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CCS by the

predictive equations for each experiment.

704

B. Abolpour et al.

Fig. 5 The calculated Error of the predicted IST by the

predictive equations for each experiment.

Variation in Fe2O3 causes to vary CCS as a curve with a

minimum at zero level when other factors are stabilized at

low level and have a descending nonlinear curve when other

factors are stabilized at high level. Increasing of Fe2O3

decreases IST linearly in both cases, i.e. other factors are stabilized in their high or low level. This variation has been shown

in Fig. 12.

Increasing of CaO causes a nonlinear decrease in the CCS

when other factors are in their low level. The CCS varies as

a curve with a maximum at level 0.6 of the CaO, when other

factors are in their high level. Increasing of CaO causes a negligible linear increase in the IST in both cases when other factors are in their high or low level. This behavior of the concrete

has been shown in Fig. 13.

Fig. 14 shows that increasing of SO3 causes an increase or

decrease in the CCS linearly when other factors are in their

high or low level, respectively. This increment has a more complex effect on the IST. Increasing of this factor causes a nonlinear decrease in the IST when other factors are in their

high level. This Figure shows that variation in the SO3 value

has no important effect on the IST when other factors are in

their low level.

As can be observed from Fig. 15 variation in Blaine has no

signiﬁcant effect on the CCS and IST when the concrete composition is stabilized at their low level. When composition of

Fig. 6

The effects of SiO2 on the CCS and IST when other factors are in their low or high level.

Fig. 7

The effects of Al2O3 on the CCS and IST when other factors are in their low or high level.

Statistical analysis of the effective factors on the main properties of the concrete

Fig. 8

Fig. 9

Fig. 10

The effects of Na2O on the CCS and IST when other factors are in their low or high level.

The effects of Cl on the CCS and IST when other factors are in their low or high level.

The effects of MgO on the CCS and IST when other factors are in their low or high level.

705

706

B. Abolpour et al.

Fig. 11

Fig. 12

Fig. 13

The effects of K2O on the CCS and IST when other factors are in their low or high level.

The effects of Fe2O3 on the CCS and IST when other factors are in their low or high level.

The effect of CaO on the CCS and IST when other factors are in their low or high level.

Statistical analysis of the effective factors on the main properties of the concrete

Fig. 14

Fig. 15

Table 3

xSiO2

xCaO

xMgO

xNa2 O

xK2 O

xSO3

xCl

xBlaine

The effects of Blaine on the CCS and IST when other factors are in their low or high level.

Level of other ﬁxed factors

xSiO2

xFe2 O3

The effects of SO3 on the CCS and IST when other factors are in their low or high level.

The effect of factors on the CCS and IST.

Considered factor

xAl2 O3

707

+

À

+

À

+

À

+

À

+

À

+

À

+

À

+

À

+

À

xAl2 O3

xFe2 O3

xCaO

xMgO

xNa2 O

xK2 O

xSO3

xCl

xBlaine

+

À

+

À

+

À

+

À

+

À

+

À

+

À

+

À

+

À

+

À

+

À

+

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À

+

À

+

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+

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+

À

+

À

+

À

+

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+

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+

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+

À

+

À

+

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+

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+

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+

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+

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+

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+

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+

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+

À

+

À

+

À

+

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+

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+

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+

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+

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+

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+

À

+

À

+

À

Eﬀect on the CCS

Eﬀect on the IST

Decrease

Decrease

Increase

Decrease

Decrease

Complex

Complex

Decrease

Decrease

Decrease

Increase

Decrease

Increase

Increase

Increase

Decrease

Increase

Decrease

Increase

Complex

Complex

Complex

Decrease

Decrease

Decrease

Decrease

Increase

Increase

Complex

Complex

Decrease

Decrease

Decrease

Decrease

Decrease

Complex

Decrease

Decrease

Complex

Complex

708

the concrete is stabilized at high level, increasing of Blaine will

increase CCS by an ascending curve and changes IST through

a curve with a maximum at about level 0.2.

The setting and hardening of cement are the result of chemical reactions between cement and water (i.e. hydration). The

hydration reactions starts directly after adding water to cement

and in the ﬁrst 30 min a part of C3A and sulfate carrier is dissolved and results more strength in concrete. This very fast

process produces heat during the initial period of hydration.

C3A phase sets quickly with evolution of heat and enhances

strength of the silicates. Coarse cements with low speciﬁc surface area usually take longer times to set due to the sluggish

hydration kinetics. On the other hand, high content of C3A

speeds up the reactions resulting in relatively short setting

times. Increasing the amount of C3A causes a signiﬁcant

increase in the CCS and also decreases the IST as Eqs. (11)

and (12).

Conclusions

In this study, the effects of various factors on the concrete

compressive strength and also initial setting time have been

investigated. The effective factors are weight percent of the

SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, Cl, SO3 of the

raw materials and the Blaine of cement particles. Interactions

of these factors with probability of a 97.5% conﬁdence have

been obtained using analysis of variance. Then the equations

have been obtained through regression to predict the concrete

compressive strength and initial setting time as function of the

mentioned factors. The mean of the calculated absolute Error

for predicted values of CCS and IST was 1.92% and 4.3%,

respectively for regression equations. Attention to the

coefﬁcients of these regression equations shows that the

quadruplet combinations of xSiO2 Á xMgO Á xSO3 Á xBlaine and

xSiO2 Á xSO3 Á xK2 O Á xBlaine have the most positive and negative

effect on the CCS, respectively. Also the quadruplet combinations of xSiO2 Á xMgO Á xNa2 O Á xK2 O and xSiO2 Á xNa2 O Á x2K2 O have

the most positive (increasing) and negative (reducing) effect

on the IST of concrete, respectively. Also, simple and applicable formulas have been developed using the genetic algorithm

to predict these parameters. The accuracy of these predictive

equations is completely acceptable. They have a less than

6% absolute mean error. Finally the effect of each factor has

been investigated when other factors are in their low or high

level and summary of the results has been presented in Table 3.

Conﬂict of interest

The authors have declared no conﬂict of interest.

Compliance with Ethics Requirements

This article does not contain any studies with human or animal

subjects.

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