Materials for Concrete.
Reading edition
Cement.—In the early stages of construction the cement for the work was obtained from the Associated Portland Cement Manufacturers, Limited, of London, which supplied the "Pyramid" brand, from the Knight, Bevan, and Sturges Works, but later the supply was obtained from a new factory at Hidalgo, near Monterrey. The total quantity of Portland cement used was 42,500 bbl. of "Pyramid" and 32,500 bbl. of "Hidalgo." The English cement was tested for the Water-Works Company in London before shipment and again at Monterrey, to conform to the British Standard Specifications; the "Hidalgo" cement was required to pass the Standard Specifications advocated by the Special Committee of the American Society of Civil Engineers. The quality in each case was of the very highest, no difficulties being experienced at any time.
Sand and Rock.—One of the chief difficulties in connection with the construction work in its initial stages was in procuring satisfactory sand for the concrete. An investigation of the quality of all the available sands in the neighborhood of Monterrey resulted in the decision to use a manufactured sand obtained from the calcareous shales in the foot-hills opposite the city, on the south side, and near the site of one of the proposed reservoirs. A quarry was opened, and the raw material was delivered by a gravity plane to a crushing plant, 230 m. from the quarry and at a level about 50 m. lower.
The plant consisted of a No. 5 Austin gyratory rock-crusher, fitted with elevators and revolving screens of various dimensions, driven by a 150-h.p. Erie steam engine; two sets of Traylor's heavy-duty crushing rolls, one having 30 by 16-in. and the other 18 by 12-in. rolls; and a Niagara sand disintegrator. This plant, except during a short period when the requirements were beyond its capacity, was able to produce all the sand and rock required for construction purposes. More than 40,000 tons of rock were quarried, the greater part of which was converted into crushed stone and sand.
Table 2 gives the chemical analysis of the chief constituents of the various sands examined.
TABLE 2.—Analysis Of Sands In The Neighborhood Of Monterrey.
No. Location. Percentage of silica (absolute), SiO2 Percentage of alumina, Al2O3 Percentage of sesquioxide, Fe2O3 Percentage of lime carbonate, CaCO3
1. Arroyo Seco, near brickyard at Monterrey 60.10 17.95 2.89 8.01
2. Arroyo Seco, near brickyard at Monterrey, No. 2 42.92 14.26 4.66 34.58
3. Near Garcia Station, Mexican National R. R., Chiquito River, No. 1 50.22 9.72 1.44 34.62
4. Near Garcia Station. Mexican National R. R., Chiquito River, No. 2 48.7 4.92 8.28 35.43
5. San Luis Potosí 85.02 5.00 7.38 2.21
6. Topo Grande, Pesquería River 40.20 5.15 4.25 46.50
7. Hornos, near Torreón 77.9 13.1 2.4 4.9
8. Salinas River, at Salinas 41.5 5.7 1.4 48.2
9. Pits near Caballeros, on Tampico Branch of Mexican Central R. R. 73.4 5.6 4.4 10.1
10. Santa Catarina River, near San Geronimo (washed sand) 12.40 2.06 1.14 81.70
11. Santa Catarina River, at Monterrey 17.4 2.50 2.00 77.00
12. Composition of rock, quarry in foot-hills opposite Monterrey, Monterrey Water-Works and Sewer Company's property 40.44 15.70 2.20 34.30
13. Manufactured sand from above quarry (run of crusher) 51.80 12.14 8.7 32.6
The chief sands used for ordinary building purposes in Monterrey are Nos. 10 and 11, which are procured from the bed of the Santa Catarina River. As these sands contain large proportions of lime carbonates, which make them very undesirable for important structures, their use was limited to relatively unimportant work. The best sands procurable were Nos. 5 and 9, but the long distance of the pits from Monterrey, and consequently the heavy freight rate, made their use prohibitive on economical grounds. The best of the available sands, although it was very fine, was No. 7, from Hornos, near Torreon, as it could be depended on for uniformity and could be obtained f. o. b. cars at Monterrey for 3.18[5] pesos per ton.
The bulk of the sand and crushed rock used was similar to Nos. 12 and 13, and reference to the cement sand tests in Table 3, will show that the manufactured sands gave very satisfactory results.
Table 3 gives the average tests made with the "Hidalgo" cement and various sands, alone and in combination, for the purpose of obtaining comparative results; the mixtures tested were composed of 3 parts of sand to 1 of cement.
TABLE 3.—Tests Of "Hidalgo" Cement With Various Sands.
Sand. At 7 days. At 28 days.
Ottawa (Standard) 305 lb. 414 lb.
Monterrey, 11⁄2 parts, Hornos, 11⁄2 parts 188 " 313 "
Monterrey 253 " 365 "
Hornos 202 " 301 "
Manufactured sand, Company's crusher 372 " 566 "
Hornos, 2 parts, Crusher sand, 1 part 231 " 352"
Hornos, 11⁄2 parts, Crusher sand, 11⁄2 parts 265 " 346 "
Hornos, 1 part, Crusher sand, 2 parts 248 " 328 "
The Hornos sand was used during a few weeks in the latter part of 1908, when the crusher was unable to produce all that was required. Its use was restricted to thick walls which were required to be water-tight, and it was always used in equal proportions with the crusher dust.