120 



REIBLING. 



The absolute dependence of the strength of mortar upon the quality 

 of the sand is strikingly illustrated in the history of standard sands used 

 for cement testing, and the experiences of this laboratory serve to 

 illustrate this fact. 



The committee on Philippine cement specifications adopted as a 

 standard sand the natural Tarlac Eiver sand, screened through 20-mesh 

 to the inch sieve and held on a 30-mesh sieve. With one exception the 

 committee saw no reason why the use of this material should not give 

 as satisfactory and reliable results as standard Ottawa or quartz sand. 

 Tarlac sand was used during many months and was thoroughly tried by 

 every method of mixing and various percentages of water; but erratic, 

 variable and comparatively low results were always obtained. Even 

 when rescreened, the different shipments gave different results; yet to 

 all appearances it is a sharp, clean sand, principally containing quartz 

 with but a very small percentage of hornblende and weathered soft 

 material. A standard cement tested according to the three specifications 

 for cement testing then in \ise gave the following results." 



Tests of a standard cement with Tarlac and Ottaiva sand and crushed quartz. 



Specifications. 



Kind of sand. 



Void 



in 



sand. 



£■6 



bDO 



3 > 



03 = 



Water. 



Tensile strength. 



Relative 



compressive 



strength. 



7 

 days. 



28 

 days. 



3 

 months. 



28 

 days. 



3 

 months. 



Am. Soc 



U. S. Armv 

 Philippine Gov- 

 ernment. 

 Am. Soc _ _ 



Ottawa „ 



Crushed quartz. 

 Tarlac 



Percent. 

 36.2 

 47.7 

 44.7 



4,183 

 3,445 

 3,601 



Per cent. 

 9.5 

 12.5 

 »10.7 



21 



305 

 287 

 220 



606 



364 

 327 

 264 



635 



395 

 330 

 302 



646 



1,633 

 1, 360 

 1,240 



3,460 



1,788 

 1, 620 

 1,370 



4,009 



Neat cement 









a Other percentages of water and methods of mixing gave lower results. 



Tarlac sand was finally condemned as a standard for cement testing, 

 and Ottawa sand adopted with very satisfactory results. 



When nearly pure, carefully screened and washed sands differ so 

 much in mortar efficiency, what can be expected of commercial materials 

 in which the impurities and granularmetric composition introduce still 

 other factors influencing their suitability for concrete construction? 



In Manila, sand from the Pasig Eiver, which flows through the city, 

 is almost invariably used for concrete construction. Although this 

 material is fairly clean and free from impurities, it is the product of 



