FEATURE
CEMENT AND CONCRETE
strength and cold-weather concreting.
ensure a lasting end product.
This includes:
• High-strength concrete,
precasting and ready-mix
• Water-tight, structural and pre-
stressed concretes
• Precision grouts, repairs and
formulated cement products.
we will take a look at the Sephaku 32, a
• Medium strength concrete for paths,
32,5N general purpose blended cement driveways and light-duty floors:
Input equals output that reaches compressive strength at One wheelbarrow of cement, three
wheelbarrows of sand and three
Apart from choosing the right type a normal rate and that is suitable for an
of cement for the right application, extensive range of building applications,
it is also critical to take an including general domestic or building
uncompromising approach to the concrete, mortar, plaster and screed.
quality of the cement you choose, to
ensure structures that will last.
It is also ideal for use with cement
wheelbarrows of stone.
• High strength concrete for columns,
slabs and heavy-duty industrial
flooring: One wheelbarrow of cement,
The guidelines allow for minimal two wheelbarrows of sand and two
wastage of between 5-10% and wheelbarrows of stone.
extenders that enhance the concrete Consult manufacturers’ guidelines are based on a 65-litre builder’s properties such as silica fume and fly for ideal mixing proportions wheelbarrow. Please note that one USE CEMENT AND
ash or slagment. As soon as you’ve selected the 65-litre wheelbarrow load of cement is CONCRETE SAFELY
cement that is most suited to your equal to two 50kg bags in volume. Concrete is the world’s most widely
CONCRETE MIXING PROPORTIONS application, you will need to consult the Concrete is made up of four elements: manufacturers’ guidelines to determine cement, sand, stone (aggregate) and the ideal concrete mixing proportions. manufacturing: One wheelbarrow of water. The cement: sand: stone ratio is The mixing proportions are also cement: (= 2 x 50kg pockets) and eight critical as it determines the compressive subject to the strength of concrete wheelbarrows of sand. strength of the concrete, which in you need, which can generally be turn establishes the capacity of the classified in the following five groups: bricklaying and plastering: One elements. Although South African
structure you build to withstand loads. • High strength (25 - 30 MPa) wheelbarrow of cement and six cements typically contain less than
• Medium strength (20 – 25 MPa) wheelbarrows of sand. two parts per million of Hexavalent
used building material, and, as with
• Dry, lean mixes for brick and block
• General purpose mortar for
• Low strength concrete for
most materials, there are potential risks
involved in handling or working with it.
Portland cement is a complex
combination of compounds that
includes minute quantities of trace
Choose the right cement for the • Low strength (10 – 15 MPa) right application • Mortar (5 MPa) foundations, domestic flooring, level), it may serve as an aggravating
Point of departure would be to • Dry, lean mixes (7 – 14 MPa) steps, paths and fencing: One factor in cases of exposure to
wheelbarrow of cement, four alkaline fluids. There have been some
select the right cement for the right
Chrome (widely regarded as a safe
application and to check that it complies Examples of concrete mixing ratios wheelbarrows of sand and four reports of allergic dermatitis after
with the relevant specifications to For the purposes of this illustration, wheelbarrows of stone. exposure to these fluids.
DIY & INDUSTRIAL TRADE NEWS APRIL 2017
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