Re: Ballast question

Railroads used gravel and other material due to ease and availability. Cinders were also thrown in as a "free" ballast supply. As equipment and trains became heavier, rail size started to increase, and a need for better holding ballast became evident as track structure started to deteriorate, which caused more maintenance. So the railroads experimented with river stone. It worked but was discovered not very well as the track seemed to float on marbles. Then they tried crushed stone, and found that crushed stone and mechanical tamper machines would make a very strong track structure. A crushed stone ballasts track would now last for an average of 5-10 years with normal maintenance where as a gravel ballasts track would require maintenance every 1-3 years.