Lab 3.docx - Laboratory 3 Hardened Concrete Properties CEE 3020 Civil Engineering Materials Submitted to Dr David Scott by Whitney Lehrer Section A4

Lab 3.docx - Laboratory 3 Hardened Concrete Properties CEE...

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Laboratory 3: Hardened Concrete PropertiesCEE 3020 Civil Engineering MaterialsSubmitted to:Dr. David Scottby:Whitney LehrerSection A4 Group C Zichen BaiNicholas VoAbstract10%Introduction10%Experiment5%Results25%Discussion25%Conclusion10%Technical Writing10%Graphics: Design5%TOTALFebruary 22, 2019
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AbstractCompression and tensile strength, two properties of hardened concrete, are key elements of concrete design and construction. They are affected by multiple factors, including mixture design, curing condition, and age. The objectives of this experiment are three-fold. The first is to test the strength of concrete cylinders using compression and tensile strength tests. The second is determine the influence of w/c ratio, aggregate type, curing condition, and concrete age on overall strength. The final objective is to use microscopy to characterize different types of concrete. To achieve these objectives, compression tests using a loading rate of 150 lb./s are performed on five cylinders to find the average compressive strength of concrete made with a 0.55 w/c ratio and crushed gravel aggregates. The modes of failure are also assessed and recorded. Similarly, tensile strength tests are run on three cylinders to determine the average tensile strength for the same type of concrete. The average amount of fractured aggregates are also counted, which indicates the strength of the aggregates themselves. Lastly, three different specimens of concrete are viewed under the microscope, and the air content and cracking profile are noted for all three to characterize the state of concrete. Based on the results of this experiment, the average compressive strength for 0.55 w/c ratio concrete with crushed rock aggregates is 3132.2 psi with a standard deviation of 153.9 psi, and the average tensile strength is 335.5 psi. When considering concrete made with differing curing environments, aggregate types, and age, it can be said that the average strength of concrete is increased when using lower w/c ratios, crushed stone over river gravel aggregates, curing in a fog room instead of ambient temperature, and aging concrete for 14 over 7 days. The aggregate type, according to this experiment, is the biggest cause of weakened concrete. Alkali-silica reactions are denoted by crackingin and around aggregates in concrete, which is seen is specimen 3 of the microscopy portion of the experiment. Air-entrained concrete is indicated by small, circular air voids heavily distributed in the concrete, as shown in specimen 2. Specimen 1 exhibits no cracking and sparse distribution of large air voids, which indicates that it is non-air entrained, non-fractured concrete. These results suggest that the strength of hardened concrete is affected by many factors, especially aggregate type, which should be considered when designing concrete structures.
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Table of ContentsIntroduction....................................................................................................................................................1Experiment.....................................................................................................................................................1Materials...........................................................................................................................................1Equipment.........................................................................................................................................1Procedure..........................................................................................................................................1Results............................................................................................................................................................1Discussion....................................................................................................................................................12Conclusions..................................................................................................................................................13
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IntroductionThe hardened properties of concrete are key to the design and use of concrete. Properties include
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