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Geology/Track Ballast - Alternative Materials.


QUESTION: Dear Keith

Which could be the alternative materials which can be used / tried out instead of Ballast or crushing stones ?. viz Cement, plaster of Paris, sand, coal, metal, non metals etc for railway tracks ?.

If we create a Word Document having a table consisting of the columns Materials,Advantages,Disadvantages and Conclusion,
Can this be a Good reference document for evaluation ?.

Awaiting your reply,

Thanks & Regards,
Prashant S Akerkar

ANSWER: Prashant:

First I think you need to evaluate the criteria for ballast.  What is its purpose, what traits are valued in the material used and what properties are benificial and which are detrimental?

Drainage, track stabalization, load bearing, weight distribution, cushioning, plant control, availability, ease of application and replacement or rehabilitation .

I have always had an interest in railroads, and have been around a lot of trackage and have pondered the different materials I have seen used, both first hand and second hand in historical photos.

In building the trans-american railroad from the US east coast to California, I do not think the actually ballasted the tracks, but just back filled the ties with soil, or maybe used sand or whatever materials they had available at the time.

Tracks were spiked directly to the ties without the benifit of a tie-track plate.

The majority of ballast I have seen has been limestone, but I have seen gravel made of other rock types, both granite and gneiss.  So I am not sure if their is a preferred material. The limestone I have seen is a blue very high CaCO3 containing limestone found along the US East Coast valued as building stone and as a source for making portland cement. It is very hard and a dark blue to gray, called Bluestone locally.

The primary criteria for ballast is probably cost, and availability since massive amounts are needed.  Whatever crushed gravel is available is used with the exception of sedimentary rock like shale or sandstone.  They weather into undesirable materials, clay and sand, neither very good at supporting weight.

To give you an idea of the amount of ballast needed:

At 1.35 tons of ballast per yard (2700 lbs/cu yard) this is 10,098 tons or about 101 cars of ballast of 100 tons each, or 144 cars of 70 tons per mile of track if the ballast is laid 8 inchs deep.

Concrete ties use 10 inches.  

So considering all this some of the materials you mention are disqualified out of hand.

Cement, plaster of Paris, sand, coal, metal,   These are all disqualified on the basis of the fact that none of them provide the essential qualities.  The first three would not drain well at all.  They would be expensive.  Plaster of paris and concrete would require limestone, and the added energy consumption to burn it to turn it into portland cement or lime.  This would make them prohibitively expensive.  Sand while readily available and cheap, does not drain well, and would not maintain stable grade, and is easily washed out by rain leading to broken ties and unstable road bed.   Coal is expensive, too soft, and weathers easily, not to mention the environmental problems of the acidic runoff from it if it is high in sulfur.  Metals would be too expensive and would break down and rust.  

One option that could be considered is clinker or slag from furnaces.  I have seen it used for ballast on a limited basis, since it is not available in the quantities needed.  They used it locally for small areas of trackage.  Slag is the glass like silica waste that floats to the top of a furnace of metallic iron during the smelting process.

Cinder has been used as well, but it is too small a grain size to be useful and has the same failings as sand.

There might be use for waste glass.  Lots of glass goes into landfills, and if recycled and melted with additives a ceramic ballast might be made.  But again the cost would make it very much more costly that common crushed stone.

Applicaiton of ballast is done by way of hopper cars, track is laid, and a hopper car of ballast is driven over the rails and ballast is applied through hoppers in the bottom of the car and then smoothed and distributed by placement of a bar or tie ahead of the rear wheels of the hopper car that acts as a brush or smoothing bar to clear the rail and push excess ballast to the side.

Only on the most expensive, fast and highly trafficked lines does the cost of concrete ballastless rails prove its worth.  There is just not many options for crushed stone because of its low cost.

---------- FOLLOW-UP ----------

QUESTION: Dear Keith

Thank you.

If we create a Word document with four columns viz. Material, Advantage, Disadvantage and Conclusion, will this be a good reference for Materials evaluation as a alternative to Crushing stones ?.

The Train should run more efficiently on the railway tracks with the New Material installed viz Cement, Sand, Plaster of Paris, Coal, Metal, Non Metal, Limestone etc instead of the crushing stones. Maintenance also has to be taken into picture for replacing the material if wear out.

I also feel Rutherford's periodic table could be a useful reference.

Awaiting your reply,

Thanks & Regards,
Prashant S Akerkar

Okay, it seems that the question is a class exercise that does not hold to the boundaries of economics or rationality.

In other words it is an intellectual exercise with no anchoring in reality.

The instructor is asking you to consider materials for ballast that have already been demonstrated by the industry to be either unsuitable, or uneconomical or just plain ridiculus.

I dont' understand the reference to the periodic table, and assume there was some classroom reference or context that has not been presented to me.

So, for the sake of the question, I would go with cement, precast into segments that will allow it to be replaced in sections, lowering the cost for replacement.  It cast in such a way to allow drainage it would provide superior stability and regularity of the track and its bed.
It would allow laser instruments to be installed to constantly measure track alignment and trueness of elevation of the roadbed.

Cons would be energy cost to make the concrete, costs for casting the sections, and transport of the sections.  If they are 12 inches thick fewer will be transported per rail car so it will require more shipment capacity per kilometer of track to install them. Concrete also has a larger carbon footprint to make that wood.


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Keith Patton


I can answer questions concerning physical and historical geology, environmental geology/hydrology, environmental consulting, remote sensing/aerial photo interpretation, G&G computer applications, petroleum exploration, drilling, geochemistry, geochemical and microbiological prospecting, 3D reservoir modeling, computer mapping and drilling.I am not a geophysicist.


I have 24 years experience split between the petroleum and environmental industries. I have served as an expert witness in remote sensing, developmental geologist, exploration geologist, enviromental project manager, and subject matter expert in geology and geophysical software development.

American Association of Petroleum Geologists
American Association of Photogrammetrists and Remote Sensing

Bachelor and Master of Science
Registered Geologist in State of Texas

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