Abstract. This study reports the experimental work undertaken to investigate the optimum grading of limestone to be used in concrete mixes. 36 concrete cubes were prepared for testing. Four different Fineness Moduli and grading were tested 2.4, 2.6, 2.92 and 3. For all tests, the cubes were left in curing until testing at the age of 3, 7 and 28 days respectively. Samples were loaded to failure and the average compressive strength was used for comparison purposes. Flow table test has been performed on the fresh concrete directly after mixing to measure workability and the average of the maximum concrete spread parallel to the two edges of the table was recorded. Results revealed that the optimum Fineness Modulus for the limestone to be used as fine aggregate in the concrete mix to get maximum compressive strength is 2.78. The flow table tests revealed an increment in the workability of fresh concrete with higher Fineness Modulus of limestone used in the concrete mix as fine aggregate. The workability of the optimum Fineness Modulus, 2.78, was found to be 412 mm which is a mix with considerable workability. An ideal grading has been recommended in this research study and checked to match the ASTM grading requirements for fine aggregate.

Mangrove wetlands are facing an existential threat from rapid socio-economic development. In this study, public environmental values regarding mangrove wetlands in the Ras Al Khaimah (RAK) city in the United Arab Emirates were assessed, considering gender, age, education, income, length of residency in RAK, knowledge of RAK mangrove and awareness of sustainability. A population sample of 427 respondents were face-to-face interviewed. Results suggest that mangrove value orientations are highly associated with length of residency in RAK and awareness of sustainability at significance levels of 0.003 and 0.005, respectively. Value orientations are less associated with age, knowledge of RAK mangrove and education at significance levels of 0.023, 0.039 and 0.095, respectively, being largely independent of gender and income. The majority of the respondents support the preservation of the mangroves even at the expense of economic development. This indicates the need to draft policies and regulations to safeguard the mangroves.

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Ultra-High Performance Concrete (UHPC) is an innovative material due to its unique properties and performance compared to conventional concrete. UHPC provides a resilient infrastructure and advances systems for sustainable use due to its extreme strength and superior durability under variable loadings and exposures. Although UHPC is a promising construction material, it faces numerous challenges before widespread implementation in the U.S. There are currently no published design guides to use UHPC in different infrastructure applications in the U.S., and accordingly, engineers and owners lack confidence in system performance. This work will focus on some challenges facing implementing UHPC in large-scale projects in the U.S., including discussing the impact of thermal or steam treatment on prestress losses and the long-term deflection response of UHPC prestressed systems.

Abstract:Concrete strength improved substantially when lateral confinement stresses are provided. This effect has been exploited in this study in composite beams at the concrete compression zone. New type of confinement is used in this research. The confinement of concrete in the compression zone is accomplished by providing U-links and stud-plate systems. The U-links are steel bars in the shape of the letter U welded internally in a steel tube at the compression concrete zone. These tubes provide confinement effect similar to the stirrups used in reinforced concrete beams. The stud-plate element used in this study is made of steel bar welded to a horizontal plate at one of its end, while the other end is welded to the top of the steel tube at the compression zone from the inside of the tube. The main function of these two elements is to provide the concrete in the compression zone with confinement stresses. The composite beam is tested in bending under single load at the mid-span. The effect of the new confinement system is studied and compared with concrete filled tube without any confinement element. The failure mechanism is also a focus of this research along with the deflection at the mid-span of the beam. The effect of the new confinement system on the structural behavior of the composite beam is presented.