1916] KUEAL ENGINEERING. 291 



"The usual rectangular-beam design formulas may be applied to the design 

 of slabs by merely substituting for 6 its value as determined by these investi- 

 gations, &=0.7L. The corresponding formulas then become — 



" It is interesting to note that in substituting for M^ and M^ in formulas 1 and 2 



PL 

 their value — - the L'b cancel, showing that the safe load-carrying capacity of the 



slab is independent of the span ; thus — 



1 becomes ^=i^/,ij ^Ld'' or pj^fjcjd^ 



4 lo o 



2 becomes ^=pfsj ^Ld' or P= p ^/ja". 



" The above investigations were made on slabs the width of which was 

 twice the span length, so that the stress at the extreme edges was very small. 

 The conclusions must therefore be applied to such cases only. When the 

 ratio of width of slab to span length is less than 2, these conclusions may or 

 may not apply, and additional investigations are now being made to determine 

 the proper value of effective width to use under such conditions." 



The action of Portland cement mortar in different salt solutions, V. Root 

 (Mitt. K. Matcrialpriifungsamt BerUri^Lichterfelde West, 33 {1915), No. 3-4, 

 pp. 229-240). — Tests to determine the influence of solutions of sodium, calcium, 

 and magnesium chlorids and sulphates in concentrations of 0.1, 1, and 10 per 

 cent on Portland cement mixtures with sand, 1 : 3 and 1 : 6, when immersed in 

 the solutions for periods as long as six mouths, showed that none of the solu- 

 tions except that of calcium sulphate had an injurious effect on the 1 : 3 mix- 

 ture. Calcium sulphate, on the other hand, showed evidences of a destructive 

 influence. With the 1 : 6 mixture only the sulphate solutions had a destructive 

 effect, but this was, however, very marked. The action was very arbitrary and 

 irregular. The chlorids of calcium and magnesium produced an increase in 

 the leaching out of lime from the cement, especially when the salt solutions 

 were concentrated and the cement mixture lean. 



Further studies are in progress on the effect of leaching solutions. 



Some tests on hydrated lime addition to concrete for road work, E, Ashton 

 {Engin. and Contract., 45 (1916), No. 9, pp. 206, 207). — Tests are briefly reported 

 in which 5, 10, and 15 per cent by weight of hydrated lime was added to 

 concrete. 



The results showed that " no greater freedom of movement of the mass was 

 noticed. As the lime was increased more difficulty was experienced in getting 

 the material into the test forms. . . . With same angle and same percentage 

 of water concrete did not flow more readily by the addition of hydrate of lime, 



