BUBAL ENGINEERING. 87 



at the ends. A firm unyielding foundation is a most essential feature, the 

 proper type to be used depending largely on the material composing the sub- 

 grade and the character of traffic for which the road is designed. Where the 

 traffic is comparatively heavy or where the material composting the subgrade Is 

 defective in any way a monolithic concrete foundation should be used. An 

 adjustable cushion of fine sand, usually 2 in. in thickness, is necessary between 

 the foundation and brick for correcting slight irregularities in the foundation. 

 The brick should be laid on edge in uniform courses running at right angles to 

 the line of the pavement, except at intersections, and joints should be broken. 

 After laying, the pavement should be carefully inspected to detect defective 

 brick. To smooth out all inequalities, it should be rolled in both directions with 

 a power roller weighing from 3 to 5 tons. In order to keep the brick in proper 

 position and protect the edges the joints should be filled, preferably with a 

 Portland cement grout. Longitudinal expansion joints of some firm and 

 durable bituminous material are deemed necessary next to the curb. The thick- 

 ness of joint should vary with the width of the pavement, i in. being suggested 

 for roadways 20 ft. or less in width, f in. for widths of 20 to 30 ft, 1 in. for 

 widths of SO to 40 ft, and li in. for greater widths. 



AYith all materials considered delivered on the work and all costs expressed 

 in cents the probable cost of constructing the brick pavement, including the 

 subgrade, the 6 in, concrete foundation, curbs, etc., is estimated by the formula: 

 Cost per square yard=1.90L+0.213 C+0.138 -8+0.157 A +0.045 B, in which C 

 equals cost of cement per barrel, 8 cost of sand per cubic yard, A cost of coarse 

 aggregate per cubic yard, B cost of paving brick per thousand, and L cost of 

 labor per hour. Ten per cent should be added to allow for wear on tools and 

 machinery and for unforeseen contingencies. Each inch subtracted or added to 

 the thickness of foundation will make a corresponding difference of from 8 to 

 12 cts. in the cost per square yard. 



Typical specifications for the construction of brick roads are presented, and 

 a method for inspecting and testing paving brick is appended. 



In conclusion the importance of proper engineering supervision is emphasized, 

 and it is stated that since brick pavements are probably more expensive to con- 

 struct than any other type of country road it is important that their construc- 

 tion should be carefully planned and well executed. 



The production of sand and gravel in 1912, R. W. Stone {V. 8. GeoL 

 8urvey, Advance Chapter from Mineral Resources of the United States, Calendar 

 Year 1912, pp. 18). — Data are given showing the production of sand and gravel 

 for various purposes in the various States during 1912. The total production is 

 reported as 68,318,877 short tons, valued at $23,081,555, a net increase in quan- 

 tity of 1,471.018 short tons and in value of $1,922,972 over the production of 1911. 



Tests of the strength of cement (Concrete- Cement Age, 2 {1913), No. 5, 

 pp. 257, 25S). — In an abstract of a paper read by H. C. Johnson before the 

 Concrete Institute at London are given the tabulated results of tests of 16 dif- 

 ferent brands of cement and mixtures thereof, conducted to emphasize the 

 need of test'ng all materials, and comprising tests for tension, compression, 

 binding, and effects of varying percentages of water. The author's conclusions 

 are that a good strength in paste is no proper indication of a good strength in 

 concrete; that the best tests of a cement's value for reenforced concrete or 

 similar work are mortar compressions cured in water and in air; that any 

 cement having a higher value in air than in water ought to be condemned: 

 that not less than 22 per cent of water should be allowed in gaging paste and 

 not less than 3 per cent plus i the percentage as used in the paste in giiging 

 mortar; that the standard of values for cement to be used in reenforced con- 

 25842°— No. 1—14 7 



