DIVISION LOCATES MATERIALS FOR PROJECTS

Division Locates Materials For Construction Projects By H. H. BROWN, Assistant Engineer of Materials

In recent articles appearing in this magazine, the Materials Division has attempted to give the readers some idea of the tests performed within this Laboratory, their significance, and their application to actual practice in highway construction work. It is the writer's intention to give the readers some idea of another phase of our work, which has heretofore not been touched upon. This is the work of selecting the sites from which sand and gravel, or rock for concrete and surfacing material, and mineral aggregate for oil surfacing, may be obtained.

Upon the completion of a location survey for a new highway project, a man is sent from the Materials Division onto this project to make a subgrade and materials survey. This man makes a study of the materials along the surveyed line, which will go into the surface of the completed roadway. If the cuts and fills are light, this is easy; but if they are heavy, it is very difficult. He tries to determine, approximately, without the aid of laboratory tests, what section or sections of he road will require subgrade sabilizer, in order to make a road which will care for traffic, and which will also make a good foundation for an oil mix pavement.

Study Aggregates Needed

Then, from the set of plans of the road, if they be finished, he notes the quantity of concrete required for the project and the location of the larger concrete structures. Then he determines the number and location of the subgrade stabilizer pits required to surface the project most economically, and the approximate yardage required from each pit. He also figures very roughly from the location of the bulk of the concrete yardage, where he wants to try to find sand and gravel, or rock.

If the project is going to be paved with oil surfacing in the near future, he determines the most economical pit locations for mineral aggregate and the approximate quantities required from each. With this information in mind, he starts out to see if nature has provided any of these materials within a reasonable distance from the points which he had determined were the most economical sources.

Need Construction Experience

In order to make a materials survey, it is essential that the man in charge of the work shall have had some experience in highway construction work, so that he may know whether or not a prospective pit can be worked economically. Also, it is very essential that he shall have had some laboratory experience so that he may know when to continue working a prospect, and when to discontinue and start looking for a more desirable appearing material. When he has found a material which he thinks will conform to our specifications, and has shown by a sufficient number of prospect holes that the desired quantity can be obtained, some laboratory experience is essential in taking the sample on which the tests are to be made.

In sampling a material, it is usually taken from the surface of the ground to the bottom of the prospect hole, but oftentimes he may encounter two or three entirely different classes or types of material, of which a part may be used for subgrade stabilizer, and part may be used for mineral aggregate, and occasionally concrete material has been found in the same pit. Or it may be that part of the material cannot be used at all, and consequently, if it be on the surface, must be excluded fromthe sample or samples, and classed as overburden to be removed. When he has satisfied himself of the quality and quantity of the material which he is seeking, he makes a sketch, showing, if it is possible without a survey, the location of the area from which he proposes to extract the material. This location may be shown with respect to the location survey, or with respect to section or subdivision lines. If the area is too far from the surveyed line, and no section corners are found in the vicinity, he requests that a survey be made.

the sample or samples, and classed as overburden to be removed. When he has satisfied himself of the quality and quantity of the material which he is seeking, he makes a sketch, showing, if it is possible without a survey, the location of the area from which he proposes to extract the material. This location may be shown with respect to the location survey, or with respect to section or subdivision lines. If the area is too far from the surveyed line, and no section corners are found in the vicinity, he requests that a survey be made.

The samples are submitted to this laboratory, and from the tests which are made here, (some of which have been explained in previous issues of this magazine) it is determined whether or not the material is suitable for the proposed use. If found to be satisfactory, the Plans Division of the Highway Department is given the sketch or survey, from which a tracing and blue print are made, showing the location and size of the area of land requested. This, then, is given to the Right-of-Way Division, which proceeds to obtain from the owner, the right to extract the desired material,