D.—7

2

The twenty-eight-day tests of these sand and cement briquettes ■will, no doubt, show an improvement upon the seven-day tests, and I will forward you the results as soon as they are completed ; but as these tests are not included in those specified, I thought it better not to delay sending in this report for them: — Table A. Description of Test. m _ M 4. Residue on sieve of 40 meshes, per lineal inch ... 6°/o s°/> 4°/° 4°/° 50 „ ... 10°/. 9f 10/» 9/. 80 „ ... 27°/= 29°/ 28°/. 29/= Specific gravity ... ... ... ... 338 3-14 3-12 3-07 Tensile strength, in pounds, per square inch— At 3 days (mean of three tests) ... ... 276 310 273 266 At 7 „ „ 316 443 401 327 At 14 „ „ ... ... 377 440 420 402 At 28 „ „ ... ... 457 463 488 480 Weight, in pounds, per Imperial bushel ... ... 108 109 108 105 Summary. The P.W. tests are: (1) The cement to weigh 1101b. per bushel; (2) to stand a tensile strain of 3001b. per square inch at seven days ; (3) to leave not more than 10 per cent, residue on a sieve of 50 meshes per inch; (4) pats of neat cement to show no signs of cracking or blowing when kept in either air or water. All the samples comply with Nos. 2, 3, and 4 of the above conditions, and, although slightly under the specified weight per bushel, the difference is so small as to come fairly within the limits of error usually allowed, as a difference of 51b. per bushel may be made by a slight difference in the method of filling the measure. I also tested each sample for maguesia, of which I found less than 10 per cent, present. In my opinion the cement is of fairly good quality, and though inferior in strength to some of the imported cements, is quite up to the standard specified in the conditions laid down in the copy of the Public Works, New Zealand, Stores Supply and Delivery Contract, which you sent to me with your instruction to examine and report upon this cement. I have, &c, E. L. Mestayek, M.lnst.C.E. H. J. H. Blow, Esq., Under-Secretary for Public Works.

Table B. Total Besults of Tests for Tensile Strength. Sample Ml : — Breaking-weight. Mean. Tensile strength at 3 days, in pounds, per square inch... 290 280 260 275 7 „ „ ... 320 305 325 316 14 „ „ ... 365 410 355 377 28 „ „ ... 490 430 450 457 Sample M 2 :— Tensile strength at 3 days, in pounds, per square inch... 330 320 280 310 7 „ „ ... 435 425 470 443 14 „ „ ... 450 470 400 440 28 „ „ ... 444 460 490 463 Sample M 3:—: — Tensile strength at 3 days, in pounds, per square inch... 280 260 280 273 7 „ „ ... 405 410 390 401 14 „ „ ... 400 390 470 420 28 „ „ ... 480 475 510 488 Sample M 4 : — Tensile strength at 3 days, in pounds, per square inch... 280 250 270 266 7 „ „ ... 300 330 350 327 14 „ „ ... 395 410 400 402 28 „ „ ... 490 470 480 480

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