IX, A, 2 Reibling: Natural Cement versus Brick 167 



inch after the clay had become sufficiently dry. Their physical 

 properties are recorded in Table III, which for the purpose of 

 ready comparison includes the corresponding average values of 

 the Iwahig product. 



The appearance and properties of brick 3 are those of the 

 best product that can be manufactured at Iwahig, unless a suit- 

 able clay for admixture can be obtained. It is unquestionable 

 that a brick with good color, smooth surfaces, clean sharp edges, 

 and sufficient strength and density to meet the requirements of 

 ordinary construction work could be obtained. For moderate 

 demands, a brick having the above qualifications would also be 

 good enough for face brick. To produce such bricks on a com- 

 mercial scale, the clay should be ground fine enough to eliminate 

 all danger from free lime, pugged and molded in a stifi'-mud 

 brick machine, and then re-pressed after the bricks had dried 

 until most of the shrinkage had taken place. The same process 

 of manufacture could be utilized to produce common floor and 

 roofing tiles and terra cotta merely by changing the dies. The 

 unit cost of manufacture should be no greater than it is at 

 present. 



However, for reasons which are given in the following 

 pages, the Iwahig clay can be utilized to better advantage with 

 the available fine-grained coral sand for the manufacture of 

 natural (or Roman) cement. And since the natural cement 

 can be made to serve equally well as, or better than, the brick for 

 most purposes, the manufacture of natural cement is probably 

 better economy than even an improved manufacture of brick. • 



While, from the standpoint of efficiency as a structural mate- 

 rial, Portland cement ranks higher in order of merit than natural, 

 or Roman cement, of which Rosendale is a type, yet for many 

 purposes natural cement is perfectly suitable in point of strength, 

 and for such purposes its considerably lower cost makes it more 

 desirable than Portland cement, 



NATURAL (OR ROMAN) CEMENT MANUFACTURED AT IWAHIG 



A previous contribution from this laboratory ^ suggests that 

 the present commercial and economic conditions of these Islands 

 favor the manufacture of what may be called an artificial Roman 

 cement. The necessity of regulating the composition is shown 

 by Eckel.' 



'Reibling, W. C, and Reyes, F. D., This Journal, Sec. A (1912), 7, 147. 

 ' Eckel, Edwin C, Cements, Limes, and Plasters. New York City (1905), 

 198-199. 



