This thesis is concerned with rapid chloride testing of concrete. In particular, it describes the development of the rapid chloride conductivity test which measures the physical resistance of concrete to the transport of chloride ions. The test was developed to be used in engineering practice for, inter alia:- • marine concrete durability research • predicting long-term chloride ingress into concrete • construction quality control. The test is of low cost, has a sound theoretical basis, and as far as can be ascertained, is the most rapid of all chloride tests developed to date. Due to the short test duration, it is possible to test concretes cured for very short periods. Samples can also be left immersed in chloride solution and re-tested at later ages to study time-dependent phenomena such as chloride binding. The chloride conductivity test involves the standardisation of the concrete pore solution by vacuum-saturating a concrete sample with a 5 M NaCl solution. A single conductivity measurement of the sample is then performed. Different concrete samples yield different conductivities primarily because of differences in their pore and micro-structure. The measured conductivity is related to the diffusibility ratio as well as to the theoretical steady state chloride diffusivity of concrete. Trial tests were performed to determine the optimum conditions for the test (sample conditioning. test procedure) and to verify the test relationships. The conductivity test apparatus was designed to: • • • accurately measure DC conductivity be inexpensive and easy to use allow rapid changeover from one sample to another. The chloride conductivity test was standardised by means of a ruggedness test (ASTM E 1169-89). which determines the allowable ranges in the critical variables involved in the test method. Proper control over these variables was subsequently set out in the test method specifications. The single-operator coefficient of variation of the test is estimated to be 6 % . while the range of typical test results may span approximately two orders of magnitude. The test is therefore very sensitive to the measured property. An extensive laboratory- and site-based experimental programme was carried out to demonstrate the possibility of using the test for the purposes stated. The laboratory tests involved the durability characterisation of a range of concrete mixes using the chloride conductivity test, an oxygen permeability test and a water sorptivity test. Toe site tests involved correlating the test results with chloride ingress in-situ in a marine environment. The chloride conductivity test was shown to be suitable for durability research due to the following characteristics: • high precision • sound theoretical basis • short test duration. The good correlation obtained between the chloride conductivity results and in-situ chloride ingress parameters verified the potential of the test to predict chloride ingress. The test should ideally be coupled with a chloride ingress model if it is to be used for the prediction of long-term chloride ingress. Such a chloride ingress model based on the chloride conductivity test has recently been developed in the UCT laboratory. The chloride conductivity test can be used for construction quality control as it is sensitive to most of the quality-related parameters: • • • • water/cement ratio cement type cement content curmg • compaction For quality control purposes the test can be thought of as an index or characterisation test. since it yields a reproducible measure of the physical resistance of concrete to the passage of chloride ions. The use of such a durability index test in conjunction with a covermeter survey after construction would help ensure compliance with specifications. The work done has indicated the possibility of developing a further test that would give a rapid indication of the chloride binding characteristics (chemical resistance to chloride ingress) of concrete. The test would involve saturating concrete with a lower concentration chloride solution ( 1 - 3 M NaCl) and then measuring the reduction in conductivity with time. With lower concentration chloride solutions, the test becomes very sensitive to a reduction in chloride concentration in the pore solution due to chloride binding.

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