893 research outputs found

    Old Concrete Makes Way for New Asphalt

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    Back in the middle seventies, the latest civil pavement engineering techniques and technology transformed the old single carriageway trunk road which linked the Western Cape towns of Cape Town and Somerset West together as well as connecting them to the eastern part of the country. This transformation changed this road into a modern dual carriageway facility. This new facility was constructed with the then latest technology involving slip form paved concrete. All went well until a new phenomenon involving the interaction of sodium monoxide in cement and the alkali minerals in the local crushed rock caused the concrete to expand and evidenced severe failure. Although this early failure was kept in check for over 40 years, the section of this road which forms part of the transport hub at Cape Town International Airport, has finally been reconstructed giving way to a highly modified bituminous binder based pavement. The new pavement consists of an asphalt base, surfacing and friction course all produced with modified bituminous binders. The supporting layers have been constructed by recovering and crushing the old concrete and combining with further cement to form the stabilised supporting layers. This is regarded as a fully green approach to salvaging old problematic pavement materials. With minimal effort and modification sound subbase layers have been created to provide the necessary support to the construction of modern asphalt layers to produce a more flexible pavement alternative for safe travelling on this busy route.Papers presented at the 38th International Southern African Transport Conference on "Disruptive transport technologies - is South and Southern Africa ready?" held at CSIR International Convention Centre, Pretoria, South Africa on 8th to 11th July 2019

    Simultaneous description of four positive and four negative parity bands

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    The extended coherent state model is further extended in order to describe two dipole bands of different parities. The formalism provides a consistent description of eight rotational bands. A unified description for spherical, transitional and deformed nuclei is possible. Projecting out the angular momentum and parity from a sole state, the Kπ=1+K^{\pi}=1^+ band acquires a magnetic character, while the electric properties prevail for the other band. Signatures for a static octupole deformation in some states of the dipole bands are pointed out. Some properties which distinguish between the dipole band states and states of the same parity but belonging to other bands are mentioned. Interesting features concerning the decay properties of the two bands are found. Numerical applications are made for 158^{158}Gd, 172^{172}Yb, 228,232^{228,232}Th, 226^{226}Ra, 238^{238}U and 238^{238}Pu, and the results are compared with the available data.Comment: 36 pages, 13 figures, 12 table
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