alexa Prediction of Some Properties of Retempered Concrete in Hot Weather

ISSN: 2165-784X

Journal of Civil & Environmental Engineering

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Prediction of Some Properties of Retempered Concrete in Hot Weather

Mereen Hassan Fahmi Rashid and Ayad Zeki Saber Agha*
Department of Civil Engineering, Erbil Technical Engineering College, Erbil Polytechnic University, Erbil, Iraq
*Corresponding Author: Ayad Zeki Saber Agha, Department of Civil Engineering, Erbil Technical Engineering College, Erbil Polytechnic University, Erbil-44002, Iraq, Tel: 009647704454107, Email: [email protected]

Received Date: Dec 02, 2017 / Accepted Date: Oct 18, 2018 / Published Date: Oct 24, 2018

Abstract

This paper present statistical study to proposed empirical equations to predicting some properties of the fresh concrete (additional water for first and second retempering, final slump and dry unit weight), also some properties of the hardened concrete (compressive, flexural, split tensile strength and modulus of elasticity) depending on the simple properties of the retempered concrete mix (water cement ratio, temperature, air content, humidity, mix proportion and unit weight). Theoretical results obtained from these proposed equations found to be in good agreement with the experimental data found in literature.

Keywords: Retempering; Concrete mixes; Fresh concrete properties; Hot weather concrete

Introduction

Using and placing concrete during the hot summer months present far different challenges than use and placement during cold weather. The summer month effects of temperature, wind, and air humidity can all have a negative impact on the performance of concrete. For purposes of concrete use and placement, “hot weather" can be defined as any period of high temperature during which special precautions need to be taken to ensure proper handling, placing, finishing and curing of concrete. Hot weather problems are most frequently encountered in the summer, but critical drying factors such as high winds and dry air can occur at any time, especially in arid or tropical climates.

Higher temperatures cause water to evaporate from the surface of the concrete at a much faster rate and cement hydration occurs more quickly, causing the concrete to stiffen earlier and improving the chances of plastic cracking occurring. Concrete cracking may result from rapid drops in the temperature of the concrete. This occurs when a concrete slab or wall is placed on a very hot day and which is immediately followed by a cool night. High temperature also accelerates cement hydration and contributes to the potential for cracking in massive concrete structures. Higher relative humidity tends to reduce the effects of high temperature.

Other hot weather problems include increased water demand, which raises the water-cement ratio and yield lower potential strength, accelerated slump loss that can cause loss of entrained air, fast setting times requiring more rapid finishing or just lost productivity. Environmental conditions and delays in the placement of concrete may cause loss in the workability of super-plasticized concrete. The loss can be restored by retempering with water or super-plasticizers. The use of water usually results in a reduction in strength. There is divergence of opinion on the engineering properties of the tempered concrete. The practice of retempering in hot-dry environments is frequently performed to increase slump beyond typical specification’s limits (of 100 ± 25 mm) in order to cope with the need for expediting the casting operations and reducing the consolidation effort.

The strength of concrete of given mix proportions are very seriously affected by the degree of its compaction. Therefore that the consistence of the mix be such that the concrete can be transported, placed and finished sufficiently easily and without segregation. The concrete mix satisfying these conditions is said to be workable. However workability is measured by slump, compacting factor or flow test. Freshly mixed concrete stiffened with time, some of the water of the mix absorbed by the aggregate and some is lost by evaporation. Particularly if the concrete is exposed to sun or wind and some is removed by the initial chemical reactions. This loss of mix water lead to reduction in slump or compacting factor therefore reduction in workability of the concrete. Generally workability reduces with the time and increasing of temperature. Therefore it is apparent that on a hot day water content of the mix would have be increased for constant workability [1,2].

Loss of slump and the consequent reduction in workability with time is an inherent property of fresh concrete, this loss in workability is accelerated in hot climates. A delay in the discharge of concrete from a truck mixer, or a delay in the placement of concrete due to other reasons could cause stiffening to the point of unworkability. Therefore in actual field application in hot climate, it may be necessary to retemper the concrete to maintain the required workability. The process or procedure adopted in achieving the desired consistency of a given fresh concrete, already mixed to the specified consistency, by the addition of water, a super plasticizer or cement paste or any combination of these, is known as retempering [3].

Hanayneh and Itani [4] attempted to study the engineering properties of retempered concrete having different normal strengths. The slump, compressive strength, modulus of rupture, splitting strength, Poisson's ratio and the modulus of elasticity were determined. Alhozaimy [5], investigated the effect of retempering on the workability and strength of ready-mixed concrete (RMC) in hot-dry environments was investigated. This study covered 12 construction sites with concrete delivered by 11 different RMC suppliers. The results indicate that the reduction in strength due to water addition is proportional to the associated increase in slump. In cases where water was added to restore the slump to the specifications limits (100 ± 25 mm), the reduction of strength was below 10%. However, when water was added to increase slump beyond these limits, the reduction of strength may be as high as 35%. The study shows the change in slump can be used to predict reduction of strength due to jobsite water additions when practical considerations preclude accurate determination of the w/c ratio.

Erdogdu [6-8] used the super-plasticizer of ASTM C (494) Type F for retempering concrete to restore its initial slump. Concrete mixes having an initial slump of about 19 cm were prepared and subjected to prolonged mixing with different mixing duration such as 30 min, 60 min, 90 min, 120 min and 150 min following an initial mixing of 5 min to ensure homogeneity. At the end of each mixing period, cube specimens of 15 cm were cast from concrete retempered to its initial slump level and tested at the age of 28 days for compressive strength. Results revealed that compared to the concrete retempered with water, those retempered with a superplasticizer admixture have yielded significantly higher strength regardless of the mixing duration. This paper present a statistical study to proposed empirical equations to predicting some properties of the fresh and hardened concrete in term of simple properties of the retempered concrete mixes, theoretical results obtained from these proposed equations found to be in good agreement with the experimental data found in literature [3].

Analysis and Results

Method of multi-linear regression analysis is used to proposed different expressions to predicting some properties of the fresh and hardened concrete depending on the simple properties of the concrete mix, the general proposed equation take the following form:

equation(1)

where:

equationare independent variables.

equation are coefficients.

Values of these coefficients are determined by incorporation of experimental data and using computer program. Depending on the least square principle:

equation(2)

where:

S = Sum of square of differences between calculated and experimental results.

y = Experimental value of the dependent variable.

Y = Calculated value of the dependent variable.

N = No. of observed points.

equation(3)

To determine value of the coefficients, the error function (S) is minimized with respect to the coefficients:

equation(4)

where i = 1,2,3…6

These equations lead to generate a set of simultaneous equations as shown below, solved by using computer programs and incorporation of experimental data to determine the coefficients value for different cases.

[A]{K} = {B} (5)

Where [A] is the coefficient matrix.

equation

equation

Properties of the fresh and hardened concrete determined for the mixes measured or tested before addition of water for retempering this stage is known as an initial stage (or first retempering), but approximately (30) minutes after the initial mixing additional water added to the concrete mix to increase the workability, this stage is known as a first retempering. Approximately one hour after the initial mixing. The second additional water is added to the concrete mix to keep workability constant; this stage is known as a second retempering. For all these stages properties of the fresh & hardened concrete are measured or tested.

All these properties of the fresh and hardened concrete relating with the selected independent variables, which represent the simple properties of the concrete mix. The independent variables equation are taken as the following form to represent the correct mix properties:

X1 = Temperature (T)

X2 = Water cement ratio (W/C)

equation

where: C, w, S and G are cement, water, sand and gravel proportions respectively.

X4 = Air content % (A)

X5 = Humidity % (H)

X6 =Unit weight kg/m3 (γ)

A computer program for developing such multi-linear regression analysis was adopted which yield the different equations by incorporation of experimental data found in literature [3]. The fresh and hardened concrete properties relating with the selected independent variables are shown in Tables 1a and 1b.

Concrete
Mix
Temperature
(°C)
Water cement
ratio (W/C)
(C+W)
/(S+G)
Air content
(A) %
Humidity
(H) %
Unit weight
(kg/m3)
Water Dosage Final Slump
(mm)
Dry U. Wt. (kg/m3) Pulse Velocity (m/sec) Losses in Slump (mm)
              7 Day 28 Day   INIT. 1R. 2 R. INIT. 1R. 2R. Before R. After R.
GI 30 0.4 0.43 2 22 2,388 0.45 0.79 76 2394 2405 2371 0.4776 0.4687 0.4632 10 37
G2 40 0.4 0.43 2 21 2,365 1.36 0.88 104 2369 2366 2376 0.4585 0.4498 0.4502 64 68
G3 50 0.4 0.43 1.8 28 2,348 1.95 2.26 101 2360 2351 2347 0.4561 0.4493 0.4491 68 63
G4 60 0.4 0.43 1.9 27 2,324 2.54 3.55 101 2347 2308 2265 0.4529 0.4478 0.4279 63 114
G5 65 0.4 0.43 1.9 30 2,263 2.68 1.8 114 2290 2251 2216 0.4383 0.4333 0.4267 90 114
G6 30 0.5 0.347 1.8 30 2.388 0.9 0.84 88 2423 2429 2430 0.4595 0.4335 0.4458 19 19
G7 40 0.5 0.347 1.8 30 2,408 0.99 0.76 71 2435 2422 2413 0.4766 0.4675 0.4646 29 25
G8 50 0.5 0.347 1.8 29 2,376 130 1.08 95 2426 2404 2368 0.4648 0.4638 0.4597 67 67
G9 60 0.5 0.347 1.8 30 2,386 1.02 1.26 88 2399 2381 2379 0.4657 0.4625 0.4604 35 50
G10 65 0.5 0.347 1.7 30 2,403 1.1 1.()6 88 2404 2415 2389 0.4677 0.4598 0.4569 69 75
G11 30 0.6 0.297 1..2 30 2,383 0 0.5 127 2411 2381 2405 0.4714 0.4622 0.4591 26 32
G12 40 0.6 0.297 1.2 30 2,409 0.82 0.7 88 2392 2392 2388 0.464 0.4617 0.4595 26 38
G13 50 0.6 0.297 1.3 30 2,393 1.06 1.23 114 2417 2386 2359 0.4636 0.4604 0.4548 70 57
G14 60 0.6 0.297 1.3 30 2,406 1.23 0.98 95 2403 2383 2398 0.4654 0.4596 0.4565 32 42
G15 65 0.6 0.297 1.2 30 2,402 1.27 0.94 95 2408 2390 2391 0.4656 0.459 0.4564 61 51
GIA 30 0.4 0.43 2 46 2,358 0.86 0.3 76 2392 2383 2377 0.4572 0.4505 0.4405 32 13
GSA 30 0.5 0.347 1.8 50 2,290 0.37 0.36 82 2414 2376 2369 0.4858 0.481 0.4696 60 52

Table 1a: Experimental data-1.

Mix equationMPa  equation1st RET. equation2nd RET.  equation MPa   equationMPa  equation× 10E4 MPa equation× 10E4 MPa
7 Days 28 Days 7 Days 28 Days 7 Days 28 Days INIT. 1R 2R INIT. 1R 2R INIT. 1R 2R INIT. 1R 2R
G1 35.72 51.64 34.82 45.99 33.59 43.72 5.10 5.20 3.93 4.75 5.06 4.00 3.478 3.174 3.084 4.019 3.785 3.821
G2 35.85 42.05 36.13 44.68 34.13 42.06 5.37 4.86 4.55 4.60 4.55 3.89 3.441 3.233 3.092 3.62 3.62 3.745
G3 35.16 43.37 35.65 43.75 33.72 41.72 5.20 4.88 H6 4.92 4.60 4.17 3.21 2.923 2.874 3.663 3.661 3.685
G4 33.58 41.44 34.01 38.96 31.09 38.27 5.06 4.58 3.72 4.33 4.29 3.70 3.021 2.974 2.57 3.521 3.243 3.139
G5 31.71 40.28 33.62 39.2 29.6 36.93 4.90 4.72 4.03 4.20 3.23 3.00 2.776 2.52 2.162 3.317 3.191 3.054
G6 33.48 36.96 30.75 37.79 29.31 37.65 5.03 4.65 4.65 3.72 3.73 3.41 3.237 3.387 3.378 3.795 3.607 3.786
G7 34.82 39.72 33.24 37.44 31.17 36.41 4.96 5.06 4.65 4.03 3.58 3.10 3.445 3.311 2.898 4.179 3.935 3.941
G8 31.58 36.64 28.9 34.97 27.1 34.2 4.79 4.79 4.31 3.72 3.51 3.31 3.321 3.273 3.326 4.056 3.805 3.957
G9 31.37 36.82 30.96 34.34 27.03 32.97 4.82 4.61 4.55 3.72 3.17 3.06 3.445 3.293 3.431 3.899 3.976 3.866
G10 31.03 38.34 30.68 37.44 29.37 35.44 5.03 4.55 4.43 3.65 2.99 3.17 3.376 3.129 3.084 - - -
G11 25.27 34.96 26.27 35.03 27.44 35.44 4.44 4.62 4.31 3.37 2.99 3.37 3.177 3.129 3.17 - - -
G12 27.1 34.41 26 33.03 24.34 30.27 4.41 4.40 3.96 3.34 2.82 2.41 3.143 3.116 2.831 - - -
G13 24.34 31.51 24.68 31.17 23.03 27.24 4.58 4.41 3.86 3.20 2.81 2.96 3.196 3.018 2.913 - - -
G14 24.62 30.34 23.65 29.58 22.68 29.44 4.31 3.68 3.65 3.03 2.75 3.03 3.143 3.116 2.831 - - -
G15 23.51 32.13 22.27 32.27 21.93 32.57 4.48 4.17 4.24 3.44 3.03 2.86 3.177 3.191 3.17 - - -
G1A 36.48 42.62 34.68 41.44 32.82 40.2 5.22 5.00 4.86 3.79 3.55 3.44 1.374 1.374 1.367 - - -
G6A 33.38 37.65 31.93 36.96 31.51 36.75 5.50 5.19 5.13 3.51 3.27 3.17 1.382 1.408 1.367      

Table 1b: Experimental data-2.

Fresh concrete

The following properties of the fresh concrete are taken as dependent variables to evaluate general empirical equations relating these properties with the independent variables equation

equation = Water dosage for first retempering (kg).

= Water dosage for second retempering (kg).

= Final slump (mm).

equation= Dry unit weight (kg/m3) for initial stage.

equation= Dry unit weight (kg/m3) for first retempering stage.

equation= Dry unit weight (kg/m3) for second retempering stage.

V = Pulse velocity (m/sec) for initial stage.

equation= Pulse velocity (m/sec) for first stage.

equation= Pulse velocity (m/sec) for second stage.

equation = Slump losses before retempering (mm).

= Slump losses after retempering (mm).

Using computer programs and incorporation of experimental data lead to formulation general equations, predicting previous dependent variables (Y) in term of the dependent variables (X) as following:

equation(7)

Where:

T = Temperature

A = Air content (%)

H = Humidity (%)

γ= Unit weight (kg/m3)

The coefficients value equation of the equation (1) and coefficient of correlation are determined for all the dependent variables and tabulated in Table 2.

Variables   K0 K1 K2 K3 K4 K5 K6 r
WdR1 6.657 0.0336 -1.0285 6.837 -0.637 -0.0014 -0.0033 0.897
WdR2  31.908 0.0267 -28.154 -20.8 -3.16 -0.028 -0.0019 0.794
Sf 372.006 0.0946 162.344 313.162 -39.654 -0.718 -0.1636 0.728
equation 1970.73 -0.8137 -320.94 -1056.5 69.008 0.394 0.3686 0.9413
equation 1914.57 -1.0874 -1217.4 -1903.2 10.497 0.25 0.75056 0.965
equation 1945.38 -1.6192 -1338.6 -2016.1 -29.369 0.4789 0.8114 0.9375
V 0.6284 -0.0004 -0.1666 -0.3715 0.0099 -0.0005 0.00003 0.765
equation 0.4415 -0.0002 0.0802 -0.0884 0.0229 -0.0004 -0.0000039 0.5495
equation 0.627 -0.0003 -0.2536 -0.4904 0.00344 -0.0006 0.000066 0.8072
equation 1106.99 0.901 -360.57 -411.13 -29.937 -0.3015 -0.3016 0.809
equation 1018.2 1.229 -167.01 -72.965 -24.95 -1.7375 -0.3458 0.9391

Table 2: The coefficients value of the eq. (1) of fresh concrete properties.

Theoretical results obtained from the proposed equations found to be in a good agreement with the experimental data. Figures 1-6 show the relationship between theoretical and experimental results.

civil-environmental-engineering-theoretical

Figure 1: Relation of theoretical and experimental results of dry unit weight ( γD ) (Kg/m3).

civil-environmental-engineering-experimental

Figure 2: Relation of theoretical and experimental results of dry unit weight after 1st retempering (γDR1)(Kg/m3).

civil-environmental-engineering-dry

Figure 3: Relation of theoretical and experimental results of dry unit weight after 2nd retempering (γDR2) (Kg/m3).

civil-environmental-engineering-results

Figure 4: Relation of theoretical and experimental results of pulse velocity (V ) (m/sec).

civil-environmental-engineering-pulse

Figure 5: Relation of theoretical and experimental results of pulse velocity after 1st retempering (VR1) (m/sec).

civil-environmental-engineering-velocity

Figure 6: Relation of theoretical and experimental results of pulse velocity after 2nd retempering (VR2) (m/sec).

Hardened concrete

The dependent variables for hardened concrete are selected to represent the compressive strength equation, flexural strength equation split tensile strength equation , static modulus of elasticity equation and dynamic modulus of elasticity equation, the following dependent variables are selected to represent hardened concrete properties:

equation= equation at age (7 days) for initial stage (MPa).

equation= equation at age (28 days) for initial stage (MPa).

equation= equation at age (7 days) for first retempering stage (MPa).

equation = equation at age (28 days) for first retempering stage (MPa).

equation= equation at age (7 days) for second retempering stage (MPa).

equation= equation at age (28 days) for second retempering stage (MPa).

equation = equation for initial stage (MPa).

equation= equation for first retempering stage (MPa).

equation = equation for second retempering stage (MPa).

equation= equation for initial stage (MPa).

equation = equation for first retempering stage (MPa).

equation = equation for second retempering stage (MPa).

equation = equation for initial stage (MPa).

equation = equation for first retempering stage (MPa).

equation = equation for second retempering stage (MPa).

equation = equation for initial stage (MPa).

equation= equation for first retempering stage (MPa).

equation= equation for second retempering stage (MPa).

equation= Losses in equation at age (7 days) after first retempering (MPa).

equation= Losses in equation at age (28 days) after first retempering (MPa).

equation= Losses in equation at age (7 days) after second retempering (MPa).

equation= Losses in equation at age (28 days) after second retempering (MPa).

equation = Losses in equation after first retempering (MPa).

equation = Losses in equation second first retempering (MPa).

equation= = Losses in equation after first retempering (MPa).

equation = Losses in equationafter second retempering (MPa).

equation= Losses in equation after first retempering (MPa).

equation = Losses in equation after second retempering (MPa).

The following equations are obtained:

equation(8)

where:

equation = Concrete compression strength (MPa)

T = Temperature

A = Air content (%)

H = Humidity (%)

γ= Unit weight (kg/m3)

Value of the coefficients equation for other variables and coefficient of correlation for all dependent variable (Y) are determined and tabulated in Table 3.

Variables  K0 K1 K2 K3 K4 K5 K6 r
equation 153.814 -0.085 -174.84 -175.51 -1.84 0.0179 0.0142 0.988
equation 83.468 -0.109 -134.79 -64.676 -9.0366 -0.1504 0.0293 0.944
equation 177.95 -0.0655 -172.93 -151.19 -6.207 -0.0414 0.0031 0.977
equation 144.69 -0.121 -173.8 -105.99 -14.2 -0.015 0.0214 0.9809
equation 218.463 -0.12 -209.7 -191.4 -11.641 -0.062 0.0043 0.971
equation 207.63 -0.133 -221.82 -172.55 -16.642 -0.115 0.016 0.9545
equation 20.648 -0.007 -13.06 -14.76 -0.085 -0.0034 -0.0014 0.911
equation 28.09 -0.0157 -20.632 -23.149 -0.792 -0.0042 -0.0011 0.903
equation 42.766 -0.0137 -35.291 -44.38 -1.4 0.023 -0.0011 0.8228
equation 21.3556 -0.0049 -25.77 -17.761 -2.201 -0.0348 0.0028 0.978
equation -0.038 -0.0142 -10.08 1.184 -0.9353 -0.053 0.005 0.961
equation 7.413 -0.0089 -11.509 -5.053 -1.0867 -0.0023 0.00266 0.8468
equation -2.377 0.0128 -16.86 -16.325 -1.3657 -0.0744 0.0099 0.913
equation -0.6543 0.0098 -16.361 -17.64 -1.2507 -0.6756 0.0091 0.8944
equation 3.61 0.0074 -22.14 -25.18 -1.4604 -0.0614 0.01 0.885
equation -16.907 0.0025 - 0.3081 1.227 0.0388 0.0724 0.914
equation -12.873 0.0076 - 0.0664 -0.1458 -0.0032 0.007 0.9188
equation 7.3513 -0.002 - -3.834 -2.6673 -0.0877 0.0022 0.95
equation -24.135 -0.0194 -1.9116 -24.323 4.3677 0.0593 0.01111 0.7868
equation -61.111 0.0121 38.748 40.9474 5.1608 -0.0001 0.00799 0.316
equation -64.65 0.0347 34.858 15.886 9.8014 0.08 0.00994 0.777
equation -124.16 0.024 87.029 107.88 7.6053 -0.0353 0.01336 0.4185
equation -7.442 0.0089 7.573 8.39 0.7071 0.0082 -0.0003 0.505
equation -23.337 0.0048 23.2311 33.6734 0.8203 -0.0246 -0.0003 0.7445
equation 21.4766 0.0093 -15.888 -19.224 -1.2656 0.0184 -0.0022 0.782
equation 13.9426 0.004 -14.261 -12.709 -1.1145 -0.0117 0.00012 0.6118
equation -1.7227 0.003 -0.4992 1.3136 -0.115 -0.0096 0.00078 0.7077
equation -5.987 0.0053 5.28 8.855 0.0947 -0.013 0.00016 0.656

Table 3: The coefficients value of the eq. (1) of hardened concrete properties.

Theoretical results obtained from proposed equations found to be in good agreement with the experimental data. Figures 7-22 show the relationship between theoretical and experimental results.

civil-environmental-engineering-concrete

Figure 7: Relation of theoretical and experimental results of concrete compressive strength (equation ) at age 7 days (MPa).

civil-environmental-engineering-compressive

Figure 8: Relation of theoretical and experimental results of concrete compressive strength ( equation ) at age 28 days (MPa).

civil-environmental-engineering-strength

Figure 9: Relation of theoretical and experimental results of concrete compressive strength ( equation) at age 7 days after 1st retempering (MPa).

civil-environmental-engineering-retempering

Figure 10: Relation of theoretical and experimental results of concrete compressive strength ( equation) at age 28 days after 1st retempering (MPa).

civil-environmental-engineering-theoretical

Figure 11: Relation of theoretical and experimental results of concrete compressive strength ( equation ) at age 7 days after 2nd retempering (MPa).

civil-environmental-engineering-age

Figure 12: Relation of theoretical and experimental results of concrete compressive strength ( equation ) at age 28 days after 2nd retempering (MPa).

civil-environmental-engineering-modulus

Figure 13: Relation of theoretical and experimental results of modulus of rupture fr (MPa).

civil-environmental-engineering-rupture

Figure 14: Relation of theoretical and experimental results of modulud of rupture (fr) after 1st retempring (MPa).

civil-environmental-engineering-experimental

Figure 15: Relation of theoretical and experimental results of modulud of rupture (fr) after 2nd retempring (MPa).

civil-environmental-engineering-relation

Figure 16: Relation of theoretical and experimental results of splitting tensile strength (fsp ) (MPa).

civil-environmental-engineering-tensile

Figure 17: Relation of theoretical and experimental results of splitting tensile strength (fspR1 ) after 1st retempering (MPa).

civil-environmental-engineering-splitting

Figure 18: Relation of theoretical and experimental results of splitting tensile strength ( fspR2) after 2nd retempering (MPa).

civil-environmental-engineering-static

Figure 19: Relation of theoretical and experimental results of static modulus of elasticity (Est ) (*10^4 ) MPa .

civil-environmental-engineering-elasticity

Figure 20: Relation of theoretical and experimental results of static modulus of elasticity (EstR2) after 2nd retempering (*10^4 MPa).

civil-environmental-engineering-dynamic

Figure 21: Relation of theoretical and experimental results of dynamic modulus of elasticity (EdyR1 ) after 1st retempering (*10^4 MPa).

civil-environmental-engineering-theoretical

Figure 22: Relation of theoretical and experimental results of dynamic modulus of elasticity (EdyR2) after 2nd retempering (*10^4 MPa).

Discussion

The experimental data given in literature [3] are used to predict empirical equation to estimate the concrete properties (fresh and hardened) depending on the mix properties and retempering of the concrete mix in hot weather. Value of the equation coeff. equation correlation coeff. (r) are determined for all independent variable. Value of (r) indicate that the estimated results are close enough to the experimental data for all independent variables as shown in Figures 1-6 for fresh concrete properties and Figures 7-22 for hardened concrete properties.

Conclusion

It is possible to estimating some properties of the hardened concrete such as concrete strength (compressive, split tensile and flexural) also static and dynamic modulus of elasticity depending on the simple properties of the concrete mix with acceptable accuracy.

1. Also this paper presented empirical equations to estimating some properties of the fresh concrete such as (additional water for first & second retempering, slump and dry unit weight) depending on the simple properties of the concrete mix(water cement ratio, mix proportion, humidity, temperature, air content and unit weight).

2. This estimation is useful to predicting some properties of the fresh and hardened concrete after first and second retempering easily without needing measuring or casting and testing control specimens to get these properties.

3. Theoretical results obtained from these equations found to be in good agreement with the experimental data found in literature.

References

Citation: Rashid MHF, Agha AZS (2018) Prediction of Some Properties of Retempered Concrete in Hot Weather. J Civil Environ Eng 8: 324. DOI: 10.4172/2165-784X.1000324

Copyright: © 2018 Rashid MHF, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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