vin, A, 2 



Reibling: Portland Cement 



115 



ORDINARY BRIQUETTES OF 1:3, OTTAWA-SAND MORTARS SUBMERGED IN 

 FRESH WATER AFTER 24 HOURS DST MOIST AIR. 



Cement. 



Tensile strength in pounds per 

 square inch. 



Relative compressive strength in 

 pounds per square inch. 



7 days. 



28 days. 



3 months. 



1 year. 



7 days. 



28 days. 



3 months. 



1 year. 



3,200 

 4,239 



As received 



299 

 315 



357 

 386 



385 

 424 



353 



424 



2,520 

 2,430 



3,159 

 3,078 



3,510 

 3,861 











When reground, the cement gave 26,3 per cent higher concrete 

 efficiency. It is estimated that the additional grinding would 

 have cost the manufacturer less than 10 centavos per barrel. 

 Computing on the basis of 5.24 pesos per barrel (the price named 

 in the latest contract of the Bureau of Supply), this additional 

 efficiency is obtained at an expense of less than 1.9 per cent of 

 the cost of the cement. When we consider that the total cost 

 of the concrete is about six times that of the cement, the extra 

 expense for finer grinding becomes almost insignificant. 



However, there are many who attach little importance to such 

 facts. Portland cement is used in a rather crude manner and 

 much of it where great strength is not of practical importance. 

 This, and the somewhat general belief that a cement which meets 

 the requirements of our specifications is good enough for all 

 ordinary purposes, has induced many to belittle the importance 

 of obtaining a more uniform and efficient product. Also, many 

 claim that it would be useless to use better cement with poor 

 aggregates such as are usually the only ones available for local 

 construction work. This attitude is founded on a basis which is 

 neither economical nor progressive. 



If weak concrete meets the requirements, then cheaper material 

 such as "adobe" stone, hydraulic lime, or natural cement should 

 be used. On the other hand, for important permanent struc- 

 tures, the greatest economy and efficiency result from the intel- 

 ligent use of the best cement obtainable at a reasonable cost. 

 This is especially true in the Philippines where most of our 

 sewers, retaining walls, bridges, buildings, etc., are frequently 

 subjected to severe destructive influences such as typhoons, 

 earthquakes, and floods. Structures must be built to withstand 

 extraordinary rather than ordinary demands upon their strength 



