DETERMINATION OF LIME REACTIVITY OF POZZOLANIC MATERIAL (IS-1727-1967)

Purpose

This method of testing covers the process of determining the reactivity of pozzolanic materials (such as fly ash) with hydrated lime, as indicated by the compressive strength of standard mortar test cubes prepared and tested under specific conditions.

Size and number of test samples

The test specimen shall be of a 50 mm cube. At least three samples must be made for each period of the specified test.

Device

  • Cube molds of 50 mm in size
  • mixing equipment
  • Cube Mold.
  • mixing equipment
  • mixer
  • paddle
  • mixing bowl
  • scraper
  • flow table
  • tamping rod
  • karni
Flow table is used to determine the flux value in lime reactivity test
Flow table is used to determine the flux value in lime reactivity test

step by step process

Step – 1 (Preparing the Mold)

The inner faces of the sample molds should be covered thinly with mineral oil or light cup grease. After assembling the molds, excess oil or grease shall be removed from the inner faces and top and bottom surfaces of each mold. The molds should then be set on flat, non-absorbent base plates that have been thinly coated with mineral oil, or light cup grease.

Step – 2 (Preparing Mortar)

Clean equipment should be used for mixing. The temperature of the water and the temperature of the test chamber at the time when the mixing operation is being carried out should be from 27 °C ± 20C

The dry content of the standard test mortar will be Lime: Pozzolana: Standard sand in proportion to 1 : 2m : 9 Well mixed by weight.


Where,

M = (specific gravity of pozzolana / specific gravity of lime)

The amount of water to be measured will be equal to that required to give a flow of 70 ± 5 percent with 10 drops in 6 seconds (as stated in) step 3 Given below)

The following quantities of ingredients are suggested for preparing mortar:


material Amount
hydrated lime 150 grams
pozzolana 300 x mg
standard sand 1350 grams

These quantities will be sufficient to prepare six test samples.

Step – 3 (Determination of Flow)

Test Mix – With the above dry ingredients, make mortar with different percentages of water until specified flow is achieved. Test each with fresh mortar. The mixing will be done mechanically by means of a machine. Place the dry paddle and dry bowl in the mixer in the mixing position.

Then pour the ingredients for the batch into the bowl and mix in the following manner:


(a) Put all the mixing water in the bowl.

(b) Add the pozzolanic mixture to the water, then start the mixer and mix for 30 seconds at a slow speed (140 ± 5 rev/min).

(c) Slowly add the full amount of sand over a period of 30 seconds, while mixing at a slow speed.

(D) Stop the mixer, change to medium speed (285 ± 10 rev/min), and mix for 30 sec.


(e) Stop the mixer, and let the mortar stand for one and a half minutes. During the first 15 seconds of this interval, quickly scrape off any mortar in the batch that has collected on the side of the bowl, then for the remainder of this interval, cover that bowl with a lid.

(f) Finish mixing for one minute at medium speed (285 ± 10 rev/min).

(g) In any case a remixing interval is required, any mortar adhering to the edge of the bowl will be quickly pounded down in one batch with the scraper prior to remixing.

When mixing is complete, the mixing paddle will be shaken to remove excess mortar in the mixing bowl.


Carefully clean and dry the Flow-table top and place the mold in the middle. Place a layer of mortar about 25 mm thick in the mold and tamp it 20 times with a tamping rod. The tamping pressure shall first be sufficient to ensure uniform filling in the mould. Then fill the mold with mortar and tamp as specified for the first layer. Cut the mortar onto a flat surface by pulling the straight edge of a trowel (held approximately perpendicular to the mold) with a cutting motion across the top of the mold. Wipe the table top clean and dry; Take special care to remove any water from the side of the flow mold. One minute after completing the mixing operation, lift the mold away from the mortar. Immediately drop the table ten times in 6 seconds from a height of 12.5 mm.

Flow is the resulting increase in the average base diameter of the mortar mass, expressed as a percentage of the original base diameter, measured over at least four diameters at approximately equal intervals.

The material for each batch of mold should be mixed separately using different dry ingredients quantity, conforming to the specified proportion and prescribed water content. Mixing of mortar shall be done mechanically as described.

Step – 4 (Molding Test Sample)

Immediately after preparing the mortar, place the mortar in a 50 mm cube mold in a layer of about 25 mm thickness and tamp 25 times with a tamping rod. Tamping will be sufficient to ensure uniform filling in the mould. Then fill the mold to overflow and tamp as specified for the first layer. When the tamping is complete, the tops of all the cubes will be slightly above the tops of the molds. Cut the mortar onto a flat surface by pulling the straight edge of a trowel (held approximately perpendicular to the mold) with a cutting motion across the top of the mold.

Step – 5 (Storage and Curing of Specimens)

Cover the surface of the sample in the mold with a smooth and greased glass plate. Place the samples under wet sacks with a plate covered with the mold for 48 h. Then remove the samples from the molds and 50 . Cure at 90 to 100 percent relative humidity0C+20c for a period of eight days. Samples should not be cured under water.

pay attention

This can be achieved by placing the samples in a wide mouth jar of one liter capacity with a screw lid on a galvanized iron sheet platform placed at the bottom of the jar. The stage is covered with a piece of paper. The water is kept below the bottom of the platform, to a depth of about 10 mm. After placing the specimen that fits the lid, the jar is sealed with insulation tape and 50 . is kept in an incubator adjusted for0 +20c for eight days.

Step – 6 (Test the Compression)

Remove the samples after curing for eight days in the incubator as described above and check the compressive strength once they have reached room temperature. Test at least three cubes. The cubes shall be tested on their sides without any packing between the cube and the steel plates on the testing machine. One of the plates shall be moved and self-adjusting on a ball, and the load shall be applied constant and uniformly, starting from zero at the rate of 35 kg/cm2/ Minute.

Step – 7 (Calculation)

Calculate compressive strength from the crushing load and the average area over which the load is applied. 1 kg/cm. Express the closest result of2,

Defective cubes and re-testing

Cubes which are clearly defective or which are made of the same specimen and give a strength of more than 15 per cent of the average value of all test specimens tested in the same period shall not be considered in determining compressive strength. After discarding such cubes, if less than two strength test values ​​are left to determine the compressive strength over a given period, a retest will be performed.

Reference

IS: 1727 – 1967


Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.