Abstraction
Three accelerated bring arounding trial methods are adopted in this survey. These are warm H2O, autogenic and proposed trial methods. The consequences of this survey has shown good correlativity between the accelerated strength particularly for the proposal bring arounding trial method and normal strength utilizing normal bring arounding method at ages 7 and 28 twenty-four hours for the five different chemical composing of cement with different H2O to cement ratios equal to 0.45, 0.55, 0.65 and 0.75. Linear and nonlinear arrested development analysis show high correlativity for the different types of the accelerated hardening methods with coefficient of correlativity ( R2 ) more than 0.9.
1.0 Introduction
Accelerated hardening of concrete is used extensively in the production of the precast concrete structural members such as pipes and prestressed merchandises are used to acquire a high early strength sufficiency to reassign the prestress force to concrete and raise the precast component. The credence of concrete in the site depends on the 28 yearss strength, at that clip, normally a considerable concrete work has been done on the first casting which makes the redress for the weak concrete is really hard and complicated, besides if it was excessively strong, the mix proportion used will be wasteful. Therefore, the production control with 28 yearss hold is non reasonable [ Neville ( 1995 ) ] . Concrete specimens are exposed to accelerated bring arounding conditions that permit the specimens to develop a important part of their ultimate strength within a clip period of ( 1-day to 2-day depends on the method of bring arounding rhythm ) .The accelerated curing process provides at the earliest practical clip, an indicant of the possible strength of a specific concrete mixture.
The accelerated strength trials used in the experimental work is presented below:
1.1 Warm Water Method.
This trial method is applied harmonizing to the ASTM C684-99 ( method A ) and BS 1881: Part 112:1983
1.2 Autogenous Method.
This trial method is applied harmonizing to the ASTM C 684-99 ( method C ) except that the satisfactory containers are unavailable in the lab, and the mean temperature lab trial is about 30 & A ; deg ; C.
1.3 Proposed Method
The rhythm includes the hold period, the temperature rise period, and the period of the hardening at the maximal temperature. It is designed to enable a turnover of one batch per one twenty-four hours, leting for chilling, demolding, cleansing, oiling, and piecing casts for the following batch. Then regular hexahedrons are tested. The curing rhythm is adopted below after projecting the concrete in 100mm regular hexahedron cast in the normal manner. The casts are covered with a top home base in good contact with the top face of the cast:
1. Delay period ( Presteaming period ) : The bring arounding rhythm is besides designed to minimise the destructive procedures in the construction of the accelerated -cured concrete by utilizing an equal hold period and a medium rate of temperature rise. Mamillian ( 1982 ) as reported by Al Qassab ( 2006 ) concluded that the loss in the 28-day strength can be reached 40 % for the steam cured concrete at 75 & A ; deg ; C with no hold period.
Consequences obtained by Lewis ( 1968 ) utilizing 100mm regular hexahedron specimens show that the optimal initial adulthood prior to the steam hardening and matching to maximal strength is about 80EsC. A survey done by Al Rawi ( 1974 ) concludes that the usage of a short hold period 1hr resulted in an appreciable in a1-day accelerated bring arounding plus 27-day normal bring arounding compressive strength of concrete, as compared with the strength obtained when 5 to 11-hr hold periods are used. Therefore, such short hold periods should non be used unless the big enlargement of the liquid stage is counteracted by some agencies such as closed stiff casts. Assuming the temperature of the mix prior to steam hardening was 20EsC, the optimal hold period will be 4-hr. Therefore, a hold period of 4-hr is used.
2. Rate of temperature rise: After a delay period of 4-hr, the casts are placed in a H2O armored combat vehicle at a temperature of 20EsC, the H2O temperature is raised to 70EsC±4EsC in approximately 2-hr, with rate of temperature rise about 25EsC per hr. As a practical method operation, a maximal rate of temperature rise is 22EsC to 33EsC [ ACI 517.2R-80 ] .
3. Maximal curing temperature and continuance: Several research workers have found that the most effectual consequences are obtained when the concrete is cured at a temperature between 66EsC and 82EsC, lower temperature are advantageous if steaming is continued for more than 24-hr [ ACI 517.2R-80 ] .
The temperature is chosen 70EsC±4EsC for 16-hr which is in assurance by the consequences of Al-Rawi ( 1977 ) for pick of healed concrete. He besides finds that there is no such difference between 70EsC and 90EsC. For 80EsC and above the hydration of the C3A will organize the three-dimensional C3AH6 stage, alternatively of hexangular stages. High steam – hardening temperatures ever require longer presteaming periods. Early strengths are higher, but 28-day strengths are by and large lower with high steaming temperatures [ ACI 517.2R-80 ] as explained above.
The coveted maximal temperature within the enclosure and the concrete is about 66EsC. It has been shown that the strength will non increase significantly if the maximal steam temperature is raised from 66EsC to 79EsC, and the steam temperatures above 82EsC should be avoided because of the otiose energy and possible decrease in ultimate concrete strength [ Kosmatka and Panarese ( 1994 ) ] .
4. Cooling period: Rapid alterations during the cooling period should be avoided so as to cut down the snap of the members from the effects of restraints [ ACI 517.2R-80 ] . The temperature of the H2O armored combat vehicle dropped about to 21EsC within about 2-hr.
This 24-hr hardening rhythm is shown in the Figure ( 1 ) and Figure ( 2 ) for typical idealised atmospheric steam-curing rhythm for pipe [ ACI 517.2R-80 ] . The casts so are removed from H2O armored combat vehicle and the regular hexahedrons are tested in half an hr.
Fig. 1: Proposed accelerated bring arounding rhythm.
Fig. 2: Typical idealised atmospheric steam-curing rhythm for pipe- ACI 517.2R-80.
2.0 EXPERIMENTAL Plan
2.1 Materials
2.1.1 Cement
Five different chemical composing Portland cements, conforming to the IQS 5/1984 were used. Three ordinary Portland cement ( Iraqi, Lebanese and Turkish ) and two sulphate defying Portland cement ( Lebanese and Kuwaiti ) .
The chemical analysis and physical belongingss of these cements are listed in Tables 1 and 2 severally.
Table 1: Chemical composing of cement used
Oxide Content %
Iraki
( OPC )
Turkish
( OPC )
Lebanese
( OPC )
Lebanese
( SRPC )
Kuwaiti
( SRPC )
SiO2
20.49
20.63
20.4
21.25
19.65
Al2O3
4.56
4.77
4.94
3.10
3.78
Fe2O3
4.35
4.64
3.84
4.00
3.89
CaO
61.82
61.89
60.34
59.08
63.93
SO3
2.31
2.14
2.68
2.11
2.30
MgO
2.59
2.13
4.58
2.02
3.30
L.O.I
2.23
1.47
2.35
3.10
2.45
I.R
1.12
1.50
0.62
1.74
1.56
L.S.F
0.92
0.904
0.89
0.86
0.85
Compound Composition ( Bogue` s Equation )
C3S
52.44
50.32
44.22
46.39
72.76
C2S
19.27
21.27
25.21
26.01
1.53
C3A
4.73
4.80
6.60
1.45
3.44
C4AF
13.22
14.10
11.67
12.16
11.82
Chemical and Physical trials are conducted by the Central Organization for Standardization and Quality Control, Ministry of Planing
Table 2: Physical belongingss of cements used
Properties
Iraki
( OPC )
Turkish
( OPC )
Lebanese
( OPC )
Lebanese
( SRPC )
Kuwaiti
( SRPC )
Specific surface ( Air permeability trial ) , m2/kg
340
380
340
360
350
Autoclave enlargement, %
0.01
0.04
0.07
0.04
0.04
Puting clip ( vicate setup ) ,
a. Initial – hour: min
Final – hour: min
2:30
4:0
3:35
4:35
3:30
5:30
1:40
4:40
2:25
4:30
Compressive strength MPa ( N/mm2 ) :
3-days
7-days
30.96
35.71
32.12
33.99
27.99
29.6
30.5
31.5
31.5
32.5
Chemical and Physical trials are conducted by the Central Organization for Standardization and Quality Control, Ministry of Planing
L.O.I: Loss on ignition, I.R: Insoluble residue, L.S.F: lime impregnation factor.
2.1.2 Fine Aggregate
All right sum from Al-Ukhaider part was used. The rating satisfy the Iraqi specification IQS 45/1984 and failed in the zone two. The sieve analysis is shown in Table 3. The sulphate content and the physical belongingss of all right sum are shown in Table 4.
2.1.3 Coarse Aggregate
The maximal size of 20mm of natural harsh sum from Al-Niba`ee prey ( crushed ) was used. The aggregative satisfies the Iraqi specification IQS 45/1984. The sieve analysis for the crushed sum is shown in Table 5. The sulphate content and the physical belongingss are shown in Table 6.
Table 3: Sieves analysis of all right sum.
Sieve size
% passing by weight
Limits of IQS 45/1984 ( Zone 2 )
10mm
100
100
4.75mm
96
90-100
2.36mm
82
75-100
1.18mm
69
55-90
600?m
47
35-59
300?m
21
8-30
150?m
5
0-10
Fineness modulus = 2.8
Table 4: Physicals belongingss and sulfate content of all right sum used in experimental work.
Properties
consequences
Specification
IQS 45/1984
Rating zone
Zone 2
IQS 45/1984
Fineness modulus
2.8
ASTM C125-03
Specific gravitation
2.6
ASTM C128-01
Absorption, %
1.5
ASTM C128-01
Moisture content, %
0.3
ASTM C566-97
Passing sieve size 75?m %
2.2
IQS No. 45-84
Max. 5 % for natural all right sum
Sulfate content ( SO3 ) , %
0.2
IQS No. 33-89
Max. 0.5 %
Trials are carried out in the Material Laboratory of the College of Engineering-Baghdad University
Table 5: Sieves analysis of harsh sum with 20mm maximal size.
Sieve size
% passing by weight
Limits of IQS 45/1984
37.5mm
100
100
20mm
96
95-100
10mm
41
30-60
5mm
2
0-10
Table 6: Physical belongingss and sulfate content of harsh sum with 20mm maximal size.
Properties
consequences
Specification
IQS 45/1984
Dry rodded unit weight, kg/m3
1680
ASTM 29/C29M/97
—
Specific gravitation ( Saturated surface prohibitionist )
2.67
ASTM C127-01
—
Absorption, %
0.8
ASTM C127-01
—
Moisture content, %
0.2
ASTM C566-97
—
Passing sieve size 75?m, %
0.9
IQS No. 45-84
Max. 3 % for natural coarse sum
Sulfate content ( SO3 ) , %
0.02
IQS No. 33-89
Max. 0.1 %
Trials are carried out in the Material Laboratory of the College of Engineering-Baghdad University
2.1.4 Mixing Water
Ordinary H2O is used for blending and hardening of the concrete, harmonizing to the IQS 1703/1992. The PH equal to 7.4 and the TDS ( entire dissolve solids means the amount of all the minerals, metals, salts dissolved in the H2O ) equal to 389ppm.
2.2 Mix Proportion
The ACI 211.1-91 mix design method recommended specifies both the upper limit and minimal value for the slack which is based on the type of building. So, it is decided to choose ( 75-100 ) millimeter as a scope for slack in all the experimental work.
In this method, the needed water/cement ratio is determined by the compressive strength and the lastingness demand. In the present work, four water/cement ratios are used ( 0.45, 0.55, 0.65 and 0.75 ) by weight as an effort to utilize low, medium and high W/C ratios. The mix proportions and accommodation to maintain the effectual W/C invariable used in fixing the trial specimens harmonizing to ACI 211.1-91 method is presented below in Table ( 7 ) .
Table ( 7 ) : The mix proportions used in fixing the trial specimens harmonizing to ACI 211.1-91 method
W/C
Water
( kg/m3 )
Cement ( kg/m3 )
All right sum ( kg/m3 )
Coarse sum
( kg/m3 )
0.45*
203
451
639
1036
0.45**
209
464
628
1036
0.55
203
369
706
1036
0.65
203
312
754
1036
0.75
203
270
788
1036
* Trial batch accommodation ( before adjusting )
** After seting
2.3 Mixing, Casting, Curing of Concrete
The cement was passed through the screen No.14 ( 1.18mm ) and the balls were removed. The commixture of ingredients is done by manus in a plastic pan. Cast Fe regular hexahedron molds, with dimensions of 100x100x100mm are prepared, cleaned and oiled before get downing commixture of concrete.
Cast was made in two beds ; the compression of concrete was done by a vibrating tabular array for 10 to 15 second for each bed. For the normal hardening, after projecting ( 30-45minutes ) , the casts were covered with Nylon bag and polyethylene sheets and for the 3-cubes accelerated bring arounding trial the process was mentioned in the hardening rhythm. For the normal bring arounding the concrete specimen was kept their molds for about 24hr, so they are demolded and placed in the hardening armored combat vehicle filled with H2O until the clip of proving ( 7 and 28-day harmonizing to prove procure ) , and for accelerated bring arounding trial the process was mentioned in the hardening rhythm.
2.4 Trials Performed
The followers are the standard trials that were carried out on the fresh concrete, and hardened concrete.
2.4.1 Fresh Concrete
A slack trial is the most usual trial used in Iraq for proving the workability of the fresh concrete. The ACI 116-90 describes it as a step of consistence. The slump trial of fresh concrete is harmonizing to ASTM C143/C143M- 00. The present experimental work is based on the mix proportion method with a slack scope ( 75-100mm ) .
2.4.2 Compressive Strength Test
The compressive strength trial of concrete regular hexahedrons of ( 100 ) millimeter was carried out in the present work harmonizing to the BS 1881: Part 116: 1983, because it is the most suited trial for the compressive strength used in Iraq. The regular hexahedron of concrete were tested at accelerated bring arounding trial ( warm H2O method, autogenous hardening method and proposal method ) with the 7, 28, 90, 180-day for normal hardening strength harmonizing to the trial process.
At each trial age, three regular hexahedrons of concrete are taken from the bring arounding armored combat vehicle and were placed in the testing machine. The burden at failure was recorded and calculates the norm of compressive strength for the 3-cubes at each age trial.
3. RESULTS AND DISCUSSION
3.1 Fresh Concrete -Slump Test
The slack consequence for different chemical composings of the 5-cements is presented in Table 8. Figure 3 illustrates that the Turkey cement is the lowest slack consequence for different W/C ratios, so the Lebanese ( SRPC ) , that is compatible with a high specific surface country of cement for Turkish- 380 m2/kg and Lebanese ( SRPC ) -360 m2/kg compared with the others lead to cut down the slack trial consequence.
Table 8: Slump trial for different types of cement and W/C ratios.
Type of cement
Slump ( centimeter )
W/C= 0.45
W/C= 0.55
W/C= 0.65
W/C= 0.75
Iraqi ( OPC )
8.5
9.5
10.0
11.5
Turkish ( OPC )
7.0
7.5
8.0
9.0
Leb. ( OPC )
8.0
9.5
10.5
11.0
Leb. ( SRPC )
7.75
8.5
9.5
10.5
Kuwait ( SRPC )
8.5
9.0
10.0
11.0
3.2 Hardened Concrete -Compressive Strength Test
The development of the compressive strength with the age ( accelerated strength for different methods, 7and 28-day normal strength ) for the 20 mixes used through the first portion of this survey is shown in the Table 9. Figures 4 to 9 show the relation between H2O to cement ratios ( 0.45, 0.55, 0.65 and0.75 ) with the compressive strength ( accelerated strength for different methods and 7, 28 twenty-four hours normal strength ) .
The curves indicate that the proposed method is the closer to the 7-day normal so the autogenic so the warm H2O method for the same H2O to cement ratio at a given age. The difference is related to the consequence of the method of the accelerated trial.
The mixes for the Kuwaiti cement ( SRPC ) show a high rate of deriving strength relation to the other mixes. This cement has comparatively a high C3S to a C2S ratio, Sr = 47.4. Meanwhile, the mixes for the Iraqi and Turkish cements ( OPC ) are more faster deriving strength than the Lebanese cement ( OPC ) , this could be attributed to a high content of the C3S = 52.44 % and 50.32 % with Sr = 2.72 and 2.365 for Iraqi and Turkey cements severally, and the C3S = 44.22 with Sr = 1.754 for the Lebanese cement ( OPC ) .
Finally the mixes for the Lebanese cement ( SRPC ) gained strength faster than the Lebanese cement ( OPC ) with closer Sr = 1.78 and 1.754 severally, although, the reviewed literature shows that the ( OPC ) cements frequently have high early strength and addition strength faster than the SRPC cement and this can be attributed to the failure of the Lebanese mixes ( OPC ) to accomplish the minimal mean strength for different H2O to cement ratios.
Table 9: Accelerated strength ( warm, autogenic and proposed method ) with normal strength ( 7 and 28 twenty-four hours ) for different type of cement -Reference mixes
Mix. No.
Cement Type
Sr.
W/C
Accelerated strength MPa
Normal strength MPa
Warm method
1-day
Autogenous method
1-day
Proposed method
2-day
7-day
28-day
1
Iraki
( OPC )
2.72
0.45
15.0
16.75
25.5
28.25
40.5
2
0.55
13.75
15.75
23.75
25.75
37.5
3
0.65
10.25
13.0
19.0
21.5
28.0
4
0.75
8.25
9.5
14.25
14.75
21.5
5
Turkish
( OPC )
2.365
0.45
14.75
16.5
25.0
27.75
40.25
6
0.55
13.0
14.75
22.25
24.75
35.5
7
0.65
9.75
11.25
17.25
19.75
27.0
8
0.75
8.0
8.75
12.75
14.25
20.75
9
Leb.
( OPC )
1.754
0.45
13.25
15.25
22.75
26.5
38.25
10
0.55
10.25
12.25
18.0
20.25
30.5
11
0.65
7.25
9.5
13.5
16.75
22.5
12
0.75
6.25
7.25
10.75
12.0
19.5
13
Leb.
( SRPC )
1.78
0.45
14.25
16.25
24.5
27.0
39.0
14
0.55
12.25
14.25
21.0
23.75
34.5
15
0.65
9.0
11.0
16.25
18.5
26.5
16
0.75
7.75
8.25
12.25
14.0
20.0
17
Kuwaiti
( SRPC )
47.4
0.45
16.75
17.75
26.0
29.0
42.75
18
0.55
14.75
16.25
24.25
26.5
39.5
19
0.65
11.5
13.5
20.5
22.5
30.75
20
0.75
9.25
10.0
15.0
15.25
24.5
Sr. = C3S/C2S
Figures 10 to 13 show the relation between the accelerated strength ( warm H2O method compared to proposed method ) with the 7and 28-day normal strength for the OPC and the SRPC. The additive line is closer to each other for the OPC and the SRPC in 28- twenty-four hours normal strength than for the 7-day normal strength and it is about the same in the proposed method and that is referred to the proposed method correlativity which is more sensible for a less difference between the OPC and the SRPC.
Fig. 3: Histogram for slump trial for different W/C ratios.
Fig. 4: Relationship between H2O to cement ratio and compressive strength of concrete ( 7-day normal strength and accelerated strength -warm H2O method )
Fig. 5: Relationship between H2O to cement ratio and compressive strength of concrete ( 28-day normal strength and accelerated strength -warm H2O method )
Fig. 6: Relationship between H2O to cement ratio and compressive strength of concrete ( 7-day normal strength and accelerated strength -autogenous method )
Fig. 7: Relationship between H2O to cement ratio and compressive strength of concrete ( 28-day normal strength and accelerated strength -autogenous method )
Fig. 8: Relationship between H2O to cement ratio and compressive strength of concrete ( 7-day normal strength and accelerated strength -proposed method )
Fig. 9: Relationship between H2O to cement ratio and compressive strength of concrete ( 28-day normal strength and accelerated strength -proposed method )
Fig. 10: Relationship between 7-day normal strength and accelerated strength utilizing warm H2O method for ( OPC ) and ( SRPC ) cements.
Fig. 11: Relationship between 28-day normal strength and accelerated strength utilizing warm H2O method for ( OPC ) and ( SRPC ) cements.
Fig. 12: Relationship between 7-day normal strength and accelerated strength -proposed method ( OPC ) and ( SRPC ) cements.
Fig. 13: Relationship between 28-day normal strength and accelerated strength utilizing proposal method for ( OPC ) and ( SRPC ) cements.
4. REGRESSION ANALYSIS MODELS
The 7 and 28-day normal hardening is used as the dependant variable and the accelerated hardening strength is the independent variable ( warm H2O, autogenic and proposed method ) . The experimental informations are presented in Table 8, Numberss of informations enters the theoretical account is 20 in each theoretical account.
4.1 Descriptive Statistical Analysis
The deliberate steps of cardinal inclination and scattering are presented in Table 10 for informations enters the theoretical accounts.
Table 10: Descriptive statistics analysis-experimental work
Accelerated strength -Warm H2O ( MPa )
Accelerated strength -Autogenous ( MPa )
Accelerated strength -Proposed ( MPa )
7-day
normal strength ( MPa )
28-day normal strength ( MPa )
No. of informations
20
20
20
20
20
Mean
11.26
12.89
19.23
21.44
30.96
Standard divergence
3.06
3.26
4.98
5.50
7.90
Discrepancy
9.39
10.64
24.77
30.29
62.42
Minimum
6.25
7.25
10.75
12.00
19.50
Maximum
16.75
17.75
26.00
29.00
42.75
No. of informations = 20
4.2 Regression Model -Warm Water, Autogenous and Proposed Accelerated Curing Test
The arrested development theoretical accounts for additive and non additive relationship between accelerated strength ( warm H2O, autogenic and proposed method ) and 28-day normal hardening strength is presented in Tables 11, 12 and 13 severally. Tables ( 14 ) , ( 15 ) and ( 16 ) severally presents the ANOVA, R2, root average square of mistake and T= ?residualpredicted 7 or 28-day normal strength for all theoretical accounts.
Table 11: Linear and non additive theoretical accounts for 7 and 28-day normal strength – warm H2O method
Table 12: Statistical analysis for 7 and 28-day normal strength – warm H2O method
Model No.
Equation
1-L-Wr.
7-day normal strength = 1.797+ 1.744x accelerated strength ( warm )
2-Q-Wr.
7-day normal strength = -6.173+ 3.250x accelerated strength ( warm ) -0.066x accelerated strength ( warm ) 2
3-P-Wr.
7-day normal strength = 2.199x accelerated strength ( warm ) ^ 0.941
4-L-Wr.
28-day normal strength = 2.357+ 2.540x accelerated strength ( warm )
5-Q-Wr.
28-day normal strength = -2.237+ 3.408x accelerated strength ( warm ) -0.038 x accelerated strength ( warm ) 2
6-P-Wr.
28-day normal strength = 3.321 ten accelerated strength ( warm ) ^ 0.922
No. of informations = 20
Model
Analysis of variance
R2
Root average square of mistake
Thymine
value
Beginning
D.F.
Sum of squares
Mean square
F value
1-L-Au.
Model ( Reg. )
1
568.06
568.06
1355.7
0.987
0.805
-1.73
Error ( Res. )
18
7.542
0.419
2-Q-Au.
Model ( Reg. )
2
568.22
284.11
654.0
0.987
0.812
7.79
Error ( Res. )
17
7.385
0.4344
3-P-Au.
Model ( Reg. )
1
1.431
1.431
1135.18
0.984
0.188
18.3
Error ( Res. )
18
.0226
0.001
4-L-Au.
Model ( Reg. )
1
1161.6
1161.63
856.93
0.979
1.079
-2.46
Error ( Res. )
18
24.400
1.355
5-Q-Au.
Model ( Reg. )
2
1165.9
582.97
493.55
0.983
1.042
-43.37
Error ( Res. )
17
20.08
1.181
6-P-Au.
Model ( Reg. )
1
1.321
1.321
685.82
0.974
0.209
46.08
Error ( Res. )
18
.0346
0.002
Model 1-L-Wr. is the best for the 7-day normal strength since F value ( 292.77 ) is more than F tabulated ( 4.41 ) , high R2 ( 0.942 ) , low root mean square of mistake ( 1.166 ) and the lowest Thymine value ( -0.62 ) . Model 4-L-Wr. is the best for the 28-day normal strength since F value ( 578.95 ) is highest than others and more than F tabulated ( 4.41 ) , high R2 ( 0.969 ) , low root mean square of mistake ( 1.187 ) and the lowest Thymine value ( -0.84 ) .
Table 13: Linear and non additive theoretical accounts for 7 and 28-day normal strength – autogenic method
Model No.
Equation
1-L-Au.
7-day normal strength = -0.171+ 1.677x accelerated strength ( autogenic )
2-Q-Au.
7-day normal strength = -1.784+ 1.951x accelerated strength ( autogenic ) -0.011x accelerated strength ( autogenic ) 2
3-P-Au.
7-day normal strength = 1.605x accelerated strength ( autogenic ) ^ 1.013
4-L-Au.
28-day normal strength = 0.062+ 2.398x accelerated strength ( autogenic )
5-Q-Au.
28-day normal strength = 8.524+ 0.967x accelerated strength ( autogenic ) +0.057x accelerated strength ( autogenic ) 2
6-P-Au.
28-day normal strength = 2.567 ten accelerated strength ( autogenic ) ^ 0.974
Table 14: Statistical analysis for 7 and 28-day normal strength – autogenic method
Model
Analysis of variance
R2
Root average square of mistake
Thymine
value
Beginning
D.F.
Sum of squares
Mean square
F value
1-L-Wr.
Model ( Reg. )
1
542.27
542.27
292.77
0.942
1.166
-0.62
Error ( Res. )
18
33.33
1.852
2-Q-Wr.
Model ( Reg. )
2
547.68
273.84
166.68
0.951
1.132
-15.7
Error ( Res. )
17
27.928
1.643
3-P-Wr.
Model ( Reg. )
1
1.352
1.352
241.6
0.931
0.273
-11.36
Error ( Res. )
18
0.101
0.006
4-L-Wr.
Model ( Reg. )
1
1150.2
1150.27
578.95
0.969
1.187
-0.84
Error ( Res. )
18
35.762
1.986
5-Q-Wr.
Model ( Reg. )
2
1152.0
576.03
288.31
0.971
1.189
-16.93
Error ( Res. )
17
33.96
1.997
6-P-Wr.
Model ( Reg. )
1
1.3015
1.301
431.24
0.959
0.234
48.64
Error ( Res. )
18
0.0543
0.003
Model
Analysis of variance
R2
Root average square of mistake
Thymine
value
Beginning
D.F.
Sum of squares
Mean square
F value
1-L-Pr.
Model ( Reg. )
1
566.24
566.24
1088.3
0.984
0.849
-0.63
Error ( Res. )
18
9.364
0.520
2-Q-Pr.
Model ( Reg. )
2
566.28
283.14
516.44
0.984
0.860
82.11
Error ( Res. )
17
9.320
0.548
3-P-Pr.
Model ( Reg. )
1
1.422
1.422
827.08
0.978
0.203
17.08
Error ( Res. )
18
.0309
0.002
4-L-Pr.
Model ( Reg. )
1
1159.0
1159.01
772.11
0.977
1.107
4.25
Error ( Res. )
18
27.019
1.501
5-Q-Pr.
Model ( Reg. )
2
1163.5
581.75
438.88
0.981
1.073
-56.94
Error ( Res. )
17
22.53
1.325
6-P-Pr.
Model ( Reg. )
1
1.3195
1.319
654.42
0.973
0.212
52.97
Error ( Res. )
18
.03629
0.002Table 15: Linear and non additive theoretical accounts for proposed method 7 and 28-day normal strength – proposed method
Model No.
Equation
1-L-Pr.
7-day normal strength = 0.349+ 1.097x accelerated strength ( proposed )
2-Q-Pr.
7-day normal strength = -0.492+ 1.193x accelerated strength ( proposed ) -0.003x accelerated strength ( proposed ) 2
3-P-Pr.
7-day normal strength = 1.164x accelerated strength ( proposed ) ^ 0.985
4-L-Pr.
28-day normal strength = 0.792+ 1.569x accelerated strength ( proposed )
5-Q-Pr.
28-day normal strength = 9.250+ 0.602x accelerated strength ( proposed ) +0.026x accelerated strength ( proposed ) 2
6-P-Pr.
28-day normal strength = 1.873x accelerated strength ( proposed ) ^ 0.949
No. of informations = 20
Table 16: Statistical analysis for 7 and 28-day normal strength – proposal method
No. of informations = 20
Model 1-L-Au. is the best for the 7-day normal strength since F value ( 1355.7 ) is highest than others and more than F tabulated ( 4.41 ) , high R2 ( 0.987 ) , low root mean square of mistake ( 0.805 ) and the lowest Thymine value ( -1.73 ) . Model 4-L-Au. is the best for the 28-day normal strength since F value is highest than others and more than F tabulated ( 4.41 ) , high R2 ( 0.979 ) , low root mean square of mistake ( 1.079 ) and the lowest Thymine value ( -2.46 ) .
Model 1-L-Pr. is the best for the 7-day normal strength since F value ( 1088.3 ) is highest than others and more than F tabulated ( 4.41 ) , high R2 ( 0.984 ) , low root mean square of mistake ( 0.849 ) and the lowest Thymine value ( -0.64 ) . Model 4-L-Pr. is the best for the 28-day normal strength since F value ( 772.11 ) is highest than others and more than F tabulated ( 4.41 ) , high R2 ( 0.977 ) , low root mean square of mistake ( 1.107 ) and the lowest Thymine value ( 4.25 ) .
5.0 Decision
1. A good correlativity has been obtained between a 1-day accelerated trial ( proposed trial method ) and 28 yearss normal bring arounding trial utilizing a period of bring arounding at the maximal temperature 70 & A ; deg ; C with a hold period of 4 hours, and a cooling period of 2 hours.
2. Proposed trial methods give the highest accelerated strength than the others and the closer to the 7-days, due to its rhythm of hardening.
3. A good correlativity has been obtained between a 1-day accelerated trial ( warm H2O method ) and a 28 yearss normal bring arounding trial, with regard to the easy rhythm readying.
4. A good correlativity has been obtained between a 2-day accelerated trial ( autogenic trial method ) and a 28 yearss normal bring arounding trial, taking into consideration that this method needs a two twenty-four hours accelerated bring arounding compared with the warm H2O and the proposal methods.
5. Linear and nonlinear arrested development analysis between accelerated strength ( warm H2O, autogenouse and proposed bring arounding trial ) and normal hardening strength for 7 and 28-day shows high correlativity with R2 more than 0.94 for different theoretical accounts.
