Time comes when a site engineer or supervisor needs to check cement quality at site within a short period of time. If site engineers don’t have a testing laboratory at site and need to evaluate quality of cement then Field testing helps in it. Field tests are easy to perform and give sufficient idea about Cement Quality. Cement Field Tests mentioned below will definitely help in these types of quality check.
Field Tests for Cements
- Expiry date of Cement: – Cement Manufacturing Date must be checked as cement strength start reducing after 90 days of manufacturing. So its very important to check the date of manufacturing of cement and confirm weather cement is within limit of expiry date. Cement strength reduces up to 20-30% after 90 days. 30-40% after 180 Days and 40-60% after a Year.
- Color Tests: – Color of the cement is Greenish Grey. Color of the cement Gives idea about Chemical composition of the cement, content of lime or clay or weather cement is well burned or not at the time of manufacturing. Process- Open the cement bag and check color visually. if its Greenish Grey then its ok to Use.
- Lumps in Cement: – Moisture contact to the cement may produce Lumps in Cement. Cement bags must be stored in Dry and well conditioned weather. Exposure to the moisture will produce Lumps in Concrete which are not acceptable, It reduces the strength of concrete. Process- Open the bag of cement, If visible Lumos are their then such cement bags must be discarded.
- Cement Temperature: – Temperature of the cement must feel cool. If the temperature of the cement is warm then it indicates the Hydration Process if the cement is started. Which is not good for cement. Means cool cement is acceptable and warm cement should be rejected. Process- Immerse open hand in the cement, If it feels Cool then its ok. If it is warm then discard it.
- Smoothness or adulteration test: – Cement Must Feel smooth if it is rubbed between fingers. If it Feels rough then it is indication of adulteration with the sand. Process- Take some cement in hand and rub it in fingers. If it feels soft then it is good to use. If cement feels rough then its not good enough.
- Water Sinking or Floating test: – Cement float on cement for some time before sinking. If you through some quantity on the surface of water it floats for some time then it sinks. Process- Take some quantity of cement, Throw it on surface of water. If it floats for some time before sinking then its ok to use.
- Cement Paste Smell: – Cement paste smells earthy. Its paste is sticky. Process- Take some quantity of cement add some water and create paste. If paste is sticky and it smells like earth or soil then its ok to use.
- Setting Time or Glass plate test: – Cement must not crack if a thick paste is kept on the glass for 24 hours. Process- Take a glass with smooth surface. Apply a thick paste of cement on it. Cement paste must be made up of 100 grams of cement. Prepare cake of paste and keep it on grass. Immerse this assembly in water for 24 hours. Don’t mess the shape of cake while immersing it into the water. Keep the corner of the cake sharp. If it doesn’t prepare crack Then Its ok to use. Note:- Cement get set in water also.
- Strength Test: – A block of cement paste is made and then some load is applied to it. If the block fails then Cement has low strength. Process- Create a block from the paste of cement. Size of block should be 25mm x 25mm by 200mm ( 1″ x 1″ x 8″ ). Keep it in water for 7 days for curing purpose. Then remove it from water and support then block with 150mm height on edges. Apply load of 34 kg at its center. If block doesn’t form cracks or doesn’t fail. then cement has enough strength. If block forms crack or fails then it doesn’t have sufficient strength.