Sephaku Ash’s facility at Kendal Power Station has the capacity of three 1000-ton finished-product silos and has six dedicated weigh bridges to load road-bulk tankers to customers in record-breaking time.
WHERE DOES FLY ASH COME FROM
By far, the most pulverised fuel ash, commonly known as fly ash, comes from coal-fired power stations operated by ESKOM.
THE PROCESS OF PRODUCING FLY ASH IS AS FOLLOWS
Coal is mined from a quarry and transported to power stations where it is stockpiled into different grades. The coal is milled in large mills into a fine powder, whereafter it is blown through a series of pre-heaters into a furnace where it burns at +- 1400 degrees Celsius.
After the burning process, the leftover coarse material is discarded at the bottom of the furnace known as ‘bottoms ash’ and stockpiled in waste dumps, while the leftover finer material is drawn through particle filtration equipment. This fine material is retained while the flue gasses are released into the atmosphere.
The fine, burnt coal particles captured in the filtration equipment are deposited into bunkers or holding bins and accessed as unclassified fly ash. Sephaku Cement has access to at least 1.1 million tons anually and has branded this as Hard Ash (see graph below).
Economy costs less than cement. Can be blended with cement to achieve a more cost-effective cement solution.
Requires less water to get concrete into a workable/placeable state [improving concrete durability]. Lower water content contributes to less shrinkage and/or cracking.
Long-term Strength Development
Is a synthetic pozzolan, which gives fly-ash-based concrete the ability to develop strength over prolonged periods.
Enables beneficiation of a waste product into useable building materials. Considerably less clinker is required to produce finished cement product which means reduced CO² emissions.
Other benefits of using fly-ash-based
Reduced risk of thermal cracking in large concrete applications.
Improved concrete resistance to sulphate attack.
Increased durability of concrete in high-chloride environments (e.g. coastal areas).
Prevents alkali-aggregate reaction in concrete.
WHERE IS FLY ASH USED
The predominant use of fly ash is in cement as an additive or improver (extender), which can either be blended at the point of cement production or at a later stage at the point of concrete production such as ready-mix or precast applications. Fly ash is used by the following industries: