CHAPTER XI 



CRUSHED LIMESTONE 



Waste Limestone for Road Metal, Railroad Ballast, and 

 Concrete. The value of the crushed hmestone used for road- 

 making, raih'oad ballast, and crushed rock concrete is greater 

 than that of any other limestone product. In 1913 the output 

 of this material in the United States was 35,169,528 short tons, or 

 approximately 420,000,000 cubic feet of limestone with a value of 

 119,072,024. The output was divided as follows: 



Road-making, 13,296,377 short tons; value $7,353,665. 

 Railroad ballast, 11,774,121 short tons; value $5,551,415. 

 Concrete, 10,099,030 short tons; value $6,167,144. 



The average price of this material was 54 cents per ton. In 

 road-making material Indiana ranked third, with an output 

 valued at $956,234, being outranked only by Ohio and New York. 

 In the production of railroad ballast Indiana was tenth, with an 

 output valued at $203,431. In the use of limestone for concrete 

 Indiana ranked sixteenth, with an output valued at $103,855. 



The two properties of limestone which are of importance 

 in road-making material are its wearing qualities and its cement- 

 ing properties. The subject of good roads has attracted wide 

 attention in a number of States, and while there is a great variety 

 of rocks which can be used as a road material, none is better 

 adapted to the work than a good, hard limestone. 



The limestone of the Mitchell formation which must be 

 removed as stripping in many of the quarries is admirably adapted 

 to road construction because it is a very hard limestone with good 

 wearing qualities. The stone, altho hard, is easily crushed be- 

 cause it is brittle, and works up easily. 



The stone of the Oolitic formation is softer and will not wear 

 long on roads that have to withstand heavy traffic. When 

 a road receives a thick covering of this stone the surface of the 

 stone coating tends to pack together and become firmly cemented. 

 If the traffic is not too heavy during the time the material is 

 setting, the road will harden down in good shape. But if the 

 traffic is too heavy the stone is ground fine before it has a chance to 

 become cemented together. The roads of Monroe and Lawrence 

 counties are to a great extent built of limestone, most of the 

 material having been taken from the Harrodsburg and Mitchell 



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