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J. Cent. South Univ. Technol. (2007)s1−0409−05

DOI: 10.1007/s11771−007−0294−7

Frost resistance of recycled concrete

QIN Yin-hui(覃银辉)1, DENG Shou-chang(邓寿昌)1, ZHANG Xue-bing(张学兵)2

(1. College of Civil Engineering and Mechanics, Central South University of Forestry and Technology,

Changsha 410004, China;

2. Department of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China)

Abstract: The frostbite situation of recycled concrete suffered one-time freezing was analyzed, and was then compared with that of 

the normal concrete. In order to improve the frost resistance of recycled concrete, antifreeze was used and good effect was obtained.

The results show that the frost resistance of recycled concrete is inferior to that of recycled concrete. Differences exist in the

microstructures of the recycled concrete and normal one, which makes the decrease of frost resistance. Antifreeze can improve the

microstructure of recycled concrete, so the frost resistance of it is improved as well.

Key words: recycled concrete; anti-frozen performance; antifreeze; freezing-thawing cycle; compressive strength

1 Introduction

The use of recycled aggregate(RA) for manufacture

of concrete started as far back as the end of World War 

Ⅱ. Rubble obtained from demolition of concrete road

 pavement, runways, foundations and building structures

has been reused successfully around the world. Duringthe Post World War Ⅱ era in the United States, rubble

from demolished concrete pavement was crushed and

reused as aggregate in unstablished base course of a

number of road construction projects. And, in one form

or another, concrete has been recycled successfully in

other countries such as China, France, Canada to

mention a far. The reuse of old concrete not only

conserves the finite raw materials, but also reduces

energy consumption and therefore the overall

construction costs.

Many research studies were carried out on the use

of RA in concrete in an attempt to understand the properties of RA concrete, however, most of the studies

are focused on the mechanical properties of the resulting

concrete. Limited work carried out on the understanding

of frost resistance of recycled concrete[1−3].

The frost resistance of recycled concrete consists of 

the following two aspects: 1) the thawing and freezing

resistance of fully hardening concrete; 2) the frost of 

recycled concrete when freezed in the early period. The

latter is universal and the main danger in winter working.

The focus of this paper is to study how minus

temperature affect the recycled concrete and obtain thelaw, and is then compared with ordinary concrete. At the

same time, improved its anti-frozen performance through

adding antifreeze, analyzed the reason how did antifreeze

influence anti-frozen performance of recycled concrete.

2 Experimental

2.1 Raw material

The main raw materials is as follows. Cement was32.5R portland cement produced by Xiangxiang Cement

Factory in Hunan Province.

Fine stuff was natural sand of Xiang River in Hunan

Province.

Coarse aggregate was recycled aggregate obtained

from concrete specimen with different grades in

Examining Center of Xiangtan University.

Water was running water.

The properties of recycled concrete is shown in

Table 1.

The formula of additional water content is shown as [4] 

⎪⎪⎪⎪

⎩

⎪⎪⎪⎪

⎨

⎧

×+

−−

=∆

−

RCA

RCA4

RCA

5021.0

)1034102.118993.1(

))8204.0exp(93617.069005.2(

m

m

mt 

W   

where mRCA is the quality of recycled aggregate.

2.2 Frost temperature of recycled concreteThe frost essence of concrete is the frost of water in

Foundation item: Project(k042013-12) supported by the Science and Technology Office of Changsha City, China

Corresponding author: QIN Yin-hui; Tel: +86-731-5094170; E-mail: qinyinhui2003@126.com

(0≤t ≤60 min)

(60 min≤t ≤24 h)

(t ≤24 h)

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J. Cent. South Univ. Technol. 2007, 14(s1)410

Table 1 Properties of recycled concrete

Design

strength

grade

W/C1) Cement

content/(kg·m−3)

Recycled

aggregate/(kg·m−3)

 Natural

sand/(kg·m−3)

Additional

water content,

∆W  

Mixture ratio2) 

C20 0.55 340 1 190 645 25.59 1 1.897 3.5 0.55

C30 0.46 380 1 220 575 26.23 1 1.513 3.211 0.46

C40 0.37 475 1 191 511 25.61 1 1.076 2.507 0.371) Mass ratio of water to cerment; 2) Mass ratio of cerment to sand, aggregate and water.

it. When water is frozen, it becomes solid state from

fluid state, the volumes expands 9% likely which damage

the concrete quality. When ordinary concrete is put at 0

℃, most water exists between cement particles and isn’t

restrained essentially. Because of this, also the strength

of recycled concrete at 0 ℃ was studied. The result is

listed in Fig.1.

Fig.1 Time—strength curve under different curing conditions

From the experiment result above, the strength of 

recycled concrete is increased after freezed for 3 d, but

the speed is very slow, which indicates that the recycled

concrete is not iced over, but hydration speed is very

slow. In another word, the freezing point of water in

recycled concrete is also below 0℃.

In order to know the frozen temperature of recycled

concrete, put recycled concrete specimen in low-

greenhouse at −5 ,℃  −10 after precuring for 0,℃ 3, 7,

10 and 14 d in standard condition, put them out after 3 d,

a group of specimen was tested immediately, another 

group of specimen was cured in standard condition for 

28 d continually, tested them when total curing age was

31 d, strength—time curves are shown in Fig.2.

From Fig.2, the strength of recycled concrete curing

for 28 d was the same approximately after frozen at −5

, −10℃ separately. For recycled concrete without℃

 precuring in standard condition, their strength wasdamaged greatly, in other words, recycled concrete has

already suffered freezing injury at −5 ℃, the frozen

temperature of recycled concrete is −5℃ about.

2.3 Frozen rule of recycled concrete

Put recycled concrete specimen in low-greenhouse

in which control temperature was −(10±1) ,℃ the

strength grade of concrete was C30 and C40, 3 d later, a

group of specimen was tested immediately, another 

group of specimen was cured in standard condition for 

28 d continually, tested them when total curing age was

31 d, the result is shown in Fig.3.

Fig.2 Time—strength curve at different temperatures 

Fig.3 time—strength curve at different curing days of 

recycled concrete

From Fig.3, precuring days are advantageous to

recycled concrete either the melting strength or the finalstrength curing for 28 d. But recycled concrete hasn’t

anti-frozen threshold strength, there is frostbite for 

recycled concrete frozen after precuring for 10 d in

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QIN Yin-hui, et al: Frost resistance of recycled concrete 411

standard condition. Compared with normal concrete (see

Fig.4[5]

), if normal concrete is precured for 1.5 d before

frozen, it will not suffer frostbite. As a result, the

anti-frozen performance of recycled concrete is inferior 

to that of normal concrete.

Fig.4 Time—strength curve at different curing days of 

normal concrete

2.4 Anti-frozen performance of recycled concrete with

antifreeze 

In order to improve the anti-frozen performance of 

recycled concrete, the means of adding admixture was

used. In the winter poor weather condition in the

northern area of our country, application of antifreeze isextremely widespread, and the dosage is also extremely

great, even it passes 5% limiting value prescribed by

international[6]. In the text, the durability of recycled

concrete with antifreeze was studied, the antifreeze was

YJ-4 antifreeze produced by Beijing New Vision

Building Construction Technology Co., Ltd, it’s superior 

mixing dosage is 1% of cement content. And its other 

technical index is shown in Table 2.

Antifreeze is advantageous to the anti-frozen

 performance of concrete, it can improve the strength of 

concrete curing at minus temperature, but if antifreeze is

applied to concrete curing in standard condition, the

result is shown in Table 3.

It can be seen from Table 3 that antifreeze does no

influence on the strength of recycled concrete curing in

standard condition, even the strength is higher than the

design strength of recycled concrete. This is because

antifreeze has the ability of water-reducing, so the factual

W/C of recycled concrete is lower than the design W/C

which will make the factual strength higher than the

design strength.

2.5 Strength development regular of recycled

concrete with antifreeze at minus temperature 

Put the shaped concrete limestone in the low

greenhouse in which the control temperature was −(10±1)℃, the designing compressive strength of recycled

concrete was C30, C40 separately. Tested them at

different curing ages, the time—strength curves of C30

and C40 are shown in Fig.5.

Fig.5 Time—strength curve at different curing days of 

recycled concrete 

Table 2 Technical index of YJ-4 antifreeze (No rust for reinforced bar)

Setting time gap of concrete Compressive strength ratioWater-

reducing

ratio

Air 

content

Bleeding

ratio Initial setting Final setting)17− R    R28 

)2287+−

 R  

Strength loss ratio

fter 50 freezing-

thawing cycles

≥12% ≥2.5% ≤90% 0−120 min 0−120 min ≥12% ≥100% ≤120%≤100%

1) Cured at minus temperature for 7 d; 2) Cured at standard condition for 28 d after cured at minus temperature for 7 d.

Table 3 Strength at age of 28 d of recycled concrete curing in standard condition with antifreeze

Design strength

gradeW/C1) 

Cement content

/(kg·m−3)

Recycled aggregate

/(kg·m−3)

 Natural sand/

(kg·m−3)

Additional

water, ∆W 

Compressive strength cured

for 28d/MPa

C20 0.55 340 1 190 645 25.59 22.49

C30 0.46 380 1 220 575 26.23 33.98

C40 0.37 475 1 191 511 25.61 46.51

1) Content ratio of water to cerment.

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J. Cent. South Univ. Technol. 2007, 14(s1)412

Regardless of the recycled concrete of C30 and C40,

the strength was developed continually even if the curing

temperature was −(10± 1)℃. When antifreeze was

adding, the hydration of cement carried on, but the speed

of cement hydration has direct ratio with curing

temperature, in other words, the higher curing

temperature, the faster hydration speed, so the hydration

speed of cement is very low at an minus temperature.

The strength develops slowly and there is no turning

 point in strength—time curve, strength development is

steady.

2.6 Freezing-thawing ability of recycled concrete

Freezing-thawing destruction was the main part of 

concrete frostbite[7]. To study the freezing-thawing

resistance ability of recycled concrete, cured the shaped

recycled concrete specimen in standard condition for 28d, saturated specimen with water, then tested them with

freezing-thawing cycle, the method of freezing-thawing

cycled was freezing slowly and melting slowly. The

results are listed in Table 4.

Table 4 Resistance ability to freezing-thawing cycle

Design

strength

grade

Times of 

freezing-

thawing

cycle

Mass

loss/%

Strength

(without

antifreeze/

MPa

Strength

(with

antifreeze)/

MPa

C20 25 0 15.53 17.56C30 50 0 28.89 34.12

C40 50 0 42.00 46.89

There is no any mass loss of recycled concrete

enduring freezing-thawing cycle many times. For 

recycled concrete without antifreeze, the strength is

damaged to a certain degree, especially for concrete C20,

its strength loss is quite obvious after 25 freezing-

thawing cycles. But for recycled concrete with antifreeze,

the strength does not change, just for recycled concrete

C20, the strength drops slightly. From the above analysis,it can be concluded that the recycled concrete C20 is not

applicable in cold area, the lowest design strength grade

of recycled concrete for freezing-thawing cycle is C30.

3 Comparison and analysis 

Compared recycled concrete with normal one, the

two have the same chemical composition, the reason why

the two have different anti-frozen abilities is that they

have different microstructures.

Figs.6 and 7 demonstrate that the interface of aggregate and cement mortar is loose relatively for 

concrete, and the thickness of interface area is different

at different places. For recycled concrete, the interface is

formatted by many loose pellet, and the interface area

has porous nature because of its high porosity percentage

of void, the farther to interface, the less of hole. At the

same time, recycled concrete has lower density and

wider interface compared with normal concrete. Interfaceis the weak link for anti-frozen

[9], because of the

existence of interface, concrete can’t form a powerful

whole, the structure integrity is destroyed. Once the two

interfaces (the one is natural aggregate-old mortar 

interface, and the other is old mortar-new mortar 

interface) of recycled concrete are frozen, the whole

structure of it will loose correspondingly, the final

strength will damage correspondingly.

Fig.6 Microstructure of recycled concrete 

Fig.7 Microstructure of normal concrete 

Adding antifreeze can improve the anti-frozen

 performance of recycled concrete greatly. The reason is

that YJ-4 antifreeze doesn’t depend on reducing freezing

 point of water to achieve its anti-frozen goal, but depend

on importing air bubble, reducing water content and

improving early strength of concrete to achieve it. It can

not react with cement, but changes the microstructure of 

recycled concrete.

Compared Fig.8 with Fig.9, it can be seen that

recycled concrete without antifreeze has large pore and

less density which is disadvantageous to seepage

resistance of concrete and influence the concrete performance. But from the microstructure of recycled

concrete with antifreeze, antifreeze makes the concrete

have the high density and decrease the size of the pore of 

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QIN Yin-hui, et al: Frost resistance of recycled concrete 413

recycled concrete which makes the interface reasonable.

On the other hand, less pore between the concrete

 particle can make concrete seepage ability increase, the

strength and durability of recycled concrete improve as

well.

Fig.8 Microstructure of recycled concrete without antifreeze

Fig.9 Microstructure of recycled concrete with antifreeze

4 Conclusions

Recycled concrete is different from normal concrete

in microstructure, so their anti-frozen performance is

also different. Concluded from the experiments above,

 just like the normal concrete, the frozen temperature of 

recycled concrete is also below 0 ℃, precuring time is

advantageous to the anti-frozen performance of recycled

concrete, the longer percuring time, the higher strength

of recycled concrete. In order to improve the anti-frozen

 performance of recycled concrete, antifreeze was used,

anti-frozen performance is improved greatly after adding

antifreeze, the strength develops continually at minus

temperature, once curing in standard condition, it is

higher than the design strength, and the ability to

resistant freezing-thawing cycled is also enhanced. Sorecycled concrete can apply in winter environment if 

adding proper admixture.

References

[1]  SAGOE-CRENSIL K K. Performance of concrete made with

commercially produced coarse recycled concrete aggregate [J].

Cement and Concrete Research, 2001, 31: 707−712.

[2]  DORUNSOGO F T. Performance of recycled concrete monitored by

durability indexes [J]. Cement and Concrete Research, 2002, 32:

179−185.

[3]  ZAHARIEVA R. Frost resistance of recycled aggregate concrete [J].

Cement and Concrete Research, 2004, 34: 1927−1982.[4]  ZHANG Xue-bing, DENG Shou-chang. Experimental research on

unit water use in recycled concrete [J]. Concrete, 2004(10): 38−40,

64. (in Chinese)

[5]  XIANG Zhu-xing. Study on early frost resistance of concrete [J].

Architectural Technology, 1992(10): 578−583. (in Chinese)

[6]  XIANG Zhu-xing. Study on durability of concrete with antifreeze [J].

Architectural Technology, 1982(10): 19−20, 31. (in Chinese)

[7]  LI Tian-yuan. Preliminary Study on Anti-frozen Performance of 

Concrete [D]. Changsha: Hunan University, 1984. (in Chinese)

(Edited by LONG Huai-zhong)