Aggregates Physical Properties and Mechanical Properties.pptx

Aggregates Physical Properties and Mechanical Properties

1. Aggregates: Physical Properties and Mechanical Properties

2. Aggregates Ag g r eg a tes ge n era l l y occu p y 6 5 - 8 % of a conc r ete ’ s volume. Aggregates are inert fillers floating in the cement paste matrix for concretes of low strength.The strength of aggregates do not contribute to the strength of concrete for low strength concrete. The characteristics of aggregates impact performance of fresh and hardened concrete.

3. Why use aggregate Reduce the cost of the concrete – 1/4 - 1/8 of the cement pr i ce Reduce thermal cracking – 100 kg of OPC produces a b o u t 1 2 Degree Celcius temperatu r e rise Reduces shrinkage – 10% reduction in aggregate volume can do u b l e shrink a ge High a g g r eg a te : cement ratio (A/C ) desir a b l e A/C mai n l y i n fl u enced b y ce m ent con tent Impa r ts u n i t w ei g ht to c o nc r ete

4. Aggregate Classification Size:- Coarse Aggregates & Fine Aggregates. Specif i c Gr a vity : - Lig h t W ei g ht, N ormal W ei g ht , a n d He a vy W ei g ht Ag g r eg a te s . A va i l a b i l i t y : - Natural Gr a vel a n d Cr u shed Ag g r eg a te s . Sh a p e : - Rou n d, Cu b ica l , An g u l a r , E l on g ated an d Fl a ky Aggregates. Texture:- Smooth, Granular, Crystalline, honeycombed an d P o r ous.

5. Aggregate Classification : Size F i ne Ag g r eg a te San d and/or crushed sto n e . < 4.75 mm. F.A. content usually 35% to 45% by mass or volume of total aggregate. Coa rse Ag g r eg a te Gr a v el and crushed ston e . >4.75 mm. T ypical l y bet w een 9.5 and 37.5 mm.

6. Aggregate Classification : Specific Gravity Normal - W ei g ht Ag g r eg a te Most common aggregates ( Ex: Sand, Gravel, Crushed stone) Produce normal-weight concrete 2200 to 2400 kg/m 3 Lig h t w eig h t Agg r egate Expanded (Shal e , Cl a y , Slate , Slag) Produce structural lightweight concrete 1350 to 1850 kg/m 3 And (Pumice, Scoria, Perlite, Diatomite) Produce lightweight insulating concrete— 250 to 1450 kg/m 3

7. Aggregate Classification : Specific Gravity He a v y w eig h t Agg r egate Barite, Limonite, Magnetite, Hematite, Iron Produce high-density concrete up to 6400 kg/m 3 Used f or Radiation Shielding

8. Aggregate Classification : Availability Natural Gr a vel River or seashore gravels; desert, seashore and windblown sands Rounded i n natu r e Fully water worn or completely shaped by attrition Cr u shed Ag g r eg a tes . Crushed r ocks of all type s Angul a r i n n atu re

9. Aggregate Classification : Shape The shape of aggregates is an important characteristic since it affects the workability of concrete.

10. Aggregate Classification : Shape

11. Aggregate Classification : Texture Surface textu r e i s t h e p r o p e r t y , the measu r e of which depends upon the relative degree to which particle surfaces a r e po l ishe d or du l l , s mooth or r ou g h. Surface texture depends on hardness, grain size, pore s t ruct u r e , and the s t ruct u r e of the r ock.

12. Aggregate Classification : Texture

13. Physical Prosperities of Aggregate : Grading Grading is the particle-size distribution of an aggregate as determi n ed b y a si e v e a n a l ysis usi n g wi r e me s h si e v es wit h s q u a r e ope n i n g s . As per IS:2386(Part-1) Fine aggregate : 6 standard sieves with openings from 150 μ m to 4 .7 5 m m . ( 1 50 μ m , 300 μ m , 600 μ m , 1.18 m m, 2.36 m m, 4.75mm) Coarse agg r egate: 5 si e v es wit h openings f r om 4.75mm to 80 mm . (4.75 m m, 10mm, 12.5 m m, 20mm, 40mm)

14. Physical Prosperities of Aggregate : Grading Grain size distribution for concrete mixes that will p r o vi de a de n se s t ro n g mi xtu r e . Ensure that the voids between the larger particles are filled with medium particles.The remaining voids are filled with still smaller particles until the smallest voids are fil l ed wit h a s mall amount of f i n e s .

15. Grading of Fine Aggregate

16. Grading of Coarse Aggregate

17. Grading of All in Aggregate

18. Fineness Modulus (FM) The results of aggregate sieve analysis is expressed by a n um b er ca l le d F i ne n ess M od u l u s . O b tai n ed b y a d d i ng the sum of the cumulative percentages by mass of a sample a g g r eg a te r etai n ed on each of a s pec i fied series of si e v es a n d d i vi d i n g the sum b y 10 . The following limits may be taken as guidance: Fin e sand : Finenes s Modulus : 2.2 - 2.6 Medium sand : F .M . : 2.6 - 2.9 Coarse sand : F .M . : 2.9 - 3.2 A sand h a ving a fineness modulus mo r e than 3.2 wil l be unsuitable for making satisfactory concrete.     100 Finess Modulus, FM   Total of Cumulative Percentage of Passing (%) 

19. Physical Properties of Aggregate: Flakiness Index The flakiness index of aggregate is the percentage by w ei g ht of p a r ticl e s i n i t whos e leas t d i mension (thick n ess) is less than three-fifths of their mean dimension. The te s t i s n o t a p p l ica b l e to s ize s s m a l le r th a n 6 . 3 mm. The flak i ness i n dex i s t a k en as t h e total w ei g ht of t h e material passing the various thickness gauges expressed as a percentage of the total weight of the sample taken. Table 3.18 shows the standard dimensions of thickness a n d le n gth g a u g es.

20. Physical Properties of Aggregate: Flakiness Index The flakiness index of aggregate is the percentage by w ei g ht of p a r ticl e s i n i t whos e leas t d i mension (thick n ess) is less than three-fifths of their mean dimension. The te s t i s n o t a p p l ica b l e to s ize s s m a l le r th a n 6 . 3 mm. The flak i ness i n dex i s t a k en as t h e total w ei g ht of t h e material passing the various thickness gauges expressed as a percentage of the total weight of the sample taken. Table 3.18 shows the standard dimensions of thickness a n d le n gth g a u g es.

21. Physical Properties of Aggregate: Flakiness Index

22. Physical Properties of Aggregate: Flakiness Index

23. Physical Properties of Aggregate: Elongation Index The e l o n g a tion i n dex on an ag g r eg a te i s t h e pe r centa g e b y w ei g ht of pa r ticl e s wh o se g r eatest d i mension (le n gth) is greater than 1.8 times their mean dimension. The elongation index is not applicable to sizes smaller than 6 . 3 mm. The el o n g ati o n i n dex i s t he total w ei g ht of the mater i al retained on the various length gauges expressed as a pe r centa g e of the t otal w ei g ht of t he samp l e ga u ge d . The p r esence of elo n g a ted p a r ticl e s i n excess of 10 to 15 per cent i s genera l l y conside r ed u n desirabl e , b u t no r ecog n ize d l i mits a r e la i d d o wn.

24. Physical Properties of Aggregate: Elongation Index

25. Physical Properties of Aggregate: Specific Gravity Indian Standard Specification IS : 2386 (Part III) of 1963 g i v es var i o u s p r oced u r es to fi n d o u t the specific g r a vity of d i f f e r ent sizes of a g g r eg a te s . Appare nt Specif c Gravit y  Specif c Gravit y  C A  Weight o f saturated aggregate in wate r  ( A 1 - A 2 ) B  Weight of the saturated surface - dry aggregate in air C  Weight of ovendried aggregate in air. A 1  Weight of aggregate and basket in water A 2  Weight o f empty basket in water Water Abso r pt i on  10  B  C  C  B C A  B C

26. Physical Properties of Aggregate: Bulk Density The cyl i nd ric a l measu r e i s f il l ed a b o u t 1/3 each time wit h tho r o u gh l y mi x ed a g g r eg a te an d tamped wit h 25 s t r o k es b y a b u l l et en d ed tamp i ng r od, 16 mm d i ameter a n d 60 cm l o n g . The net w ei g ht of the a g g r eg a te i n the measu r e i s d etermined a n d the b u lk de nsity i s c a lc u l a ted i n kg/l i t r e .