No. CCLXXXIX.
EXPERIMENTS MADE AT NARORA, LOWER GANGES CANAL, ON THE STRENGTH OF DIFFERENT THICKNESS OF MORTAR JOINTS.
[Vide Plate.]
BY LIEUT. E. W. CRESWELL, R.E.
DIFFERENT thickness of mortar joints to be tested were is", š", 1", 1", &". A level site close to the weir sluices was selected (as the blocks of brickwork were afterwards to be put into the talus of that work), and five rows of brickwork bars built, 15' x 214 x 21', each row containing ten bars, and were numbered A to E.
Mortar joints in row A were all to", in row B 3", and so on, in order mentioned above, row E being ".
The foundations for these bars were made one foot deep, see plan. The centre 10 foot portion of the foundations being of bricks laid in mud, the end 2 feet 6 inch portions of bricks laid in mortar, a thin layer of mud was spread over the whole surface of top of foundation, so that there might be no adhesion whatever between the superstructure and the foundations.
The bricks were sand-moulded kiln burnt, were carefully gauged and sorted, so that each bar might be built with the required joint and still the total dimensions of bar as directed be attained.
The mortar used was two parts steam ground coal burnt kankar lime to one part sand, mixed with water in a country bullockchakki.'
The joints in every direction were carefully kept of the required thick- ness, and English bond employed. The bars were all completed in August 1877.
In May and June 1878 the brickwork of the central 10 feet portion of the foundation was removed, and the bars were now simply supported both ends by the 2 feet 6 inch pillars.
In order to break the bars, two stone slabs 2' 6" X 6" 6" were placed one foot apart on top of the brickwork (as shown in Figs. 1 and 3) and 21
