UNIVERSITY CO-OP
Lightweight Concrete - Spring 2014
Overview: The Spring 2014 semester was the second semester that the University Co-op Materials Lab conducted a hands-on investigation into lightweight concrete. During the Fall of 2014, the work focused on creating lightweight concrete samples with the use of traditional aggregates such as Perlite and expanded shale. The following semester, our goal evolved into creating lightweight concrete using recycled materials as a substitute for water, aggregate, and cement. This publication highlights Spring findings. The research investigated the use of expanded glass, EPS regrind, and sawdust as lightweight aggregates, and latex paint as a replacement for water. The research began first by creating a wide range of samples to determine aggregate mixtures of interest. Utilizing the most promising mixes, larger cylindrical samples were created, cured, and then tested to discover their compressive strength. This report documents this process and our initial findings. Research and report by: Samuel Rojas and Corey Rothermel
Lightweight Concrete A Composite Material Precedents Expanded Glass EPS Regrind Sawdust Latex Paint Methods Cube Samples Cylindrical Test Samples Conclusions
Concrete: a composite material Various Suppliers
Traditional concrete is a composite material composed of three main elements: cement, aggregate, and water. Additionally, admixtures are used to enhance various properties of the concrete mix. Cement is the fundamental ingredient of concrete, and serves as the binder that ties together the aggregate. Portland cement is the most common type of cement in general usage. The process of creating Portland cement is energy intensive, and involves heating limestone and clay in large kilns to produce clinker, then grinding that byproduct with sulfate. In terms of overall material composition, fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel, and crushed stone
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are commonly used aggregates. On its own cement is a brittle material, but with the addition of aggregates it becomes durable. When combined with water, cement forms a paste through a process called hydration. The cement paste is what glues the aggregate together and fills the voids in concrete. Water-to-cement ratio is very important in a concrete mix. Low water content makes stronger, more durable concrete. As the water content increases, concrete becomes more fluid and workable, but loses strength. There are a variety of chemical and mineral admixtures that give concrete specific properties. Common chemical admixtures are accelerators, retarders, air entrainers, plasticizers, pigments, corrosion inhibitors, and bonding agents. Mineral admixtures are primarily by-products from other industries that have pozzolanic properties and can be used as a partial substitute for cement in various ratios and quantities. The most common are fly ash, ground granulated blast furnace slag, and silica fume. There are many variations of concrete, including lightweight concrete. It can be easier to form, cheaper to transport, and have improved properties such as thermal and fire resistance. It can be used for both structural and non-structural purposes, and can be achieved through the use of alternative aggregates, foamed concrete, or autoclaved aerated concrete. This project originated from a desire to build concrete furniture for our Lab. We used traditional Type I/II Portland Cement from the Alamo Cement Co. Initially we experimented with traditional aggregates such as limestone fines, expanded shale, and Perlite, but eventually expanded our project to use re-use aggregates as much as possible. In addition, we acquired two mineral admixtures with pozzolanic properties that could be used in future research. Fly ash, a residue from the coal industry, and rice husk ash, a residue from the rice production industry, both can be used as a substitute for Portland cement.
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Precedent: concrete canoe University of Texas at Austin, Chapter of the American Society of Civil Engineers (ASCE)
Beginning in 1988, the American Society of Civil Engineers has annually hosted a concrete canoe competition for engineering students nationwide. The competition is graded on performance both in design as well as the race itself. Students are responsible for the design and fabrication of a lightweight concrete canoe. The University of Texas chapter of the ASCE was a starting point for our research. In 2013 the University of Texas concrete canoe team had the lightest canoe at the Texas-Mexico Region competition by nearly 30 pounds. The team experimented with various lightweight aggregates testing for weight, cohesion, and strength. Their final canoe design was composed of traditional Portland cement mixed with different sizes of expanded glass aggregate. The team provided the Materials Lab with cylindrical samples of a few of their mixtures, providing a spring board for our research.
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Field trip: Center for Maximum Potential Building Systems (CMPBS)
In the Spring of 2014, the Materials Lab hosted a field trip to the Center for Maximum Potential Building Systems. Pliny Fisk III, the founder of the CMPBS and a former UT professor, is considered one of the foremost experts in sustainable and green design as it pertains to a building’s life cycle. His research has led to local, state, and national policies and standards relating to green building. In addition, the CMPBS has undertaken extensive research into lightweight and sustainable forms of concrete over the past four decades. Pliny was one of the first to use fly ash, a byproduct of coal burning, as an alternative to Portland cement. While eliminating Portland cement is sustainable, Pliny found that promoting coal burning to obtain fly ash is an equally unsustainable alternative. Over time his research evolved to begin use of Magnesium Oxide, a byproduct of brine, as a better sustainable alternative.
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Aggregate alternative: expanded glass PoraverÂŽ Expanded Glass
Expanded glass is a lightweight aggregate that comes in multiple pellet sizes and densities, and is made from recycled waste glass. Glass is not biodegradable and will remain in its solid waste form indefinitely. The process of making the pellets entails heating the glass to between 850° and 950° Celsius before mixing in select gases which cause the glass to form bubbles. The temperature is then raised once again to expand and break down the gas, leaving only the expanded glass structure. Different gases react differently to the temperature increases and can be used to control the size of the final pellets. Following the removal of gases, the expanded glass is air cooled - allowing it to harden into its final pellet form.
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Our research used expanded glass pellets from Poraver速, of Dennert Poraver GmbH. Poraver速 offers a base product line of six granularity sizes ranging from .1mm to 8mm. The company also offers additional sizes between .04mm and 16mm based on needs for a specific project. The product is marketed as lightweight, alkali-resistant, non-flammable, and sustainable. Depending on the granularity size used, Poraver expanded glass can be used as a substitute for both the fine and course aggregate in a concrete mixture. Research prior to our undertaking suggested that the larger expanded glass pellets would produce a lighter sample due to an overall reduced density of material, due to their hollow nature. Our initial tests suggested that while the smaller pellets add weight and density, but by they also increase the compressive strength. For our initial tests, we had four sizes at our disposal: .04-.125, .5-1, 1-2, and 2-4 mm. Our research entailed using the expanded glass sizes as a direct substitute for either the coarse or fine aggregate, as well as utilizing multiple expanded glass sizes to replace both the coarse and fine aggregates in traditional mixtures.
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Aggregate alternative: EPS regrind HDi Plastics, Inc.
Expanded Polystyrene (EPS) is a rigid, closed-cell foam with many useful properties such as shock absorbency, compression resistance, durability, thermal insulation, shaping versatility, and light weight. It is used across the globe in a wide variety of applications such as protective packaging, building insulation, safety helmets, and disposable utensils. EPS is produced by injecting gas into heated styrene, and the resulting product is 98-percent air. EPS, commonly referred to by the trademarked brand Styrofoam, is notorious for its inability to biodegrade over long periods of time. As an alternative to landfill disposal, EPS can be recycled by grinding the material back into individual bead-sized particles that can then be reintroduced into the molding process. Conversely, 10
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EPS can be melted down to form large patties that can re-enter the original formation process. The EPS industry has achieved an average postconsumer recycling rate of 14% and average post industrial recycling rate of 25% for the past fifteen years, one of the highest among all plastics. Recycled EPS can be used to make building materials such as thermal insulation panels, prefabricated concrete blocks, and co-mingled plastics products such as decking, lumber and interior trim. Technical considerations generally limit the level of recycled content loading from 10 to 20-percent to maintain minimum performance standards. EPS regrind can also be used in concrete as a substitute for traditional aggregate. This type of concrete is not as strong as stone-based concrete mixes, yet it has other advantages allowing its use where lighter loads are desired or where increased thermal and sound insulation properties are necessary. For the purpose of our research, we were mainly interested in the light weight properties of EPS. Samples were made experimenting with various quantities of EPS regrind and combinations with expanded glass aggregate. The resulting weight of the samples was considerably reduced from the control sample of traditional concrete. Initial compressive strength testing has provided additional information on the relation between various percentages of EPS regrind and corresponding strength, cohesiveness, and brittleness.
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Aggregate alternative: sawdust UTSoA Wood Shop
Sawdust or wood dust is a by-product of cutting, grinding, drilling, sanding, or otherwise pulverizing wood with a saw or other tool, and is composed of fine particles of wood. It is widely used to make particleboard and wood pulp, yet it has a variety of other uses including fuel, mulch, as an alternative to cat litter, soaking up liquid spills, or manufacturing charcoal briquettes. A mixture of sawdust, sand and cement has been used to make wall panels in New South Wales, Australia for many years. The practice has been researched and applied in parts of the US, UK, and Canada as well. In some instances, sawdust concrete has been used for flooring as well as walling.
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A successful example can be attributed to Walt Friberg, a former Agricultural Engineering faculty member at the University of Idaho, who built a house primarily out of sawdust concrete in the 1940’s in Moscow, Idaho. The mix he used was one part cement, one part diatomaceous earth, three parts sawdust, three parts shavings, and one part clay - all volume measurements. The result was a low-cost, high-insulating, fireresistant, lightweight concrete. One inch of Friberg’s sawdust concrete has the insulating value of 12 to 14 inches of ordinary concrete, is excellent for floors and walls where high insulation is desired and the load can be carried by a veneer of bricks or boards. Sawdust concrete can be sawed, drilled, and nailed just like wood, and is amazingly fire-resistant. During our research, one cube sample was made with wood shavings from the School of Architecture wood shop, resulting in an unusually long curing time. As a result, our attention turned primarily on the use of other light-weight aggregates such as EPS regrind and expanded glass. Based on the above comments however, future research should pay closer attention to sawdust concrete mixes incorporating the use of diatomaceous earth and clay.
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Water substitute: latex paint Austin ReBlend - City of Austin Resource Recovery department
Latex can be defined as either natural or synthetic. Natural latex is a milky fluid found in many plants, such as poppies and spurges, that exudes when the plant is cut and coagulates on exposure to the air. The latex of the rubber tree is the chief source of natural rubber. Synthetic latex resembles this, consisting of an emulsion, or a stable dispersion in water of polymer particles, used to make paints, coatings, and a variety of other products. The addition of latex to concrete reduces the water requirement, resulting in a cured concrete with higher compressive strength. It also forms elastic membranes throughout the matrix of the concrete, reducing the formation of voids and hairline cracks during the curing stage. Latex Modified Concrete (LMC) resists penetration of oil, water, salts and aids in the
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adhesion of new concrete to old. The flexural strength is improved, and there is an increase in abrasion resistance. For our research we used Austin ReBlend paint as our source of latex. Austin ReBlend is a post-consumer blend of paint made by the City of Austin’s Household Hazardous Waste at their Travis County resource recovery facility. The Household Hazardous Waste facility is where Austin residents are able to drop off hazardous materials, such as latex paint, to be properly disposed of by the city. In an effort to promote sustainability the department launched the ReBlend program by mixing the various latex paints dropped off to create the new blended product that is available to Austin Residents free of charge. By recycling the paint in this manner the city is keeping hazardous paint out of landfills, reducing the overall waste input, preserving water which is used to create new paint, and minimizing the amount of raw materials that go into paint. The paint is available in two colors, Beige and Dark Beige, and comes in 3.5 gallon containers. Cube sample No. 20 was prepared with latex paint as a total substitute for water, resulting in a very cohesive concrete mix with a particularly slow curing process and somewhat flexible and pliable texture. Other samples were prepared with a small percentage of latex paint diluted in water, which did not present the same problems. Compressive strength testing will provide additional information on the relation between the water to latex ratio and corresponding mix properties.
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Methods Cube Test Samples
Initial mixes were created using reusable formwork to produce smaller cubic samples before producing the larger cylindrical cores from our best samples. We utilized six plywood pieces that had an interior space of 3x3x3� to create a consistent volume to use as a baseline to compare different samples. Once cured, we removed the screws from the form and the samples easily popped free. Due to available supplies, our methods of mixing and pouring the concrete were basic. We mixed the dry ingredients by hand before adding the liquids, then also mixing by hand. Once combined, the mixture was poured into the formwork and vibrated manually to level. Moving forward, a concrete mixer and vibrator would be useful tools to improve the consistency of the mix and to help in reducing water content. In addition, adherence to proper curing methods is recommended.
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Cylindrical Test Samples
The methodology employed for the cylindrical samples is quite similar to that used to create the cube samples. The engineering department at the University of Texas donated 4 plastic 3”x6” cylindrical molds for our use. They advised us to drill holes in the bottom and cover the hole with duct tape allowing us to pop our cores out with an air compressor once cured, giving us the ability to reuse the plastic molds. Upon selecting a mixture worth testing we would calculate the required material input based on the volumetric difference between our cube (28.125 in³) and cylindrical molds (100.531 in³) equating to roughly a four fold increase. Attempting to fill out the mold completely and reduce air pockets we would pour roughly a third of the material in, vibrate, and then repeat. We removed the cores after four or five days of curing, to be tested after 28 days.
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Cube test sample: 01 (control)
Material Composition 6: Quikrete 1: Water
Attributes Weight: Dimensions: Volume: Density:
951.200 g / 2.907 lb 3 x 3 x 3” 28.125 in³ 0.075 lbs/in³
Results Sample was created using only Quikrete purchased from the hardware store to create a baseline standard for traditional concrete. Sample has smooth faces on all sides.
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Cube test sample: 02 (lightweight control)
Material Composition 1: Portland cement 2: Sand 3: Expanded shale 1: Water
Attributes Weight: Dimensions: Volume: Density:
736.580 g / 1.683 lb 3 x 3 x 3” 28.125 in³ 0.060 lbs/in³
Results Sample was created using expanded shale, a lightweight stone aggregate, which is common practice in industry for making lighter concrete. Sample is approximately 20% lighter than the control.
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Cube test sample: 03
Material Composition 1: Portland cement 2: Sand 3: EPS regrind 1: Water
Attributes Weight: Dimensions: Volume: Density:
444.600 g / 0.980 lb 3 x 3 x 3” 28.125 in³ 0.035 lbs/in³
Results Sample followed the traditional 1-2-3 ratio mix substituting EPS regrind in for the large aggregate. The sample is approximately. 55% lighter but visibly has a poor ratio of contents.
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Cube test sample: 04
Material Composition 1: Portland cement 2: Sand 3: Expanded glass (4-8) 1.25: Water
Attributes Weight: Dimensions: Volume: Density:
607.110 g / 1.338 lb 3 x 3 x 3” 28.125 in³ 0.048 lbs/in³
Results Continuing to use the 1-2-3 ratio to test different aggregates, this sample uses larger EG pellets. These pellets weigh more than the EPS regrind.
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Cube test sample: 05
Material Composition 1: Portland cement 2: Sand 3: Expanded glass (0.5 - 1) 1: Water
Attributes Weight: Dimensions: Volume: Density:
494.160 g / 1.089 lb 3 x 3 x 3” 28.125 in³ 0.039 lbs/in³
Results Using the 1-2-3 ratio this sample shows that the smaller EG pellets offer weight reduction from the larger EG pellets.
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Cube test sample: 06
Material Composition 1: Portland cement 2: Sand 3: Expanded glass (2-4) 1: Water
Attributes Weight: Dimensions: Volume: Density:
527.830 g / 1.164 lb 3 x 3 x 3” 28.125 in³ 0.041 lbs/in³
Results Using a third size of EG pellets, the results are as one would expect. The EG (2-4) sample weighs more than the (.5-1) sample and less than the (4-8) sample.
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Cube test sample: 07
Material Composition 1: Portland cement 2: Sand 3: Expanded glass (.04-.125) 1: Water
Attributes Weight: Dimensions: Volume: Density:
630.640 g / 1.390 lb 3 x 3 x 3� 28.125 in³ 0.050 lbs/in³
Results Sample tested the smallest EG size which is a very fine powder as opposed to a pellet. The sample is much denser and heavier than the previous samples lacing a large aggregate.
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Cube test sample: 08
Material Composition 1: Portland cement 2: Sand 3: Sawdust 1: Water
Attributes Weight: Dimensions: Volume: Density:
468.670 g / 1.033 lb 3 x 3 x 3” 28.125 in³ 0.037 lbs/in³
Results Sample tested using sawdust as the larger aggregate. Sample took over a month to harden and has poor cohesion. Upon removing from the formwork the sample crumbled.
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Cube test sample: 09
Material Composition 1: Portland cement 2: Sand 2: EPS regrind 0.75: Water
Attributes Weight: Dimensions: Volume: Density:
562.440 g / 1.240 lb 3 x 3 x 3” 28.125 in³ 0.044 lbs/in³
Results Sample reduced the proportion of EPS regrind thus increasing the cement compared to sample 03. Sample has a better ratio for cohesion but weighs more.
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Cube test sample: 10
Material Composition 1: Portland cement 1.5: Sand 2.5: EPS regrind 1: Water
Attributes Weight: Dimensions: Volume: Density:
468.670 g / 1.033 lb 3 x 3 x 3” 28.125 in³ 0.037 lbs/in³
Results Sample tested using sawdust as the larger aggregate. Sample took over a month to harden and has poor cohesion. Upon removing from the formwork the sample crumbled.
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Cube test sample: 11
Material Composition 1.5: Portland cement 1: Sand 2.5: EPS regrind 1: Water
Attributes Weight: Dimensions: Volume: Density:
433.160 g / 0.955 lb 3 x 3 x 3� 28.125 in³ 0.034 lbs/in³
Results Sample once again removed sand in favor of additional cement for added cohesion. Weight change was negligible suggesting cement and sand have similar weights.
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Cube test sample: 12
Material Composition 2: Portland cement 3: EPS regrind 0.75: Water
Attributes Weight: Dimensions: Volume: Density:
375.950 g / 0.829 lb 3 x 3 x 3” 28.125 in³ 0.030 lbs/in³
Results Sample completely removed sand using only cement, our lightweight aggregate, and water. Sample is lighter and has a good cohesion.
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Cube test sample: 13
Material Composition 1: Portland cement 2: Expanded glass (.04-.125) 3: EPS regrind 1: Water
Attributes Weight: Dimensions: Volume: Density:
289.370 g / 0.638 lb 3 x 3 x 3” 28.125 in³ 0.023 lbs/in³
Results Sample once again uses the traditional 1-2-3 ratio, but substitutes the smallest EG in for sand and uses EPS as the larger aggregate. Significant weight reduction.
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Cube test sample: 14
Material Composition 0.5: Portland cement 1: Expanded glass (0.5 - 1) 1.5: EPS regrind 0.75: Water
Attributes Weight: Dimensions: Volume: Density:
185.660 g / 0.409 lb 3 x 3 x 3” 28.125 in³ 0.015 lbs/in³
Results Using the same ratio as sample 13 except substituting in EG (.5-1) instead of the (.04-.125). This is our lightest sample, however cement to aggregate volume created a poor sample.
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Cube test sample: 15
Material Composition 0.75: Portland cement 1: Expanded glass (4 - 8) 1.25: EPS regrind 0.75: Water
Attributes Weight: Dimensions: Volume: Density:
302.550 g / 0.667 lb 3 x 3 x 3” 28.125 in³ 0.024 lbs/in³
Results Sample increased the cement content at the expense of the EPS content. The largest EG was also used. This sample is extremely light weight and has a good cohesion.
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Cube test sample: 16
Material Composition 0.75: Portland cement 1.25: Expanded glass (.04-.125) 1: Expanded glass (2 - 4) 0.875: Water
Attributes Weight: Dimensions: Volume: Density:
483.170 g / 1.065 lb 3 x 3 x 3” 28.125 in³ 0.038 lbs/in³
Results Sample uses two sizes of expanded glass. Too much water was used adding weight but the sample offers a good mixture of contents to create a strong and cohesive cube.
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Cube test sample: 17
Material Composition 0.5: Portland cement 1.25: Expanded glass (.04-.125) 1.25: Expanded glass (4 - 8) 0.75: Water
Attributes Weight: Dimensions: Volume: Density:
407.060 g / 0.897 lb 3 x 3 x 3� 28.125 in³ 0.032 lbs/in³
Results Sample 17 improves upon sample 16 using the largest EG pellets and less water. This sample is lighter while still having a strong cohesion.
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Cube test sample: 18
Material Composition 1: Portland cement 2: Expanded glass (0.5 - 1) 1: Water
Attributes Weight: Dimensions: Volume: Density:
449.140 g / 0.990 lb 3 x 3 x 3” 28.125 in³ 0.035 lbs/in³
Results Sample 18 is similar to sample 12, using the EG (.5-1) has both the large and fine aggregate. The sample demonstrates that the EPS is lighter than the EG (.5-1).
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Cube test sample: 19
Material Composition 0.75: Portland cement 1: Expanded glass (.04-.125) 1.5: Expanded glass (4 - 8) 0.75: Water
Attributes Weight: Dimensions: Volume: Density:
390.700 g / 0.861 lb 3 x 3 x 3” 28.125 in³ 0.031 lbs/in³
Results Sample 19 builds a third reference for samples 16 and 17. The sample settled in a way suggesting too much water was used or additional cement was needed.
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Cube test sample: 20
Material Composition 0.33: Portland cement 0.66: Expanded glass (.04-.125) 1: EPS regrind 0.75: Latex paint
Attributes Weight: Dimensions: Volume: Density:
350.270 g / 0.772 lb 3 x 3 x 3” 28.125 in³ 0.028 lbs/in³
Results Sample introduced latex paint as a water substitute. Replacing the water 100% yielded a sample that never fully cured.
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Cube test sample: 21
Material Composition 0.75: Portland cement 1: Expanded glass (4 - 8) 1.25: EPS regrind 0.33: Water 0.33: Latex paint
Attributes Weight: Dimensions: Volume: Density:
313.440 g / 0.691 lb 3 x 3 x 3” 28.125 in³ 0.246 lbs/in³
Results Sample 21 uses sample 15 as a basis, but instead uses a combination of water and latex paint. The sample appears more cohesive and our assumption is also a greater strength.
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Cube test sample: 22
Material Composition 0.75: Portland cement 1: Expanded glass (0.5 - 1) 1: Expanded glass (4 - 8) 0.33: Water 0.33: Latex paint
Attributes Weight: Dimensions: Volume: Density:
384.110 g / 0.847 lb 3 x 3 x 3” 28.125 in³ 0.030 lbs/in³
Results Building upon previous sample, this sample uses EG (.5-1) instead of the EPS adding weight to the cube. This sample has better cohesion while still being relatively light.
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Cylindrical test sample: 01
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Material Composition 9.5: Quikrete 1.5: Water Attributes Weight: Dimensions: Volume: Density:
3586.500 g / 7.929 lb 4” x 8” cylinder 100.531 in³ 0.079 lbs / in³
Testing Maximum load: 3,759 psi Shape of failure: Shear off top Results This cylinder was modeled after cube sample No. 1. It was prepared with Quikrete to serve as a control sample. Since it contains sand and traditional aggregate, the sample presented the largest weight and compressive strength - as was expected. It primarily served as a way to compare traditional concrete to light-weight aggregate samples. Through the load applied in the compression strength test, a portion of the sample sheared off at the very top towards a side.
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Cylindrical test sample: 02
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Material Composition 2.25: Portland cement 3: Expanded glass (4 - 8) 3.75: EPS regrind 1.25: Water 1: Latex paint Attributes Weight: Dimensions: Volume: Density:
1279.900 g / 2.822 lb 4” x 8” cylinder 100.531 in³ 0.028 lbs / in³
Testing Maximum load: 556 psi Shape of failure: Single vertical crack Results This cylindrical sample had a similar composition to cube sample No. 21, although in different proportions. When removing it from the plastic mold, the bottom edges were chipped. Through the load applied in the compressive strength test, the sample remained solid yet presented vertical cracking along one side. The high content of EPS regrind seems to have given the mix its low compressive strength.
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Cylindrical test sample: 03
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Material Composition 2.25: Portland cement 3: Expanded glass (0.5 - 1) 3: Expanded glass (4 - 8) 1.25: Water 1: Latex paint Attributes Weight: Dimensions: Volume: Density:
1454.500 g / 3.207 lb 4” x 7.75” cylinder 97.390 in³ 0.033 lbs / in³
Testing Maximum load: 881 psi Shape of failure: Split down center Results This sample is composed almost exactly to the last of the cube samples, No. 22. The material amount calculations were a slightly short, therefore the mold was not filled entirely. As with sample No. 2, some of the bottom edges chipped when pulling it out of the mold. This sample presented a higher compressive strength, possibly attributed to the lack of EPS regrind in the mix. The load caused the sample to split in half right down the middle.
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Cylindrical test sample: 04
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Material Composition 2.25: Portland cement 3: Expanded glass (0.04 - .125) 3.75: Expanded glass (2 - 4) 1.25: Water 0.5: Latex paint Attributes Weight: Dimensions: Volume: Density:
1654.200 g / 3.647 lb 4” x 8” cylinder 100.531 in³ 0.036 lbs / in³
Testing Maximum load: 1251 psi Shape of failure: Three cracks splitting Results As with previous samples, this cylinder had part of the bottom edge chipped away when it came out of the mold. It did not contain any EPS regrind, yet included two smaller sizes of expanded glass aggregate. Although not the lightest, this cylinder had the highest compressive strength. The load from the compressive strength test gave the sample three vertical cracks sheering apart in multiple places.
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Cylindrical Test Sample: 05
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M
Material Composition 2.675: Portland cement 3.5: Expanded glass (4 - 8) 3.325: EPS regrind 2: Water Attributes Weight: Dimensions: Volume: Density:
A
1077.100 g / 2.375 lb 4” x 7.5” cylinder 94.250 in³ 0.025 lbs / in³
Testing Maximum load: 547 psi Shape of failure: One vertical crack Results This mix was modeled after cube samples no.15 and cylinder sample No.2. With a high EPS regrind content and the larger expanded glass aggregate dispersed within the mix, this sample presented the lightest weight out of all other samples. It also had the second lowest compressive strength.
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Cylindrical Test Sample: 06
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Material Composition 1: Portland cement 2: Expanded glass (0.04 - 0.125) 3: EPS regrind 1: Water Attributes Weight: Dimensions: Volume: Density:
1103.300 g / 2.432 lb 4” x 8” cylinder 100.531 in³ 0.024 lbs / in³
Testing Maximum load: 319 psi Shape of failure: Shear on bottom Results This particular sample lost about 5% of volume due to the bottom not being cohesive when inserting into the mold. The mix design performed well in terms of weight, yet had the lowest compressive strength of all samples. Because of the way it was cured in the mold, it was expected that the compressive load caused the sample to fail at the bottom end.
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Cylindrical Test Sample: 07
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Material Composition 1.75: Portland cement 3.75: Expanded glass (0.04 - 0.125) 3.75: EPS regrind 2.25: Water 0.5: Latex paint Attributes Weight: Dimensions: Volume: Density:
1334.800 g / 2.943 lb 4” x 8” cylinder 100.531 in³ 0.029 lbs / in³
Testing Maximum load: 558 psi Shape of failure: Two vertical cracks Results The mix design on this cylinder was very similar to cube sample no.13. After mixing all the materials, the consistency was dry and required adding more water to give it fluidity. In terms of weight, this mix performed about average. In terms of compressive strength, this had the third lowest value out of all cylinder samples. Failure from the load came in the form of two vertical cracks, yet the sample maintained its integrity.
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Cylindrical Test Sample: 08
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Material Composition 1.75: Portland cement 3.75: Expanded glass (0.04 - 0.125) 3.75: EPS regrind 2.25: Water 0.5: Latex paint Attributes Weight: Dimensions: Volume: Density:
1334.800 g / 2.943 lb 4” x 8” cylinder 100.531 in³ 0.029 lbs / in³
Testing Maximum load: 558 psi Shape of failure: Two vertical cracks Results The mix design on this cylinder was very similar to cube sample no.13. After mixing all the materials, the consistency was dry and required adding more water to give it fluidity. In terms of weight, this mix performed about average. In terms of compressive strength, this had the third lowest value out of all cylinder samples. Failure from the load came in the form of two vertical cracks, yet the sample maintained its integrity.
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Cylindrical Test Sample: 09
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Material Composition 3: Portland cement 1.5: Expanded glass (1 - 2) 2: Expanded glass (2 - 4) .75: Expanded glass (4 - 8) 4.5: EPS regrind 1: Forta Ferro 2: Water Attributes Weight: Dimensions: Volume: Density:
1100.900 g / 2.449 lb 4” x 8” cylinder 100.531 in³ 0.024 lbs / in³
Testing Maximum load: 609 psi Shape of failure: Shear bottom both sides Results This sample was a mirror of cylindrical sample No. 8, with the addition of polymer reinforcement fiber. The intent was to increase the compressive strength of the mix through the addition of the fibers. Surprisingly, not only was the weight lighter but the compressive strength was less as well. However, when the sample was taken of the mold, it presented an irregular surface at the bottom. The compressive load caused the sample to fail at the bottom, so perhaps the results are mis-representative of the mix’s potential. Further analysis is recommended.
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Conclusions: Concrete presents a unique opportunity to use recycled materials that would otherwise end up in the landfill. This research investigates the use of materials that have the potential to reduce the high energy required to produce concrete, and the re-use of what otherwise might be considered waste materials. We explored alternatives to traditional materials used in concrete such as expanded glass, EPS regrind, and sawdust, in order to produce lightweight concrete. The applications for lightweight concrete are numerous. These may include sidewalks, terraces, roof gardens, wall panels, furniture, and art pieces. The main disadvantage that lightweight presents is its much lower compressive strength as compared to traditional concrete, attributed to the use of lighter, less durable aggregates that lend the concrete less structural integrity. While this semester-long project focused on the use of expanded glass and EPS regrind, there are a wide array of other materials that could be used to make concrete both lightweight as well as more “sustainable.� Moving forward, the project will expand to include materials that combine to produce both lightweight and structural concretes with the larger goal of creating a mixture with maximum re-use content.
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Materials Lab Investigation
We recommend exploration with the following materials: Cement substitutes: • Magnesium Oxide • Rice husk ash (solid and powder) Aggregate substitutes:
• Sawdust • Recycled building materials • Glass, ceramic, brick powder Admixtures / reinforcing: Basalt Re-bar Aircrete interior insulation Organic fiber reinforcement (then can use salt water) Bamboo strips, fibers
• • • •
Water substitutes: • Latex Sawdust concrete: • Sawdust, wood shavings, diatomaceous earth, and clay
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