US1645891A - Method of hardening and toughening broken-mineral aggregates consisting of trap rock, limestones, sandstones, and types of shale rocks - Google Patents

Description

Patented Oct. 18, 1927.

UNITED STATES 1,645,891 PATENT OFFICE.

1 JOSEPH HAY AMIES, OF PHILADELPHIA, PENNSYLVANIA.

METHOD OF HARDENING AND TOUGHENING BROKEN-MINERAL AGGREGATES CON- SISTING OF TRAP ROCK, LIMESTONES, SANDSTONES, AND TYPES OF SHALE ROCKS. I

No Drawln g.

One of the objects of this improvement. is to increase the hardness and toughness of broken granite, limestone, sandstone, and types of shale rocks. Broken stones'now ad- 5 mitted to be used for bituminous and alkaline concrete manufacture, must provide, ten centigrades of co-efiiciency. Otherwise, they would not be accepted by the engineers and bureaus of highways. The hardest and toughest mineral known is the diamond. This is stated as one hundred. Broken stone must provide a toughness and hardness, equal to one-tenth of this standard, in order to be acceptable for concrete making. This degree of hardness and toughness is termed, tencentigrades of coefliciency. This is equal to the hardness and toughness of the set of cement binders. It is called the co-efficiency of the broken stones, that is, the broken stones are co-equal in toughness and hardness with" the binder, itself. The importance of this exacti'on lies in the fact that if either the broken stones or the binder should be too weak to stand the exactions of trafiic, poor concrete would result:

Another important object of this improvement is to secure greatlyfieduced cost in making concretes.

My process is as follows To each five hundred pounds, I may say, of broken stones placed in an agitator or mixer. I may add about ten pounds of finely granulated quick lime, whilst the same has just begun to slake. This batch quantity of broken stones, in about thirty seconds. after being placed in the said agitator, may be dumped into a sheltered bin or shed. Curing will proceed after the treated broken stones have been stored up. They may however, be immediately employed. Care should be taken to have the broken stones clean,

' that is, free from soil, or stone dust, be-

cause these will consume the causticity of 15 the slaking lime needed in the process. If

the stones are unclean not only will the action of the lime be weakened but the. already slaking lime will not secure a close touch with the broken stone aggregates.

0 It will be seen that great expense in making concretes will be saved by the above process, because broken granite that is naturally hard enough to serve in the manu facture of concretes is very confined. At

36 least seven-tenths of the territories of the mal voids of the stone aggregates appeared Application filed August 12, 1926. Serial No. 128,906.

United States, must, for reasons, be deprived of standard broken aggregates. They are, for the same reasons, prohibited on the ac count of costs, in said territories. This ty e of broken granite aggregates, that attain thedemanded co-efliciency, naturally, costs at the quarries or ledges, where broken, from three to six times more than broken soft limestones, and sandstones and shale rocks. In addition to this, owing to the distance of-haulage and freightage, the final costs of broken trap rock granite, would give an extended expense in manufacturing concretes, many times greater than if'the above referred to broken limestones and other lighter and weaker broken stones could be used. Not only this, but broken trap rock granite weighs from one hundred to one hundred and twenty five pounds to. the cubic foot, when clean, that is. free of stone dust and soil. Whilst, the lighter broken stone, referred to, weigh no more, on an average, than forty-five to seventyvfive pounds to the cubic foot. Therefore, a ton of the lighter stone would make a very much larger bulk than would the heavier trap rock broken aggregates, per ton. But broken stones are not sold by bulk, but by weight. The heavier stone concretes would give only a spread of four to five square yards per ton, Whilst, the lighter broken stones would give a spread .of from seven to ten, and even, sometimes, twelve square yards to the ton. On account of the weakness of the lighter broken stones referred to, they are not employed, at all, in concrete making. Therefore, important industries are prevented,

provided the said lighter and weaker broken stones could be brought up to the standard of co-efliciency, as they can be, by the herein defined process.

To ascertain to what extent this process would induce the said increase in hardness and toughness, standard tests were made. No increase in weight was found, yet, when the broken aggregates were sawed through and opened and subjected to magnification, it was found that no inherent moisture seemed to be present therein. The infinitesito be filled with a bluish colored substance. The aggregates that had not been subjected to the action of the slaking lime, presented readily discernable inherent moisture in the said voids. Moreover, where water in the said voids was absent or partly absent, air was present, because voids are not permitted to be unfilled, or partly unfilled, by nature. This fact, accounts for the disintegration of rock when subjected to alternates of air and water, and changes of temperatures. What the reaction of the slaking lime upon the inherent moisture, within the broken stones might be has not been learned. A continuation of tests showed a considerable increase in the toughness and hardness of the broken granite, and limestone and sandstone and shale rocks. These were sufiicient to raise many of them to the standard of coetficiency. I

Even mortar made with sand and gravel and pebbles and cobbles, will become, as to the aggregates themselves, much harder and tougher, in time b being mixed with slaking lime. Former y it was the custom to mix these materials with slaking lime not because there was any supposed object in using slaking lime, but because calcium hydroxide-had not become commercial. It was not thought that the aggregates themselves became harder and tougher, but only the binder. itself became harder and tougher.

But, it should be observed, that it is the larger and coarser aggregates that protect the binders ,when associated with finer particles and thiis actually take the support of the composition when subjected to heavy weight and considerable attrition. This is shown always when mortar composed of lime and Portland cement binders and fine substances such as sand and stone dust,'readily and quickly abraise and break up; i

It has been observed that the a gregates themselves became harder and toug er when mortars were made with slaking lime instead of being made with calcium hydroxide. In the latter case little increase in hardness and toughness occurs. It takes a long time to effect this chemical reaction in the case of mortars, even where coarser aggregates are employed. Thls process would not serve in utilities to which the herein improvement a sufiicient increased hardness and toughness can be secured, to serve in making concretes for the entire territory of the country.'

In building highways, especially, light,

portable crushers would follow, from ledge to ledge, of the lighter rock and provide broken aggregates, along the way, as the building of the highway would proceed, thus saving large costs in the construction thereof. The lighter stones, referred to, are very discursive and might be found to serve, conveniently, the entire demand of the United States. These consummations are very much to be desired, and will be of great service in many utilities, especially in highways and street constructions.

Having described my method what I claim 1s The process of toughening and hardening lighter mineral aggregates to increase their coefiicienc-y which comprises treati-n said aggregates in a clean condition wit calcium oxide whilst in the aet of-slaking, in the approximate vproportion of ten pounds of calcium oxide to five hundred pounds'of 'ag'gregates.

In testimony whereof, I have hereunto signed my name. i

JOSEPH HAY AMIES.

Images