Browsing by Author "Loedolff, Gerrit Francois"

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    Kussande van die Wes-Kaap en die benutting van superfyn-duinsand in beton.
    (Stellenbosch : Stellenbosch University, 1985) Loedolff, Gerrit Francois; Hugo, F.; Stellenbosch University. Faculty of Engineering. Department of Civil Engineering.
    ENGLISH ABSTRACT: A survey of the Coastal sands along the False Bay coast, the Peninsula and the West coast as far North as Kreeftebay, was made and the physical properties of the sands were determined. With coastal sands is meant the sands in the vicinity of the highest water level and nearer to the sea and that of the dunes close to the sea. Since coastal sands have either an excess or a lack of 0,150 mm particle sizes, a method was sought by which concrete and mortar mixes could be designed. The most difficult part, namely superfine dune sand i.e. sand with a fineness modulus of less than 1.0, was thoroughly investigated. By determining the packing abilities and investigating packing step by step a method by which mixes could be judged by best packing or lowest porosity, was found. With this norm available by which mixes could be judged, grading curves received new attention. It was found that basic grading curves could be very valuable and methods to construct basic grading curves were consequently described. The final overall grading curve of the mix must be balanced around the basic grading curve to obtain best packing. It was also apparent that fine coarse aggregate of 4,8 to 6 mm particle sizes, played a major role when concrete was to be made. Bleeding and bleeding capacities of dune sands were also investigated. External bleeding indicates that something could be wrong with the mix, while internal bleeding is actually the detrimental factor with regard to greater shrinkage and possibly less strength. The most important aspect is therefore to determine the bleeding capacity of the mix and a method is developed to do just that.Shrinkage was also investigated and it was found that shrinkage of superfine dune sand mortar mixes increased as the w/c ratio increased above 0,50. With w/c = 0,50 and less the shrinkage of superfine dune sand mortars was not significantly different from that of normal sand mortars. In conclusion the applications and uses of poorly graded dune sands in the building trade, were discussed. Concrete mixes with dune sands will visually appear to be different from the concrete one is used to. It will have a drier appearance but as long as it is thoroughly compactable to a low porosity one must accept it. All dune sands can be used in the building trade either as concrete bricks or blocks, or for mortar in bricklaying, or for plastering or rendering or for concrete but in some cases aid in the form of coarser or finer sand or of finer coarse aggregates of 4,8 or 6 mm sizes or perhaps of admixtures such as plasticisers, will be needed. Since many of the findings and concepts developed in "Die Rol van Water in Beton"< 12 ) by the author, are used in this work, this publication should be read in conjunction with this thesis.