O.sub.2] from the remaining bicarbonates hence creating great structural disturbance.
For IGC200 and 1GC300 the strength is similar because of the shrinkage in IGC300 due to higher evaporation on drying. But compare to other compositions, the strength is low for both 200 and 300[degrees]C treated samples due to higher amount of water used in its preparation. The Young's moduli are still very good and fair enough to compare with literature available values [21,22]. The comparison between various properties of silicate mortar, cement blocks, fired clay bricks and geopolymer mortar, is given in Table 4. It can be seen that the greater strength with lower thermal conductivities compared to other conventional construction materials are obtained by this technique. In addition to enhanced properties, the processing time is too short comparatively.
4. Conclusion
The new technique of manufacturing silica with higher mechanical properties not only can be utilized for manufacturing castable bricks but also for extruded bricks and in other processing related to silica. Silicates being most abundant minerals on the surface of the earth can be utilized through this technique as construction material effectively. Least amount of sodium hydroxide and sodium silicates are required to activate and harden the mortar. Heat treatment up to 200[degrees]C impart insolubility properties because of the condensation reactions and the elimination of SiOH. With respect to extruded clay bricks an enormous amount of energy is saved in the manufacturing process. Higher strength and higher young's moduli, least amount of activating and setting agents, lower thermal conductivities, cheapest raw sand and lower times of manufacturing compared to conventional Portland cement, clay bricks and geopolymer mortars, are the key advantages of this processing technique. DTA, SEM and porosity analysis justifies the higher strength and rigidity moduli of the samples in terms of polycondensation reactions of silanol groups.
HIGHLIGHTS
* Water insoluble silicate mortars were produced.
* Optimum properties were obtained by controlling processing temperature and composition.
* Higher level of mechanical properties were achieved in silicates aggregates.
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Post by jkirk3279 on Mar 17, 2017 9:41:12 GMT -8
Whew.
I went through it AGAIN.
It's like chewing a tough cut of meat. You have to start by cutting it into smaller pieces.
The aluminum I was wondering about comes from clay, which isn't in this recipe except in trace amounts.
Geopolymerization works with the aluminum in clay, as well as directly with the silica in sand.
Takeaway; the finer the sand used the better.
Also, you can buy aluminum paste for the sign industry.
I just remembered I have some on the shelf.
It's stored under mineral oil in a tightly lidded container because it's extremely flammable.
So, in practical terms...
We can make or buy Waterglass. I found some for $28 a gallon used for floor sealer.
The online ad didn't have the concentration listed though, which we would need.
Baking Soda is cheap.
I am wondering if powdered glass would supply the silica needed, and what grades of sand are commercially available.
A cement mixer can become a ball mill with some rocks thrown in it.
And the uncured Waterglass will just wash off.
I'll need to hit Google to determine how to make the activator solution.
I didn't see any ratios Waterglass/sand.
The result is Silicon-Oxygen-Silicon mortar, and with reinforcement, possibly it can be painted on the inside of a form and fired.
The heat resistance is quite satisfactory.
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lawry
Junior Member
Posts: 113 
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Post by lawry on Mar 17, 2017 11:57:21 GMT -8
I made some clay and silicate bricks two weeks back and I didn't add water I just varied the silicate amount. I only added silicate no hydroxide.
I think the mix I made needs extrusion.
When I put the samples in the oven they get very soft. Softer than they were before the heat. I removed them and the drier mix is now no longer pliable. I will fire it soon.
Last year I tried to geopolymerise the same clay with silicate and hydroxide at ambient temps and I failed... (I left the brick out in the rain and it fell apart)
I will definitely try this new recipe out and give feedback, I have all the ingredients.
I think this one needs Karl's critique though...
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Post by jkirk3279 on Mar 18, 2017 19:18:36 GMT -8
Some of these recipes mention "powdered Waterglass".
Is that a commercial product?
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