TESTS OF PAVING BRICKS.
The tests herein reported were made on paving brick from twenty four paving brick factories in Illinois, Indiana, Ohio, Missouri and Kansas. The samples of each make and grade were selected by repre sentatives of the State Geological Survey at the yards of the factory. An effort was made to secure representative samples. 'The collectors were familiar with paving brick and their properties and exercised care in the selection, and it is believed that the brick obtained are fairly representative of the product of the various factories at the time the selection was made. In many cases samples of two to five grades of brick, varying from the softer grade to very hard burned, were ob tained. The letter at the beginning of the mark or designation of the various samples is the initial of the collector who selected the brick, and the letter at the end refers to the grade of burning of the brick, a being the softest burned lot. In some cases the a grade was consid erably under-burned and in others it represented the best grade.
The brick were held before making the tests, and the samples which were collected early in the spring were left for some time in their orig inal packages in the open air and were subjected to dampness from the • spring rains. However, before the tests were made, the brick were stacked openly under a tent and left for some time through hot dry weather so that each brick had ample opportunity to become dried throughout. The bricks which arrived last came direct from the kilns to the tent during dry weather without having become damp and were tested first. In this way the earlier brick were given from three to five weeks in which to dry. As the tent was open at the ends so that good circulation of air prevailed, the bricks had the opportunity 'to be thor oughly dried. While no tests were made on the amount of moisture con tained, it is thought that all the bricks were as dry as they could be under the average humidity conditions of summer weather and without being dried in an oven. It is certain that the amount of moisture in the brick was as low as is required by the provisions of the N. B. M. A. specifications for the rattler test.
The rattler test of the brick was made in the Road Laboratory of the Civil Engineering Department of the University of Illinois. The standard N. B. 11I. A. rattler of the Road Laboratory was used. The number of bricks and blocks agreed closely with the standard specifica tions, although the relative cubical content of the rattler and the charge was not calculated for each lot, but the charge was varied with the judg ment of the operator. At least 9 and not more than 10 blocks were con
sidered a charge, and at least 10 and not more than 12 of the brick size. The results of the rattler test are given in Table I. The brick were weighed at the end of 450, 900, 1,350 and 1,800 revolutions and the corresponding losses are given in the tables. Table II shows the pro portions of the final or total loss at the end of each of these periods given in per cent of the final loss, and Table III shows the percentage of the total loss for each of the four stages.
The rattler tests were made under the direction of Mr. R. C. Purdy. Acknowledgment is made to Professor I. 0. Baker of the Civil Engineer ing Department of the • University of Illinois for the facilities afforded in making the rattler tests.
After the brick were rattled, five of each set, two from one chamber and three from the other chamber, were taken to the Laboratory of Applied Mechanics and the amount of absorption determined. The brick were not dried further, but the conditions were such that the amount of moisture present would have little effect upon the determina tions reported.
From the remainder of the brick not rattled, as many as could be spared up to ten of each kind were taken to the Laboratory of Applied Mechanics of the University of Illinois, and the transverse or cross breaking test made upon them. The method of making this test is fully explained in the paper by Professor Talbot on the Quality of a High Grade Paving Brick and the Tests used in Determining Them. Crush ing tests were made on half-brick placed flat-wise as described in the paper just referred to. The results for the absorption, transverse, and crushing tests, as furnished by Professor Talbot, are given in the tables. The average values for absorption, cross-breaking, and crushing are given in Table IV, and the detailed results follow in Table V. Transverse and crushing tests were not made on the Purington, Edwardsville and Streator Paving Brick Co. brick.
The absorption and transverse tests were made by Mr. C. H. Pierce, Instructor in Theoretical and Applied Mechanics, and the crushing tests by Mr. H. L. Whittemore, Associate in Applied Mechanics, and this work was under the direct supervision of Professor A. N. Talbot.
The general selection of the brick at the yards and the arrangements therefor were made by the State Geological Survey. Mr. R. C. Purdy, of the Department of Ceramics of the University of Illinois, had general supervision of the arrangements for testing.