Physical and Chemical Changes Which Affect Concrete - Paper Example

The Scope of Solution Considered

Three solutions are proposed to address physical and chemical changes which affect concrete and result in its deterioration. These solutions are; High Performance Concrete (HPC), Fiber Reinforced Concrete (FRC), and Fiber Reinforced Polymer Concrete (FRPC). Each of these solutions offers unique advantages that confirm their suitability for addressing concrete deterioration. The advantages of each of the alternative solutions to concrete deterioration are captured by the capacity to withstand load vibrations, tensile and compression strengths, and the resultant durability of the project.

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High performance concrete is concrete whose design and manufacture aims to achieve durability. As a result, HPC is stronger than conventional concrete which makes it suitable for structures such as bridges that experience high capacity loads, colossal traffic and are designed for safety. Whereas HPC is derived from the same components that make conventional concrete, the proportions of its mixtures are rationed to achieve optimality concerning strength and durability which are necessary for the environmental and structural requirements of any essential project. High performance concrete exhibit about 800psi or more concerning compressive strength (Merlo Construction, 2018). This level of compressive strength is critical because it helps to achieve the much-needed special care that is necessary for efficient production and testing of the concrete project and which may help to achieve special structural design requirements. HPC also reduces the construction costs.

High performance concrete also has the right toughness and tensile ductility requirements and frequently incorporate fibers to achieve specified optimal requirements. Besides these requirements, the possible environmental requirements which may need the use of HPC include environments that require high early strength, high modulus of elasticity, high abrasion resistance, long life, and high durability as a result of extreme weather conditions and low diffusion and permeability. Such environments are every day for concrete projects including bridges. Additionally, HPC is applicable in mitigating concrete deterioration as it has a high resistance to chemical attack, has a high resistance to frost and deicer scaling damage, ensures toughness and impact resistance, brings about volume stability, are easily placeable, allow for compaction without segregation, and provides an environment which inhibits bacterial and molds growth. The process of making HPC involves the careful selection of material and optimized mixture techniques (Kosmatka, Kerkhoff, & Panarese, 2011).

Fiber Reinforced Concrete refers to a composite material made up of a mixture of mortar, concrete, and cement. In addition to these components, the strength of FRC is reinforced with the aid of discontinuous, discrete, uniformly dispersed suitable fibers. There are various types of FRC which come with several advantages. The fiber utilized in FRC can be flat or circular and have aspect ratios ranging between 30 and 150. The fibrous elements added to FRC are responsible for its strong structural integrity. Fiber reinforcement is essential for concrete projects. Concrete is a brittle material with tensile strength to compressive strength ratio of about 1:10 (Afroughsabet, Biolzi, & Ozbakkaloglu, 2016). In typical projects, therefore, this inefficiency is addressed using steel reinforcing bars. However, this approach does not offer the optimal conditions required for specific projects.

The use of fiber as reinforcement elements and a replacement to steel bars helps to increase the energy absorption capacity of material toughness which is necessary for projects such as bridges. Additionally, fiber also increases the flexural and tensile strength of concrete. As such, FRC is applied in a wide range of projects and guarantees reduced costs, reduced maintenance, and increased strength and stability.

The American Concrete Institute (2018) refers to Fiber Reinforced Polymer Concrete (FRPC) as a composite material that consists of a polymer matrix combined with fiber reinforcement on top of standard concrete. Typically, such materials are made of strengthening fibers which are customarily embedded within the resin matrix. Such fibers are meant to add stiffness and strength. FRPC helps to achieve efficient stress transfer from one fiber to the next by way of shear stresses. Additionally, they are noncorrosive, nonconductive and lightweight. These three characteristics fit well when considering the physical and chemical deterioration of concrete projects such as bridges (Hensher, 2016).

Modern projects are increasingly employing FRPC due to their rapid hardening capacities. The high mechanical strength exhibited by FRPC materials places them in pole position as the choice materials for specific projects. Additionally, they provide resistance against chemical erosion which eats into a project. FRPC is applicable for bridge overlays with polymer impregnated concrete being the more useful category.

Comparative Assessment of Candidate Solutions

Costs

There is some element of cost advantage in all the three solutions. High Performance Concrete is more expensive than conventional concrete. Comparably, HPC's economic benefits result from the reduction in the implementation of concrete. Additionally, the cost benefits of HPC arise from the geometric sections of bearing elements of the built space and the reduced demand for the maintenance of the resulting structures. HPC use permits the reduction of the intersection of elements of materials as well as the costs of a fixed load, thereby significantly reducing the overall material cost. The cost of fiber reinforced concrete is higher than that for HPC. This high cost occurs due to the added components which increase costs by up to $10 per yard. Likewise, fiber reinforced polymer concrete attracts higher costs due to its higher performance. So, concerning cost, HPC offers the best bargain (Kosmatka, Kerkhoff, & Panarese, 2011).

Tensile Strength

Ordinary concrete has a tensile strength of 8.2 MPa. High performance concrete has a superior tensile strength at 30.2 MPa. This improved performance ensures that the project has a longer life. The tensile strengths of fiber reinforced concrete depend on the type of fiber employed for the reinforcement. The addition of natural fibers as concrete composites adds tensile strength by up to 53 percent as compared to the conventional concrete. There is an overall positive result with regards to the strength of composite material and the tensile strength of the resultant fiber reinforced concrete. Materials that have higher fiber concentrations also show higher tensile strength values. Generally, fiber reinforced to have a mean tensile strength of up to 4.5 MPa. The split tensile strength for fiber reinforced polymer concrete rises to up to 6.5 MPa depending on the reinforcement used. Therefore, with regards to tensile strength, high performance concrete ranks higher than fiber reinforced concrete and fiber reinforced polymer concrete (Kosmatka, Kerkhoff, & Panarese, 2011).

Durability

Normal concrete has a lifespan of between 50 and 150 years. This longevity is evident in most of America's old bridges and projects. As a result of its high compression strength and tensile strength, high performance concrete is highly durable compared to conventional concrete. Similarly, fiber reinforced concrete is designed to be more durable. This durability is ensured through the improved performance under intense environmental conditions, proper load resistance capacity and physical and chemical deterioration defense (Merlo Construction, 2018). The overall outcome of the addition of these elements is highly durable concrete projects that have higher life spans compared to conventional concrete. Fiber reinforced polymer concrete is equally designed for durability. The reinforcement components are such that they offer the most significant resistance to chemical and physical deterioration. FRPC is the refined version of FRC concerning the role of reinforcement material and their role in adding durability. As such, comparatively, all the three leads to more durable projects compared to conventional concrete.

Recommended Solution

The recommended solution would be high performance concrete. Whereas projects developed using conventional concrete cannot withstand the tear and wear that results from the daily traffic that they are designed for, high performance concrete allows for the improvement of the quality of concrete to withstand such deterioration that arises from both chemical and physical elements. The chemical formula that creates high performance concrete incorporates elements that are used for conventional concrete. The difference is in the rationing of the elements. This disparity is unlike the other alternatives whose new elements add to the costs. Compared to the other two alternatives, high performance attracts the least costs for a project. This advantage does not only apply to the initial cost (Afroughsabet, Biolzi, & Ozbakkaloglu, 2016).

High performance concrete ensures that the resulting projects require minimal maintenance. Additionally, given their durability, it takes relatively long before projects erected using high performance concrete call for maintenance. The high tensile strength prepares projects built using high performance concrete for heavy loads and high traffic which are traditionally associated with the tear and wear. Lastly, high performance concrete is resistant to corrosion, contraction and expansion and other physical damage causes which have traditionally lead to tear and wear of bridges.

Design and Implementation Challenges

Compared with conventional concrete, high performance concrete is extremely expensive. This aspect makes it less attractive as a construction material. The high cost of UPC emanates from the increasing cost of materials used. The second challenge with UPC is the little knowledge of its life-cycle cost. Whereas the high durability characteristics of UPC can be theoretically determined, there is no documentation of previously inspected, repaired, or replaced project which employed UPC in its construction (American Concrete Institute, 2018). As such, there is insufficient evidence regarding the value advantage of UPC over normal concrete.

There are three significant challenges associated with fiber reinforced concrete. Foremost, such concrete requires exactness in the proportioning of the fiber components. It has been determined that the slightest variation in component ratios result in altered concrete performance, particularly its strength. Secondly, as a result of the high control issues around fiber reinforced concrete, it attracts higher costs. Thirdly, there is an increase in the specific gravity of fiber reinforced concrete. As a result of the introduction of additional components, FRC is more cumbersome than conventional concrete. Structurally, this factor would be disadvantageous.

Fiber reinforced polymer concrete has a significant impact on the cost aspect of a project. Fiber composites result in high recurring costs. They also lead to a higher material cost which discourages their application as alternatives. Whereas projects made of fiber reinforced polymer concrete have relatively long lifespans, they are associated with extremely high maintenance and repair costs (Hensher, 2016).

References

Afroughsabet, V., Biolzi, L., & Ozbakkaloglu, T. (2016). High-performance fiber-reinforced concrete: a review. Journal of materials science, 51(14), 6517-6551.

American Concrete Institute. (2018). Fiber Reinforced Polymer. Retrieved from https://www.concrete.org/topic...