DETERMINING COMPRESSION AND CRIMPING STRENGTH OF CEMENT 2.3.1. Test equipment
- Mold steel 40 x 40 x 160 (mm).
- Ballast machine.
- Mortar mixer.
- Compression testing machine.
2.3.2. Prepare the test sample
- Manufacturing mortar in proportion to weight: one part of cement, three parts of standard sand and half part of water (X: C: N = 1: 3: 0.5). A batch of three test samples consists of: 450 ± 2 g of cement, 1350 ± 5 g of standard sand and 225 ± g of water.
- Mixing mortar mixture:
+ Before mixing get wet mop rags and tools in contact with mortar.
+ Pour water into the mixing jar and add cement slowly. Put the mixer right away and run at low speed for 30 seconds. Then, add sand and mix at high speed for 30 seconds.
+ Stop the mixer for 90 seconds to scrape the surrounding mortar to the mixing jar wall and mix into the center of the bowl.
+ Continue mixing at high speed for 60 seconds.
- Model making:
+ The mold before casting the mold must be scanned with thin oil to avoid grout sticking to the mold side.
+ Conducting casting sample after the mortar is prepared.
+ Mold and funnel are clamped firmly onto the ballast table. Pour mortar into the mold: divided into 2 layers, each ballasted 60 pieces.
+ Remove the funnel and remove the excess grout with a metal rod.
+ Sample notation.
- Maintenance of test samples:
+ Put the glass, steel or waterproof materials on the mold surface.
+ Place the mold after casting the sample in a humid air room or cabinet and the moisture must touch the sides of the mold.
+ Molds are not stacked.
+ For a 24-hour test, dismantling the mold shall not exceed 20 minutes before the test.
+ For tests with a sample age greater than 24 hours, dismantling the mold 20 to 24 hours after pouring.
+ Samples are submerged in water (placed horizontally or vertically whichever is convenient) at a temperature of 27 ± 20C. If the specimen is horizontal, the vertical sides are in the correct vertical direction and the mortar is pushed upwards.
+ Place the sample on a non-corrosive grid and keep it apart from each other so that water can get into the 6 sample faces. During the period of immersion, the distance between the samples or the depth of water on the surface of the samples should never be less than 5 mm.
+ In each tank, only soak the cement samples with chemical composition.
+ Use tap water to fill the tank for the first time and sometimes add water to keep the water level unchanged. Time to soak the sample is not allowed to replace all the water.
+ Take samples to be tested at any age (outside 24 hours or 48 hours when removing the late mold) from the water not more than 15 minutes before testing.
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