Copyright © FAB Online LLC. All rights reserved.
Finally installed the raised bottom of hopper chamber. I used 22ga. galvanized roofing sheet metal. I used two layers for added strength. Had to remove the back bulkhead to get it in there. I used silicone all around for a tight, semi-permanent seal. This should reduce waste and make it easier to keep clean. I have started gathering materials to build a ball mill as I have not locally sourced a fine sand.
This page is dedicated to projects using my new Green Dragon aircrete forming machine. I will initially post my construction of the machine itself and later add projects using the aircrete. Sorry I didn't start this from the beginning to show the complete process but will try to add each stage from now on. To this point I have cut out all openings, modified and mounted the hopper, fabricated and mounted the trap door, installed the water dispersing tubes, modified and painted and attached a metal folding sawhorse, and built and mounted an electrical control box.
I had to remove the auger to get measurements for the false bottom so I decided to take a picture so everyone could see the completed "guts" of the Green Dragon. Take your time to get the auger exactly on the shaft where it needs to be with everything but the metal blades and spacers installed. The small plastic bushing is meant to fit inside the small hole at the end where the drill hooks on. I had to sand mine a little to get it to fit. I used two roll pins to secure it to the shaft. To install the blades and spacers I used a 3/8" PVC bushing to start the spacer. Once it was about 1/8" onto the hexagonal shaft, I placed a blade on the shaft and used a 1" x 3/4" bushing with a 6" piece of 1" PVC pipe to start the blade. Once tapped down 6", I was able to push it the rest of the way by hand. I snugged each spacer and blade up to the end and continued. The instructions didn't say if the blades hade to be orientated a certain way so I just chose one and made sure I placed each blade on the shaft the same way. Curious to see if this will hold up over time. I have used several cement mixing machines before and this is a new design to me. Connected the drill also so the GD is ready for business!
Installed foam generator as per instructions. Nothing unusual from instructions. Cut marked line with hack saw on the farthest line from joint. Used dremel to shape elbow going into main tube. Connected air line from control box which was the last item to be connected. Also installed auger (not shown) no alterations from instructions.
1. If superplasticizer is being used its dosage should not be more than 0.2 bwc.
2. Ignore the amount of water contained in the foam in the mix design calculation.
3. Determine the amount of air (kg/m3) in the mix from consideration of a unit volume, and from the target density of the foam, estimate the required quantity of foam. Worked out final mix proportion for trials.
4. Usually the total cement content lie between 300 to 500 kg/m3. The gain in strength is small above cement content of 500 kg/m3.
5. Fly ash is added, at level of up to 100% of the OPC content, to enhance workability and increase long-term strength of foamed concrete. Because of greater surface area of OPC/FA mixes have a greater water demand than OPC/sand mixes. The addition of fly ash to a mix leads to a more uniform bubble structure in the paste, which in turn improve some of the engineering properties of the concrete.
6. Fly ash can be used as a total replacement for sand to produce foamed concrete with a dry density of up to 1400 kg/m3.
7. In all cases trial mixes should be done with proposed materials to determine workability, plastic density, if need be the mix should be modified. Specimens shall be cast and tested for the compliance of required specifications.
8. To minimize shrinkage the W/C or W/C+FA ratio should be kept as low as possible.
9. Total fly ash based foamed concrete products are eco friendly as no sand is used.
10. Foamed concrete should be allowed to dry under shade for a period of 28 days to complete initial curing. In low humidity environments wet burlap is helpful to cover the concrete during the curing process.
Above pictures show the detail on my electrical "control box". Keeps water and electricity separate!
The above tables show the density and compressive strength of air-crete using different mixes. Note the large increase in compressive strength over time. Here is more info I gleaned from a few sources and put together.
Foamed concrete, also called cellular light weight concrete is produced by the mixing of Portland cement, sand including or alone fly ash, water and preformed stable foam. The foam is produced by mixing foaming agent and water and pumping it through a foam generator. The air content is typically between 40 to 80 percent of the total volume. The bubbles vary in size from around 0.1 to 1.5 mm in diameter. Foamed concrete differentiates from (a) gas or aerated concrete, where the bubbles are chemically formed through the reaction of aluminum powder with calcium hydroxide and other alkalis released by cement hydration and (b) air entrained concrete, which has a much lower volume of entrained air is used in concrete for durability. The 28 days strength and dry density of the material vary according to its composition, largely its air voids content, but usually they range from 1.0 to 25.00 N/mm2 and 400 to 1800 kg/m3. The plastic density of the material is about 150 to 200 kg/m3 higher than its dry density. There is at present, no guidance or standard method for proportioning foamed concrete, because the hardened density of foamed concrete depends on the saturation level in its pores. CLC can be produced in a density range of 400 kg/m3 to 1,800 kg/m3, with high insulation value and a 28-day cube crushing strength of up-to 275 kg/cm2.
The high density range from 1200kg/m3 (Crushing strength 65 kg/cm2) to 1800 kg/m3 (Crushing strength 250 kg/cm2) is structural grade material utilized for:
(a) In-situ casting of structural (load-bearing) walls and roofs of low rise individual or group housing schemes.
(b) Manufacture of reinforced structural cladding or partitioning panels.
(c) Making pre-cast blocks (500x250x200/100 mm) for load- bearing walling masonry for low rise buildings. The highest density that can be achieved using only cement and foam is about 700kg/m3 . To reach the densities required to use for building load bearing structures, we will need to add fly ash or sand or both. Tables below show amounts required for desired densities.
The above chart shows particle sizes and conversions. Foamed concrete is commercially made using a "fine " sand which corresponds to a sieve size of 60-120. Finding this grade of sand locally is challenging. QUIKRETE® Commercial grade sand is available in, Fine No. 1961 #30 - #70 (0.6-0.2 mm). This would be acceptable for our use if you can get it. It is not available where I live. The last option beyond paying shipping for "sand" is making it yourself. Commercial productions uses giant ball mils to create their own grades of sand. Maybe a smaller version similar to a rock tumble can be utilized for the same purpose.