XI, A, 5 



Witt: Philippine Paving-brick Materials 



215 



No. 9. In most respects this is one of the best clays tested. 

 Its working and drying qualities, tensile strength, behavior in 

 the kiln, and color are excellent. It should produce a building 

 brick, satisfactory in color and structure. It does not begin 

 to vitrify until about cone 9. This would be a considerable 

 advantage in making building brick, because the temperature 

 would not have to be so carefully controlled as with a clay having 

 a low fusing point. Unfortunately, however, the material could 

 not be economically used for paving brick on account of the 

 high temperature that would be necessary in the kiln. 



Temperature-porosity data. — Of the samples tested so far, only 

 Nos. 1, 2, 5, and 9 show burning qualities suitable for plotting 

 temperature-porosity curves. The curves for these samples are 

 shown on fig. 1. 



Only one of them (No. 1) is apparently suitable for paving 

 brick. Nos. 2 and 5 have short vitrification ranges, and No. 

 9 has a vitrification temperature too high for practical purposes. 

 Clay 1 corresponds, in general, in chemical analysis and most 

 of the physical tests to some materials now being used for 

 paving-brick manufacture in the United States. 



Table V. — Chemical analyses and some physical tests of a number of clays 

 used in the m,anufacture of paving brick in the central part of the 

 United States.^ 



Sample 

 No. 



Mois- 

 ture. 



Loss on 

 igni- 

 tion. 



Silica 

 (Si02). 



Alu- 

 mina 



(Al2- 



Os). 



Ferric 

 oxide 

 (Fe2- 

 Os). 



Mag- 

 nesia 

 (MgO). 



Cal- 

 cium 

 oxide 

 (CaO). 



Potas- 

 sium 

 and 



sodium 



oxides 

 (K2O, 



Na20). 



Tensile 

 str'gth 

 of raw 

 clay per 

 square 

 centi- 

 meter. 



Linear 

 shrink- 

 age. 



Water 

 of plas- 

 ticity. 





Per ct. 



Per ct. 



Per ct. 



Per ct. 



Per ct. 



Per ct. 



Per ct. 



Per ct. 



Kilos. 



Per ct. 



Per ct. 



1 



0.50 



8.18 



60.89 



16.40 



8.20 



1.61 



0.55 



4.15 



5.038 



2.10 



14.40 



2 



0.27 



3.54 



68.50 



16.98 



5.77 



1.71 



0.99 



2.97 



4.023 



0.90 



13.40 



3 



0.81 



7.02 



58.35 



18.09 



6.14 



2.03 



1.20 



4.58 



12.503 



5.82 



19.60 



4 



1.02 



10.45 



55.18 



19.22 



8.19 



1.67 



0.56 



2.85 



9.094 



3.25 



15.23 



5 



0.60 



10.09 



54.37 



23.61 



6.14 



1.61 



1.58 



2.78 



22. 586 



3.60 



13.35 



6 



0.43 



7.97 



57.09 



19.07 



7.92 



1.91 



0.80 



4.69 



7.529 



3.30 



16.30 



7 



1.29 



8.08 



58.42 



25.05 



3.04 



1.52 



0.46 



2.30 



10. 025 



4.50 



13.40 



8 



0.68 



4.86 



63.41 



18.61 



5.82 



1.16 



0.41 



3.60 



8.527 



3.30 



13.00 



9 



1.06 



5.95 



58.67 



20.40 



7.40 



1.37 



0.63 



3.27 



4.996 



3.00 



13.30 



10 



0.02 



8.00 



55.61 



21.81 



7.66 



1.63 



0.56 



3.56 



5.032 



3.20 



13.20 



11 



0.83 



9.40 



55.02 



20.35 



6.26 



1.70 



0.87 



3.64 



9.071 



2.70 



17.20 



12 



0.79 



4.39 



66.29 



20.32 



7.90 



2.01 



0.48 



4.46 



9.882 



4.20 



16.60 



13 



3.05 



6.70 



60.31 



19.11 



6.14 



1.73 



2.73 



1.44 



9.208 



5.00 



17.70 



14 



0.86 



5.14 



63.42 



16.24 



6.62 



1.87 



1.64 



4.83 



8.634 



1.94 



11.80 



15 



L49 



7.01 



56.25 



18.79 



8.02 



1.33 



2.39 



4.60 



14. 174 



5.50 



16.50 



16 



1.57 



5.08 



68.15 



12.89 



7.62 



0.59 



1.02 



2.93 



13.062 



4.20 



14.40 



17 



0.98 



6.75 



62.70 



16.95 



8.98 



1.47 



1.17 



3.03 



9.865 



4.60 



16.50 



18 



2.56 



6.66 



68.62 



17.74 



8.48 



0.98 



1.26 



3.92 



8.626 



3.70 



16.40 



" BuU. m. state Geol. Surv. (1908), No. 9, 285, 287. 



