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The Design and Creation of Sustainable Concrete using Alternative Binders to Cement and an Alternative Base Mix By Alexander May

Senior Capstone Paper

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Page 1: Senior Capstone Paper

The Design and Creation of Sustainable Concrete using Alternative Binders to Cement and an

Alternative Base Mix

By

Alexander May

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Description and Purpose of Experiment:

The purpose of this experiment was to provide myself with hands on experience into the introductory process of creating a sustainable building material (a building material that seeks as its end to be both structurally useful in building applications and to negatively impact as little of the human and natural environment as possible). Throughout this process it was my goal to: 1. Conduct research so that I could create a sustainable building material using an informed and intelligent process. 2. Create a material mix design outlining what materials and how much of each material I would use in the creation of my building material. 3. Begin the experimentation process that is necessary to go from the creation of a mix design to the creation of a viable building material. It is also important to note that throughout this process I would be working alongside and guided by architect and former builder Tom Hahn, Associate Director of the Ecosa Institute.

The building material that we chose to create was a more sustainable concrete than standard concrete. Concrete is used 10 times more than any other construction material (1.1). And I can understand why it is so widely used, when I look at its benefits from a construction prospective. It is an incredibly strong and long lasting material. Its plastic quality resulting from its need to be poured before it hardens, allows for it to be used in rapid and versatile building applications. And the materials that constitute it are abundant. But taking a step back and evaluating how the use of concrete affects the wellbeing of humans and the natural environment, it is my belief that along with concrete’s significant benefits come its significant problems. And it was my goal, to have the addressing of these problems, guide the creation of my own sustainable building material.

One significant problem I believe concrete to have, comes from its reliance on using cement as a binder. The first problematic factor of this reliance is that the production of cement results in high emissions of the greenhouse gas C02. These emissions contribute to 3% of global human created C02 emissions (2). The second problematic factor of this reliance comes from the large scale quarrying that is required to acquire limestone, the main material that used in the manufacturing of cement. Limestone quarrying can result in water and air pollution and a massive degradation of the above ground environment (3,4). The second problem I am inspired to address through the creation of my sustainable concrete is that of the offsite quarrying that is typically carried out when sourcing the rest of the materials that make up concrete. This problem I believe is on a much smaller scale than the large scale quarrying related to making cement, because many of the remaining materials that go into concrete come from an average of 30-50 miles away in many parts of the country (5). This leads to the quarrying impacts of sourcing the remaining concrete materials to be more dispersed and therefore less detrimental than large scale quarrying. But I still believe it is important to ask the question, Can this can be addressed? Because the more construction projects can use onsite materials to build with, the less offsite excavation is required, resulting in less negative human and environmental impacts. In response to addressing the problem of concrete’s reliance on cement, we chose to experiment with using alternative binders to cement in the creation of our concrete. In

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order to be acceptable for this experiment, any alternative binder we chose, had to emit less C02 in its production than cement and/or have less of an impact from quarrying in its production.

In response to the second problem, that of concrete’s reliance on offsite quarrying, we designed our base mix (materials minus the binders that would make up our concrete) attempting to partially replicate what it would be like to make a concrete with onsite materials.

With the general idea of what our sustainable concrete would consist of, we then outlined the process of how we were going to actualize our idea. First we would choose our alternative binders and base mix materials that would go into our concrete. Then we would choose what percentage of each material would constitute our base mix. This base mix would be what each alternative binder would be combined with when making our concrete. Then we would test the compression strength of that base mix design using cement as our binder. Compression strength is one of the main attributes that standard concrete is quantitatively evaluated on, and the strength by which we would be evaluating the quality of our sustainable concrete. If cement gave our base mix sufficiently strong compression strength, we would know that our base mix ratios were adequate. If cement, a standard and already well-designed binder, could not bind our base mix or give it sufficient compression strength, we would need to redesign our ratios, rechoose our materials or both. Assuming that our base mix made a viable concrete with cement, we would then proceed to test our base mix with our alternative binders. After evaluating the strength of those results, we would then discard the alternative binder mixes that were too weak and revise the mix designs of the strongest ones. And lastly we would conduct one more round of testing to evaluate the compression strength of our revised concrete mixes.

We would test the strength of each concrete mix by making industry-standard structural test cylinder samples of each mix and then sending the cylinders to a materials testing lab for compression testing. Also because we wanted our cylinders to represent concrete that could be actually used in the field, it was necessary for the consistency of our concrete mixes to have pourable consistencies.

A note on the evaluation of our concrete regarding its compression strength:

Compression strength is the strength at which a material can resist compression forces or two positive forces pushing in towards the center of a material from two opposing sides. If you place an object in one hand, then put your hands flat together with the object in the middle and push your hands together, you are generating a compression force on the object. If you exceed the compression strength of the object it will break, if not then you are not applying a strong enough compression force. The compression strength of our concrete mixes would be based on how many pounds per square inch (PSI) of compression force they could resist before breaking (fracturing, crumbling etc.) The testing lab that we would be sending our cylinders to has a machine that exerts a compression force on a cylinder while displaying that force in PSI on a scale. When the

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cylinder breaks, one only has to read the scale to see how much of a compression load the concrete cylinder withstood.

A standard concrete can take a compression load of 3000 PSI (6). A concrete of this strength is generally used in building applications such as making concrete patios and walkways (6). To give an example of how strong 3000 PSI is, it would take an area of concrete the size of 2 silver dollars or 2 square inches to withstand the weight of an average (how many pounds) American car (7). But the strength of concrete or any other impressive building material did not just become what it is overnight. Concrete has had a tremendous amount of money put into its research and development. Because we were unsure what compression strength our concrete would exhibit, we needed a range at which to evaluate the quality of our concrete. And this range needed to be based on the minimum strength at which we would consider our concrete usable/viable in the field. Because concrete is generally used as a load bearing material, we chose to evaluate the viability of the compression strength of our concrete from the perspective of it being used as a structural load-bearing wall.

If we were to design a structure with 12” wide or “thick” load-bearing walls, an average roof in our climate would exert 13.75 PSI on each load-bearing wall (see appendix A. for more detailed explanation). Therefore the minimum compression strength or (Fc) at which we would evaluate if our concrete were sufficient was if it reached an Fc of 13.75 PSI. That is the “design strength,” after safety factors were applied. The safety factors that we would be applying came from the safety factors that Bruce King provides for earthen walls in his book “Buildings of Earth and Straw” (8). Even though we were designing a concrete, the material composition with our decomposed granite and natural binders would be closer in composition to earthen building materials like “rammed earth” or “poured earth”, rather than to standard concrete. The same would be true even when we would be using cement as a binder. The method of applying the safety factors are: Take the ultimate compression strength or the compression strength that our cylinders would break at and divide that number by 10. The number that would result from this safety factor would be our concrete’s Fc or the compression load, which our concrete could safely support. So in order to find our minimum compression strength that we would consider our concrete sufficient at, we would need to reverse the safety factor and multiply 13.75 x10 which=137.5 PSI or our minimum acceptable strength. Of course, higher Fc values are better, as they allow for greater safety factor, higher loads (perhaps because of greater roof weights or spans) and taller walls.

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Background on Alternative Binders and Base Mix Materials: Alternative Binders:

The five alternative binders we chose for this experiment were: prickly pear juice, psyllium husk, lime, magnesium oxide/fertilizer cement and fly ash.

Prickly pear juice comes from the prickly pear cactus (Opuntia ficus indica). It requires no quarrying to be harvested and emits no C02 in its processing, as the cactus needs only to be soaked in water for the binding agent to be created. Though if this cactus were farmed and harvested on a large scale its environmental impacts would need to be re-evaluated. We chose to experiment with this binder from knowledge of its popular use as a binding additive in plaster. Its binding characteristics come specifically from the pectin in the pad of the prickly pear cactus (9.1). When used as an additive in plaster, prickly pear juice increases the adhesion and stabilization of the plaster along with helping it better set (9.1). It is also important to note that while prickly pear juice has been used for many years as an additive in plastering, we found no reference to it being used as a concrete binder in literature or from talking to plastering and concrete experts.

Psyllium husk comes from the psyllium plant or (Plantago). As with the prickly pear cactus, due to its plant rather than mineral nature, it requires no quarrying to be harvested and emits no C02 in its conversion into a binder as it also only needs water to facilitate its binding properties. We were aware of psyllium’s binding properties from knowledge of its commercial use as a soil binder/stabilizer in such applications as the construction of trails and driveways (10, 11.1).

Lime or calcium/magnesium oxide is derived from limestone similarly to cement. Therefore, our choice of using lime as a binder did not offset the large scale quarrying process that is required for cement production. And its production also requires a heating process in a kiln similarly to cement to convert it to a usable state (this is where large scale CO2 emissions occur in cement production). But the production of lime outputs 20% less CO2 than cement (12). And lime also reabsorbs significant amounts of CO2 while it cures (12). All of which makes lime based on our criteria a more sustainable binder than cement. Lime’s binding properties come from the cementing affect that takes place when it reacts with clay minerals found in soil when water is added (13.1). It is this cementing affect that made lime “the most commonly used “cementitious binder until about a century ago, which in the era of the industrial revolution was replaced by portland cement (13.2). Nevertheless lime is still in use today as a binder in mortars, exteriors and interior stuccos, plasters and in structural foundations such as walls, roofs and floors (13.3).

Fly ash is a byproduct of coal fired electric generating power plants. When coal is combusted to produce electricity, three general types of coal combustion by products (CCBP’s) are created. With one of them being fly ash. Because fly ash is a byproduct and thus no quarrying or CO2 emissions is related to its specific production, we believe that it could be considered a sustainable binder considering our two criteria. And looking

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beyond our criteria, considering that only 30% of fly ash is recycled (national average), we see that any utilization of fly ash is a sustainable move by preventing it from entering the waste stream (14). The binding properties of fly ash come from the calcium oxide that can be found within its makeup. This calcium oxide reacts with water creating a hydration reaction, which hardens and binds the particles within it together. When fly ash has a significant amount of calcium oxide (at least but usually more than 10%) it is called Class C fly ash and has self-cementing properties (15). When fly ash does not have a significant amount of calcium oxide it is classified as Class F fly ash and needs an additive to make it cementitious. Lime is one of the additives that can make Class F fly ash cementitious, as it is composed largely of calcium oxide, the main material needed for the binding hydration reaction to occur. Fly ash is used commercially as an additive in portland cement to make it stronger and more durable. And in some studies the cementing properties of fly ash alone prove very significant (see appendix B.).

A note on fly ash and lime:

The only fly ash that we could find in the southwest was Class F fly ash. Because of this we had to add our lime to it to make it a usable binder.

A note on our choice of magnesium oxide/fertilizer cement:

We originally decided on using solely magnesium oxide (MgO) as our fifth alternative cement binder. When we received our MgO from a generous contributor, we realized that we did not have enough MgO to complete a full round of testing with it. So we did some revising to our initial plan, so as to use the amount that we received in a way where we would still acquire useful results towards our overall project goal. Along with the virgin MgO, we surprisingly received a separate batch of magnesium oxide/fertilizer cement. We decided as well that it would benefit our project if we made testing cylinders also using this alternative cement binder.

Unfortunately the Fc of our one concrete testing cylinder that we made with solely MgO was never recorded. We are unsure as to how this happened. We believe that the cylinder was received by the testing lab, but they have no record of it being tested. Because we initially decided to use solely MgO as an alternative binder, our research confirmed that it met our sustainable criteria and so is explained in this paper. As we were not aware that we would use MgO/Fertilizer in our research stage, it is outside the scope of this project to confirm if magnesium oxide/fertilizer cement does or does not meet our sustainable criteria. Though, it can be assumed because George Swanson-an environmentally conscious building designer, and the man that sent us the MgO-uses MgO/Fertilizer as a sustainable alternative to cement, that the addition of the fertilizer does render the use of MgO as an alternative cement unsustainable. But in order to say that conclusively, further research of the fertilizer regarding our sustainable criteria would have to be carried out.

MgO comes from magnesium deposits within the earth. Magnesium deposits are abundant and cover roughly 8% of the world’s surface (16.1). Like cement and lime, magnesium oxide has to be mined for the raw material, making this binder not mitigate

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the negative quarrying aspect of cement. But like lime, magnesium oxide takes 20-40% less energy to produce than cement, making it another sustainable option (16.2). Also like lime, magnesium oxide was overshadowed by portland cement even though it was a very popular building material historically. However it is making a slow comeback and is currently being manufactured in forms similar to cement where one just needs to add water and they’ll be ready to go.

Magnesium oxide can also be mixed with phosphate fertilizers in order to create a magnesium phosphate cement. The fertilizer that we received was a mono-potassium-phosphate or (MPK). Magnesium phosphate cements are considered to have “very good adhesion to a wide variety of aggregates and substrates” (17).

Base Mix Materials:

Not including the binder, the remaining materials that make up concrete are: gravel/crushed stone (course aggregate), sand (fine aggregate), water, and air. In order to address the second unsustainable problem associated with concrete, that of offsite quarrying, we decided to try and use materials that would be representative of the southwestern region in which we live, with the intent that we could eventually develop a concrete that used only on-site materials. For this reason we chose to use decomposed granite as our fine aggregate. Because in the Southwest, granite is a very common soil and when it weathers it forms much of the soil that makes up this region. However for the testing, in the interest of keeping our variables as constant as possible, and in keeping our focus in this experiment on our binders, we sourced our decomposed granite from a local quarry about 20 miles away from our testing site, and our coarse aggregate from a local nursery.

Because our choice of fine aggregate would be sourced offsite, we we’re not completely overcoming the unsustainable offsite quarrying factor of cement. What we were doing though, was taking a step towards that direction. When one is usually sourcing fine aggregate for concrete he or she will be getting a specific size washed sand. Because we were sourcing decomposed granite, we would be representing more closely a southwestern backyard soil. But further experiments would need to be carried out solely focusing on refining mix ratios for a true backyard soil for this unsustainable problem to be more fully addressed.

Our course aggregate was also not sourced on site, but sourced at a local nursery. Figuring out how to source onsite course aggregate was not prioritized for this experiment. We wanted to better experiment with the fine aggregate required in concrete, seeing as it better represents a soil found in a southwestern backyard. Because course aggregate comes from larger rock that would have to be broken down to an average needed size, the process for creating course aggregate would be better attempted in an experiment dedicated solely to it.

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Methods of choosing Ratios for Binders, Base mix and Material Mix:

Choosing the Binder Ratios:

The first thing we needed to figure out was what percentage of each binder we would use in our concrete mixes, with the ideal being, we would use the same percentage of each binder in every concrete mix. This would allow us to more directly compare and refine the results of our binders Fc equally. And this would keep with our desire of having as many consistent variables throughout our experiment as possible. But we did not want to create an arbitrary binder ratio to use, because all binders and materials in general respond very specifically to certain stimuli. For example, the ratio of water to cement that maximizes cements strength is very narrow, and if the ratio is slightly off, the strength of the concrete quickly reduces. For this reason we needed to research applications in which our binders had been previously used.

Results from our research:

A note on the binder percentages given below:

The example percentages below representing how each alternative binder has been used, are percentages by weight. Some of our resources did not have the percentages by weight but instead by volume. And some of the resources did not have the ratios in percent form. To be consistent with standard material testing all the below ratios are in percent by weight, and may have been converted.

Prickly pear juices use as an additive in plaster:-0.2 % by weight of total plaster mix (9.2) -1.4 % weight to total plaster mix (18.1)

Psyllium Husk use as an additive in plaster, cob adobe floor-1: 9558 or 0.01% by weight to total cob floor mix (18.2)

Lime as a soil stabilizer-3-10% by weight to total mix (13.4)-5-6% by weight to total mix (11.2)

Fly Ash as a binder-16% by weight to total mix (see appendix c.)

Fly Ash/Lime as soil stabilizer-9% (6% fly ash with 3% lime) binder to total subgrade soil mix (19.1)-14% (8% fly ash with 4% lime) binder to total subgrade soil mix (19.1)

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MgO -40-50% of aggregate by weight. The more impurities in the soil, the higher the percentage that should be used. (George Swanson MgO expert)

MgO /Fertilizer or Mgo/MPK-As we obtained this alternative binder after our research phase of the experiment, we decided to use this binder in the same percentages as the other binders. This will be explained in more detail below.

Cement as a binder in conventional concrete-16% by weight to total mix (see appendix D.)

Our research demonstrated that our alternative binders are used in varying proportions. This was to be expected, as no two materials are alike and thus chemically respond as binding agents in different ways. What we were looking for though were ratios that had similarities that would allow us to narrow in on a universal binder ratio, to experiment with across the board. Both psyllium and prickly pear juice were used in the lowest percentages by weight of the total weight of the mixes they were added to. With psyllium being used at .01% of total weight of mix and Prickly Pear Juice being used at .2% and 1.4% of total weight of mix. Though because both of these materials were demonstrated to be used only as additives, we decided that when we used them as binders in our concrete, we would increase the percentages by which they would be used. Lime had the 3rd highest binder ratio ranging from 3-10%, followed closely by fly ash/lime and only exceeded by a little came fly ash and cement. The only ratio that we observed as being a complete outlier was MgO with a 40-50% to total weight of material ratio.

Taking all of this into consideration we decided that we could create a spread of the same ratios to test all of the binders with. And we realized the most critical aspect of the spread would be that it would need to evenly represent the ratios we had researched.

The ratios chosen for all of the binders except MgO were 4%, 8%, 16%. The lowest percentage accounted for our estimates of how much we should inflate prickly pear juice and psylliums percentages and the highest percentage accounted for the higher percentages demonstrated in the use of lime, fly ash/lime, fly ash and cement. As mentioned in the section above, we decided to use the MgO/Fertilizer binder to see how it compared with the rest of our binders.

Because the percentage of MgO required was so high, we only had enough of it to make one concrete cylinder using 40% MgO.

Choosing the Base Mix and Material Mix ratios:

A standard mix of concrete focuses on three main parts, the binder, fine aggregate and coarse aggregate with the ratio being 1:2:3. So essentially the weight of the binder + fine

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aggregate = weight of course aggregate. Using this as a guideline we decided that our binder + fine aggregate would always equal by weight the weight of the course aggregate. And that because our concrete cylinders would always weigh around 10 lbs, the binder + fine aggregate would always equal 5 lbs and the course aggregate would always equal 5 lbs (see appendix E. for explanation of cylinder weight).

The following table demonstrates how our binder/fine agg. ratios would fluctuate while the course aggregate would stay consistent.

The only other material we needed to consider was water. One of our criteria for our sustainable concrete was that it needed to reach a consistency that would allow it to be poured, because concrete needs to be poured to be used and we wanted to create a concrete that could one day be used in the field. With this in mind then, it was our priority to not predetermine the ratio of water we would use in each mix, but to instead mix water with each of our different concrete mixes until each one resulted in a consistency that would allow it to be poured.

Sourcing Our Materials

Unlike the rest of the binders that were sourced from manufacturers or bought at retail stores, we had to make the prickly pear juice. Making prickly pear juice requires mixing water and the pads of a prickly pear cactus in an airtight container for 1-2 weeks (9). During this period a fermentation process occurs making a thick mucilaginous mixture. The mixture should smell very strong and the mucilage should be like a thick gel or goo. If the juice is too watery, continue letting it sit while checking on it daily. The prickly pear cactus that we sourced for this experiment came from private property within the Prescott National Forest in Prescott, Arizona. The pads were sourced on December 2nd 2012. We harvested enough pads to fill two 5 gallon buckets 60% of the way up. We then filled the buckets 3.5” from the top with water. And sealed both buckets with airtight lids. We observed that after 2 weeks the consistency of the mucilage was too runny, so we let them sit another 7 days.

Psyllium can be bought at any grocery store as it is popularly used as a digestive health product in brands such as Equate and Metamucil. We bought 29 oz or roughly 2 lbs of Equate psyllium for $7.00 from Wal-Mart. It should be noted that sourcing it in this way, when large quantities are required, would be incredibly expensive making it uneconomical. Luckily Psyllium can be sourced in much larger quantities from wholesale supply companies.

Table 1. Material Mix RatiosBinder Fine Aggregate Course Aggregate4% .4 lbs 46% 4.6 lbs 50% 5 lbs8% .8 lbs 42% 4.2 lbs 50% 5 lbs16% 1.6 lbs 34% 3.4 lbs 50% 5 lbs

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Lime, once it is converted from limestone is called quicklime or lump lime. Before quicklime can be used as a binder it must be mixed with water to undergo a hydration reaction that converts its oxides into hydroxides. This process turns it into a usable dry powder or “dry hydrated lime” (13.5). This dry hydrated lime can be found at home improvement stores under the name Type S Lime. Type S Lime is ready to use right out of the bag. It just needs to be mixed with water. However, its binding properties become stronger if it is mixed with water and left to sit submerged under water. The longer it sits the better its binding properties become. We bought one 50 lb bag of Type S lime for $10.00 from Lowes building supply. We then mixed it in a tub with water until it turned the consistency of a thick yogurt. For the mixing process we filled 2 5 gallon buckets with dry lime powder. We then alternated between adding in lime and water. We then mixed the materials together with a power drill and a mixing paddle attachment (essentially a large whisk). When the consistency of the mix was stressing the drill from being too thick we would add water and vice versa. Once the mix was the consistency of a thick yogurt we made sure that no clumps or dry lime remained. Lastly, we poured enough water over the mix until it was evenly covered with 2.5” of water, and covered the whole mixing tub with a piece of ply wood to prevent contamination of our mix. It is important to check the mix every few days to ensure that it is still covered by water. If the water evaporates the lime will start calcifying or essentially turning back into limestone and lose its binding properties.

Fly ash so far as we know is not sold at any home improvement retailer such as Lowes or Home Depot. However because it is a by-product of coal combustion it can be sourced from coal fire power plants. We sourced our fly ash from the Headwaters Resources. Headwaters is “america’s largest manager and marketer of coal combustion products”, and was the only source of fly ash in the southwest that we could find. The only fly ash that was available from them was Class F fly ash. This meant that we would have to add a calcium oxide or hydroxide to create the cementitious chemical reaction needed. Luckily we had Type S Lime which has been fully hydrated making it calcium hydroxide. The fly ash arrived in 2 5 gallon buckets and was ready to be mixed with our Type S Lime.

Similarly to fly ash, MgO is not sold at any general home improvement retailer. It can be sourced however from select manufacturers. Fortunately we were able to have some sent our way from George Swanson a builder, teacher and consultant that works with MgO.

We sourced our fine aggregate/ decomposed granite and our course aggregate/.5” rock from Mortimer’s nursery in Prescott, Arizona. The quarry where Mortimer’s gets this granite is in Dewey, Arizona 16 miles east of Prescott.

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Materials and Methods for Testing Sustainable Concrete:

Testing Day #1: Testing Base Mix with Portland Cement

Purpose: The purpose of Testing Day #1 (T.D.#1) was to test if our base mix with cement as a binder could reach Fc of over 137.5 PSI (our minimum acceptable Fc). If our base mix could not reach our minimum Fc with a standard binder, then it would be unwise of us to use it as our standard base mix when testing the binding capabilities of less standard alternative cement binders. If our concrete cylinders from T.D.#1 did not reach our minimum Fc, we would rethink and redesign our base mix.

Materials used in Testing Day#1:

Binder Mix:-25 lbs of course aggregate (15lbs for 3 cylinders (1=5lbs) and 10 extra lbs for mistakes)-25 lbs fine aggregate (15lbs for 3 cylinders (1=roughly 5 lbs)and 10 extra lbs for mistakes)-5 lbs of cement (3 lbs for 3 cylinders (1=roughly 1 lb) and 2 extra lbs for mistakes)

Materials for Making the Test Cylinders:

-2 scales (1 scale to measure up to 50 lbs, and 1 scale to measure up to 5 lbs in oz)-3 containers for weighing ingredients (1 for aggregate, 1 for cement, 1 for water)-3 5 gallon buckets (1 for mixing all ingredients together, 1 for rinsing materials, 1 for extra use)-Sponges (cleaning materials)- Tamping Rod (helping concrete material in cylinder settle)- Rubber Mallet (helping concrete material in cylinder settle)- Metal Scraper (helping keep concrete material in cylinder flush with lid so it will close)-Metal Scoop (for scooping concrete into cylinder -3 4”x8” cylinders -Permanent marker (for writing information on cylinder)

A note on materials for making the test cylinders:

We used the same materials for making the test cylinders each testing round so the above material will not be written for the subsequent testing days. The only exception is the number of cylinders, because each testing day we did test a different number of them. Also for further information on how some of these mixing materials are used

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Methods:

Testing Day # 1 (T.D.#1) was conducted in Prescott, Arizona on November 11, 2011. First the dry ingredients for cylinder A. were weighed and put in a 5-gallon bucket (see table 2.). A “rule of thumb” standard construction guideline ratio of water to cement or 1:2 was chosen for each mix. For A. this was 0.2 lbs water/ 0.4 lbs cement. Next we mixed the dry ingredients with the powerdrill and mixing paddle to ensure an even distribution of the materials. Then we added water and mixed again with the powerdrill until the water was absorbed and dispersed evenly. After evenly mixing in the water, we noticed that the mix was too dry and unpourable. We added another 0.2 lbs of water, making the water to cement ratio 1:1. After thoroughly mixing, our mix was still unpourable. We kept adding and mixing in water in 0.2 lb increments until our mix was pourable. The final water to cement ratio for A. was 2:1. We assumed that because mix A had so little cement (4%) as opposed to the (16%) average that is in standard concrete, that this 2:1 ratio was going to be an outlier. Once the mix could be poured we transferred the materials into a cylinder following all of the guidelines in ASTM C 31 procedure checklist except for guideline 11 (see appendix G.). For cylinder B. the same steps were followed and again the water to cement ratio of 1:2 was too dry. We continued adding water in 0.2 lbs increments until we reached a 1:1 ratio of water to cement. At this ratio the mix was adequately saturated to be made into a cylinder but still not pourable. We decided that because we were only testing the viability of our binder mix on this testing day we would make cylinder B. with a 1:1 cement to water ratio. We decided this with the premise that we would use our last cylinder to use the same cement ratio as B. but this time add water until it could be poured. This would allow us to evaluate if our binder mix with cement had a higher Fc if it could be poured vs. if it was mixed with just enough water to be made into a cylinder. If the 1:1 ratio had a higher Fc, it would demonstrate that the base mix might need to be redesigned in the future to allow for optimum strength at pourability. The pourable water to cement ratio of cylinder C. can be seen in table 3.

Note: Table 2. shows our initial ratios while table 3. shows the actual ratios used in making the cylinders.

Table 2. Initial Ratios for Testing Day #1Course Aggregate Fine Aggregate Cement Water

A 50% 5 lbs 46% 4.6 lbs 4% .4 .2 3.2B 50% 5 lbs 42% 4.2 lbs 8% .8 lbs .4 6.4 ozC 50% 5 lbs 42% 4.2 lbs 16% 1.6 lbs .8 12.8 oz

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Table 3. Actual made ratiosCourse Aggregate Fine Aggregate Cement Water

A 50% 5 lbs 46% 4.6 lbs 4% .4 lbs .8 lbs 12.8 ozB 50% 5 lbs 42% 4.2 lbs 8% .8 lbs .8 lbs 12.8 ozC 50% 5 lbs 42% 4.2 lbs 8% .8 lbs 1.2 lbs 19.2 oz

After each cylinder was made it was stored in an above freezing area for 48 hrs. Then 7 days after being stored, the cylinders were taken to the Material Testing Lab (MTI) in Prescott, Arizona. Once received at MTI, the plastic cylinder casings were stripped and the concrete cylinders were stored in a 50 degree water tank. 28 days is one of the standard periods of time allocated to allow concrete to set before its Fc is tested. So on November 29th 2012 the Fc of the cylinders were tested.

Results:

The Fc results in PSI of cylinders A, B and C of T.D.#1 are:

A. 165B. 480C. 400

Average: 348

Discussion:

The results of T.D.#1 demonstrate that our base mix as it is designed, met our minimum Fc requirement of 137.5 PSI. It was exciting to see that all three of our cylinders met our minimum Fc requirement. This means that we could even construct a load-bearing wall with our weakest mix cylinder (A). If one was applying the use of this concrete mix in the field and was most interested in using as little cement as possible, then our results demonstrate that a 4% cement mix would be sufficient if a Fc requirement of 165 was desired. But if maximum compression strength was desired, then our results demonstrate that at least up to 8%, the more cement used the more of a compression load our concrete could withstand. As it was exciting to find that in cylinders (B) and (C) we exceeded our minimum strength requirement by over half.

The affects of the levels of fluid consistency on our concrete remains unclear evaluating these results. It is clear that (B), the cylinder with an unpourable fluid consistency was the strongest mix. But (C), the cylinder with the same percentage of cement and pourable consistency showed impressive Fc as well. We recommend that further testing on the variable of water to binder ratio regarding strength be conducted as we find our results interesting but inconclusive at this time.

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In regards to the factor that was influencing our need to alter the water to cement ratio for each cylinder, we hypothesized that it was the decomposed granite/ fine aggregate that was providing the inconsistency. Unlike the specific sized and washed-clean sand that is used in standard concrete for fine aggregate, our decomposed granite varied in size, and was composed not only of sand but also silt and clay, since it was “unwashed”. Because silt and clay are smaller in size than sand, our base mix had an increased particle surface area for water to adhere to. And because we were rationing our water considering only our binder as the water adhering variable, we were not getting one consistent percentage of water that could be universally used for each cylinder. With this realization we decided it would be better to create a “water to binder + fine aggregate ratio” which would then include all our variables that reacted with water. So for the rest of our experiment, we decided that we would mix the 8% binder first, mixing enough water with it until it could be poured (as opposed to using a predetermined water to binder ratio) and then use that percentage for the 4% and 16% binder mixes. Therefore making a consistent water to binder +fine aggregate ratio for each binder.

In conclusion our base mix proved to be viable and we could now test it with our alternative binders.

Testing Day #2: Testing Concrete using Alternative binders and Base Mix

Purpose: The purpose of Testing Day #2 (T.D.#2) was to test the Fc of our concrete mixes that consisted of our alternative cement binders and our base mix. We would also be creating another concrete set of our base mix/cement, that could be compared to the rest of our results to help us additionally evaluate their quality. We chose not to use our base mix/cement concrete results from T.D.#1 as our additional evaluator for the following reasons. 1. A 16% binder ratio was never tested in T.D.#1 2. We wanted to make all of the concrete sets on the same day, thus minimizing inconsistent variables (e.g., different air and water temps) whenever possible. 3. We would now be able to evaluate how our new method of creating the water to complete material mix ratio affected Fc by comparing the base mix/cement set from T.D.#1 to the base mix/cement set from T.D.#2.

Materials used in Testing Day #2:

Binder Mix:

-155 lbs of course aggregate (95lbs for 19 cylinders (1=5lbs) and 60 extra lbs for mistakes)-155 lbs of fine aggregate (95 lbs for 19 cylinders (1=roughly 5 lbs) and 60 extra lbs needed for mistakes)-6 lbs of each binder (3 lbs for 3 cylinders (1=roughly 1lb) and 3 extra lbs for mistakes)

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Materials for Making the Test Cylinders:

Cylinders- 19 4”x8” cylinders

Methods:

Testing day #2 (T.D.#2) was conducted on December 15, 2011 in Prescott Arizona. We mixed each material following the same process as T.D #1. See table. 4 for ratio chart. When it came to mixing in the water, our revised method created a consistent water to binder ratio for each set. Once we had mixed each cylinder we again transferred them to an above freezing area for 48 hours. We then took our cylinders to MTI after 7 days. This time MTI did not store all of our cylinders in the water tank. Standard concrete after 48 hours is bound well enough to be submersed in water. When the lab techs at MTI took some of our concrete samples out of the cylinders (7 days after T.D.#2), some of the concrete cylinders did not fully hold their shape. The lab techs then put the concrete samples back in the plastic cylinders until the 28th day, when the compression testing took place. It should be noted that after 28 days the prickly pear juice concrete cylinders showed no sign of hardening. The consistency of the concrete was like mud and if taken out of the plastic cylinder casing would of lost complete shape. Therefore the prickly pear juice could not be strength tested.

Table 4. Alternative Binder Cylinder TestsCourse Aggregate Fine Aggregate Binder Water

Psyllium A.1 50% 5 lbs 46% 4.6 lbs 4% .4 lbs 3.6 lbs 57.6 ozA.2 50% 5 lbs 42% 4.2 lbs 8% .8 lbs 3.6 lbs 57.6 ozA.3 50% 5 lbs 34% 3.4 lbs 16% 1.6 lbs 3.6 lbs 57.6 oz

Lime B.1 50% 5 lbs 46% 4.6 lbs 4% .4 lbs .62 lbs 10 ozB.2 50% 5 lbs 42% 4.2 lbs 8% .8 lbs .62 lbs 10 ozB.3 50% 5 lbs 34% 3.4 lbs 16% 1.6 lbs .62 lbs 10 oz

Fly ash/ Lime C.1 50% 5 lbs 46% 4.6 lbs 4% .4 lbs 1.18 lbs 19 ozC.2 50% 5 lbs 42% 4.2 lbs 8% .8 lbs 1.18 lbs 19 ozC.3 50% 5 lbs 34% 3.4 lbs 16% 1.6 lbs 1.18 lbs 19 oz

MgO/MPK D.1 50% 5 lbs 46% 4.6 lbs 4% .4 lbs .87 lbs 14 ozD.2 50% 5 lbs 42% 4.2 lbs 8% .8 lbs .87 lbs 14 ozD.3 50% 5 lbs 34% 3.4 lbs 16% 1.6 lbs .87 lbs 14 oz

MgO D.4 50% 5 lbs 10% 1 lb 40% 4 lbs 1 lb 11 oz 27 oz

P.P. Juice E.1 50% 5 lbs 46% 4.6 lbs 4 % .4 lbs .25 lbs 4 ozE.2 50% 5 lbs 42% 4.2 lbs 8% .8 lbs .25 lbs 4 ozE.3 50% 5 lbs 34% 3.4 lbs 16% 1.6 lbs .25 lbs 4 oz

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Portland C. F.1 50% 5 lbs 46% 4.6 lbs 4% .4 lbs 1 lb 16 ozF.2 50% 5 lbs 42% 4.2 lbs 8% .8 lbs 1 lb 16 ozF.3 50% 5 lbs 34% 3.4 lbs 16% 1.6 lbs 1 lb 16 oz

A note on table.4: P.P. Juice (prickly pear juice)

Results:

The compression strength results in PSI of binders A-F are as follows:

A.1. 44 B.1. 70 C.1. 55 D.1. 90 E.1. 0 F.1. 750 A.2. 60 B.2. 112 C.2. 80 D.2. 134 E.2. 0 F.2. 1075A.3. 55 B.3 114 C.3. 78 D.3. 112 E.3. 0 F.3. 1050

Avg. 53 Avg. 98.6 Avg. 71 Avg. 112 Avg. 0 Avg. 958.3

A note on the cylinder tests:

Psyllium- the psyllium cylinders were to spongy to be fractured or broken. While psyllium may or may not be ideal for a main binder in concrete, further testing on its use in surfaces that require significant give would be interesting.

Binders Setting-Also the fact should be reiterated here that when MTI, following standard concrete procedure, took many of the concrete samples out of their plastic cylinder casings many of them lost some shape. This would inevitably break some of the tightly held bond that the binders created, but it can only be speculated by how much. If we were to redue this exact test, it would be recommended to let the concrete mixes stay in the cylinders until the 28th testing day. And that even extending the testing day 2x to 56 days would be recommend to allow some of the known slower setting binders like lime reach full strength potential.

Discussion:

The results of T.D.#2 demonstrated that none of our alternative binders met our minimum Fc requirements. While this is clear, it is unclear what the variables were that attributed to these low Fc results. In material testing there are many factors to be considered. It could have been the content of other materials within our decomposed granite that we didn’t account for, such as the percentage of clay content. For example lime binds best with a soil of high clay content while cement binds best with a lower clay content soil (13.6). Or the low Fc results could have been affected by the water ratios we used. Even though we mixed each cylinder to the same pourable consistency, certain binders may have been stronger with more or less water. But these are just speculations as it could have been any number of variables that we are simply unaware of.

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The reason we did not try to design our concrete mixes accounting for all of these unknown variables was due to the scope of this project. We chose at the onset to have our focus be on testing a wide range of alternative binders, rather than to test a narrow range. We realized that because of this approach we would be conducting less research about more binders than more research on less binders. This would inevitably result in us not being able to consider all the variables that would affect the Fc of our binders. For example, testing our lime with our soil to reach a lime to soil ratio regarding clay content is a lengthy lab experiment all on its own. Being realistic we realized that one can only account for so many variables in every experiment, hence why many experiments are needed in any scientific pursuit. We also wanted to use a wide range of alternative cement binders because the lack of published research we found on prickly pear juice and psyllium led us to realize the chance of success on a first round of testing would be unlikely. But that we could at least start the experimental ball rolling in the hopes that ourselves or others would continue with the research where we left off.

In comparing the average Fc results of 958.3 PSI of cement binder cylinder set (F) from T.D.#2 to the average Fc results of the cement binder cylinders (A,B,C) from T.D.#1 of 348 PSI, it is clear that our new method of finding our water to binder ratio greatly enhanced the Fc of our cement/base mix. This finding demonstrated to us how changing one variable or improving one method of mixing the materials together could have an enormous impact on the quality of a building material. In this case specifically we improved the strength of the cement/base mix when looking at the averages by over half. And this was a benefit in the right direction for us, for even though cement was used in both experiments as an evaluative tool, the fact that we were using cement to bind decomposed granite was still a very beneficial improvement towards addressing offsite quarrying. Even after the safety factor of 10 is applied to (F)’s average PSI strength we were still looking at a building material with a load bearing capacity 95.8 PSI. A capacity that considerably exceeded our 13.75 PSI minimum Fc requirement that would be needed to be used as a load bearing wall in our hypothetical house. And to get a better perspective of set (F)’s Fc, consider that rammed earth - a commercially used earthen building material - has a general ultimate Fc of 800 PSI, that is 158.3 PSI weaker than our set (F)’s ultimate Fc. It is important to note, however, that this is just a comparison of Fc strength, as the final evaluation of a material rests upon a considerable amount of variables.

Taking all of this into consideration, we decided that we should try and refine set (F) of T.D.#2. Because we used cement as a binder in set (F) we knew that this was the obvious factor we needed to refine, while still trying to improve its Fc. From our research we knew that fly ash, one of the materials that we already had on hand, is commonly used in concrete as a cement additive/partial replacement material. And we also knew that the combination of cement and fly ash could result in an excellent concrete while mitigating the percentage of cement used (20). With these considerations we decided that our next experiment would incorporate the use of fly ash as a cement replacement.

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We also wanted to incorporate the use of fiber in our next experiment. One reason for this was that many onsite construction locations have various kinds of plants, which equal as a source of fiber. If plant fiber increased the Fc of our concrete, then we would be representing different possible solutions to making viable concrete using onsite materials. Just as we decided to use decomposed granite to represent southwestern soil, for the sake of reducing unknown variables, we decided to use straw to represent natural fibers. The end goal again would be the experimentation with actual onsite fibers. The other fiber that we decided to use was plastic fiber, a fiber that is used in standard concrete to increase strength. We chose to use this fiber for two reasons. The first reason being that it would provide for a standard comparison to our natural fiber, similarly to our use of cement in our previous experiments. The second reason we wanted to use plastic fiber was that we were simply trying to find ways to make our fly ash/cement concrete have a higher Fc strength. And because so little plastic fiber is used when added to concrete, if it increased our concrete’s Fc we believed that incorporating it would be a sustainable benefit. For the stronger our concrete, the less reliance on standard concrete one would have.

In our next experiment we would make two separate cylinder sets to evaluate how fly ash and our fibers affected the Fc of our cement/base mix concrete. Regarding the experimentation of using fly ash as a partial cement replacement, one set (A) would be the constant consisting of no fly ash only a cement/base mix. And the other set (B) would consist of a cement/fly ash/base mix. In this set we would use a standard fly ash partial replacement percentage of 30% fly ash and 70% cement for each of our binder ratios 4,8,16% (1.3). When each set of cylinders was compression tested a simple Fc comparison would provide the results we needed. In regards to evaluating the affect of our fibers on our Fc, each set would have two cylinders incorporating a high and low percentage of each fiber. And each set would have one cylinder with no fiber at all. This would 1. Give us the ability to evaluate the effectiveness of adding the fiber vs. not adding it 2. Allow us to evaluate at what amount either high or low amounts of fibers exhibited a benefit if any at all 3. Allow us to compare both within each set and across each set what the affect the different fibers had in regards to being used with different binder mixes

Testing Day #3

Purpose of experiment: The purpose of Testing Day #3 (T.D.#3) was to test the affect fly ash as a partial cement replacement and straw and plastic fiber would have on the Fc of our cement/base mix concrete mix.

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Materials used in Testing Day #3:

Binder Mix:

-75 lbs of course aggregate (50 lbs for 10 cylinders (1=5 lbs) and 25 extra lbs for mistakes-75 lbs of course aggregate (50 lbs for 10 cylinders (1=roughly 5 lbs) and 25 extra lbs for mistakes-3 lbs of fly ash binder (1.2 lbs for 5 cylinders (1=.24lbs) and 1.8 lbs extra for mistakes-12.5 lbs of cement binder (2.8 lbs for fly ash/cement cylinder for 5 cylinders (1=.56 lbs) with 3.2 lbs extra for mistakes) and (4 lbs for cement only cylinders for 5 cylinders (1=.8 lbs) and 2.5 lbs extra for mistakes)-1 oz of plastic fiber and 2 oz of straw fiber

Cylinders-10 4”x8” cylinders

Methods:

We conducted T.D.#3 on February 2, 2012 in Prescott, Arizona. We mixed all the materials including the fibers, made the cylinders and took the cylinders to MTI using the same process as testing days #1 and #2. Our method of figuring the water ratio for each binder set was conducted using the same method as T.D.#2, and again provided a consistent pourable consistency for each set. For ratios used in making the concrete sets, please reference (table 5.).

Table 5. F.A./P.C and Portland Cement Binder and Fiber TestsCourse Aggregate Fine Aggregate Fiber Binder Water

F.A./ P.C. A.1 50% 5 lbs 42% 4.2 lbs N/A 2.4% .24 lbs 1 lb 16 oz5.6% .56 lbs

Plastic fiber A.2 50% 5 lbs 42% 4.2 lbs .025 oz 2.4% .24 lbs 1 lb 16 oz5.6% .56 lbs

Plastic fiber A.3 50% 5 lbs 42% 4.2 lbs .05 oz 2.4% .24 lbs 1 lb 16 oz5.6% .56 lbs

Straw Fiber A.4 50% 5 lbs 42% 4.2 lbs .25 oz 2.4% .24 lbs 1 lb 16 oz5.6% .56 lbs

Straw Fiber A.5 50% 5 lbs 42% 4.2 lbs .5 oz 2.4% .24 lbs 1 lb 16 oz5.6% .56 lbs

Portland C.B.1 50% 5 lbs 42% 4.2 lbs N/A 8% .8 lbs 1 lb 16 ozB.2 50% 5 lbs 42% 4.2 lbs .025 oz 8% .8 lbs 1 lb 16 ozB.3 50% 5 lbs 42% 4.2 lbs .05 oz 8% .8 lbs 1 lb 16 ozB.4 50% 5 lbs 42% 4.2 lbs .25 oz 8% .8 lbs 1 lb 16 ozB.5 50% 5 lbs 42% 4.2 lbs .5 oz 8% .8 lbs 1 lb 16 oz

A note on Table.5: F.A. (fly ash) P.C. (portland cement)

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Results:

The compression strength results of sets A. and B. are as follows.

A.1. 199 B.1. 795 A.2. 398 B.2. 398 A.3. 366 B.3. 960 A.4. 398 B.4. 863 A.5. 469 B.5. 880 Avg. 366 Avg. 779

A note on the results:

When we received the Fc results from T.D.#3, we noticed that there was a clear discrepancy. The results demonstrated that the Fc results of the cement/base mix were incredibly low with an average Fc of 366 PSI. This would of not been odd if there was one or at most two cylinders with a low Fc, due to unforeseen variables. But because we were using the same cement/base mix ratios as T.D.#2 with an avg. 958 Fc with only added fibers, 5 incredibly low Fc cylinder results were very circumspect. However the results from the fly ash/cement concrete set showed the exact Fc results we would have expected for the cement/base mix. And because the fly ash/cement mix was our experimental mix, it makes much more sense that our avg. 366 PSI results would be for that set. Because the cylinders were already tested (with the cylinders long separated from the material in them that was tested) and the results already recorded it was too late to be sure what exactly happened. Our final decision was that the error of the results was clear enough for the results to be switched and recorded in this paper as the fly ash/cement mix being A. and the cement/base mix being B.

Discussion:

It is clear from the results of T.D.#3 that set (B) the cement/base mix demonstrated to have a higher average Fc than set (A). From this it can be concluded that the addition of fly ash as a partial cement replacement did not improve the Fc of our cement/base mix concrete. Though while the addition of fly ash to our base mix was not superior to using cement alone, the results from (A) demonstrate that a binder of fly ash/cement does provide a viable compression strength. As all the cylinders in set (A) met our minimum strength requirement and in 4/5 cylinders it exceeded it by half. But when trying to evaluate these results a question surfaces. While it is clear that fly ash does not increase the Fc of our cement/base mix concrete when used as a partial cement replacement, does fly ash increase the Fc strength of our cement/base mix concrete when used as an additive? In other words if 100% of the cement percentage was already added to our base mix, would an addition of fly ash increase the Fc of the final concrete. If it would then

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using it as a cement additive when making our concrete would be beneficial because it could make a required Fc strength of concrete be met with less cement. In order to answer this question, we would need to make a new set of cement/base mix concrete using the same percentage of cement that was used in (A) and compare its Fc with (A). If (A) from T.D.#3 had a higher Fc than the new set, the addition of fly ash would be seen as beneficial making the results from T.D.#3 (A) be positive. If the Fc results of the new set were higher than (A) fly ash as an additive would clearly provide a negative benefit all around. Making the results of (A) even though they met the minimum Fc requirement still not be impressive. To conclude, because further testing is required, it is unclear what benefit if any fly ash can have on our sustainable concrete, which makes the evaluation of the Fc of (A) undetermined.

In regards to how the fibers affected the Fc of each set, the results remain mostly unclear. Regarding plastic fiber, in set (B) the .05 oz amount resulted in a stronger Fc, where as in (A) the results are inversed. Regarding the straw fiber both sets demonstrate that the higher amount of straw resulted in a higher Fc. And in set (B) the mix with no fiber (B.1) was higher than the avg. Fc of the plastic fiber mixes. But B.2. proves to be an anomalous low mix as B.3. with just .025 more oz than B.3 is the highest Fc cylinder in the whole set. And in set (A) the no fiber mix (A.1) is the lowest out of all of the mixes. To conclude further testing based on narrowing in on methods of testing the percentages of fibers would need to be carried out for any conclusive statements to be made.

Final Discussion:

We did not create a final concrete mix design as the end result of this project. What we did create were data and results from three experiments. Our experiments demonstrate that we designed a successful method of finding the proper ratio of water to each total concrete mix in order to create a pourable earthen-material based concrete. They demonstrate that we have created a concrete that partially mitigates off site quarrying while at the same time having a Fc that far exceeds the requirement for it to be used as a load-bearing wall. And our data and results demonstrate the many questions and further exploration that is required to create a more sustainable concrete, while indicating the potential for further investigation of onsite sourcing of the fine and coarse aggregate necessary for an alternative aggregate. (see appendix F. for discussion of possible applications of building material)

And beyond the data and the results lie our process of executing the experiment. This process has demonstrated to me how challenging the design and creation of alternative building materials can be. I liken it to starting and running a business. If we were to continue this process until we had created a final sustainable concrete we would need to raise capital, continue researching, find more permanent testing space and if we wanted our concrete to be used commercially, market our final product. The amount of experimentation and testing alone that would be required to refine our concrete until it was sufficient would be a Herculean task. Furthermore, every building material has to be

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tested for much more than Fc for it to be acceptable for use, which would entail other extensive testing.

But learning this was just as important to me as our experimental results. For I wanted to know, first hand, even if it was just a glimpse, what it was like to design and create a building material. Now every time I navigate the urban world, every time I walk on the side walk or drive on the freeway I have a better and more intimate understanding of the materials themselves and what it took to make them what they are. I have a better understanding of the incredibleness of nature that provides the raw materials, the intelligence, sweat and toil of the human effort required to refine them for our use and the challenge required to continue refining our building materials for the betterment of all.

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Appendix:

A: Creating our Minimum Compression Strength- We believed that the concrete we were designing would be most appropriately applied to building walls. For this reason we decided that when evaluating the strength of our concrete we would use compression strength, the most prominent force applied to a load-bearing wall. We also decided that the minimum compression strength we would consider acceptable throughout our experiments would be the same as the minimum compressive strength of an average earthen load-bearing wall in PSI. The process by which we obtained our minimum compressive strength is as follows.

We needed a common house design so we chose one with roof trusses resting on the sidewalls of a house. This means that the sidewalls of the house would be carrying the weight of the entire roof. An average roof weighs 20 lbs per sq. ft (dead load), and in our elevation in Prescott, Arizona, if it snowed could carry another 40 lbs per sq. ft (live load). This means our 2 side walls would have to be able to withstand a 60 lbs per sq. ft combined load. We also chose our load bearing walls to be 1 ft wide x 9 ft. high (other common design factors), and would be carrying a roof that spanned 30 ft, meaning each wall would be carrying 15 ft of that span. In order figure out how much each wall would have to hold if there was snow on the roof and it weighed its combined load, we then multiplied the length of 1 ft of wall length by the weight of the roof bearing on it with its combined dead and live load. In other words we multiplied 15 sq. ft x 60 lbs sq. ft which equaled a combined roof load of 900 lbs per sq. ft.

But when one is calculating how much weight a wall is going to hold one has to also factor in how much weight the bottom of the wall is going to hold, because the material at the bottom of the wall is holding the rest of the above wall plus the roof. If our wall was 9 ft, we then needed to multiply 9 ft x 120 lbs/cu. ft (120 lbs/cu. ft. is common weight for earthen wall materials). This gave us a 1080 lbs/cu. ft wall load. In order to figure out the total load then, we combined the roof and wall load at 900+1080 and got 1980 lbs. sq. ft. In order to convert this to PSI, because our wall was 12” wide we were able to divide 1980 lbs/144 square inches to get 13.75 PSI, hence, our minimum compression strength required.

But it is absolutely dangerous to use a building material that equally meets any load requirement. Because if there was an earthquake or in this case a way above average snow, then the roof would collapse. Instead one uses a building material that can withstand much higher loads than are required and then applies safety factors that try and account for seen and unforeseen factors that would increase the stress on the material. Because our building material was similar to an earthen building material, we referenced the book, “Buildings of Earth and Straw” written by the earthen material expert Bruce King to obtain our safety factors (?). In it he recommends to use the standard building safety code regarding earth-building materials, by dividing the ultimate compression strength of a building material by 5. But he goes even farther than this because he understands that earthen materials are more inconsistent than standard building materials. So after dividing the ultimate compression strength of a building material by 5 he then

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cuts that number in half in addition. Or more simply one can just take the ultimate compression strength and divide the number by 10. He goes on to share that some conservative engineers might even go so far as to divide the ultimate compression strength of a given material by 16 to get the usable design strength.

B. Demonstration of Class C fly ash compression strength: Class C fly ash has been demonstrated to have a compression strength of 1160 PSI, when mixed with only water (19.2).

C. Explanation of fly ash to total mix percentage: Class C fly ash as can be seen in appendix B., has a significant Fc with only water added. And fly ash used in the lab can be used as a 70% partial cement replacement (1.2) Because fly ash can make concrete at such high percentages, we decided that a good starting point to use if we were just using fly ash to make a concrete, would be to use the same percentage that cement is used at. And the average percentage to total weight that cement is used at in standard concrete is 16%.

D. Average concrete material ratios: 1 part cement/ 2 parts sand/ 3 parts gravel or approximately 16%: 33%: 50% by weight.

E. Discussion of how we figured out the weight of our testing cylinders: Because we were making concrete, we figured out the volume of our testing cylinders, and then how heavy concrete/volume is.

F. Discussion of possible applications for our building material: While we did not conclude our experiment with the design of a final sustainable concrete, we had many different concrete mix designs that demonstrated Fc above our minimum Fc requirement. As discussed before, we feel that the characteristics of our concrete make it most applicable to be used in the creation of load bearing walls but there are other applications such as using it for interior floor slabs that its use may also be applicable. At this stage, with the concrete mixes we created, it would be a challenge to use them in outdoor applications because they weren’t dense enough to prevent damage from freeze/thaw cycles and dusting from traffic would be an issue. But used in load bearing walls or in interior floors, our concrete mixes could be more easily sealed.

Lastly it should also be stressed that we only conducted compression strength tests on our concrete mixes. In real life applications building materials undergo such stresses as tension stress (the opposite of compression stress) and elemental stresses from (e.g., wind, fire, water, earthquake etc.), and that building materials need tests for some or all of these depending on how they will be used.

G. Omission of guideline 11 from ASTM C 31- Guideline 11 states that the cylinders need to set at a 60-70 degree temperature. Lab techs at MTI told me that usually in the field it is more important to keep the concrete cylinders above freezing. And so many construction workers and lab techs will just put them in insulated coolers or in trash bins with sand. So they said it was not a big deal to follow this guideline

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H. Evaluation and discussion on experimental process- Throughout our entire design process it was always our goal to keep our variables constrained and our mixing process consistent. With every testing day we improved our technique and became more proficient at mixing the materials and making the testing cylinders. However there are still many factors that we could improve on. In regards to making the cylinders. We found that when we scooped out the large aggregate from its storage bucket to our mixing bucket, the finer aggregate would settle to the bottom of the bucket. Therefore as we continued to make our cylinders, the sizes of the aggregates that we used would eventually become more uniform in size and also smaller. One idea to remedy this would be to separate out the large aggregate for each cylinder and make sure each pile by eyeing it had the same ratio of different size aggregate. Or one could just thoroughly mix the aggregate in the storage bucket after each cylinder was made. It is also extremely important to be careful and conscientious when weighing each material that goes into the mixing bucket. It was very helpful to have multiple people when we were weighing the materials so we could double check our numbers if we got confused, have other people look at the scales and talk out the ratios if we needed to change our system.

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Works Cited

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2. ConcreteThinker.com [Internet]. Website Publisher: Portland Cement Association. Date of Publication unknown. Webpage c 2012. Cited 5-1-2012. Available from: http://www.concretethinker.com/technicalbrief/Concrete-Cement-CO2.aspx

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Available from:http://bossconstruction.com/boss-construction-llc/concrete-questions#what_is_PSI

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10. Author unknown. Soil Binders. Place of Publication unknown. California Stormwater BMP Handbook. 2003; 7 pg. Cited: pg. 2-3

11. Calkins, M. Materials for Sustainable Sites: A Complete Guide to the Evaluation, Selection and use of Sustainable Construction. New York City, NY: John Wiley and Sons. 2008; 464 pg. Cited: (11.1) pg. 423 (11.2) pg. 170

12. GreenSpec.co.uk [Internet]. Website Publisher: Greenspec. Date Website Published: Unknown. Website Copyrighted: 2012. Cited: 5-2-2012Available from: http://www.greenspec.co.uk/lime-mortar-render.php

13. Holmes, S. Wingate, M. Building with Lime: A Practical Introduction. South Hampton Row, London: Intermediate Technology Publications. 1997; 307 pg. Cited: 13.1. (pg. 157) 13.2. (pg. 5) 13.3 (pg. 1) 13.4 (pg. 153) 13.5 (pg. 267) 13.6 (pg. 158)

14. FlyAsh.SustainableSources.com [Internet]. Website Publisher: Sustainable Sources. Date Website Published: Unknown. Website Copyrighted: 2012. Cited: 5-2-2012Available from:http://flyash.sustainablesources.com/

15. Siddique, R. Khan, M. Supplementary Cementing Materials. London, NY: Singer. 2011. 350 pg. Cited: pg. 7

16. Swanson, G. Magnesium Oxide, Magnesium Chloride, and Phosphate-based Cements. Publication Unknown. Date Published Unknown. 9 pg. Cited: 16.1 (pg. 2) 16.2 (pg 2) Authors website: geoswan.com

17. PremierChemical.com [Internet]. Website Publisher: Premier Chemicals. Date Website Published: Unknown. Website Copyrighted: 2007. Cited: 5-3-2012Available from:http://www.premierchemicals.com/corner/articles/cements.htm

18. Bee, B. The Cob Builders Handbook: You Can Hand-Sculpt Your Own Home. Summerville, SC: Groundworks. 1998. Cited: 18.1 (pg. 158) 18.2 (pg. 56)

19. Beeghly, Joel. Recent Experiences With Lime-Fly Ash Stabilization of Pavement Subgrade Soils, Base, and Recycled Asphalt. Presented at the 2003 International Ash Utilization Symposium. 2003. 18 pg. Cited 19.1 (pg. 11) 19.2 (pg. 3)

20. FlyAsh.com[internet] Website Publisher: Headwaters: Date Website Published: Unkown. Website Copyrighted: 2005. Cited 5-4-2012

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