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Masonry cements
444
U, S. BC:RF,At~ OF STANDARDS NOTES.
[J. l:. ].
outlets for this material because the increasing use of synthetic fibers for textiles, and other adverse economic developments are leading to the accumulation of an increasing surplus of this i m p o r t a n t agricultural crop. Next to the textile industry, the paper industry is the largest consumer of cellulose. In view of the m a n y inquiries received by the bureau concerning the paper industry as a potential user of raw staple cotton, the question was discussed with various users of cotton fiber for paper-making. T h e consensus of their opinions is as follows. Raw staple cotton as produced at the present time cannot compete with the highest grade of textile cotton wastes used for paper-making as the price differential still favors the latter considerably, and any lowering of the price of staple c o t t o n is reflected in the price of the textile wastes. There is considered to be no great difference in the way the two different classes of materials react in the paper-making processes or in the quality of paper prepared from them. C o t t o n linters, the shorter cotton strands left after removal of the staple cotton, and which is lower in price, is used to some extent in the paper industry but it appears to lack, for most purposes, some of the desirable paper-making properties possessed by the textile wastes. F r o m the above opinions, it appears t h a t the use of raw staple cotton for paper making hinges largely on the economic factors, and probably the only way the present unfavorable cost ratio could be overcome would be by the production of the staple cotton on a generally mechanized basis. According to a recent news item, study in this direction is being made at the University of N o r t h Carolina. It is of interest that, according to historical records, raw cotton was the first source of cotton fibers for paper making, being largely used, apparently, from the 7th century until the I I t h century when it began to be displaced by waste textile materials. M A S O N R Y CEMENTS.
The tests of the masonry cements outlined in Technical News Bulletin No. I74 (October, I93I) have brought o u t the great variation in their properties. M e a s u r e m e n t s were made
April, t93e.l
U. S. Bt~EA~: ol." STaXt)alCDS NOTES.
445
of the spread upon a plate of the neat pastes d r o p p e d from an a p p a r a t u s similar in principle to the S a y b o l t viscosimeter. T h e ratio of the weight of c e m e n t to w a t e r to produce pastes having the same spread varies from I : I to 2.8 : I. T h e a p p a r e n t specific g r a v i t y of the pastes varied from 0.83 to 1.93. T h e a p p a r e n t specific gravities of the m o r t a r s made from the c e m e n t s have been found to range from 1.59 to 2.24. T h e variations in these specific gravities a p p e a r to be some function of the a m o u n t of waterproofing material contained in the c e m e n t and of the weight of the c e m e n t per unit volume. W h e n equal a m o u n t s of sand are added to equal a m o u n t s of pastes having the same neat spread the resulting m o r t a r does not have e q u i v a l e n t flows on the flow table, these flows v a r y i n g from 56 to I6O. T h e range in sewm d a y compressive strength of a I : 3 b y v o l u m e mix, using a mixture of s t a n d a r d and pit run O t t a w a sand as aggregate varies from 15 to 4,O8,~ lbs./in. ~ T h e yields of the m o r t a r s v a r y considerably. T h e w a t e r r e q u i r e m e n t to produce a m o r t a r flow of from w o to 115 on the s t a n d a r d ten inch flow table varied from .73 to 1.3.5 b y volume. T h e c e m e n t s requiring the greatest a m o u n t of w a t e r would not, as might be expected, give the greatest yield. T h e plastic m e a s u r e m e n t s on the modified M c M i c h a e l viscosimeter varied from 5 I o to 2,36o for m o r t a r mixes t h a t all had a flow table m e a s u r e m e n t of Ioo. Certain c e m e n t m o r t a r s show a decrease, some an increase, in flow table m e a s u r e m e n t due to the mixing given in the plasticimeter, all m o r t a r s being given the same a m o u n t of agitation. Within the plastic limit the c e m e n t s have a range of from 2oo to 1,2OO grams shear resistance. T h e a m o u n t of w a t e r t h a t could be added to a c e m e n t and have the m o r t a r remain within the plastic range varied from 5 to 6 per cent., with b u t few exceptions. This is true for c e m e n t s requiring small a m o u n t s as well as large a m o u n t s of water. T h u s at one extreme a c e m e n t was plastic with from 11 to t 7 per cent. w a t e r and at the o t h e r extreme a c e m e n t was plastic with from 2 4 to 2 9 per cent. of water.
U, S. BC:RF,At~ OF STANDARDS NOTES.
[J. l:. ].
outlets for this material because the increasing use of synthetic fibers for textiles, and other adverse economic developments are leading to the accumulation of an increasing surplus of this i m p o r t a n t agricultural crop. Next to the textile industry, the paper industry is the largest consumer of cellulose. In view of the m a n y inquiries received by the bureau concerning the paper industry as a potential user of raw staple cotton, the question was discussed with various users of cotton fiber for paper-making. T h e consensus of their opinions is as follows. Raw staple cotton as produced at the present time cannot compete with the highest grade of textile cotton wastes used for paper-making as the price differential still favors the latter considerably, and any lowering of the price of staple c o t t o n is reflected in the price of the textile wastes. There is considered to be no great difference in the way the two different classes of materials react in the paper-making processes or in the quality of paper prepared from them. C o t t o n linters, the shorter cotton strands left after removal of the staple cotton, and which is lower in price, is used to some extent in the paper industry but it appears to lack, for most purposes, some of the desirable paper-making properties possessed by the textile wastes. F r o m the above opinions, it appears t h a t the use of raw staple cotton for paper making hinges largely on the economic factors, and probably the only way the present unfavorable cost ratio could be overcome would be by the production of the staple cotton on a generally mechanized basis. According to a recent news item, study in this direction is being made at the University of N o r t h Carolina. It is of interest that, according to historical records, raw cotton was the first source of cotton fibers for paper making, being largely used, apparently, from the 7th century until the I I t h century when it began to be displaced by waste textile materials. M A S O N R Y CEMENTS.
The tests of the masonry cements outlined in Technical News Bulletin No. I74 (October, I93I) have brought o u t the great variation in their properties. M e a s u r e m e n t s were made
April, t93e.l
U. S. Bt~EA~: ol." STaXt)alCDS NOTES.
445
of the spread upon a plate of the neat pastes d r o p p e d from an a p p a r a t u s similar in principle to the S a y b o l t viscosimeter. T h e ratio of the weight of c e m e n t to w a t e r to produce pastes having the same spread varies from I : I to 2.8 : I. T h e a p p a r e n t specific g r a v i t y of the pastes varied from 0.83 to 1.93. T h e a p p a r e n t specific gravities of the m o r t a r s made from the c e m e n t s have been found to range from 1.59 to 2.24. T h e variations in these specific gravities a p p e a r to be some function of the a m o u n t of waterproofing material contained in the c e m e n t and of the weight of the c e m e n t per unit volume. W h e n equal a m o u n t s of sand are added to equal a m o u n t s of pastes having the same neat spread the resulting m o r t a r does not have e q u i v a l e n t flows on the flow table, these flows v a r y i n g from 56 to I6O. T h e range in sewm d a y compressive strength of a I : 3 b y v o l u m e mix, using a mixture of s t a n d a r d and pit run O t t a w a sand as aggregate varies from 15 to 4,O8,~ lbs./in. ~ T h e yields of the m o r t a r s v a r y considerably. T h e w a t e r r e q u i r e m e n t to produce a m o r t a r flow of from w o to 115 on the s t a n d a r d ten inch flow table varied from .73 to 1.3.5 b y volume. T h e c e m e n t s requiring the greatest a m o u n t of w a t e r would not, as might be expected, give the greatest yield. T h e plastic m e a s u r e m e n t s on the modified M c M i c h a e l viscosimeter varied from 5 I o to 2,36o for m o r t a r mixes t h a t all had a flow table m e a s u r e m e n t of Ioo. Certain c e m e n t m o r t a r s show a decrease, some an increase, in flow table m e a s u r e m e n t due to the mixing given in the plasticimeter, all m o r t a r s being given the same a m o u n t of agitation. Within the plastic limit the c e m e n t s have a range of from 2oo to 1,2OO grams shear resistance. T h e a m o u n t of w a t e r t h a t could be added to a c e m e n t and have the m o r t a r remain within the plastic range varied from 5 to 6 per cent., with b u t few exceptions. This is true for c e m e n t s requiring small a m o u n t s as well as large a m o u n t s of water. T h u s at one extreme a c e m e n t was plastic with from 11 to t 7 per cent. w a t e r and at the o t h e r extreme a c e m e n t was plastic with from 2 4 to 2 9 per cent. of water.