Water Permeability Of Concrete Research Articles

Water permeability and chloride penetrability of high-strength lightweight aggregate concrete

This paper presents an experimental study on the water permeability and chloride penetrability of high-strength lightweight concrete (LWC) in comparison to that of high-strength normal-weight concrete (NWC) with or without silica fume. The results were also compared with those of the concrete at a normal-strength level of about 30–40 MPa. In order to compare the water permeability and chloride-ion penetrability, LWC and NWC had the same proportion by volume. The only difference between them was the coarse aggregate used. The results indicated that at the strength level of about 30–40 MPa, the water permeability of the LWC was lower than that of the corresponding NWC. However, the water permeability of the high-strength LWC and NWC was of the same order. The resistance of the LWC to the chloride penetration was similar to that of the corresponding NWC both in the normal-strength and high-strength levels. As the compressive strength of the LWC was lower than that of the corresponding NWC, the results indicated that for a given 28-day strength, the LWC would probably have high resistance to water and chloride-ion penetration than the NWC. The results indicated that the resistance to the chloride penetration does not seem to be correlated to the water permeability of the concrete. There appears to be, however, a direct relationship between the rapid chloride penetrability determined by ASTM C1202 and the observed chloride penetration depth determined by the immersion and salt ponding tests.

Mix Design and Properties of Water Permeable Concrete Compacted by Vibration.

The purpose in this study is to investigate the rational mix design method of water permeable concrete sat isfying environmental and structural requirements such as a proper coefficient of permeability and compres sive strength. Voids in the concrete were classified into the three types of void of permeable, non permeable and entrained air, and the absolute volume of aggregates, and the volume ratio of cement paste to aggregates were defined in this study. Thus, the new mix design method for a water permeable concrete by vibrating compaction was proposed and applied availably for the practical mix proportion. Mechanical properties such as modulus of elasticity, tensile strength and flexural strength of the water permeable concrete were also measured.

Effect of Shrinkage and Load-Induced Cracking on Water Permeability of Concrete

Research on the durability problems of concrete structures has focused on the efficacy of concrete as a barrier against aggressive environments. Research laboratories have used permeability tests on intact concrete for assessment and effectively ignored in-service cracking such as shrinkage and load-induced cracks on the apparent water permeability. Shrinkage cracking was achieved by rapid oven drying concrete specimens at 105 deg C; load-induced cracking was achieved by loading 200-mm-by 100-mm diameter specimens in uniaxial compression levels to stress of 0.3, 0.5, 0.7, and 0.8 of the average cylinder crushing strength. Water permeability was chosen as a measure of the barrier quality. Experimental variables that included five different mixes yielded standard deviations of nominally identical samples that exceeded apparent differences in behavior attributed to the imposed stress. Significant differences in coefficient of permeability were obtained between virgin and oven-dried and resaturated specimens. These results support the view that orientation and distribution of shrinkage cracks were effectively isotropic, whereas load-induced cracks were strongly oriented and localized but did not have a measurable effect on the permeability of specimens that were unloaded when tested, thus indicating significant elastic recovery of the cracked concrete, which caused cracks to close.

Effect of curing on water permeability of concretes prepared with normal Portland cement and with slag and silica fume

The effect of curing on the coefficient of permeability of concretes was studied. Concretes, grades 35 and 40, were prepared from a normal Portland cement and from a high slag blended cement. The effect of the addition of silica fume to both of these binders was also studied. The water permeability of various concretes was measured using the constant flow method. The coefficient of permeability was evaluated for concretes subjected to three types of curing: samples were continuously moist cured for 7 or 28 days, or were subjected to 28 days of intermittent curing. Twenty-eight days of intermittent curing was found to be as effective in reducing permeability as 7 days of continuous moist curing. Twenty-eight days of continuous moist curing gave the lowest coefficient of permeability. The addition of silica fume to normal Portland cement considerably reduced the permeability, and concretes prepared with high slag blended cement had lower permeability than did those prepared with normal Portland cement.

Methods for the Determination of Water Permeability of Concrete

Two test methods have been successfully used to determine the water permeability of different concretes. The methods are based on the determination of coefficient of permeability using either a constant flow or a depth of penetration technique. The flow method has generally been found to suit concretes with higher permeability, while the penetration method is used for concretes with very low permeability. Presently no clear guidelines exist for the selection of the appropriate method for a particular type of concrete. This study was carried out to examine the correlation between the two methods. A broad guideline has also been established for the selection of the appropriate method for a particular concrete with respect to its binder composition, 28-day compressive strength, and age. The concretes examined were prepared from five types of binders and with a grade range of 35-50 MPa.

Water-permeability measurement of high performance concrete using a high-pressure triaxial cell

Water permeability of concrete is used to indicate its durability. Accurate and reproducible measurement of water permeability is difficult and becomes more difficult as the quality of concrete increases. When high-performance concrete (HPC) is tested, these concerns become more pronounced. HPC is used widely to improve the durability and performance of structures but there are few test procedures able to evaluate its permeability-related properties. In this study the water permeabilities of concretes including HPC were measured using a highpressure triaxial cell with a sensitive and automated measurement capability. Special analysis procedures were developed to obtain useful data from the extremely low volume of water being measured. This method was able to measure a wide range of permeability values from 10 −12 m/s to 10 −16 m/s, with reproducible measurements on replicates.

Clam' Tests for Measuring in-Situ Permeation Properties of Concrete

Abstract This paper descirbes a simple test measuring the sorptivity (a measure of the absorption property if concrete) and the air and water permeability of concrete on site. Using this test, the decay of pressure is monitired for the air permeability test.whereas water penetrating into the concrete at a constant pressure of 0.01 bar and 1.5 bar are recorded for the sorptivity and the water permeability tests respectively. These tests are essentially non-destructive in nature and a skilled operator is not needed. It is possible to carry out a number of tests quickly and efficiently on site without prior planning. It has been found that statistically satisfactory results can be obtained from a mean of three tests. As the flow lines are largely concentrated within 40 mm from the surface, reasonably reliable results can be obtained by drying the surface even if the surface under test is initially wet.

A high pressure triaxial cell with improved measurement sensitivity for saturated water permeability of high performance concrete

The measurement of the saturated water permeability of concrete is of great interest, but with the rapid improvements in properties of high performance concretes, the most common problem is the ability and accuracy of measuring the very small flow volumes. A high pressure triaxial cell with improved measurement sensitivity, capable of continuously measuring saturated water permeability of the order of < 10 −15 m/s, is presented in this paper.

Simple Method for Measuring Water Permeability of Concrete

A Simple test to estimate the permeability of concrete is described. Movement of water under gravity through a 12.5 x 10 mm (0.5 x0.4 in) disk of concrete is monitored at atmospheric presure. Steady-state conditions are reached typically in 7 to 14 days, and values of permeability can be determined reliably in 14 to 20 days. The reproducubility of the test is satisfactory, and preliminary measurements indicate that it can discriminate between concretes that have been subjected to different curing conditions or excessive loads.

Methods of measuring the air and water permeability of concrete

Synopsis This paper describes simple and portable apparatus for estimating the air and water permeability of concrete in situ. The methods used require a small hole 5·5 mm diameter and 30 mm deep to be drilled in the specimen. The hole is plugged with a catalysed liquid silicone rubber which sets to give a resilient seal to the small cavity in the concrete. A gas- and liquid-tight connection is obtained by inserting a hypodermic needle through the silicone ruhber. The results obtained using the apparatus on laboratory-prepared concrete show good correlation with both water/cement ratio and compressive strength; it is suggested that the proposed methods may prove useful for predicting the durability of concrete. The techniques are sensitive enough to detect differences in aggregate porosity. The moisture content of the concrete has a major injiuence on the readings; a miniaturized moisture meter is being developed so that corrections can be made for this effect.