What is the Relationship between Entrapped Air to Strength-Durability of Concrete?
Strength and Durability Properties of Concrete with Starch Admixture . by considering the relationship between amylose and amylopectin. However, for quality control purposes, relationships need to be developed between compressive strength and durability indices so that they could be utilized to. 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.
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.Relation Between W/c Ratio and Compressive Strength of Concrete
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. Of these four states, only OD and SSD correspond to a specific moisture state and can be used as reference states for calculating moisture content. In order to calculate the quantity of water that aggregate will either add or subtract to the paste, the following three quantities must be calculated: Most stockpiled coarse aggregate is in the AD state with an absorption of less than one percent, but most fine aggregate is often in the wet state with surface moisture up to five percent.
This surface moisture on the fine aggregate creates a thick film over the surface of the particles pushing them apart and increasing the apparent volume. This is commonly known as bulking and can cause significant errors in proportioning volume. The density of the aggregates is required in mixture proportioning to establish weight-volume relationships. Specific gravity is easily calculated by determining the densities by the displacement of water.
All aggregates contain some porosity, and the specific gravity value depends on whether these pores are included in the measurement. There are two terms that are used to distinguish this measurement; absolute specific gravity and bulk specific gravity. Absolute specific gravity ASG refers to the solid material excluding the pores, and bulk specific gravity BSGsometimes called apparent specific gravity, includes the volume of the pores.
For the purpose of mixture proportioning, it is important to know the space occupied by the aggregate particles, including the pores within the particles. The BSG of an aggregate is not directly related to its performance in concrete, although, the specification of BSG is often done to meet minimum density requirements.
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For mixture proportioning, the bulk unit weight a. The bulk density measures the volume that the graded aggregate will occupy in concrete, including the solid aggregate particles and the voids between them. Some experts have suggested that the method can also be used to measure the total pore volume of capillary and gel pores in the concrete [ 10 ].
Difference between Strength & Durability - NISCHINTH
Martys and Ferraris have shown that the sorptivity coefficient is essential to predict the service life of concrete as a structural material and to improve its performance [ 11 ].
The water absorption by immersion is also considered to be a relevant parameter about the performance of concrete. Several experimental investigations have shown that the capillary permeability is substantially affected by the curing condition [ 12 ].
Sufficient curing is essential for a concrete to provide its potential performance [ 13 ]. Theoretical relations between sorptivity and permeability are established in the literature [ 1415 ]. However, these relations have not been extensively evaluated experimentally. In this study, the total capillary and gel pore volume was not measured directly but was estimated using the water uptake from soaking testing.
The main objective of the present work is to study the effect of water absorption on durability of concrete such as compressive strength, permeability, sulfate attack, and chloride diffusion.
Within these tests, mechanical test, impermeability test, sulfate attack test, and chloride migration tests are realized. A detailed analysis is also presented in order to establish useful relationship between these parameters. Materials and Methods 2. Materials In experimental studies, the OPC The chemical composition of this cement is given at Table 1. The crushed stone aggregates and quartz sand with a fineness modulus of 2.
The maximum particle size of aggregates is 20 mm. As a result of experiments, the specific gravities of sand and crushed stone are andrespectively. Concrete admixture used was polycarboxylate water reducers.
Chemical composition of cement. Methods All concrete mixtures were prepared in the laboratory. Cores of mm were prepared for permeability test, and mm concrete cylinders were also prepared for chloride ions diffusion testing.
All specimens were cast in steel molds and compacted using a vibrating table. In order to achieve different water absorption, specimens were subjected to different curing methods as follows: Sorptivity of concrete was evaluated by penetration height and water absorption, and the introduction of this testing method was shown in Figure 1.
For penetration height, the surface with a length of 3—5 mm of the sample was in contact with water, as shown in Figure 1. 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. 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.
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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.
Difference between Strength & Durability
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.