RECYCLED AGGREGATE HIGH-STRENGTH CONCRETE · Pervious Concrete, 2017; Rattanachu, Tangchirapat, & Jaturapitakkul, 2019) ... steel (steel 52) of 16 mm diameter and 16 cm high rebars

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 10, Issue 09, September 2019, pp. 128-146, Article ID: IJCIET_10_09_014

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=9

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication

RECYCLED AGGREGATE HIGH-STRENGTH

CONCRETE

Mohamed Emad

M. Sc. Candidate, a Civil Engineer, Egypt.

Noha M. Soliman

Associate Professor, Civil Engineering Department, Faculty of Engineering,

Menoufia University, Egypt.

Alaa A. Bashandy

Associate Professor, Civil Engineering Department, Faculty of Engineering,

Menoufia University, Egypt.

ABSTRACT

The use of recycled aggregates from demolished constructions as a coarse

aggregate for concrete becomes a need to reduce the negative effects on the

environment. This study aims to study the effect of using recycled materials (such as

crushed concrete, crushed ceramic and crushed red brick) as coarse aggregate for

high-strength concrete on the main properties of high-strength concrete. Also, the

behavior of reinforced beams cast using that type was studied to investigate their

behavior in terms of the deflection, strain values, initial cracking load, crack pattern

and ultimate loads. Main variables are recycled aggregate type (recycled crushed

concrete, crushed ceramic and recycled crushed red brick), replacement ratio (as

25%, 50%, 75% and 100% from dolomite as coarse aggregate), age of test (after 7, 28

and 56 days). The test results showed that high-strength concrete made with recycled

aggregate behave in a similar manner as that made with dolomite as aggregate. Also,

a decrease in the range of about 13.1-67.2%, 17.6-72.0%, 24.3-74.6% and 6.5-71.1%

for compressive, splitting tensile, flexure and bond strengths and bond strength

compared to that cast using dolomite.

Keywords: Recycled aggregate; High-strength concrete; Super plasticizer; Beams

Cite this Article: Mohamed Emad, Noha M. Soliman, Alaa A. Bashandy, Recycled

Aggregate High-Strength Concrete. International Journal of Civil Engineering and

Technology 10(9), 2019, pp. 128-146.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=9

1. INTRODUCTION

Recycled aggregates are those aggregates produced from the demolished constructions. The

utilization of recycled aggregate in concrete production increases due to environmental and

economic considerations to produce recycled aggregate concrete (RAC) [1, 2]. RAC is the

concrete, which made with recycled aggregate as partially or fully replacement of natural

Recycled Aggregate High-Strength Concrete


coarse aggregate. Since recycled aggregate produced from different sources with an

occupation of around 75% of the concrete volume, it is necessary to a suitable recycled

aggregate with sufficient quality. This requires advancing processing techniques using special

facilities to control the quality of recycled aggregate [3, 4]. Well-chosen recycled aggregates

as concrete coarse aggregates are efficient in concrete with strength loss up to 20% of those

with natural aggregates which mean it is efficient for light and medium loads with different

special concrete types [3, 5, 6].

The most significant difference in the physical properties of coarse recycled concrete

aggregates (RCA) reported in most studies is its higher water absorption capacity as compared

to coarse natural aggregates due to the higher porosity of the mortar adhered onto the

aggregate in RCA. The smaller size of RCA has higher values of adhered mortar and higher

water demand of the concrete mixture due to the high porosity of adhered mortar [7, 8, 9].

Recycled aggregates were used efficiently with several concrete types such as lightweight,

self-compacted, self-curing, pervious, high-strength concretes (Bashandy, Eid, & Abdou,

Lightweight Concrete Cast Using Recycled Aggregates, 2017; Bashandy, Safan, & Ellyien,

AICSG9, 2016; Bashandy A. A., Behavior and Durability Evaluation of Recycled Aggregate

Pervious Concrete, 2017; Rattanachu, Tangchirapat, & Jaturapitakkul, 2019)

High-strength concrete "HSC" is widely used in the construction industry, like tall

buildings and bridges due to it is high-strength, high stiffness, high durability, reduced creep,

economical cost, good impact resistance, drying shrinkage and resistance to abrasion [14].

HSC is achieved by adding different mineral materials like fly ash, silica fume, Super

plasticizer, fibers, etc. [15]. HSC may or may not require special materials, but it surely

requires high-quality materials with adequate suitable proportions. In the manufacture of

HSC, the use of clean and strong aggregates is essential. Also, a lower water-cement ratio

along with super plasticizer is needed [16]. HSC is efficient to cast concrete elements with

long spans or those which need a high concrete grade [17, 18].

As using recycled aggregates to cast high-strength concrete, increasing replacement ratio

may decrease the concrete strength [13]. Also, ground bagasse ash and recycled concrete

aggregate with a replacement for cement up to 50% and coarse aggregate, respectively had a

clear negative influence on the durability of concrete [13].

On another hand, increasing the replacement ratio may contribute to reducing the risk of

explosive spalling in high-strength concrete under elevated temperature [19]. Under elevated

temperatures, the rate of drop in compressive and splitting tensile strength was lower in the

case of RA-HSC compared to that of NA-HSC above show that RA-HSC exhibits lower

thermal cracking and fewer color changes compared to that of NA-HSC [20].

In this research high-strength concrete cast using recycled aggregates with different

recycled aggregates and different replacement ratios (as 0, 25, 50, 75, and 100% of natural

coarse aggregate used) were evaluated to produce recycled aggregate high-strength concrete

(RA-HSC).

2. RESEARCH SIGNIFICANCE

High-strength concrete considers one of the most recently used concretes due to its superior

properties. Using demolished waste construction materials as concrete coarse aggregates to

produce recycled aggregate "RA" concrete is a new trend to reduce waste materials bad

impacts on the environment. Using both together is suggested.

The importance of this research is based on the necessity to identify the data available on

the properties and the behavior of the high-strength concrete cast using recycled aggregates.

The novelties of this investigation are three points; obtaining recycled aggregates high-

strength concrete "RA-HSC" using crushed red bricks, a comparative study on the using of

Mohamed Emad, Noha M. Soliman, Alaa A. Bashandy


three types of recycled aggregates compared to using natural aggregates to cast RA-HSC, and

the evaluation of the structural performance of reinforced RA-HSC beams.

3. METHODOLOGY

The conducted tests in this investigation are carried out in the Laboratory of Construction

Materials, Department of Civil Eng., Faculty of Eng., Menoufia University, Egypt. The

conducted experimental program is divided into two stages. The first stage was performed to

study the effect of using recycled aggregates "RA" compared to using natural aggregates with

high-strength concrete "HSC" to obtain "RA-HSC". The slump of fresh RA-HSC as a fresh

concrete property was discussed. The hardened concrete properties of "RA-HSC" were

derived in terms of compressive, splitting tensile, flexural and the bond strengths. The second

stage was performed to study the behavior of reinforced concrete beams cast using RA-HSC.

The main variables in the experimental program are coarse aggregates used (dolomite,

crushed concrete, crushed ceramic or crushed red brick), the percentage of replacement ratio

of coarse aggregate (as 0, 25, 50, 75, or 100% of natural aggregate used), and age of testing

(after 7, 28 or 56 days). In this section, the materials used, concrete samples, and test

procedures are presented.

3.1. Materials

The cement used is ordinary Portland cement (CEM I, 42.5N) used from Lafarge company. Its

chemical and physical characteristics satisfy the requirements of the Egyptian Standard

Specifications (E.S.S.4756-1/2013) [21].

The fine aggregate used in the experimental program is natural siliceous sand. Its

characteristics satisfy the requirements of the Egyptian Code of Practice (E.C.P.203/2018)

[22] and (E.S.S.1109/2008) [23]. It is clean and nearly free from impurities with a specific

gravity 2.58 with a fineness modulus of 2.72. Its physical properties are shown in Table 1. Its

grading is shown in Table 2. The coarse aggregates used are two types; natural and recycled

aggregates. Crushed dolomite is a natural aggregate and three types of recycled aggregate

(crushed normal strength concrete, with average compressive strength of 20-35MPa, crushed

ceramics) and (crushed red brick) are used. They had a maximum nominal size of 25 mm. The

grading of all coarse aggregates followed the limits of (ASTM C-33) [24]. Their physical

properties are shown in Table 3. Its grading is shown in Table 4 and Fig. 1. Mixing water of

drinkable clean water, fresh and free from impurities is used for mixing processes of the

tested samples according to the (E.C.P.203/2018) [22]. Reinforced steel bars high-strength

steel (steel 52) of 16 mm diameter and 16 cm high rebars are used as embedded rebar's in

standard concrete of dimensions 150×150×150 mm to determine the bond strength between

concrete and steel bars. It meets the requirements of (E.S.S.262/2011) [25]. The steel used in

stage two is the high tensile steel (ST.52) of 12 mm diameter and mild steel (ST.37) of 8 mm

in diameter.

Table 1: Physical and mechanical properties of the sand used

Property Value

Specific gravity 2.6

Volume weight (t/m3) 1.73

% Absorption (%) 0.78

Void ratio (%) 33.8

Fineness modulus 2.72



Table 2: Grading of the sand used according to (E.S.S.1109/2008).

Sieve size (mm) 9.5 4.75 2.36 1.18 0.6 0.3 0.16

%Passing used sand 100 98 93 80 51 5 0

%passing (E.S.S.1109/2008) 100 95-100 80-100 50 - 85 25 - 60 5- 30 0-10

Table 3: Physical properties of the coarse aggregates used.

Property Dolomite Crushed

ceramics

Crushed

concrete

Crushed red

brick

Specific gravity (t/m3) 2.64 2.32 2.4 1.66

Absorption (%) 0.8 6.4 3 7.48

Aggregate crushing value (ACV) (%) 17.5 21.25 24.88 40.91

Table 4: Grading of the aggregates used.

Sieve size (mm) 25 19 9.5 4.75 2.36

Limits (% Passing ASTM C-33) 100 90 – 100 20 - 55 0 - 10 0 – 5

Dolomite (% Passing) 100 93 50 5 0

Crushed ceramics (% Passing) 100 91 23 1 0

Crushed concrete (% Passing) 100 94 26 5 0

Crushed red brick (% Passing) 100 100 30 2 1

Figure 1. Sieve analysis of coarse aggregates used.

Mixing water of drinkable clean water, fresh and free from impurities was used for mixing

and curing processes of the tested samples according to the (E.C.P.203/2018) [22].

Two types of admixtures are used; water reducer chemical admixture and pozzolanic

additive. A high-range water-reducing (HRWR) admixture (Sikament R-2004) was used to

improve the workability of concrete without as the additional amount of water as a third-

generation super plasticizer is used as a concrete additive. It meets the requirements of

(ASTM C-494, Types G, and F) [26]. Its main properties are shown in Table (5). Silica fume

is a pozzolanic admixture, which contains silica of about 95% in powder form, was used.

Physical and mechanical properties and chemical are shown in Tables (6) and (7) as provided

by the manufacturer.



Table 5: Technical information of SP (Sikament R-2004) used. (as provided by the manufacturer)

Base Appearance Density Chloride

content

Air

entrainment Compatibility

An aqueous solution

of modified

polycarboxylate

Turbid liquid 1.08±0.005

kg/liter Nil Nil

All types of

Portland cement

Table 6: Physical and mechanical properties of the silica fume used. (as provided by the manufacturer)

Description Value

Structure of material Condensed micro

silica

Color Amber

Density (kg/liter) 0.55–0.70

Chlorine ratio <1

Specific surface area (m2/kg) 15,000

Activity index (%) >95

Particle ratio (<0.045 mm) <40

Table 7: The chemical components results of the silica fume used (as provided by the manufacturer).

Chemical

composition SiO2 Al2O3 Fe2O3 CaO MgO SO3 K2O L.O.I.

Average (%) 95.93 0.52 0.05 0.2 0.18 0.1 0.4 2.9

3.2. Preparing and Testing of Concrete Samples

The proportions of high-strength concrete mix used are chosen based on previous researches

(Burg and Ost, 1994 and Bashandy et al., 2017) [27, 28].

The conducted experimental program is divided into two stages. The first stage was

performed to study the effect of using recycled aggregates compared to natural aggregates to

obtain "RA-HSC" as shown in Fig. (2). The fresh concrete properties of recycled concrete

aggregate are discussed in terms of slump values. The hardened concrete properties of "RA-

HSC "are derived in terms of compressive, splitting tensile, flexural and the bond strengths

(after 7, 28 and 56 days). These experiments have been done to obtain the best values of

compressive strength, tensile splitting strength, flexural strength, and bond strength to cast

reinforced RA-HSC beams.

The second stage was performed to study the behavior of reinforced concrete beams cast

using "RA-HSC" as shown in Fig. (2). The second stage investigates the behavior of high-

strength reinforced concrete beams cast with recycled aggregates under three-point loading

system. The load-deflection curves, first cracking loads and ultimate loads were measured in

those beams.

The main variables in this experimental program are recycled aggregate type (crushed

concrete, crushed ceramic and crushed red brick compared to dolomite as natural coarse

aggregates) and the replacement ratio of coarse aggregate (as 0, 25, 50, 75, and 100% of

natural aggregate used).



Figure 2 The two stages of the experimental program.

The proportion used in this research is chosen based on the research conducted by

Bashandy et al., 2017 [28]. The main variables considered in the mixes are the type of coarse

aggregate (three types of recycled coarse aggregate which are crushed concrete, crushed

ceramic and crushed red brick compared to dolomite as a natural aggregate) and coarse

aggregate replacement ratio (as 0, 25, 50, 75, or 100%).

The Proportion of concrete Mixes used in stage "1" are given in Table (8) and the

proportion of concrete mixes used in "stage (2)" are given in Table (9).

The samples used in this study at the first stage are cubes of dimensions of 100×100×100

mm, cylinders have the dimensions of 100×200 mm, prisms have the dimensions of

100×100×500 mm and cubes have dimensions of 150×150×150 mm are cast to determine the

compressive, the splitting tensile, the flexure, and the bond strengths, respectively as shown in

Fig. 3.

Five reinforced concrete beams cast using optimum mixes obtained from the first stage

were used to conduct the second stage. Beams with dimensions of 100×100×1000 mm. Beam

details and reinforcement is shown in Fig.4

Table 8: Proportion of concrete mixes used for stage "1".

Mix code

Components

C

(kg/m3)

W

(kg/m3)

S.F

(kg/m3)

S.P

(kg/m3)

F.A

(kg/m3)

Coarse aggregate

Coarse type

Weight of

dolomite

(kg/m3)

Weight of

recycled*

(kg/m3)

dolomite 564 158 89 11.5 593 1068 0

CC 25

564 158 89 11.5 593

cru

shed

con

cret

e 801 175

CC 50 534 350

CC 75 267 525

CC 100 0 700

CR 25

564 158 89 11.5 593

cru

shed

cera

mic

801 198

CR 50 534 395

CR 75 267 593

CR 100 0 790

CRB 25

564 158 89 11.5 593

cru

s1h

ed

red

bri

ck 801 214

CRB 50 534 728

CRB 75 267 641

CRB 100 0 855



Table 9: Proportion of reinforced concrete mixes used for stage "2".

a. Compressive strength

test.

b. Indirect tensile

strength test.

c. flexural strength test. d. Bond strength test

Figure 3. Hardened concrete tests.

a. Details of tested beam sample. b. Loading frame and dials used.

Figure 4. Details and reinforcement beam sample.

1.

2 12 mm 2 12 mm

150

mm

100 mm

300 mm

900 mm

1000 mm

7Ø

8 m

m/m

`

2Ø12 mm 2Ø12 mm

p

7Ø8 mm/m`

Mix code C

(kg/ 3)

W

(kg/ 3)

S.F

(kg/ 3)

S.P

(kg/ 3)

F.A

(kg/ 3)

Coarse aggregate

Coarse type

Weight of

dolomite

(kg/m3)

Weight of

recycled

(kg/m3)

C

56

4

15

8

89

11

.5

59

3

Dolomite 1068 0

B 2 crushed ceramic 0 790

B 3 crushed red brick 0 855

B 4 50% crushed

ceramic 534 395

B 5 50% crushed red

brick 534 428



4. TEST RESULTS AND DISCUSSIONS

4.1. Effect of Replacement Ratio

This study aims to study the effect of using recycled materials as coarse aggregate for

concrete (such as crushed concrete, crushed ceramic and crushed red brick) on the main

properties of high-strength concrete.

The fresh concrete properties are discussed due to the effect of the replacement ratio of

coarse aggregates. The fresh concrete properties were recorded in terms of slump values. The

results showed that the slump values decrease as the replacement ratio increase when using

crushed concrete and crushed red bricks compared to using dolomite. When using crushed

ceramics, slump values increased.

Table 10 and Figs. 5 to 28 show the results of hardened concrete properties. Based on test

results, it can be noted that the compressive strength values of tested samples decreased by a

range of about 13.1-67.2% as shown in Figs. 5 to 10. The splitting Tensile strength values of

tested samples decreased by a range of about 17.6-72.0% as shown in Figs. 11 to 16. The

flexure strength values of tested samples decreased by a range of about 24.3-74.6% as shown

in Figs. 17 to 22. The bond strength values of tested samples decreased by a range of about

6.5-71.1% as shown in Figs. 23 to 28.

Generally, cast using crushed ceramics is better than cast using crushed concrete and

crushed red brick as recycled aggregates. That may refer to lower absorption of ceramics as

well as its lower crushing factor, which led to higher strength compared to crushed concrete

and crushed red brick. Results satisfy previous researches conducted by Bashandy et al.,

(2017) [28].

Table 10: The main hardened concrete properties of tested samples. units

Tested samples Compressive

Strength Tensile Strength Flexure Strength Bond Strength

Age 7 28 56 7 28 56 7 28 56 7 28 56

0%-Pure

Dolomit 66.60 71.0 81.3 5.3 5.6 5.8 1.0 1.1 1.1 3.2 3.8 4.3

CC 25% -23.4 -24.1 -24.4 -33.9 -29.9 -21.3 -50.7 -48.7 -37.8 -6.5 -16.2 -12.8

CC 50% -25.4 -25.9 -27.3 -45.9 -41.2 -32.3 -53.0 -51.3 -40.5 -17.7 -25.5 -25.9

CC 75% -27.4 -27.0 -32.8 -47.9 -44.1 -35.9 -57.0 -55.2 -44.6 -31.0 -31.1 -29.2

CC 100% -33.8 -31.2 -35.6 -55.9 -50.7 -43.3 -64.9 -60.5 -48.3 -35.5 -40.4 -35.8

CR 25% -15.9 -13.1 -21.0 -27.9 -24.2 -17.6 -42.0 -29.8 -24.3 -11.0 -14.3 -16.1

CR 50% -20.7 -17.9 -25.5 -31.9 -29.9 -25.0 -51.0 -42.5 -30.5 -18.8 -19.0 -25.1

CR 75% -25.2 -25.4 -29.3 -43.9 -41.2 -35.9 -55.9 -49.7 -37.6 -22.1 -29.2 -27.6

CR 100% -33.3 -29.7 -34.0 -45.9 -46.9 -37.8 -61.8 -57.0 -45.8 -44.4 -47.9 -45.7

CRB 25% -38.7 -36.9 -42.6 -45.9 -46.9 -41.4 -62.2 -60.5 -54.0 -28.8 -33.0 -34.2

CRB 50 % -52.3 -49.4 -52.5 -49.9 -48.8 -46.9 -67.2 -66.3 -56.8 -42.1 -40.4 -44.0

CRB 75 % -64.8 -63.5 -62.0 -70.0 -60.2 -56.1 -71.2 -67.9 -63.2 -51.0 -53.4 -57.2

CRB 100 % -67.2 -66.0 -64.4 -72.0 -71.6 -67.1 -74.6 -69.5 -65.2 -71.1 -66.5 -65.4



Fig. 5. Compressive strength of replacement

ratios after 7day.

Fig. 6. Compressive strength of replacement

ratios after 28day.

Figure 7. Compressive strength of replacement

ratios after 56day.

Figure 8. Compressive strength of crushed

concrete aggregate at deferent replacement

ratios after 7, 28 and 56 day

Figure 9. Comprise strength of crashed

ceramics aggregate at deferent replacement

ratios after 7, 28 and 56 days.

Figure 10. Compressive strength of crashed red

bricks aggregates at deferent replacement ratios

after 7, 28 and 56 days.

Figure 11. Splitting tensile strength of

replacement ratios after 7day.


replacement ratios after 28 day.




replacement ratios after 56day.

Figure 14. Splitting tensile strength of crushed

concrete aggregate at deferent replacement


Figure 15. Splitting tensile strength of crashed

ceramics aggregate at deferent replacement


Figure 16. Splitting tensile strength of crashed

red bricks aggregate at deferent replacement


Figure 17. Flexure strength of replacement

ratios 7days.


ratios 28days day).


ratios 56 days.

Figure 20. Flexure strength of crushed concrete

aggregate at deferent replacement ratios after 7,

28 and 56 days.



Figure 21. Flexure strength of crashed ceramics


28 and 56 days.

Figure 22. Flexure strength of crashed red brick


28 and 56 days.

Figure 23. Bond strength of replacement ratios

7days.


28days.


56days.

Figure 26. Bond strength of crushed concrete


28 and 56 days.

Figure 27. Bond strength of crashed ceramics


28 and 56 days.

Figure 28. bond strength of crashed red bricks

aggregates at deferent replacement ratios after

7, 28 and 56 days.



4.2. Effect of Varying Aggregate Type

As using a replacement ratio of 25%, 50%, 75% and 100%, the effect of varying aggregate

types at different ages on the compressive strength values are shown in Figs. 29 to 32.

Splitting tensile, flexure and bond strengths of different recycled aggregates used compared to

using dolomite are shown in Figs. 33 to 36, 37 to 40 and 41 to 44, respectively. Based on test

results, the strength values of tested samples depends mainly on the aggregate type. Also, the

strength values decrease as increasing replacement ratio of dolomite with recycled aggregate.

Cast using crushed ceramics is better than cast using crushed concrete and crushed red

brick as recycled aggregates. That may because of the variation in aggregate crushing value.

Results agreed with previous researches conducted by Bashandy et al., (2016) (Bashandy,

Safan, & Ellyien, AICSG9, 2016).

Figure 29. Effect of a replacement ratio of 25%

compressive strength.






Compressive strength.


splitting tensile strength.










flexure strength.


flexure strength.


flexure strength.


flexure strength.


bond strength.


bond strength.




bond strength.

Figure 44. Effect of a replacement ratio of

100% bond strength.

4.3. The behavior of reinforced concrete RA-HSC beams

4.3.1. The Initial Cracking and Ultimate Loads.

Effects of using recycled aggregate on the behavior of RA-HSC beams are discussed in this

section. The initial cracking loads and failure load are shown in Fig. 45. The average initial

cracking loads of reinforced recycled aggregate high-strength concrete RA-HSC beams nearly

behave in the same manner of those cast using natural aggregates.

As using recycled aggregates, initial cracking loads of crashed ceramics, crushed concrete,

and crushed red bricks decreased by about 8.33%, 16.66%, and 25%, respectively compared

to using dolomite as natural aggregate. When considering ultimate loads, crashed ceramics,

crushed concrete, and crushed red bricks decreased by about 18.20%, 18.67%, and 19.50%,

respectively compared to using dolomite as natural aggregate.

Based on obtained results, one can note that using crushed ceramics is suggested to be

used as recycled aggregate then using crushed concrete. Also, using crushed red bricks is not

recommended for structural elements. That may because the higher porosity of the crushed

red brick than the porosity of the crushed ceramics. Results agreed with previous researches

conducted by Bashandy et al., (2017) [28].

4.3.2. Ductility Ratio

The ductility of the beam can be expressed based on the deflection of the beam through the

displacement ductility index, μ = Δu/Δy. The ductility ratio can be defined as the ratio of the

element curvature at the ultimate moment to its curvature at yield. According to ACI

Committee 363 [29], the ductility index μ= Δu/Δy, where Δu is beam deflection when a beam

collapsed and Δy is beam deflection when longitudinal reinforcement yielded, according to

(Sung et al., 1989) [30].

The ductility indexes of all beams were listed in Table (11). In the case of high-strength

RA-HSC cast using recycled aggregates, the ductility indexes of control beam cast using

dolomite are lower than RA-HSC cast using recycled aggregate. the ductility indexes

increased by about 18.9%, 12.7%, and 16.01%, respectively compared to that cast using

dolomite as natural aggregate.

From the Table, the experimental deflection ductility index ranges from 4.485 to 5.33. In

general, a high ductility index indicates that a structural member is able to largely deform

prior to failure. Beams with a ductility index up to 2 lacked adequate ductility and cannot

redistribute moment. Beams with a ductility index considered overbearing for adequate

ductility, especially in the areas of seismic design and redistribution of moments [17, 31, 32].



Table 11: Initial cracking load, ultimate loads, and displacement ductility ratios for tested beams.

Beam

Load (kN )

Pcr / Pu

Displacement (mm)

Displacement Ductility

Ratio (∆u/∆y ) Avg.

* Initial

Cracking

Load (Pcr)

Avg. *

Ultimate

Load (Pu)

∆ y ∆ u

D 24 84.6 0.28 0.7 3.02 4.31

CR 22 69.2 0.32 0 .45 2.25 5.0

C C 20 68.8 0.29 0.453 2.31 5.05

CRB 18 68.1 0.26 0.457 2.38 5.20

*The listed values are the average values for each two similar beam samples

4.3.3. Deflection Values

The deflection values were obtained at mid-span (point A) as shown in Fig. 46 and at the

quarter of the span (point B) as shown in Fig. 47. The load-deflection curves of the different

beams indicated that the load is relational to the deflection values at the center and at the

quarter of the lower surface of the tested beam up to the appear of the first crack in RA-HSC.

For tested beams, the load-deflection curves can be classified into three different zones;

the first is the post-cracking zone up to the cracking which continued up to the yielding point,

and the post-yield zone, up to failure. At the initial stage, the stiffness of the beam showed

almost identical histories at a low level of loading and up to the cracking load, as this stage is

controlled by the tensile strength of concrete. The second zone showed a distinct behavior in

the different beams. The slope of the curve in this zone is almost linear and of crucial

importance in design, it is a direct function which represents the effective stiffness of the

beam. Regarding the post-yield zone, the beams showed the ability to withstand a higher load

until failure.

The recorded deflection values for reinforced RA-HSC beams show that the maximum-

recorded deflection value was obtained when cast using crushed ceramics then cast using

crushed concrete followed by those casts using crushed red brick compared to control beams.

That may refer to their stiffness and ductility ratios.

Values were nearly in accordance with Bashandy et al., (2017) [28]. Based on results, cast

using crushed ceramics is suggested for RA-HSC when it is suggested to using recycled

aggregate instead of natural aggregates.

4.3.4. Strain Values

The results of tensile strain values of tested beams are shown in Fig. 48. It also shows that the

modulus of elasticity of ceramics is higher than crushed concrete, and crushed red brick by

about 9.09%, 8.25%, and 4.76%, respectively. Based on that, one can note that using crushed

ceramics is better in the range of this study.

When studying the modulus of toughness, results show that using crushed ceramics is best

compared to using crushed concrete and crushed red bricks by about 26.66%, 27.08, and

33.7%, respectively compared to using dolomite.

That may because of the crushing factor as well as high porosity of the crushed red brick

compared to that of the crushed ceramics. That may comparable with research conducted on

RA-HSC by Bashandy et al., (2017) [28].

4.3.5. Crack Pattern

The crack patterns of all tested beams were recorded then they were illustrated at each load

increment up to failure. After that, they were photographed.

In general, most tested beams in this investigation are failed in flexure. The number of

cracks in RA-HSC beams increases during loading stages. Figure 49 shows the crack pattern



for the control beam cast using dolomite. The crack pattern of RA-HSC beams indicated that

the failure modes of all tested beams are a flexural failure and flexure-shear failure. The width

of the cracks is nearly equal. The number of cracks when using crushed ceramics is higher

than using crushed concrete, crushed red bricks, and control beam. The number of cracks of

RA-HSC beams cast using crushed red bricks is higher than RA-HSC beams cast using

crushed ceramics due to the higher ductility of beams cast using crushed ceramics.

Figure 45. Initial cracking loads and ultimate

loads for tested beams.

Figure 46. Load-deflection values for RA-HSC

beam mid-span "point A".

Figure 47. Load-deflection values for RA-HSC

beam mid-span "B". Figure 48. Load-tensile strain values for RA-

HSC beams.

Figure 49. The crack pattern for beam samples "crashed ceramics", " crushed concrete " and " crushed

red brick " of RA-HSC tested beams.

5. CONCLUSIONS

Based on the experimental results, the following conclusions can be drawn as follow:

Recycled aggregates can be used efficiently compared to natural aggregate to obtain high-

strength concrete cast using recycled aggregates for structural concrete with medium loads.

As increasing the recycled aggregate replacement ratio, the strength of RA-HSC decreases.



The strength of the RA-HSC cast using dolomite is higher than that cast using crushed

concrete, crushed ceramics and crashed red bricks as coarse aggregates by a range of about

7.35-13.1%.

The recorded deflection values for reinforced RA-HSC beams at points "A" and "B" (midpoint

and quarter of the beams, respectively) showed that the maximum-recorded deflection value

obtained when cast using crushed ceramics than cast using crushed concrete and crushed red

bricks.

The recorded cracking loads and ultimate load values for reinforced RA-HSC beams are

nearly the same range for the three aggregate types used but RA-HSC beam cast using crushed

red bricks is lower than other both.

The crack pattern of RA-HSC beams showed that the failure modes of all tested beams are the

flexural failure and flexure-shear failure.

The number of cracks in the case of RA-HSC cast using crushed red bricks is higher than that

when using crushed concrete, crushed ceramics, and control beam.

Finally, recycled aggregate high-strength concrete can be obtained by using crushed

concrete or crushed ceramics. Some recycled aggregate is efficient in structural elements

when choosing carefully from demolished waste materials. To obtain better workability with

sufficient strengths, super plasticizers and pozzolanic additives are recommended. This type

of concrete can be applied to cast prefabricated non-structural concrete sections or elements.

AKNOLOGEMENT

We avail this opportunity to express our deep sense of gratitude and wholehearted thanks to

the laboratory of Properties and Testing of Materials at the Faculty of Engineering, Menoufia

University to present and complete this work. This research did not receive any specific grant

from funding agencies in the public, commercial, or not-for-profit sectors.

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Documents

RECYCLED AGGREGATE HIGH-STRENGTH CONCRETE · Pervious Concrete, 2017; Rattanachu, Tangchirapat, & Jaturapitakkul, 2019) ... steel (steel 52) of 16 mm diameter and 16 cm high rebars