Concrete field testing

A simplification of the polarization resistance technique is the linear polarization technique in which it is assumed that the relationship between E and i is linear in a narrow range around E . Usually only two points ( , 0 are measured and B is assumed to have a constant value of about 20 mV. This approach is used in field tests and forms the basis of commercial corrosion rate monitors. Rp can also be determined as the dc limit of the electrochemical impedance. Mansfeld et al. used the linear polarization technique to determine Rp for mild steel sensors embedded in concrete exposed to a sewer environment for about 9 months. One sensor was periodically flushed with sewage in an attempt to remove the sulfuric acid produced by sulfur-oxidizing bacteria within a biofilm another sensor was used as a control. A data logging system collected Rp at 10-min intervals simultaneously for the two corrosion sensors and two pH electrodes placed at the concrete surface. Figure 2 shows the cumulative corrosion loss (Z INT) obtained by integration of the MRp time curves as ... 

These observations were later confirmed in field tests where significant increases in initial and final concrete strengths were measured (see Table 16.15). As yet, no satisfactory explanation can be offered for these results. 

Non-dispersible concrete can be poured into a water-filled form without a tremie pipe to produce dense structural repairs. This type of material has particular advantages over conventional concrete both in terms of the quality of the repair produced and the reduction in placement cost associated with plant and diver manpower requirements. Field tests carried out on a commercially available AWA[46] show that bonding capability, pumpability and flowability around reinforcement are improved over conventional tremie-placed concrete. The quality and strengths of cores show AWA concrete to be suitable material for in situ structural concrete construction at considerable water depths [46]. 

The corrosion rates of rebar in concrete are high when the chloride content of the environment is high. Extensive laboratory test data on the corrosion of rebar in concrete are available.92 Field test data are limited by comparison. 

This chapter discusses current research on the use of sulfur in recycled asphaltic concrete pavements. In addition, it describes the results of laboratory tests and theoretical predictions using the latest linear viscoelastic layered pavement analysis methods (15,16) to compare the performance of various sulfur-asphalt concrete pavements with conventional asphalt concrete pavements in a variety of climates. The relationship between pavement distress and performance used in the computer program was established at the AASHTO road test (17). Finally, the results of domestic field tests of sulfur-asphalt pavements are presented along with a discussion of future trends for the utilization of sulfur in the construction of highway pavement materials. 

A most important requirement for using carpet waste FRC is, of course, that its properties must meet or exceed specifications. As for conventional concrete, field and laboratory testing for quality control must be carried out. 

The field test consisted of decontaminating the PCB-tainted concrete surface. Before and after 21 hr of photochemical treatment a 1.2 m area was sampled extensively (n = 8) to quantify PCB residues. Treated and control samples were located on alternate positions of a grid to minimize sampling error. 

Field Test. Before treatment the concrete floor was contaminated with 81 + 31 ug Aroclor 1260/100 cm (n =... 

The field test of this photochemical reactor to our knowledge represents the first demonstration of a photochemical treatment process for in-situ remedial cleanup of PCB contaminated surfaces. At this site PCB oils were deposited 7 to 13 years prior to treatment and represent residues weathered by volatilization and allowed to thoroughly migrate in the concrete surface layers. It is expected that overlying dust and soil may have provided shade, possibly reducing the PCB destruction efficiency. PCB sorbed on particulate matter would react more slowly due to reduced light penetration. 

Another problem arises because often only one, the most volatile, component of the inhibitor blend can be analysed using an amine electrode as in the case of proprietary migrating corrosion inhibitors [1,9]. In this way, the diffusion of the volatile part of the inhibitor blend can be measured but no information on the diffusion of the non-volatile fraction can be obtained. Both components of an inhibitor blend are needed at the steel surface to get an inhibiting effect (Figure 13.3). However, only the volatile component diffuses easily through the porous concrete. This may explain the discrepancy between solution experiments and mortar or field tests [1,9,11]. It has also been reported that the volatile component of organic inhibitor blends evaporates [1,9]. 

Only calcium nitrite, introduced more than thirty years ago, has a long and proven track record as a corrosion inhibitor for reinforced concrete [1,4]. MFP and alkano-lamine-based organic inhibitor blends are increasingly used but unfortunately most of the commercial apphcations lack rigorous control of the inhibitor effect. One of the very few comparative field tests on chloride-contaminated concrete studied MFP and a proprietary alkanolamine inhibitor added in the side-walls of a tunnel (16). The inhibitors were applied by the producers. The measurements of macrocell currents and half-cell potential mapping revealed that both inhibitors were virtually ineffective at the chloride concentrations of 1-2 % by mass of cement present [16]. 

The use of corrosion inhibitors could be a promising technique in restoring reinforced concrete structures, offering benefits as reduced costs and inconvenience of repairs. It has, however, to be taken into account that the use of corrosion inhibitors in repair systems is far less well-established than their application as admixtures in new structures. The performance of proprietary corrosion inhibitors in repair systems marketed under different trade names is not yet sufficiently documented by independent research work, especially when considering field tests. 

Laboratory tests on a limited number of samples indicated no significant difference from conventional concrete in terms of compressive or flexural strength. Results from field testing, which involved the construction and heating of panels to increase the rate of hydration, indicated that the addition of waste nylon fibers into Portland cement concrete panels can reduce plastic and shrinkage cracking by approximately 90%... 

In 1994, Termidor 80 WG (Rhdne-Poulenc), the active ingredient of which is fipronil, was installed in Forest Service field tests in a conventional layout. Figure 5 shows the number of years without termite attack for Termidor 80 WG in the concrete slab tests. As of 2003, there were no termite attacks at any of the plots at the four sites, down to the lowest labeled rate of 0.0625% a.i. However, it was noticed that termite pressure in the fipronil control groups at all four sites was less than expected (Figure 6, shaded bars). Termite attack in the control plots rarely surpassed about 30%. The simplest explanation for this was that it was simply a bad time for termites and termite pressures were low, leading to low attack rates at the control plots. If this were the case, it could not be said that the results in the test plots were due to the presence of fipronil it may simply be that there were few termites present. This presented a significant problem for regulatory officials. 

Field tests in the Florida Keys showed that the anodes retained physical integrity for at least 4.5 years. Laboratory test indicated that concrete resistivity does not represent a main limiting factor in performance of such anodes and that periodic water contact (as encountered in the splash/evaporation zone of marine bridge substructures) is actually necessary for long-term anode performance. This low-cost method is a competitive alternative to impressed current cathodic protection systems and a significant improvement over gunite repairs. SHRP-S-405, 10... 

Experimental studies of salt weathering on concrete 3.1 Long term field tests... 

Some other five years field tests were carried out by Irassar and Di Maio 14 1. Concrete cylinders with the size of 0150 x 300mm were buried at half height in a soil containing approximately 1% sodium sulfate. There are several important common experimental observations of the above field experiences ... 

In summary, according to the above analysis the appearances of long term field tests did not show convincing evidences to support "salt weathering" causing the deterioration of concrete partially exposed to sodium sulfate environment. 

The "salt weathering" on concrete was just received a lot of attention in the recent years. Based on the above analysis of a limited number of research reports, the experimental results already showed convincing appearances that were completely opposite to the basic principles of salt weathering distress on porous materials. On the contrary, the experimental results of long term field tests and indoor tests rather tended to indicate that chemical sulfate attack is the mechanism for the concrete damage. 

An important result of long term field tests is the negative role of mineral additions in the concrete sulfate resistance. Normally, the indoor tests [74 oi always showed that the mineral additions can improve the sulfate resistance of cementitious materials based on the full immersion in 5% sulfate solutions stored at 23.0 + 2.0°C. However, the long term field tests showed that the mineral additions accelerated the concrete decay. 

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