PROGRESS REPORT ON RESEARCH OF PAVING BRICK FROM IOWA SHALES ¹

ABSTRACT Test on full size pavers made from 11 shales showed that five would make an excellent paving material and others had possibilities of making a block that would give service. Various processes were tried as soft‐mud, roller expression machine, dry‐press, and a new belt machine, also additions of magnesium and colloidal materials. The soft‐mud, roller expression machine gave equal if not better results than the stiff‐mud process, and the other processes required higher temperatures to get a suitable block for test. Magnesium reduced the rattler test from 27% to 22% and changed the color to buff similar to that of fire clay. The colloidal materials made the shale more refractory and hence the brick were too soft for the rattler test.