Effect of W/C Ratio on Durability and Porosity in Cement Mortar with Constant Cement Amount
Strength and durability are the most important and critical parameter of rock and these two are the key point to evaluate the rock for different purposes. Several. The Relationship between Entrapped Air to Strength-Durability of Concrete are to have a fully compacted dense concrete with the help of available, affordable. Request PDF on ResearchGate | Correlation between compressive strength support load, but also an indirect measure of its elasticity and durability [16, 17].
Since the surface of the sample became dark when it absorbed water, penetration height at the side of samples was observed during testing. For water absorption, the surface and middle segments were cut from samples, respectively, and thus surface water absorption and internal water absorption were also measured. Before testing, specimens were sealed on the top and sides and placed in a water bath so that the open bottom was constantly submerged in a depth of 3—5 mm.
Weight of samples was measured after 4 days, and water absorption was measured.
What is the Relationship between Entrapped Air to Strength-Durability of Concrete?
A water pressure of 1. Resistance to sulfate attack was evaluated through dry-wet cycle testing. Compressive strength was measured during testing. Permeability height of concrete. Rapid migration test is a non-steady state migration using an external electrical field for accelerating chloride penetration. The test is relatively simple and rapid with the test duration in most cases being 24 hours.
The concrete samples with size of mm diameter and mm thickness were cut into 50 mm thick slices, from surface and center of samples, respectively. Results and Discussion 3. Water Absorption Permeability height can be measured through soaking testing, and results about this are given in Figure 3.
It can be shown that penetration height increased apparently with time within 12 h. For different curing methods, penetration height was not the same. It indicated that different curing conditions will cause different permeability of samples.
Penetration height of samples: Sorption depends on both the capillary pressure and effective porosity. Capillary pressure is related to the pore size through the Young-Laplace equation, and effective porosity refers to the pore space in the capillary and gel pores. In addition, different pore size leads to different capillary pressure, and capillary pressure of concrete can be calculated by the average pore size.
In order to consider surface effect, both surface water absorption and internal water absorption were investigated. Water absorption is measured by measuring the increase in mass as a percentage of dry mass.
Figure 4 gives results of surface and internal water absorption. It can be seen that surface water absorption is higher than internal water absorption for all the specimens. This is due to the rapid loss of water at the cover concrete during curing. As can be expected, higher water absorption corresponds to a higher penetration height. Under this curing condition, the surface concrete rapidly loses its water of hydration. On the other hand, for internal water absorption, samples exposed to different curing conditions presented similar results.
So, curing methods has great influence on surface properties. In order to investigate the influence of curing on microstructure of concrete, microstructure of concrete samples exposed to different curing conditions was also analyzed by SEM. As there was a large difference in surface water absorption, microstructure of surface concrete was further studied. Figure 5 showed photos of surface concrete obtained by SEM, and Figure 5 a stands for the sample exposed to condition b, while Figure 5 b stands for the sample exposed to condition d.
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From Figure 5different structures can be seen. For the sample cured in condition b, the microstructure was more compact. However, for the sample cured in condition b, there were holes and loose structure. These are consistent with the results of water absorption. Surface and internal water absorption of samples: SEM photos of concrete samples: Relations between Water Absorption and Compressive Strength After being cured for 28 days, compressive strength was measured, and Figure 6 presents results of compressive strength.Rock Strength - Stress and Strain
Effects of sorptivity on compressive strength are seen in Figure 7. Figures show that both of surface sorptivity and internal sorptivity have no clear relationship with compressive strength.
Although the specimens differ in surface water absorption, there is little difference in internal water absorption. Furthermore, the high surface water absorption only decreased compressive strength of cover concrete.
The whole strength of concrete depends on both surface and internal structures. So, strength of concrete cannot be evaluated by water absorption. Compressive strength of samples. Relationship between water absorption and compressive strength: Relations between Water Absorption and Permeability Permeability coefficients of samples with different curing conditions were measured, and results were given in Figure 8.
Relationship between permeability coefficient and water absorption was also analyzed, as shown in Figure 9. From the figures, we can see that there was no clear relationship between permeability coefficient and internal permeability coefficient. However, apparently, a linear correlation exists between permeability coefficient and surface permeability coefficient.
The permeability coefficient increased with the increase in surface water absorption.
- Effect of W/C Ratio on Durability and Porosity in Cement Mortar with Constant Cement Amount
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As we know, both of permeability and water absorption were affected by the pore structure of cement paste, and liquid transfers from surface into interior.
So, it indicated that surface water absorption provides great influence on permeability. In addition, the high correlation coefficients of 0. In addition, obviously, internal water absorption had little impact on permeability. Permeability coefficient of samples. Relationship between water absorption and permeability: Relations between Water Absorption and Sulfate Attack Resistance to sulfate attack is evaluated by the loss of strength.
During sulfate attack testing, compressive and flexural strengths of specimens were measured after different dry-wet cycles. Relative strengths after 30 dry-wet cycles were presented in Figure Results shown in Figure 11 demonstrated the effect of water absorption on resistance to sulfate attack. Higher relative strength indicates greater resistance to sulfate attack.
It has been discussed earlier that impermeability reduced with the increasing value of surface water absorption. This characteristic was quite similar to the behavior exhibited by resistance to sulfate attack.
What is the relationship between strength and durability of concrete? - Quora
Based on Figure 11there was a linear correlation between surface water absorption and loss of compressive strength due to sulfate attack. In addition, loss of compressive strength showed a higher rate of decrement indicated by steep slopes of the curve. By contrast, the loss of compressive strength did not appear to depend upon internal water absorption, as shown in Figure 11 b.
The relationships between two parameters were calculated and their correlation results are presented in Figure 11 a. Relative strength of samples after sulfate attack. Relationship between water absorption and resistance to sulfate attack: Relations between Water Absorption and Chloride Attack The rapid migration test provides value ofwhich is also under the assumption of constant chloride binding capacity during the test. Capillary absorption is an important mechanism related to the chloride ingress into concrete.
Nonsaturated concrete in contact with a salt solution will absorb this solution by capillary forces [ 16 ]. Water Evaporation and Porosity For water loss, distinct difference is not observed within a few hours but can be observed with extended drying periods to 10 days. The samples with higher porosity can have larger room for keeping water so that water loss from each sample shows different amount with drying process.
This shows consistent result with previous research [ 24 ]. In the saturation from 3clear difference is not measured since the mortar with larger water loss has larger amount of free water as well. The water loss and saturation are presented in Figure 5 and they are plotted with measured porosity in Figure 6.
The amount of water loss increases to 7. Moisture Diffusion Coefficient and Porosity Concrete with large product of hydrate has dense pore structure. The results of sorptivity, surface concentration, and moisture diffusion coefficient are listed in Table 5 and presented in Figure 8 with measured porosity.
Results of sorptivity, surface concentration, and moisture diffusion coefficient. Porosity and Durability Performance 3. In order to analyze the changes in pore size, pore volumes in 5 groups of pore diameter are evaluated. Figure 9 shows the pore volume in 5 specified groups. PSD in different pore radius.
In 2 groups of pore radius below 0. The finer pores are easily filled with swelling of cement particles so that higher gradients of changing porosity are evaluated in the first 2 groups. The results of regression analysis shown in Figure 10 b are listed in Table 6 with determinant coefficients.
The second group 0. The results are shown in Figure 11 and those from regression analysis are listed in Table 7. Results of regression analysis for normalized porosity and durability performance. Relationships between normalized porosity and durability performance. Nonlinear relationships of square root of porosity are found in water loss and air permeability.
Sorptivity and moisture diffusion coefficient are related to square of porosity. Except for saturation, durability performances can be related to porosity change with high determinant coefficient.
This paper presents quantitative patterns and relationships between porosity and durability performances in the cement mortar with constant cement contents.