3 research outputs found
Mixture-proportioning of economical UHPC mixtures
No full text[EN] Ultra-High Performance Concrete (UHPC) offers innovative applications to concrete structures based on enhanced mechanical properties. The use of local materials is necessary to reduce the UHPC cost and save materials and energy. This research focuses on developing economical UHPC mixtures using locally available materials. A testing program, including 51 concrete mixtures, is developed to evaluate the effect of different fine materials, supplementary cementitious materials, steel fibers, curing regimens, and mixers type. The amount of steel fibers and type of fine materials are influential factors to the concrete cost. Mixer type does not have a significant influence on UHPC strength. By using a binder content of 1163 kg/m(3) and incorporating fly ash as a part of the binder by 40% by weight, the cost was $283/m(3) without steel fibers.This research is supported by the University of Arkansas at Fayetteville, the Ton Duc Thang University, and the Higher Committee for Education Development in Iraq (HCED). The authors would like to thank Grace Construction Products Company, Griffith, F., Deschenes, R., and Casillas, B. for their help during the experimental program. The first author is further thankful to Mr. Adnan Alsalman, Ms. Suhailah Alasadi and Ms. Cindy Lopez for their inspiration and support.Alsalman, A.; Dang, CN.; Martí Vargas, JR.; Hale, WM. (2020). Mixture-proportioning of economical UHPC mixtures. Journal of Building Engineering. 27:1-15. https://doi.org/10.1016/j.jobe.2019.100970S11527Lechner, T., Gehrlein, S. F., & Fischer, O. (2016). Structural behaviour of composite dowels in thin UHPC elements. Steel Construction, 9(2), 132-137. doi:10.1002/stco.201610012Abbas, S., Nehdi, M. L., & Saleem, M. A. (2016). Ultra-High Performance Concrete: Mechanical Performance, Durability, Sustainability and Implementation Challenges. International Journal of Concrete Structures and Materials, 10(3), 271-295. doi:10.1007/s40069-016-0157-4Rossi, P., Arca, A., Parant, E., & Fakhri, P. (2005). Bending and compressive behaviours of a new cement composite. Cement and Concrete Research, 35(1), 27-33. doi:10.1016/j.cemconres.2004.05.043Alsalman, A., Dang, C. N., & Micah Hale, W. (2017). Development of ultra-high performance concrete with locally available materials. Construction and Building Materials, 133, 135-145. doi:10.1016/j.conbuildmat.2016.12.040Habel, K., Charron, J.-P., Braike, S., Hooton, R. D., Gauvreau, P., & Massicotte, B. (2008). Ultra-high performance fibre reinforced concrete mix design in central Canada. Canadian Journal of Civil Engineering, 35(2), 217-224. doi:10.1139/l07-114PREM, P. R., BHARATKUMAR, B. H., & IYER, N. R. (2013). Influence of curing regimes on compressive strength of ultra high performance concrete. Sadhana, 38(6), 1421-1431. doi:10.1007/s12046-013-0159-8Alsalman, A., Dang, C. N., Prinz, G. S., & Hale, W. M. (2017). Evaluation of modulus of elasticity of ultra-high performance concrete. Construction and Building Materials, 153, 918-928. doi:10.1016/j.conbuildmat.2017.07.158Wu, Z., Shi, C., He, W., & Wu, L. (2016). Effects of steel fiber content and shape on mechanical properties of ultra high performance concrete. Construction and Building Materials, 103, 8-14. doi:10.1016/j.conbuildmat.2015.11.028Shi, C., Wu, Z., Xiao, J., Wang, D., Huang, Z., & Fang, Z. (2015). A review on ultra high performance concrete: Part I. Raw materials and mixture design. Construction and Building Materials, 101, 741-751. doi:10.1016/j.conbuildmat.2015.10.08
A study on the sea level variations and the 'Milghuba' phenomenon in the coastal waters of the Maltese Islands
No full textThe phenomenology, generation and associated dynamics of short period seiche oscillations observed along the northern coast of the Maltese Islands are studied from a set of densely sampled, long term hydro-meteorological observations made at a permanent sea level gauge, together with simultaneous observations of bottom pressure recordings at offshore positions and across the Malta Channel. This coastal seiche, known locally as the 'milghuba' manifests itself in conjunction with the occurrence of mesoscale atmospheric gravity waves travelling in the lower troposphere. The associated open sea waves excite the water bodies of the various inlets, bays and harbours into resonant oscillations which reach a range of up to lmin Mellieha Bay. Numerical experiments based on the free surface, non-linear Princeton Ocean Model (POM) in 2D mode explain the response characteristics of two adjacent wide-mouthed open embayments. The seiche-induced barotropic circulation and impact on the flushing of Mellieha Bay are studied by means of an advection-diffusion scheme implemented within POM. Sea level signals on the synoptic, planetary wave and seasonal scales dominate the residual spectrum A multiple regression model and a novel analytic technique based on the wavelet transform provide in combination a very effective means of studying the composition of the sea level signal and the dependence of its variability in time on one or more correlated parameters. Atmospheric pressure is the predominant factor determining the sea level variability at frequencies lower than 0.75cpd. In the upper synoptic frequency (0.3 < f < 0.5cpd) the response is very close to isostatic, with an average gain of 0.7. At other frequencies the overall response is non-isostatic implying that other factors besides mesoscale atmospheric pressure forcing contribute to the sea level variability. On account of the station's position close to the latitudinal axis of the Strait of Sicily, these signals are important in understanding the control of the Strait on intra-basin exchanges. Seasonal changes in the mean sea level show a major minimum in Marchand a major maximum towards the last months of the year. Besides the usual steric and direct meteorological effects, this variability is attributed to adjustments in the mass balance of the whole Mediterranean basin
