STATE GEOLOGIST. 205 
MIXING AND SPREADING CONCRETE. 
J2. Mixing Sand and Cement.—The sand and cement shall be thoroughly 
mixed dry in a tight mortar box and then made into a mortar of the proper 
consistency and thoroughly worked over with hoes. 
13, Additions of Stone—Broken stone or gravel thoroughly cleaned of 
dirt, drenched with water, but containing no loose water in the heap, shall 
then be added to the mortar in the proper proportion. The concrete will 
then be turned and mixed until mortar adheres to each fragment. 
14. Consistency of Concrete-——The concrete thus mixed shall have such 
a consistency that when rammed the mass will not shake like jelly, but will, 
when struck, compact within the area of the face of the rammer without 
displacing the material laterally. 
15. Immediate Use of.—The concrete thus prepared shall be immediately 
placed in the work. It shall be spread and thoroughly compacted by ramming 
until free mortar appears on the surface. 
16. Mixing and Laying.—The whole operation of mixing and laying each 
batch of concrete shall be performed in an expeditious and workmanlike 
manner, and be thoroughly completed before the cement has begun to set. 
17. Re-tempering. — No re-tempering of concrete will be permitted, and 
concrete in which the mortar has begun to set will be rejected. 
18. Conform to Grade—The upper surface of the concrete shall be made 
to conform perfectly to the grade of the sidewalk to be laid. 
19. Minimum Temperature-—No concrete shall be laid when the tem 
perature at any time during the day or night falls below thirty-five (35) 
degrees Fahrenheit. 
WEARING SURFACE. 
20. Composition. —Upon the concrete base there shall be spread a finish 
coat, or wearing surface, one (1) inch thick composed of one (1) part cement, 
%, of one part crushed quartzite rock, and %4 of one part clean, sharp sand. 
23. Spreading. —This wearing surface shall be placed on the concrete 
as soon as the same is tamped and before it has begun to set. It must be 
quickly and evenly spread, and will then be floated and troweled to a true 
smooth surface conforming to the grade given. 
22. Blocking, — The surface of the sidewalk before the mortar sets will 
be cut into blocks, with a wedge-shaped tool, leaving a clean groove one-half 
an inch deep, one-eighth of an inch wide at the bottom, and one-quarter of an 
inch wide at the top. The blocks will be rectangular in shape, with straight 
sides, measuring not less than four nor more than six feet on a side. 
23. Walk at Curbing.—When the walk extends to the curb line it shall 
be one-half (14) inch above the curbing for the full width, unless otherwise 
ordered by the Engineer, with a neat bevel and a slight lap at its junction 
with the curbing 
REQUIREMENTS OF MATERIALS. 
CEMENT. 
24. Kind,—All cement used shall be the best imported Portland cement. 
It will be subjected to rigid inspection, and that rejected shall be immediately 
removed by the Contractor. 
