PORTLAND CEMENT TESTING. ' 177 



All the requirements of standard American cement specifications are 

 based upOn cement action characteristic of a colder climate. It would 

 be possible, of course, to manipulate the cem.ent testing itself in tropical 

 countries at the temperature limits specified in American standards; 

 but this could only be done at great inconvenience and at a large exjDense 

 and furthermore it would not be practical, as the results of tests so 

 conducted would not be true criteria of the behavior and value of the 

 cement when used in construction work. The allowances and require- 

 ments due to the efEect of the relative difference in temperature between 

 temperate and tropical climates should therefore be taken into account 

 in local cement specifications. 



During the past year this laboratory has received a number of letters 

 upon this subject from manufacturers, engineers, contractors, testers 

 and other cement workers. These either request information or make 

 statements regarding the influence of local climatic conditions upon 

 various phases of cement action and manipulation. A diversity of opin- 

 ion has been expressed in regard to the efEect of these influences by 

 men familiar with cement work, and probably this is due to the fact 

 that Portland cement is a very variable product and therefore local 

 conditions which would improve the quality of one brand would injure 

 another, and vice versa, and during the past year our endeavor has been 

 to secure a sufficient number of results with various brands of cement to 

 throw some light on the effect produced by this climate on the tests. 



Careful cement testing with due consideration of all conditions is of 

 the greatest importance in a country such as this, where much of the 

 material comes a long distance by sea, and where the rejection of a 

 shipment means a proportionately greater loss to the dealer, owing to 

 the cost of transportation, and also to the engineer, as construction work 

 may be delayed. On the other hand, construction work is very expensive 

 in this Archipelago and therefore a rigid interpretation of specifications 

 is necessary to provide against all possibility of the use of dangerous 

 cement. 



Contrary to the general belief, the difl'erence between local climatic 

 conditions and those of the temperate climates exerts very little influence 

 upon the usual standard Portland cement tests themselves. Provided 

 the cement is of good quality the warmer temperature prevailing here 

 usually tends to give higher results. Of course, the fineness is not 

 affected by it, and the specific-gravity determination is made independ- 

 ently of the surrounding temperature. The "accelerated soundness" 

 tests especially, are benefited, as the cement does not suffer as great a 

 change in temperature; and hence expansion and warping is not so 

 marked. Climatic conditions improve the characteristics of early tensile 

 strength of most cements, as the variation in temperature from day to 

 day and from hour to hour is only slight, the temperature of the water 

 bath is higher than in cold climates, and the temperature during gauging 



