COMPRESSIVE AND TRANSVERSE STRENGTHS OF BRICKWORK. LXXL 



square foot for mortar comprised of one part of Portland cement 

 to two parts of the coarse river sand, and of the four tests made 

 with mortar of the same materials, but in the proportion of one 

 to four the load was 149 tons per square foot. Brickwork in 

 cement is generally built with mortar comprised of one part of 

 cement to three parts of sand, but the materials of the mortar and 

 the workmanship are not generally as good as in the test piers. 

 The bricks, however, are generally as good as these used, and 

 occasionally better. Taking all these circumstances into consider- 

 ation it appears that the crushing strength of ordinary good brick- 

 work in cement mortar is about 150 tons per square foot, and the 

 safe load may be taken at least from 15 to 20 tons per square 

 foot. 



In lime mortar brickwork the average of three tests of the same 

 bricks with mortar comprised of one part of stone lime to two 

 parts of the same sand was 85 tons per square foot; and with 

 mortar comprised of one part of lime to four parts of sand was 

 46-5 tons per square foot, from which it appears that the safe 

 working loads may be taken as at least 5 and 9 tons respectively. 



6. Conclusion in regard to transverse strength of brickwork. — It 

 will be observed that the lime mortar beams were tested after 

 nearly a year, but that they all failed by horizontal shearing of 

 the mortar, the bricks remaining uninjured, so that the modulus 

 of rupture calculated in the ordinary way has not the usual mean- 

 ing. Comparing the intensities of horizontal shearing stress 

 developed in testing the beams with the average results obtained 

 by testing the shearing resistance (Figs. 10 and 11), and with the 

 results of testing briquettes of the mortar, in which small square 

 discs of the brick had been inserted when moulding the briquettes, 

 thereby developing the direct adhesive strength of the mortar to 

 the brick, it is difficult to account for the failure of the mortar in 

 the beams at the low stresses indicated. The shearing strengths 

 of the two mortars, as in Figs. 5 and 6 were 21*5 and 20*7 Bbs. 

 per square inch respectively, and the adhesive strengths 13*2 and 

 9*8 lbs. per square inch respectively. The deeper beams gave 



