Although ultra high-performance concrete (UHPC) has great performance in strength and durability, it has a disadvantage in the environmental aspect; it contains a large amount of cement that is responsible for a high amount of CO2 emissions from UHPC. Supplementary cementitious materials (SCMs), industrial by-products or naturally occurring materials can help relieve the environmental burden by reducing the amount of cement in UHPC. This paper reviews the effect of SCMs on the properties of UHPC in the aspects of material properties and environmental impacts. It was found that various kinds of SCMs have been used in UHPC in the literature and they can be classified as slag, fly ash, limestone powder, metakaolin, and others. The effects of each SCM are discussed mainly on the early age compressive strength, the late age compressive strength, the workability, and the shrinkage of UHPC. It can be concluded that various forms of SCMs were successfully applied to UHPC possessing the material requirement of UHPC such as compressive strength. Finally, the analysis on the environmental impact of the UHPC mix designs with the SCMs is provided using embodied CO2 generated during the material production.
Tendons that vertical moor TLPs are a major cost driver in deepwater TLPs. Carbon fiber composites have many of the desirable material properties for use as TLP tendon as an alternative to steel. This paper investigates the performance and cost impact on the overall TLP design. The focus is on the comparison of global performance of two generic Gulf-of-Mexico TLPs with steel and composite tendons in 7,000 ft water depth. Fully dynamically coupled TLP-tendon system dynamics of both TLPs has been analyzed in time domain with hydrodynamic input complete to 2 nd order. The use of composite tendons leads to improvements on global performance related to airgap, maximum horizontal offset and maximum tendon tension. These improvements have been achieved despite the fact that the heave natural period of the TLP with composite tendons has been increased to 4.72 second from 4.2 second for the TLP with steel tendons. It is demonstrated that use of composite tendons in lieu of steel results in significant reduction in pretension, hull size and hull steel.
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