This may be caused by air bubbles in the test sticks that occurred while packing a sawdust mixed into plaster molds, thus making the test stick test result flexural resistance standard.
Either the bubbles in the sticks test occurred while packing sawdust mixed plaster into a mold test rods, the bending strength test results do not meet the standards.
The cause may be caused by bubbles in the bar test occurred while packing sawdust mixed with plaster into the mold bars test the test results of flexural resistance does not meet the standards.