Kussande van die Wes-Kaap en die benutting van superfyn-duinsand in beton.

[摘要] ENGLISH ABSTRACT: A survey of the Coastal sands along the False Bay coast, thePeninsula and the West coast as far North as Kreeftebay, was madeand the physical properties of the sands were determined. Withcoastal sands is meant the sands in the vicinity of the highestwater level and nearer to the sea and that of the dunes close tothe sea.Since coastal sands have either an excess or a lack of 0,150 mmparticle sizes, a method was sought by which concrete and mortarmixes could be designed. The most difficult part, namelysuperfine dune sand i.e. sand with a fineness modulus of lessthan 1.0, was thoroughly investigated. By determining thepacking abilities and investigating packing step by step a methodby which mixes could be judged by best packing or lowestporosity, was found.With this norm available by which mixes could be judged, gradingcurves received new attention. It was found that basic gradingcurves could be very valuable and methods to construct basicgrading curves were consequently described. The final overallgrading curve of the mix must be balanced around the basicgrading curve to obtain best packing. It was also apparent thatfine coarse aggregate of 4,8 to 6 mm particle sizes, played amajor role when concrete was to be made.Bleeding and bleeding capacities of dune sands were alsoinvestigated. External bleeding indicates that something couldbe wrong with the mix, while internal bleeding is actually thedetrimental factor with regard to greater shrinkage and possiblyless strength. The most important aspect is therefore todetermine the bleeding capacity of the mix and a method isdeveloped to do just that.Shrinkage was also investigated and it was found that shrinkageof superfine dune sand mortar mixes increased as the w/c ratioincreased above 0,50. With w/c = 0,50 and less the shrinkage ofsuperfine dune sand mortars was not significantly different fromthat of normal sand mortars.In conclusion the applications and uses of poorly graded dunesands in the building trade, were discussed. Concrete mixes withdune sands will visually appear to be different from the concreteone is used to. It will have a drier appearance but as long asit is thoroughly compactable to a low porosity one must acceptit.All dune sands can be used in the building trade either asconcrete bricks or blocks, or for mortar in bricklaying, or forplastering or rendering or for concrete but in some cases aid inthe form of coarser or finer sand or of finer coarse aggregatesof 4,8 or 6 mm sizes or perhaps of admixtures such asplasticisers, will be needed.Since many of the findings and concepts developed in Die Rol vanWater in Beton< 12 ) by the author, are used in this work, thispublication should be read in conjunction with this thesis.

[发布机构] Stellenbosch University