Home | ENGINEERING | Cement: Natural Aggregates and Bulking

Civil - Construction Materials: Lime, Cement, Aggregates, Mortar

Cement: Natural Aggregates and Bulking

   Posted On :  15.07.2016 02:07 pm
Cement: Natural Aggregates and Bulking

Natural Aggregates: These are obtained by crushing from quarries of igneous, sedimentary or metamorphic rocks. Gravels and sand reduced to their present size by the natural agencies also fall in this category.


Natural Aggregates: These are obtained by crushing from quarries of igneous, sedimentary or metamorphic rocks. Gravels and sand reduced to their present size by the natural agencies also fall in this category. The most widely used aggregate are from igneous origin. Aggregates obtained from pits or dredged from river, creek or sea are most often not clean enough or well graded to suit the quality requirement. They therefore require sieving and washing before they can be used in concrete.

Bulking: The increase in the volume of a given mass of fine aggregate caused by the presence of water is known as bulking. The water forms a film over the fine aggregate particles, exerts force of surface tension and pushes them apart increasing the volume. The extent of bulking depends upon the percentage of moisture present in the sand and its fineness. With ordinary sand bulking varies from 15-30 percent. It increases with moisture content up to a certain point (4-6%), reaches maximum, the film of water on the sand surface breaks, and then it starts decreasing. Figure 6.2 shows the bulking of sand with moisture content. In preparing concrete mixes if sand is measured by volume and no allowance is made for bulking, the moist sand will occupy considerably larger volume than that prepared by the dry sand and consequently the mix will be richer. This will cause, less quantity of concrete per bag of cement. For example, if the bulking of sand is 10% and if mix ratio is 1:2:4, the actual volume of sand used will be 1.1 2 =2.2 instead of 2 per unit volume of cement. If this correction is not applied the actual dry sand in the concrete will be , instead of 2 per unit volume of cement. The mix proportion then would be 1:1.82:4 rather than 1: 2: 4. Which indicates lesser production of concrete. Also, there will be chances of segregation, honeycombing and reduced yield of concrete.

 

Bulking of sand can be determined, in field, by filling a container of known volume (A) with damp sand in the manner in which the mixer hopper will be filled. The height of sand in the container is measured. The sand is then taken out of container carefully, ensuring no sand is lost during this transaction. The sand is then either dried and filled back into the gauge box, or the container is filled with water and the damp sand is poured in to displace the water. Whichever method is adopted, the new depth of aggregate in the container gives the unbulked volume (B).

Then percentage bulking expressed as a percentage of the dry volume = A B

Note: The dry and fully saturated (flooded) sand occupy almost same volume


Tags : Civil - Construction Materials: Lime, Cement, Aggregates, Mortar
Last 30 days 13 views
Related words :

What is Cement: Natural Aggregates and Bulking Define Cement: Natural Aggregates and Bulking Definition of Cement: Natural Aggregates and Bulking where how meaning of Cement: Natural Aggregates and Bulking lecturing notes for Cement: Natural Aggregates and Bulking lecture notes question and answer for Cement: Natural Aggregates and Bulking answer Cement: Natural Aggregates and Bulking study material Cement: Natural Aggregates and Bulking assignment Cement: Natural Aggregates and Bulking reference description of Cement: Natural Aggregates and Bulking explanation of Cement: Natural Aggregates and Bulking brief detail of Cement: Natural Aggregates and Bulking easy explanation solution Cement: Natural Aggregates and Bulking wiki Cement: Natural Aggregates and Bulking wikipedia how why is who were when is when did where did Cement: Natural Aggregates and Bulking list of Cement: Natural Aggregates and Bulking school assignment college assignment Cement: Natural Aggregates and Bulking college notes school notes kids with diagram or figure or image difference between Cement: Natural Aggregates and Bulking www.readorrefer.in - Read Or Refer

​TOP MENU

OTHER SUGEST TOPIC