Modeling Concrete Compressive Strength and Strain Development Modified With Variation of Fly Ash and Superplasticizer as Partial Replacement
Eluozo SN and Dimkpa K
Published on: 2021-11-10
Abstract
The study purpose of this Study is to monitor the growth rate of compressive strength and strain from modification of concrete partially replace cement with fly ash and superplasticizer, the study express the behavior of compressive and strain under the influences of these two addictive, the study figured out the relative effect of the addictive influence on the compressive strength and strain of the model concrete based on their effects in different dimensions. It has also provided the platform whereby the strain and compressive strength can be monitored considering some predominant influence from concrete characteristics such as void ratios, porosity and water cement ratios. These are reflected on the variation of strain and compressive strength growth rates as it is expressed from the figures, linear trend were observed, but variation of concrete strain and compressive strength were also experienced in various figures, the study observed the behavior of strain in concrete, such subjection of stress are through an applied load that generates cracks on concrete, when tensile strain exceed its capacity. This behavior are reflected on the compressive variation observed from the results, Measuring the deformation of these materials is through the applied load as it reflection on the behavior of strength development from the target model concrete, the study has experienced strain behavior on concrete when combined with materials characteristic modulus. These condition were observed on the study through the developed model modified with fly ash and super plasticizer, the results express how these parameters affect strain and compressive strength from mixed designed concrete, predictive values were simulated analytically to determine the strain and compressive strength at every seven days of curing , this were to monitor concrete strain strength development on the model concrete as it increased within seven days of curing to the optimum values recorded at ninety days, predictive values were subjected to validation, and both parameters generated best fits correlation.
Keywords
Modeling strain; Concrete strength; Fly ash; SuperplasticizersIntroduction
The development of High-Strength Concrete and monitoring the Mechanical properties (HSC) can be separated in two groups as short- term these are mechanical properties and long-term mechanical properties. Stress strain from concrete through HSC definitely depends on the design model that determined the behavior of these materials as a parameters, these condition includes aggregate type and experimental parameters such as age at testing, strain level including its interaction between specimens and testing machine. The stress-strain model applied for NSC cannot be lengthy for application in HSC through nature of the loading curve changes significantly [1,2]. Rising of steeper sudden develop drop in strength after maximum value presents difficulty in numerical modeling of stress-strain behavior of HSC recommends that HSC performs like a real composite material and its equivalents of stress-strain can be drawn to the behavior applied in rock mechanic [3,4] it is investigated reported that there is less internal micro cracking in HSC than NSC for the same axial strain imposed, HSC are observed to experience less lateral strain, and consequently efficiency of internment on compressive strength of HSC is frequently limited compared to NSC. Reducing w/c ratio increases the strength of concrete [5]. Nevertheless, the strength of hydrated cement is low associated with the strength of coarse aggregates. Comparing two strengths it become necessary obvious that decreasing w/c ratio doesn’t increase the strength significantly, strength of HSC developed better performances, it necessary that strength and quality of coarse aggregates should experiences increased, in addition to other factors. Typically, w/c ratios between 0.2- 0.4 are used for HSC. Further it observed that Low w/c ratio reduces the workability [6] observed that an influence of silica fume on strength development of HSC is most prominent during 7 to 28 days after mixing. Measured compressive strength of HSC is determined based on testing variables, namely, mold type, specimen size, end conditions and strain rate 4×8 in. (102×204 mm) cylinder specimens have been shown to produce (ACI, 2010). ACI-318 (ACI, 2011) defines the secant modulus of elasticity as the ratio of stress and strain at 40% of the compressive strength. As strength of concrete increases, its modulus of elasticity increases as well. Poisson’s ratio is not affected by compressive strength, curing method and age of concrete [7-15].
Theoretical Background
Results and Discussion
Table 1: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Curing Age |
Predictive Values of Compressive Strength [100%, CA] |
Experimental Values of Compressive Strength Variation [100%, CA] |
7 |
23.403909 |
22.93 |
14 |
36.20573 |
34 |
28 |
36.692793 |
37.2 |
Table 2: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Curing Age |
Predictive Values of Compressive Strength 90 % CA + 10% steel slag |
Experimental Values of Compressive Strength Variation [ 90 % CA + 10% steel slag] |
7 |
24.530225 |
23.323 |
14 |
35.610156 |
34.11 |
28 |
38.487096 |
38.55 |
Table 3: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Curing Age |
Predictive Values of Compressive Strength 80% CA + 20 % steel slag |
Experimental Values of Compressive Strength Variation 80% CA + 20 % steel slag |
7 |
28.66521 |
27.57 |
14 |
38.15046 |
37.26 |
28 |
40.00856 |
41.25 |
Table 4: Predictive and Experimental Values of Tensile –Strength at Different Curing Age.
Curing Age |
Predictive Values of Tensile Strength [100%, CA] |
Experimental Values of Tensile Strength Variation [100%, CA] |
7 |
2.241157 |
2.36 |
14 |
3.24354 |
3.21 |
28 |
3.391321 |
3.32 |
Table 5: Predictive and Experimental Values of Tensile Strength at Different Curing Age.
Curing Age |
Predictive Values of Tensile Strength 90 % CA + 10% steel slag |
Experimental Values of Tensile Strength Variation [ 90 % CA + 10% steel slag] |
7 |
2.490865 |
2.52 |
14 |
3.461955 |
3.49 |
28 |
4.061343 |
4.28 |
Table 6: Predictive and Experimental Values of Tensile –Strength at Different Curing Age.
Curing Age |
Predictive Values of Tensile Strength 80% CA + 20 % steel slag |
Experimental Values of Tensile Strength Variation 80% CA + 20 % steel slag |
7 |
2.673303 |
2.59 |
14 |
4.103106 |
3.95 |
28 |
4.435216 |
4.52 |
Table 7: Predictive and Experimental Values of Tensile –Strength at Different Curing Age.
Curing Age |
Predictive Values of Tensile Strength slag 70% CA + 30% steel slag |
Experimental Values of Tensile Strength Variation 70% CA + 30% steel slag |
7 |
2.775685 |
2.66 |
14 |
3.430997 |
3.5 |
28 |
3.731405 |
3.54 |
Table 8: Predictive and Experimental Values of Tensile –Strength at Different Curing Age.
Curing Age |
Predictive Values of Tensile Strength 60% CA + 40 % steel slag |
Experimental Values of Tensile Strength Variation 60% CA + 40 % steel slag |
7 |
2.5018428 |
2.48 |
14 |
3.127685 |
3.24 |
28 |
3.4667015 |
3.33 |
Table 9: Predictive and Experimental Values of Tensile –Strength at Different Curing Age.
Curing Age |
Predictive Values of Tensile Strength 60% CA + 40 % steel slag |
Experimental Values of Tensile Strength Variation 60% CA + 40 % steel slag |
7 |
2.583478 |
2.48 |
14 |
3.041768 |
3.12 |
28 |
3.306888 |
3.38 |
Figure 1: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Figure 2: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Figure 3: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Figure 4: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Figure 5: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Figure 6: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Figure 7: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
Figure 8: Predictive and Experimental Values of Compressive Strength at Different Curing Age.
(Figure 1-8) nine explain the behavior of these material as partial replacement for cement at the optimum curing age of twenty eight days, the figure expressed gradual increase of strength development to the optimum rate, the rate of increase on the strength observed from all the figure were monitored using two addictive, this minerals were applied as partial replacement for cement used at different dosage with constant water cement ratio, the study shows it refection of two different addictive reactions on the mix design, two of the addictive monitor for this study expressed the required strength based on the model concrete applied, this implies that the rate of strength developed from the study are based on the model concrete design, these was expressed from the graphical representation. The figures shows the rate of homogeneous gradual increase of the strength generated from the application of these two minerals through their mixed designed output, constant slight increase at the optimum rate explained the required increase observed at the optimum level of strength development in concrete. The study were subjected to simulation applying analytical solution that developed a model for the study, validation were applied using experimental values for verification, both predictive and experimental values generated best fits correlation.
Conclusion
The research explain the behavior of modifiers such as fly ash and super plasticizer content generating compressive strength and strain at different curing age. The study has explain the behavior of different percentage of the two addictive combined for the study, the growth rate of compressive strength and strain concrete model mix design are based on the these two modifiers, the behavior of compressive strength and strain express reflection of this additives based on different dosage and curing age, homogeneity of the aggregated also expressed tremendous impact on the strength, these are based on the design output, concrete characteristics such as porosity and void ratios were observed to determine the variation of compressive that also reflect on its strain at different curing age, water cement ratios and mixed proportion through mixed design also pressured the growth rate variation of compressive strength and concrete strain, the variation in volume through the decrease on the concrete were observed when there an applied load, the study has observed the reaction of these two addictive on the mixed design developed to determine compressive strength and concrete strain, these condition expressed the total behaviour of compressive strength and partially replace of cement with fly ash and superplasticizer, this concept implies that there is subjection of stress through an applied load as it generates cracks on concrete, these were expressed when tensile strain exceed it capacity, The derived model was subjected to model validation with experimental values, and both parameters developed best fit correlation.
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