Construction Material Use of Geopolymer Concrete Essay

Executive Summary Concrete is the most heavily used construction material in the modern world, and given the current global trends towards sustainability there is a need for significant advances, particularly in the construction sector. Copolymer concrete (GAP) is a recent development in construction materials demonstrating similar structural properties to that of Ordinary Portland Cement (OPAC) based concrete, yet whilst at the same time addressing the environmental footprint of the industry and economic concerns.

GAP makes use of hazardous waste from several manufacturing process, which has obvious economic and environmental benefits. This allows GAP to have a far lower, in some cases up to 80%, embodied energy and carbon content than traditional concrete. In terms of structural properties, GAP can have a characteristic compressive strength of up to mamma, depending on curing conditions and mix design. For example, 30 to mamma is indicative of strength attainable within 3 to 4 days of pouring, yet for OPAC based concrete this is roughly 5 days.

However, academics have also put forward curing conditions can have a significant impact on these figures, with some studies wowing mamma achievable in as little as 6 hours (Journey et al. 2011). In addition, GAP has a higher tensile strength which in some applications may make steel reinforcement obsolete. GAP properties such as low shrinkage and improved acid, sulfate and fire resistance, give it improved durability. This therefore makes GAP a viable replacement for project applications such as sewerage systems, corrosive environments and radioactive and hazardous material containment.

TABLE OF CONTENTS Executive Summary I 1 Introduction 1 2 Structural properties 2 2. 1 Copolymer concrete mix 2 2. 2 Strength and Durability 3 2. Curing and workability 3 3 Need for copolymer concrete 4 4 Applications 5 5 Environmental concerns 6 6 Conclusions: 9 7 References 1 1 Introduction Concrete is the most heavily utilized construction material on the global stage. A staggering one cubic meter is consumed per person per year, a trend that is almost certain to continue, if not accelerate (Turner & Collins 2013). Considering the enormous scale of its use, even small innovations have the potential to create widespread benefits.

The traditional binder in concrete, Ordinary Portland Cement (OPAC), presently contributes somewhere between five and seven per cent of global anthropogenic carbon dioxide, CO, emissions (Cotoneaster et al. 2013; Turner & Collins 2013). Copolymer concrete (GAP), which substitutes copolymers in place of OPAC as the binder, has an approximately 80% lower carbon footprint than traditional concrete. While the practice of using copolymers as a binding agent has been known for over 60 years, it is only recently that developed has rapidly advanced, particularly in countries such as Australia (Journey et al. 011). With the current global attitude shifting towards a more sustainable future, innovation in traditional incorrect offers the potential to reshape the fields of engineering and construction and address these concerns. The copolymer binder used in place of OPAC in GAP can be sourced from industrial by-product material. The base material should be rich in Silicon (S’) and Aluminum (AAA), and can react with an alkaline solution, creating a isoperimetric binder (Raman ; Seeker 2011).

Fly ash, both low and high calcium content varieties, would therefore be an example of base material; however it could also be a combination of various materials, such as metropolitan and slang. Regardless, the basic reaction with he alkaline solution is similar, resulting in a compact, well cemented composite (Raman ; Seeker 2011). The Concrete Institute of Australia (CIA) released a document in 2011 stipulating a recommended practice for GAP, however this in itself is limited to low calcium fly ash sourced materials, noted as Class F (Journey et al. 2011).

Australia has a great abundance of untilled fly ash, and as such it is prudent to focus discussion accordingly. Aside from the significant environmental drive to develop GAP, there has been proven durability aspects demonstrated in structural applications, some of which ate back sixty years. Despite this, commercial impetus has been lacking in decades past, and only now is this starting to reverse. GAP is available in Australia, with an expectation that utilization will increase into the future as Australia transitions to a lower carbon economy (Journey et al. 2011).

The CIA has documented procedures addressing practical concerns of transport, placement, workability, curing and safety. This framework should ensure uptake of GAP will move forward. Structural properties The structural properties and composition of GAP differ to that of ordinary concrete. These points of difference arise from the variance in the forming chemical reactions. Copolymer concrete mix Traditional concrete is a mixture of OPAC, aggregate, water and sometimes admixtures. GAP replaces hydrated OPAC with a copolymer binder, which is usually formed from the interaction of an alkaline solution with a reactive luminosities powder.

Practically, this is a mixture to TTYL ash and blast terrace slang, boot torts to industrial waste from coal combustion and iron-making respectively. It is important to note that although it is common to partially replace OPAC with either fly ash, blast runner slang, or both, this is not GAP. The difference lies in the total replacement of hydrated OPAC. This meaner OPAC and water from traditional concrete, are replaced with a copolymer binder comprising of fly ash, blast furnace slang and an alkaline solution. An alkaline solution is required to accelerate the dissolution and reaction to form the cement paste (Journey et al. 011). This overcomes the issue of slow hydration usually experienced in blended OPAC. Aggregates, both coarse and fine, for GAP are the same as the traditional material as described in AS 2758. 1-1998 (Chowder ; DOD 2013). There are however, a few entrants which should be raised. Portland cement cannot use alkali reactive aggregates because, after a long period of time, an alkali-silica reaction may occur, causing expansion and cracking within the concrete. GAP on the other hand, may utilities these aggregates to increase and enhance the hardened concrete tensile strength (Journey et al. 2011).

Unlike OPAC concretes, GAP may also consist of recycled aggregate (Tattered et al. 2011). Admixtures which are commonly used in traditional concrete to tailor properties, such as a requirement for set-retardation or set-acceleration, towards a specific application are not necessary, or effective in GAP. Admixtures may also degrade the alkaline solution used in GAP. Having said that, many newer admixtures are able to control the concrete setting and strength of GAP (Journey et al. 2011). Strength and Durability Relative proportions of constituent materials define resulting strength and characteristics of concrete.

Change et al. (2007) reported that GAP was able to obtain a compressive strength of about 39 to 49 Amp, with a curing time within 24 to 72 hours and a curing temperature ranging between 60 to CHIC. However other researchers eave shown that GAP compressive strength may reach up to mamma in as little as 6 hours with the right curing conditions (Journey et al. 2011; Hardtop ; Range 2005; NORMA 2003). For comparison, AS 3600, the standard governing concrete structures in Australia, allows for design with concrete strengths up to mamma.

The tensile strength of GAP is generally accepted as greater than that of traditional concrete. GAP tensile strength varies from 4. Mamma to 7. Mamma as shown by Hardtop and Range (2005). This can be compared to that of Portland cement which has a tensile strength ranging from amp to amp (Chowder ; DOD 2013). Both GAP and OPAC based concrete have similar characteristics in both Poison’s ratio and Young Modulus. GAP has a Poison’s ratio ranging from 0. 12 to 0. 16 in compression, however higher strength mixtures have been reported with values up to 0. 4-0. 26. The Young modulus for both types of concrete depends on the grade of concrete, however experimental results suggest GAP has a lower elastic modulus than OPAC concrete (Journey et al. 2011). Durability mechanisms between G C and OPAC concrete are very deterrent due to the chemical processes which form the materials. Hardened GAP has a structure more eke a glass, rather than a hydrate like OPAC concrete. This makes it extremely durable, with acid and fire resistance better by orders of magnitude (Journey et al. 2011).

Wallach and Range (2006) showed that a GAP soaked in 5% sodium sulfate for 80 days had an expansion of 0. 015%, less than the 0. 5% which would be considered as a failure under sulfate attack. Curing and workability Kong and Santayana (2008) showed that GAP reaches 70% of its maximum strength within the first three to four days, compared to OPAC concrete which takes approximately five to seven days. Therefore the distinct time difference may allow rejects with a shorter timeshare to utilities GAP and finish in a shorter time frame.

Curing is influenced by temperature, time, moisture and ambient conditions. Curing regime has been shown to significantly affect strength development. For example, a heat cured low calcium flay ash based GAP has been observed to gain its full compressive strength within one day, showing no further increase as time progressed (Journey et al. 2011). Workability of GAP is similar to that of Portland cement based concrete. Adding naphthalene sultanate-based super-plasticizer will increase workability in GAP, forever this will decrease compressive strength of the concrete.

This is a similar case with water to both OPAC concrete and GAP, as it will increase the workability, yet decrease the compressive strength of the concrete (Hardtop ; Range 2005). Need for copolymer concrete GAP has numerous advantages over OPAC concrete. GAP has superior acid resistance when compared to OPAC concrete. According to the test of Mississippi State University, the OPAC loses 25% mass in the pH = 1 environment after approximately 50 years. However, GAP will take over 1400 years to lose that much (Journey ; Johnson, 005).

High acid resistance will directly save vast amounts of money, which may be used in fixing or maintaining the structure. While GAP has greater durability by orders of magnitude above OPAC concrete, there is a major drawback. Chloride diffusion in some Spec’s is much higher than OPAC concrete, and so steel reinforcement should not be used in salt water environments under these circumstances. Alternatives to steel reinforcement such as epoxy encapsulated glass fiber rods or post-tensioning ducts are possible approaches to address this issue (Journey et al. 011). Shrinkage of GAP may present a future hurdle to its widespread adoption. Under AS 3600, the maximum recommended shrinkage is 850 mirror strain for OPAC concrete. While heat cured GAP has been observed to shrink less than 100 micro strain, ambient cured G C may nave values as nigh as micro strain (Journey et al. 2011). According to the test in Table 3. 1 (Journey & Johnson 2005), the shrinkage of GAP is approximately 3 times lower than OPAC. Table 3. 1 : Relative drying shrinkage.

Shrinkage (incriminations), after; mamma OPAC concrete mamma GAP concrete 100 Amp GAP mortar days (Journey & Johnson 2005). Shrinkage(Incriminations),after; | 60 Amp Phosphorescent | 60 Amp Cooperate | 100 Magic mortar | 28 days | 350 | 125 190 1 The underlying alkaline solution in GAP is a highly corrosive material. Operationally this meaner they are more difficult, and therefore expensive, to handle, and incur significant occupational health and safety issues. It has been shown that the chemical substances in GAP materials are very harmful to health due to the strong proportion base on pH 14.

Eyes, skin and nose can be damaged by the sodium hydroxide (Cambric & Hammerer, n. D. ). Similar hazardous materials are used in any other industries, and so these concerns can be alleviated. For example, similar alkali solutions in Australia are used at a rate of greater than 1 million tones per year (Journey et al. 2011). Applications The possible applications for GAP are enormous since concrete is the most widely used construction material worldwide. Harnessing the benefits of GAP over OPAC concrete will result in widespread application.

With growing concern for all industry to become more echo-friendly, the current limited use of GAP is under constant growth. The workable life cycle of GAP, as compared to OPAC concrete, is far longer, especially n situations where acid resistance is necessary. In sewerage systems where OPAC concrete is currently used and typically has a design life cycle of approximately 50 years, GAP could be utilized with an expected to serviceable life cycle of 300 years and more (Journey et al. 2011). In the case of low calcium GAP, its resistance to sulfate is far greater than OPAC concrete.

Not only that, but because GAP can be produced to have higher flexural and tensile strengths, it is plausible to design without the necessity of mild steel reinforcements. This idea can be further applied in low load bearing cases like pipeline, where the major reason for failure is corrosion of the steel reinforcements (Journey et al. 2011). The high durability of GAP also could play a role in containing hazardous wastes. For example, radioactive Cesium which is a common by-product in nuclear reactors can be better held by GAP than OPAC concrete.

Spilling, in its most general form, is defined as the violent or non-violent breaking off of layers, or pieces, of concrete from the surface of a structural element when it is exposed to high, and rapidly rising temperatures, such as those experienced in fires (Koura & Endangers 2009). This can cause a dramatic decrease in structural strength and load bearing capabilities GAP otters superior tire resistance to O so its use in confined areas would be particular beneficial. This characteristic of GAP is ideal to be used in tunnels and underground tubes (Shah 2011).

Since the behavior of GAP is similar to OPAC concrete, design according to AS 3600 is still appropriate. In addition to in situ applications, GAP has also been used in production of precept railway sleepers, sewer pipes and box culverts. While current design methods are still appropriate, changes would be useful to incorporate the prosperity of the material. For example, the much faster strength development and stronger bond development could be incorporated. Also, many design procedures could be modified to reduce, or in some cases remove the need for steel reinforcing (Journey et al. 2011).

This is because with selected aggregates, concrete tensile strength can be increased sufficiently above that assumed in design methods. In a practical sense, the Australian Standards would also need to be opened up so as to allow the use of concrete, regardless of the cement, which with reference to this paper would be copolymer cement. Environmental concerns Certain types of concrete, and their production systems, have become harmful sources of pollution and deterioration of the world’s environment. The application of GAP in the built environment sector offers the possibility to address these sustainability issues.

Fly ash and granulated blast furnace slang, the major components to copolymer cement, are by-products of the coal and steel industries. These materials provide effective solutions to reusing waste products and lowering environmentally harmful emissions. Global OPAC production is put forward by Journey et al. 2011) to account for between 5 and 10% of total global carbon dioxide (CO) emissions. The current global trend towards sustainable practices, in particularly with prices on carbon, mandates this figure has not only environmental, but also financial impacts on the industry.

To control emissions within the cement production industry, the production methods of OPAC and copolymer cement must be examined, along with the advantages and disadvantages that contribute to hazardous waste. Financial cost of cement production is directly related to the energy usage of electricity and fuel (Well, Tomorrow’s & Buchwald 2009). By interpreting financial and material data obtained from a cement production life cycle, and from the life cycle of the resulting structure, the concepts of embodied energy and carbon are useful in quantifying environmental effects.

Basically these are measures of the total amount of energy and carbon embodied into an object through its entire lifestyle. An example of a cement life cycle feedstock is shown below. This illustrates the pathway of production, and also what the main contributing factors to financial cost and energy consumption are. Figure 5. : Cement production lifestyle feedstock (Well, Tomorrow’s ; Buchwald 2009). Due to the nature to cement production, cement resource locations and distances traveled to obtain resources are varied, and so it is necessary for a statistical based approach to estimate transport emissions (McClellan et al. 011). This becomes a contributing factor in the “overall cost and emissions” (O’Brien, Menace & Memory 2009). Once we have included all life cycle components ranging from mining, production, binder and transportation, we are then able to show comparative figures of CO missions between OPAC and copolymer cement (Well, Tomorrow’s ; Buchwald 2009). McClellan et al. (2011) illustrated the substantial beneficial difference resulting from copolymer cement, compared to OPAC, usage of an “approximately 72% reduction in cost, and 97% reduction in greenhouse emissions”.

Journey et al. (2011) postulated that full GAP adoption will allow for between a 4 and 8% reduction in total global carbon emissions. Figure 5. 2 illustrates the impact the construction industry, and in particular, concrete structures have on global climate targets. In essence the graph puts forward that in order for the planet to meet its emissions targets, significant GAP uptake is required. For example, if 1990 carbon emissions levels were to be the goal, almost full uptake would be required for the construction industry to meet its fair share of emissions savings. Figure 5. : World predictions for cement and SCM usage, with data overlain for CO emissions (Journey et al. 2011). Three cases are presented to illustrate relationship between carbon emission targets and copolymer uptake. Note that SCM refers to supplementary competitions materials, such as fly ash and granulated blast furnace slang. Industrial waste produced by large commercial, and mining, companies has become a reoccurring environmental and waste management issue. It is unjust that industries continue using primitive solutions, setting aside the issue for future generations to resolve, such as witnessed with industrial waste landfills.

In this respect, the underlying advantage of GAP is put by Graveled, Defender and Lorenz (1997)to be “if the physical properties [of concrete] can be conserved, while the product is still acting as a manifestation system, a novel process of toxic waste utilization will have been developed”. This is further developed into two main objectives such that the physical properties should be stable, suitable for further building applications, and able to encapsulate toxic materials.

The second objective would be to determine the mechanism and efficiency of this manifestation of industrial waste, not only in the sense of using it in the actual material itself, but also in its ability to contain hazardous waste, such as spent radioactive isotopes Arrested, Defender ; Lorenz 1997). Conclusions: The concept to GAP NAS history dating back to the mid twentieth century, however immemorially, the benefits have not been truly realized with very slow adoption rates.

At its core, copolymer cement is manufactured from fly ash and blast furnace slang, industrial waste of coal and steel production respectively, mixed together with an alkaline solution. Unlike blended OPAC which hydrates in the presence of water, the alkaline solution in copolymer cement is the primary solvent, accelerating dissolution and the chemical reaction. This point of difference has numerous repercussions in terms of the resultant concrete material. GAP has vastly superior durability specifications when compared to OPAC concrete, uh to its glass like structure.

This gives it far better chemical resistance, in particular acid resistance, as well as greater fire resistance. These properties lead to applications of GAP such as in sewerage systems, tunnels and underground tubes. While GAP has a lower modulus of elasticity than OPAC concrete, it has far greater tensile and compressive capacity than traditional concrete. In fact, the need for reinforcing steel in some applications would no longer be required as the tensile strength is greater than current provisions in design codes. Depending on curing notations, GAP can also attain a strength of up to mamma within one day.

The innovative material also has vastly superior bond strength to reinforcing steel. Although it is a concrete material, small changes to design codes will be required to account for these points of difference, to harness the maximum benefits. Not only that, but refinement is also needed to allow use of concrete, regardless of the competitions material used. This worded specification needs attention in current standards Perhaps one of the more important benefits of GAP, particularly in the current global rend towards more sustainable practices, is in its ability to address the significant environment footprint of the construction industry.


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