The perfect sand. Sand requires two key characteristics: Gradation Particle shape. Gradation. An even gradation will minimise voids in a matrix for concrete or asphalt, so minimising the amount of paste required to hold the matrix together (either oil of cement).
An even gradation will minimise voids in a matrix for concrete or asphalt, so minimising the amount of paste required to hold the matrix together (either oil of cement).
The shape of sand particles is critical to minimise the surface area of fine aggregate, to minimise the amount of glue needed to bind the ingredients and to maximise the workability of the mixture.
The flatter or more elongated the particle the greater the surface area.
As particles become smaller, their relative surface area increases geometrically.
However the relationship between surface area and cement requirement is not directly proportionate, indeed Murdock showed that the minus 75 micron particles have relatively less effect on surface area...
Effect of Surface Area
Particle Size Fraction
38 – 19
19 – 9.5
9.5 – 4.75
4.75 – 2.36
2.36 – 1.18
1.18 – 0.60
0.60 – 0.30
0.30 – 0.15
3/4” – 3/8”
3/8” - #4
#4 - #8
#8 - #16
#16 - #30
#30 - #50
#50 - #100
Control over the filler content (either minus 75 micron or 63 micron particles).
The effect of crushed fine aggregates.
Blending, and variable inputs.
These tiny particles always cause concern, due to the possible presence of clays or other deleterious matter that might absorb water, and so increase cement demand.
Most rock fines are beneficial in a concrete mix, filling voids and reducing cement demand, while improving workability.
7- 9 % of good rock filler within the fine aggregate component of concrete has generally proven to produce the best results.
The quality of the filler can be assessed using a Methalene Blue test.
The addition of crushed sand to a concrete mix invariably adds strength, however it usually reduces workability and can effect finishability, depending upon how well shaped the crushed component is, even assuming a good gradation.
Natural sand is invariably better shaped.
Crushed sand rarely has an even gradation, but is often blended with a fine natural sand to achieve a good gradation.
The two critical factors in such a blend are the shape of the crushed sand particles and the consistency of the natural sand.
A crusher capable of making lots of – 500mm particles, whose output is always well shaped and consistent.
An airscreen capable of both separating and controlling filler content, and returning a variable controlled amount of oversize to the crusher.
An enclosed plant that is computer controlled, both quiet and dust free – an environmental sustainable solution.
The Kemco V7 plant is a Dry system, and can only process feed material with a moisture content less than 2%.
The plant operates to produce a fine finished product, it is not a significant reduction crushing plant. Feed size should be limited to 7mm, to make a minus 5mm sand, or to 5mm to make a minus 3mm sand. These feeds are usually surplus or even waste products in many quarries.
While the plant takes up a relatively small footprint, the dust collector stands over 17 metres tall.
The 60 refers to plant throughput, and on average one would expect to see 50 tonne of Kayasand per hour, and 10 tonne per hour of filler.
Production varies according to the amount of filler included in the feed, and the reduction ratio required, (more recirculation will generate more filler).
It appears that the Kemco V7 plant is the only plant available in the market today that is capable of producing a single sourced manufactured sand, that does not require blending, and which will in some instances out perform natural sand in concrete.
It is also the only plant that is capable of varying that gradation to find the ideal sand for the purpose, and able to consistently manufacture that gradation and quality.
Kemco have run over 300 tests with all types of feed materials - in the last 7 years they have sold nearly 50 plants in Japan.
Kemco will not sell a plant without thoroughly testing the source rock, after which they will provide a warranty not only for the gradation, but also for the production and operating cost.
Kayasand is the name given to sand produced by the Kemco V7 system, so named after its inventor, Takato Kaya. The sand features are:
It is well shaped throughout the gradation
Its filler content can be precisely selected
Its gradation can be varied by recirculating oversize, and by skimming any oversize from the discharge to the dust collector
It has a small fixed amount of moisture added to the dicharge, which prevents it from segregating while stored or transported, ensuring a consistent delivered product.