Test method for crack-resistant mortar
Test method for crack-resistant mortar
1, anti-crack mortar can use time:
After the standard anti-crack mortar is prepared, it shall be placed according to the operable time provided by the manufacturer under the standard conditions of the laboratory (1.5h if it is not specified). At this time, the material shall have good operability.
2. Tensile bond strength of crack-resistant mortar and immersion tensile bond strength:
On ten 70×70×20 cement mortar test blocks, the standard anti-crack mortar was put into the standard mold, and the test pieces were made into standard ones. During molding, the test pieces were compacted with a scraper, covered with PVC film, and cured at laboratory temperature for 7 days, and then taken out to continue curing for 20 days under laboratory standard conditions. Adhere the steel upper fixture with two sets of epoxy resin or other high-strength adhesives and leave it for 24h.
Test: 5 test pieces, put them in horizontal state, and measure the maximum tensile strength, i.e., bond strength, at a tensile speed of 5 mm/min along the vertical direction of the surface of the test piece on a tensile testing machine.
For the other five specimens, place them horizontally on the standard sand at the bottom of the water tank, and then inject water to a place about 5㎜ away from the surface of the mortar block. After standing for 10 days, take them out, test them with their sides facing down, dry them in a (50 2)℃ incubator for 24h, and then place them in a standard environment for 24 h. Then place them in a horizontal state, and measure the maximum tensile strength at a tensile speed of 5㎜/min along the vertical direction of the specimen surface on a tensile testing machine.
3. Compressive strength:
According to GB/T17671-1999 cement mortar strength test method, the test pieces shall be manufactured and maintained, and the compressive strength and flexural strength tests shall be conducted according to the cement method.
4. Pressure analysis ratio of anti-crack mortar: (flexibility)
According to GB/T17671-1999 cement mortar strength test method, the test pieces shall be manufactured and maintained, and the compressive strength and flexural strength tests shall be conducted according to the cement method.
Compression ratio calculation: T﹦Rc/Rf test: T— compression ratio Rc— compressive strength Rf— flexural strength.
5. Water absorption:
6. Freeze-thaw: 12 specimens of 70.7×70.7×70.7 shall be manufactured and cured for 28 days.
(1) load the specimen into a freezer at-15 ~-20℃;
(2) use steel welding to match the blue frame of the specimen, and put the specimen into the frame.
(3) equipped with weighing is 5㎏, sensitivity is 5g case scale.
(4) equipped with a dissolving tank, which can keep the water temperature within the range of 15 ~ 20℃ after loading the specimen.
⑤ Pressure testing machine.
After the specimen is cured for 26 days, it is taken out of the curing box, and after the appearance is checked and recorded, two groups of specimens
Soak in water at 15 ~ 20℃ at the same time, the water level is 20㎜ higher than that of the specimen, take it out two days later, dry it with a wrung towel, and weigh it by number. One group was put into the basket and moved into the freezer, while the other group was put into the standard curing box to continue curing. The specimen is 20mm at the bottom and 50mm adjacent in the freezer.
When the temperature in the freezer is lower than-15℃, put the test piece in and keep the temperature in the freezer within the range of-15 ~-20℃. The freezing time is 4h each time. After freezing, take it out and put it in a dissolving tank, and keep it at 15 ~ 20℃ to melt. The specimen shall be melted in the tank for no less than 4h, and the freeze-thaw cycle will end after melting. Take out the specimen and send it to the freezer for the next cycle test.
Every five cycles, an appearance inspection shall be conducted, and the damage of the specimens shall be recorded. When four of the six specimens in this group are obviously damaged (delamination, cracking, through joint), the freeze-thaw test of this group of specimens shall be terminated.
After the freeze-thaw test, the freeze-thaw specimen and the reference specimen shall be dried at 105 5℃ at the same time, and then weighed and pressure tested. If the surface damage of freeze-thaw specimen is serious, it should be repaired with cement paste, and then put into the standard environment for maintenance for 2 days, and then test the pressure at the same time with the comparison specimen.
After freeze-thaw test of mortar specimen, the strength loss rate and mass loss rate shall be calculated by the following formula respectively.
