LABORATORY INSTRUCTION MANUAL FOR ENG 3731: MATERIALS (AND METHODS) OF CONSTRUCTION............

Laboratory I: Tests on Coarse and Fine Aggregates

Purpose: To obtain the fineness modulus, density, and voids ratio of fine and coarse aggregate samples

Materials and Apparatus:

 - sample of fine aggregate

                - sample of coarse aggregates

                - digital weighing scale

                - sieve sifter for fine aggregates

- sieve sifter for coarse aggregates

- various cleaning brushes (point and wire)

Procedure:

7.1.1        Part 1: Sieve Analysis of fine aggregate

Step 1: Take 500g sample of fine aggregate (as per CSA code provisions, the aggregates must be completely dry). This is determined by weighing the material on a digital scale. Also weigh each sieve of the mechanical sifter, and the pan, and record the weights.

Step 2: Place the aggregate in the top sieve of the well-cleaned mechanical sifter (sieves used are # 4, # 8, # 16, # 30, # 50 & # 100). This apparatus is used for shaking the aggregates (similar to the principle used in a paint-mixing machine) and sieving them. The mechanical sifter has a bottom pan (to receive the material passing # 100 sieve) and a lid to close the sifter during the test. After placing the lid on the sifter, agitate the sifter for about 10 minutes.

           

Step 3: Determine the weight of aggregates that are retained in each of the sieves, by weighing each of the sieves (along with the retained aggregates), and subtracting the weight of each sieve. Also record all the weights of aggregates retained in each of the sieves. To ensure that all materials are collected, clean each sieve carefully using the proper type of brush. Use the paint brush for the finer sieves, the copper brush for intermediate sieves and the steel wire brush for the coarse sieves. Also verify whether the sum of weights of aggregates, retained in all the sieves, and the bottom pan is equal to the initial weight of the aggregates taken.

Step 4: Tabulate the data and determine the percent retained in each sieve. From these values calculate the (cumulative) percentage of material that would have been retained in the sieve if the whole volume of material was to be sifted in that sieve alone. Then add the percentage of material retained in all the sieves and divide by 100 to get the fineness modulus. Also prepare a column to determine the cumulative percentage passing through the sieve to plot the fineness modulus curve (as specified in CSA 23.1).

Step 5: Plot a graph of percent passing by weight vs sieve size, with the limits specified in CSA standard A23.1 for fine and coarse aggregate sizes superimposed.

Note:  (1) All sieves have to be cleaned prior to experiment.

            (2) See the sample calculations given at the end of this section.

 

PART 2: Sieve Analysis of Coarse Aggregate

Procedure:

Step 1: Take 5000 grams of coarse aggregates by weighing the material in a digital scale. Weigh each of the clean sieve, along with the bottom pan, and record their weights.

Step 2: Place the aggregates in the mechanical sifter (sieve sizes used are 1 ½”, 1”, ¾”, ½”, 3/8”, & #4). This apparatus is used for shaking the material (similar to the principle of a paint-mixing machine) and sieving it.

Step 3: Determine the aggregates that are retained in each individual sieve, as mentioned earlier in Part I, and record the data. To ensure that all materials are collected, use the steel brush to clean each sieve.

Step 4: Tabulate the data and determine the percent retained, and the percentage that would have been retained in each sieve, if that sieve alone was used to sieve the whole volume. The fineness modulus is obtained by adding the percentage of material retained in all the sieves and dividing it by 100.

Step 5: Plot a graph of percent passing by weight vs. sieve sizes.

Note: All sieves have to be cleaned prior to experiment.

Part 3: Bulk Density and Voids Ratio of Fine Aggregates

Step 1: Take a bucket (of volume, say, 2.5 litres) and weigh it. Place the aggregates in the bucket (whose volume is already determined by dividing the weight of the volume of water that is contained in the completely filled bucket by the weight density of water. In addition, the bucket must be properly dried before placing fine aggregate in it) to fill 1/3^rd its capacity each time. Rod each portion 25 times. The steps are repeated till the bucket in is filled with fine aggregates. Remove excess aggregate using the tamping rod as a straight edge.

Step 2: Determine the weight of fine aggregates by weighing the bucket full of aggregates, and subtracting the weight of empty bucket.

Step 3: Determine the bulk weight density of fine aggregates by dividing the weight of the aggregates by the volume of the bucket.

Step 4:   Also determine the volume of voids in the fine aggregate, using the following equation.

             

% voids in fine aggregates =

{[(Sp. Gr. of fine aggregates)*g_w - g_{bulk density}]/[g_w*(Sp. Gr. of fine aggr.)]}*100

Part 4: Bulk Density and Voids Ratio in Coarse Aggregates

            Repeat the procedures given in Part 3 for fine aggregates, and obtain the bulk density and voids ratio for coarse aggregates.

Part 5: Sample Calculations for Fineness Modulus, Bulk Density and Voids Ratio

1.                  Sieve analysis of a 1000-g sample of fine aggregates resulted in the following data. Find the fineness modulus.

Sieve size	# 4	# 8	# 16	# 30	# 50	# 100
Weight retained (g)	26	130	240	252	210	138

Calculations:

Sieve #	Weight retained (g)	Percent retained	Percent coarser	Percent finer
4	26	2.6	2.6
8	130	13.0	15.6
16	240	24.0	39.6
30	252	25.2	64.8
50	210	21.0	85.8
100	138	13.8	99.6
			Cumulative = 308

                Fineness modulus = 308/100 = 3.08

2.                  Find the volume of voids in a 3 cubic yards of coarse aggregates, of bulk density equal to 102 lbs/(cubic feet). The specific gravity of particles is 2.65.

% of Voids = [(SG*W - B)*100]/(SG*W)

Specific gravity, SG = 2.65

Density of water, W = 62.4 lbs/(cu. ft.)

Bulk density, B= 102 lbs/(cu. ft.)

% of voids = [(2.65*62.4 - 102)*100]/(2.65*62.4)

                        = 38.3%

Volume of voids = (38.3/100)*3 = 1.143 cu. yards

                                                = 1.143*27 = 31 cu.ft. 

               

Materials and Apparatus (Laboratory # 1):

Figure # 1

 

           

 

           

7.1.1.1                                      Coarse aggregate                     Fine aggregate

Figure # 2

 

                                    Digital weighing scale

Figure # 3

 

                        Sieve for fine aggregates                                Sieve for coarse aggregates

Labroratory # 2

“Tests on Cement Mortar”

(a)   Normal Consistency of Cement Mortar

(b)   Setting Time of Cement Mortar

(c)    Compressive Strength of Cement Mortar Cubes

(Casting it earlier to test it lat)

Laboratory II: Normal Consistency & Setting Time and the Determination of Compressive Strength of Cement Mortar.

Purpose: To prepare samples of cement mortar specimens for: (1) Determination of normal consistency and setting time tests; and (2) compressive strength of mortar cement test.

Materials:   - Sand

                        - Portland Cement

                        - Water

Apparatus: -        Vicat Apparatus

                        -           Digital weighing scale

-           Moulding tray for cubes

-           Beaker (for taking water)

-           Universal Testing Machine

-                      Tamping rod

-                      Mixing bowl

-                      Trowel

-                      A stop-watch

Procedure:

7.1.2        PART I: Normal Consistency and Setting Time

            Step 1: Obtain 500g sample of Portland cement by weighing on the digital scale.

Step 2: Obtain 145ml of water in a beaker, which gives a water/cement ratio of 0.290:1 (this ratio may vary between 0.25 to 0.31).

Step 3: Combine both the Portland cement and water in the mixing bowl. Wait approximately 30 seconds for water absorption.

            Step 4: Start mixing using the mixing machine at a slow speed for 30 seconds.

Step 5: Turn off the machine for 15 seconds and scrape down the mortar from the sides of the bowl using a scraping stick.

Step 6: Turn on the mixing machine again, for approximately 60 seconds at medium speed.

Step 7: Within a minute, remove the mortar from bowl, press the mortar into the conical ring and put it on the Vicat Apparatus, using a rectangular glass (on bottom), and smooth the top with a trowel.

Step 8: In the Vicat Apparatus release the large-sized plunger (10 mm) to penetrate the sample. Find the depth of penetration. If the penetration of the plunger is 10 ± 1.0 mm, then the consistency is called the normal consistency. Otherwise, decrease or increase the percentage of water and mix the cement and water once again to carry out the above steps till the normal consistency is obtained.

Step 9: Once the normal consistency is determined, then use the same paste to determine the initial and final setting times. In this case, the 1-mm-diameter Vicat needle is allowed to penetrate the setting cement paste. Start the timer when this cement paste was made.

Step 10: When the 1-mm-diameter Vicat needle penetrates to a distance of 25 mm, then the time taken by the cement paste (from its mixing to the present time) is said to be its initial setting time.

Step 11: When the 1-mm-diameter Vicat needle just penetrates the surface of the setting cement paste and stops, then the time taken from the time of mixing of the paste to this time is called the final setting time.

PART II: Compressive Strength of Cement Mortar

Step 1: Obtain 1375 g sample of sand, 500 g sample of Portland Cement by weighing material on a digital scale (in this the ratio of cement to sand is 1:2.75. This ratio can also be 1:1.5, 1:2, or 1:2.5, which can be tried by other groups at the instructor’s discretion.

Step 2: Obtain 240 ml sample of water in a graduated cylindrical beaker, which is equivalent to the specified water/cement ratio of 0.48:1 (the ratio can vary from 0.45 to 0.60 and this ratio can be changed at the instructor’s discretion).

Step 3: Combine the two dry samples (Portland cement and sand) in the mixing bowl and mix for approximately 5 minutes.

Step 4: Slowly add water to the mixing bowl and mix the contents until the desired consistency is achieved.

Step 5: Remove mixed contents from bowl and place it in even portions in five cubes in the moulding tray, which has already been wiped on the inside with the given oil.

Step 6: Tamp all five cubes to ensure uniform filling of the moulds. Smooth the top with trowel.

Step 7: Cure the specimens for fourteen days in water so that it may attain the desired design compressive strength.

Step 8: The cubes are removed from water, area of loading face of cubes determined, and then placed in between plates of Universal Testing Machine.

Step 9: Apply load to the specimen faces that are in contact with the machine.

            Step 10: Apply load until failure, and note the load.

            Step 11: Compute and record compressive strength of cement mortar.

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