What are the research that are related to the durability and strength analysis of concrete blocks? 1, Views · What is the bond strength. Strength and Durability ofConcrete: Effects of Cement Paste-Aggregate Interfaces Part E, the experimental part, illustrates the relationship between the ITZ In summary, the goal of this research was to investigate the role of the transition. Strength and Durability Assessment of Portland Cement Mortars . According to Glavind , the goals of sustainable concrete should be achieved .. an exponential relationship between compressive strength and ER at all.
Durability Test Results 3. Compressive Strength and Porosity The larger water content in cement mortar leads coarse pore distribution. Pore size distribution PSD and porosity are presented in Figure 2. Averages from 3 samples are plotted for the evaluation of porosity and strength, respectively.
PSD and total porosity. Chloride Diffusion Coefficient and Porosity Chloride diffusion coefficient is dependent on pore structure since pore can be both room for holding chloride ion and route for ion diffusion [ 2938 ]. 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.
Strength and Durability Assessment of Portland Cement Mortars Formulated from Hydrogen-Rich Water
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. The penetration resistance offered by the mortars was plotted versus time.Panel Discussion :: Relationship Goals (Part 5)
The initial and final setting times were calculated from the same plot when penetration resistance values reached 3. Apparent porosity for day hardened 50 mm side mortar specimens was determined in accordance with ASTM C [ 19 ]. Capillary absorption test on the cubic specimens was performed after 28 days of curing in accordance with UNI EN This test measures the amount of water absorbed through capillary absorption by a dried specimen. The side surfaces of the specimens were sealed with a sealant for contact with water up to a depth of 5 mm.
The ER test on mortars was performed at 7, 28, 56, and 90 days using an ER measuring device with two electrodes. The electrodes were attached to two sides of the specimens; the ER was calculated using the formula where is the area of the cross section, and is the sample length.
The samples were ground and treated with acetone to remove water and thereby mitigate the hydration reaction. Exactly 1 mg of sample was mixed with mg KBr to make a pallet. To observe the morphology and the extent to which hydration products formed at the microlevel, scanning electron microscope SEM analysis backscattered mode was performed on 7- and day hydrated samples CWM0 and HWM0. The samples were coated with platinum to prevent charging and analyzed at 15 kv at 12kx magnification.
Results and Discussion 3. Setting Time and Apparent Porosity Figure 1 represents the initial and setting times of all the fresh mortar mixtures used in this experimental program.
As shown in the figure, increased HRW concentrations decreased the setting time of the mortars. The final setting times for the same mixes were, and 62 minutes. This decrease in setting time both initial and final setting times with the increase in HRW concentration indicates the set accelerating effect of HRW in mortar mixtures.
The fast early and final setting times are attributed to the rapid hydration of an HRW environment. It is known that a set accelerator reduces the duration of the induction period required for the growth of cement hydrates, which leads to a higher degree of hydration at an early age [ 2526 ]. The day apparent porosity exhibited by all mortar mixtures is also shown in Figure 1. The results indicate that increasing HRW concentrations lead to lower porosity in the mortars. The day apparent porosity of HWM0.
The reduced porosity indicates the presence of fewer open pores and voids, which implies a dense microstructure. Additionally, it is presumed that in HWMs better degree of hydration leads to a reduction of capillary pore volume because capillary pores become filled with hydration products, and gel pore volume is increased as more gel is formed.
This leads to reduced total porosity in the case of HWMs. Setting time and day apparent porosity of cement mortars.
Compressive, Flexural, and Splitting Tensile Strength The compressive strength development of all the mortar mixtures during the entire curing period is shown in Figure 2 a. The compressive strength results presented are the average of 6 specimens for each mortar mix. As shown in the figure, the compressive strength increased with the curing time irrespective of the mixture.
The day compressive strength of all mortar mixtures was in the range of A higher strength gain for HWMs was also observed at later ages 56 and 90 days. The percentage increase in compressive strength for HWM0. This remarkable increase in compressive strength at an early age indicates the set accelerating effect of HRW. The enhancement in compressive strength in HWMs is attributed to their more compact and dense microstructure caused by precipitation of more hydration products calcium hydroxide CH and CSH in the hydrogen-rich environment, which leads to reduced apparent porosity and fewer intermittent pores.
Those hydrated products contribute to high compressive strength by reducing the porosity and improving the microstructure of the paste matrix and interfacial transition zones in the cement-sand interface of the mortar mixtures.
It is a well-established fact that the strength of cement mortars is primarily the result of a three-dimensional network of hydrate phases that offer resistance to external loads without breakdown. The flexural strength of all mortar mixtures increased systematically with the compressive strength Figure 2 b. At all ages 7, 28, 56, and 90 daysan ascending trend was observed for flexural strength in all mixtures.
The day flexural strength of all mortar mixtures was in the range of 6. The highest day flexural strength was in HWM0. The variation in the splitting tensile strength of the mortar specimens with age is shown in Figure 3. The splitting tensile strength did not show a significant increase in mortars fabricated using low concentrations of HRW 0. The highest splitting tensile strength of 2.
Unlike the compression and flexural strength results, relatively fewer sharp variations in tensile strength were observed. In general, HRW has a positive effect on the splitting tensile strength of mortars, which we attribute to its filling effect caused by the precipitation of more cement hydrates. Variation in the splitting tensile strength of mortar mixtures with age. The HRW increases the pH of normal water from 7 to It is stated elsewhere [ 27 ] that, at a pH value below 8.
However, at an increased pH value, calcium and silicate species exist as hydroxylated species Ca OH 2 and silicate anions, respectively. Aluminum, silicate, and iron are also present in lower amounts [ 29 ].
Capillary Absorption The absorption and transmission of water, capillary absorption, indicate the volume of voids in cement mortar systems. A higher capillary absorption value indicates more permeable voids.
Water is the carrier of various harmful ions; therefore, capillary absorption is an important test for the durability of construction materials.
Generally, higher mechanical strength correlates with a lower capillary absorption coefficient. Figure 4 shows the capillary absorption coefficient for all the mortar mixtures at 28 days. In this figure, it is observed that increase in HRW concentration results in the reduction in capillary absorption.
The higher uptake of water in CWM0 is caused by its larger capillary pores, whereas the lower water uptake in the HWMs occurs because they have fewer interconnected flow channels. In the HWMs, the hydration products occupy more space than they do in CWM0; in other words, the formation of hydration products reduces capillary porosity.
Thus, the higher degree of hydration leads to decreased capillary porosity [ 30 ].
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Capillary absorption coefficients of mortar mixtures at the curing age of 28 days. As shown in the figure, the UPV values increase with curing age irrespective of the mixture. Factors such as pore structure, material properties, mix proportion, and the interfacial zone between aggregates and cement paste all affect UPV values. It is ascertained that HRW induces precipitation of more hydration products compared to the CWM, leading to denser, more compact microstructures.
- Effect of W/C Ratio on Durability and Porosity in Cement Mortar with Constant Cement Amount
- Strength and Durability Assessment of Portland Cement Mortars Formulated from Hydrogen-Rich Water
As a result, the porosity of the cement matrix was reduced and the continuity of pores diminished. As expected, the use of HRW increased the density of mortar because the higher degree of hydration leads to the formation of more cement hydrates and reduced apparent porosity.
A significant increase in ER was noticed with age for all mixtures. As shown in the figure, the ER exhibited by all mortar mixtures at the curing age of 28 days was found to be in the range of 7— According to ACI [ 32 ], corrosion is less likely to occur when ER is equal to or greater than At 28 days, that criterion was met by only HWM0. Moreover, it is ascertained that the increase in HRW concentration enabled mortars to develop a denser, more compact microstructure, which reduced the interconnectivity between pores and thus resulted in higher ER.
That is, it is presumed that the denser microstructure, less-continuous pore system, and reduced porosity allow the HWMs to demonstrate better resistivity.
Effect of W/C Ratio on Durability and Porosity in Cement Mortar with Constant Cement Amount
ER is an important parameter that governs the corrosion of reinforcement in concrete. The densification of microstructures increases both ER and the compressive strength of mortars [ 33 ]. It is known that as the compressive strength increases, the ER also increases. Some researchers have found a significant correlation between the two parameters, which led them to formulate logarithmic, exponential, and linear relationships [ 34 ].
In this investigation, we observed an exponential relationship between compressive strength and ER at all curing ages, with a regression coefficient of 0. It is presumed that alkaline environment in the pore solution HWMs would provide an appropriate environment for the steel bars embedded so that they can passivate and remain passivated against corrosion.
The increased alkalinity leads to a denser pore structure, which apparently is overweighing the increased ionic concentration in pore water.