. Standard methods of testing and specifications for cement. eans of a wire screenor some similar arrangement. A moist closet is so much moreeffective in securing uniformly moist air, and is so easily devised andso inexpensive, that the use of the damp cloth should be abandoned. 51. A moist closet consists of a soapstone or slate box, or awooden box lined with metal, the interior surface being covered withfelt or broad wicking kept wet, the bottom of the box being keptcovered with water. The interior of the box is provided with glassshelves on which to place the test pieces, the shelves being
. Standard methods of testing and specifications for cement. eans of a wire screenor some similar arrangement. A moist closet is so much moreeffective in securing uniformly moist air, and is so easily devised andso inexpensive, that the use of the damp cloth should be abandoned. 51. A moist closet consists of a soapstone or slate box, or awooden box lined with metal, the interior surface being covered withfelt or broad wicking kept wet, the bottom of the box being keptcovered with water. The interior of the box is provided with glassshelves on which to place the test pieces, the shelves being so ar-ranged that they may be withdrawn readily. 52. After 24 hours in moist air, the pieces to be tested after 45 METHODS FOR TESTING CEMENT longer periods should be immersed in water in storage tanks orpans made of non-corrodible material. 53. The air and water in the moist closet and the water in thestorage tanks should be maintained as nearly as practicable at 21°cent. (70° Fahr.). Tensile Strength 54. The tests may be made with any standard SECTION A-B Roller turned and accurately bored to easy tuiuinK fit FORM OF CLIP Fig. 6 55. The clip is shown in Fig. 6. It must be made accurately,the pins and rollers turned, and the rollers bored slightly largerthan the pins so as to turn easily. There should be a slight clearanceat each end of the roller, and the pins should be kept properlylubricated and free from grit. The clips should be used withoutcushioning at the points of contact. 46 METHODS FOR TESTING CEMENT 56. Test pieces should be broken as soon as they are removedfrom the water. Care should be observed in centering the testpieces in the testing machine, as cross strains, produced by imperfectcentering, tend to lower the breaking strength. The load shouldnot be applied too suddenly, as it may produce vibration, the shockfrom which often causes the test piece to break before the ultimatestrength is reached. The bearing surfaces of the clips and testpieces must
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