Page:California Highways and Public Works Journal Vols 8-9.djvu/11

 By T. E., Member A. S. C. E., Materials and Research Engineer.

HE comparatively recent advent of the motor vehicle occasioned the development of the new science known as “Modern” road building. Road building, as such, is one of the oldest sciences. In the days of the horse drawn vehicle and slow transportation, however, the need and demand for good roads was relatively limited. The great increase in the wealth of the country and consequent astounding increase in volume and speed of vehicular traffic has occasioned a demand for good roads. The volume of expenditures and importance of the work justifies a thorough investigation and study of improved methods of construction to the end that greater ultimate value may be received for each dollar expended.

We are living in an era of Highway Research, and California, through its State Highway Department, has contributed its share towards the successful development of improved methods of construction and maintenance.

In carrying out this program over sixty special lines of investigation have been carried on during recent years. Many important investigations are now under way.

Some of the most important of these active investigations are the following:

Coarse aggregate department, showing abrasion crushing and screening equipment.

One end of the asphalt testing department.

1. Study of Concrete Curing Methods.

The accepted method of curing concrete has been by keeping it moist with water usually for a period of ten days or more. Curing by water, however, frequently offers considerable difficulty and expense. Alternative methods of curing by means of an impervious membrane of asphalt, paper-sodium silicate, etc., have been offered and are being thoroughly investigated by this department. Pavements are cured by the different methods and cores cut and tested to determine, if possible, the relative strength secured. A number of sections have been constructed and are now under close observation. In order that the results may be comparable close control must be kept of the proportioning, mixing, and curing operations. Complete records must be kept of slump of the concrete and of the atmospheric conditions during and subsequent to construction.

2. Study of Metal Culvert Performance.

Four years ago a study was commenced of the condition of the corrugated metal culverts which have been installed on the State Highway System. The condition of some 5000 culverts was investigated at that time. This study has been continued and will be continued in the future to determine, if possible, the probable life of culverts made of