XXXII. W. II. WARREN. 



A series of tensile tests extending over 12 months, of the same 

 cement mixed in the proportion of one part of cement to three of 

 sand, showed that Nepean River sand was about the same strength 

 as the Sydney white sand. 



In this series of compressive tests recorded in tables and plotted 

 in Figs. 1, 2, and 3, the mixing of the concrete in the proportions 

 stated, the preparation of the cubes, and all the conditions of 

 testing which could influence the results have been carefully 

 attended to, so that they may be considered as laboratory tests. 

 The cement used, however, is inferior to some of the best known 

 brands to-day, which accounts for the results being rather low 

 throughout. 



Series II. were not plotted as they were only tested at two ages, 

 but Series III., made from practically the same concrete, have 

 been plotted in Figs. 4 to 8 inclusive. The concrete in both 

 Series II. and III. was not made as carefully as in a laboratory, 

 which has been already explained. It will be observed that the 

 cement used was not the same throughout. 



Fig. 4 shows the results of testing bluestone concrete 2 inch 

 gauge and less, in which the proportions 1-2-5 and 1-2-6 give 

 about the same strength in compression, whereas 1-2-4 is con- 

 siderably lower, here the stronger concrete appears to be due to 

 the greater proportion of stone to mortar. In the remaining 

 curves 1-3-4, 1-3-5, and 1-3-6 the proportions of mortar to stone 

 appears to make very little difference. In tests Nos. 1 to 6, 

 Series II., the bluestone is 1^ gauge and the cement is different, 

 the size of the cubes is 12 inches instead of 6, but in other respects 

 the concrete is similar to that in Series III. recorded in Fig. 4, 

 here also 1-2-5 is slightly better than 1-2-4, and 1-2-4 than 1-2-6, 

 again 1-3-5 is better than 1-3-4 or 1-3-6. 



Fig. 5, Series III., shows the compressive strength of sandstone 

 concrete 2^ gauge, and Nos. 7 to 12, Series II., show also the 

 strength of similar concrete in which the cement and the size of 

 the cubes is different, but in other respects the conditions appear 

 to be similar, excepting that the 12 inches by 12 inches cubes 



