This document summarizes research on the tensile strength characteristics of "no aggregate concrete" (NAC), which is concrete without crushed stone or sand aggregates. It outlines the motivation to study NAC due to declining aggregate reserves and costs. The objectives are to determine the optimum NAC mix and how its tensile capacity varies over time and with mix proportions. The methodology tests the splitting tensile strength of NAC mixes at various ages. Results show that NAC can achieve tensile strengths close to normal concrete, and that strength increases with higher cement or fly ash content but lowers density. NAC exhibits a lower tensile to compressive strength ratio than normal concrete.

1. D.D NAKANDALA -110379D
TENSILE STRENGTH
CHARACTERISTICS OF
“NO AGGREGATE CONCRETE”

2. Content
• Introduction
• Necessity
• Objectives
• Aggregates role in concrete
• No aggregate concrete - NAC
• Fly ash as the substituting material
• Tensile characteristics of concrete
• Methodology
• Results
• Comments on NAC

3. Introduction
• Concrete is the single most widely used
material in the world
• Basic composition
• Present issues in manufacturing concrete
• Solutions proposed

4. Necessity
• Conventional crushed stones and sand
reserves are depleting and the industry is
in the need of a substitute material. Also
some countries import aggregates at a
very higher rate. Cost of concrete
increases due to this.

5. Objectives
• Optimum mix for No Aggregate Concrete
• Tensile capacity of No Aggregate Concrete
• Variation of tensile capacity with time
• Variation of tensile capacity with different
mix proportions.
• Properties of No Aggregate Concrete
• Applicability of No Aggregate Concrete in
construction activities

6. Aggregates role in concrete
• Impacts on both physical and mechanical
properties
• 75% of the concrete volume
• Primary objectives of adding aggregates to
the concrete
• Adverse effects on concrete due to the
presence of aggregate

7. No aggregate concrete - NAC
• What is “No aggregate concrete” ?
• Why “No aggregate concrete” ?
– Cost
– Strength (N.Kalidas-2013)
– Permeability (N.Kalidas-2013)
– Density (Fahrizal Zulkarnain-2008).
– Durability (A.C.I-1987)/(Clarke-1993)
– No transition zone (Thomas-2000)

8. Tensile characteristics of concrete
• Generally low in concrete (G30 – 2 - 3 MPa)
• Methods of testing
– Direct shear test
– Splitting tensile test
• Why is it an important parameter?

9. Methodology
• Cast cylinders (150 x 300) for normal
grade 30 concrete, NAC for grade 30,
NAC with 10% cement increase, NAC with
10% fly ash increase.
• Conduct splitting tensile test for 7 days, 14
days and 28 days.
• Compare results
• Develop stress – strain graph for NAC &
determine the Elastic modulus.

10. Mix Designs
• Mix 1 – Normal Concrete( G -30 )
• Mix 2 – No Aggregate Concrete (G – 30 )
Constituents 1m3
Cement 350kg
Coarse aggregate 1075kg
Fine aggregate 875kg
Water 300 l
Admixture 5.25 l
W/C ratio = 300/1425 = 0.43
Constituents 1m3
Cement 350kg
Flyash 1400kg
Water 300 l
Admixtures 8.6 l
W/B ratio = 300/1750 = 0.17

11. Mix Designs
• Mix 3 – No Aggregate Concrete (G – 30 )(10% cement Increased)
• Mix 4 – No Aggregate Concrete (G – 30 )(10% fly ash Increased)
Constituents 1m3
Cement 315kg
Flyash 1540kg
Water 335 l
Admixtures 8.5 l
W/B ratio = 335/1855 = 0.18
Constituents 1m3
Cement 385kg
Flyash 1365kg
Water 328 l
Admixtures 8.5 l
W/B ratio = 328/1750 = 0.18

12. Results
• Tensile strength comparison between normal grade 30
concrete and NAC
Days
NAC
(MPa)
Normal Concrete
(MPa)
7 1.92 1.72
14 2.07 2.61
28 2.36 3.07

13. Results
• Variability of tensile strength with changes in mix proportions in
NAC
Days
NAC
(MPa)
NAC (10%
cement
increased)
(Mpa)
NAC (10% fly
ash increased)
(Mpa)
7 1.92 1.77 1.17
14 2.07 2.25 1.63
28 2.36 2.45 1.98

14. Results
• Density variation in normal concrete and NAC
Days
NAC
(kg/m3)
NAC(10%
cement
increased)
(kg/m3)
NAC(10% fly
ash
increased)
(kg/m3)
Normal
Concrete
(kg/m3)
7 2106 2077 2048 2384
14 2092 2064 2032 2352
28 2075 2054 2018 2344

15. Results
• Relationship with compressive strength and tensile strength in
NAC
(tensile strength/compressive
strength) * 100
Normal concrete 9.36 %
NAC 6.02 %
NAC(10% cement
increased) 6.03 %
NAC(10% fly ash
increased) 6.35 %

16. Results
• Stress – Strain graph and Elastic modulus of NAC
E =
(𝐬𝟐 – 𝐬𝟏)
(𝛆𝟐 – 𝟎.𝟎𝟎𝟎𝟎𝟓𝟎)
E = 11.58 GPa

17. Other Comments on NAC
• Brittleness
• Workability
• Setting time
• Surface Condition
• Mixing procedure

18. QUESTIONS?

19. THANK YOU