Concrete laboratory testing

Table VI. Recycled Asphaltic Concrete Laboratory Test Results...

FIGURE 26.42 Comparison of the correlation coefficients between laboratory side force measurements with the six compounds of Table 26.2 on wet, blunt Alumina 180 and a concrete road test track as function of log ajv and log v (left) with function of temperature and log v (right). 

Asphalt concrete is properly proportioned to resist the potentially damaging effects in the road. Asphalt concrete paving mixtures should be evaluated for the following properties stability, flow, air voids, stripping resistance, resilient modulus, compacted density, and unit weight. Table 4.18 provides a list of standard laboratory tests that are presently used to evaluate the mix design or expected performance of fresh and hardened asphalt concrete. 

Sulphur concretes appear well suited for use in environments corrosive to Portland cement concretes. The extensive work by the U.S. Bureau of Mines shows their material performs admirably in such environments. When used as a lining, the initial stress-strain behaviour will allow the material to adapt to the main structural element and relieve internal stresses without cracking. Corrosion resistance will be maintained by the material thereafter, even though the stress strain behaviour alters. On its own, the material retains sufficient strength to withstand typical loads involved in this type of application (eg. liquid container). Sudicrete has not been tested much in this area, although laboratory tests show similar promise. 

Laboratory tests with zinc embedded in concrete have shown unstable and fluctuating zinc potentials in the range of-470 to -390 mV vs SCE [17] and roughly -0.5 V vs SCE [18]. 

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. 

Friede (43) published a series of equations for calculating the depth of the corroded zone for concrete specimens exposed to carbonic acid attack as a function of the physical and mechanical properties of corroded and noncorroded specimens, i.e. density, volume, mass, modulus of elasticity and strength. The equations, however, do not take into consideration such factors as the composition of the concrete or the degree of attack to which it is subjected. In addition, the wide variation in test results, obtained from laboratory tests performed to verify the theoretically derived equations, limit their applicability. 

The principles and criteria for estimating these properties and also equipment used to perform tests of all kinds for these oils in different countries are basically identical. However, concrete laboratory, stand, motor and operational methods can differ appreciably. Besides, there are differing viewpoints among experts even from the same country regarding the classification of the methods, i.e. this classification is substantially conditional. 

The experimental setup consists of a concrete container with gas vent surrounded by an engineered barrier system made of a 20/80 % bentonite/sand mixture, placed in layers, a granular backfill of the upper cavern and a concrete plug. In total, 12 different materials are considered in the numerical model (cf. Fig. 1). As the surrounding rock matrix is very impervious, only the relatively high-permeable shear zone is considered for flow outside of the EBS. Most important material parameters are given below. These parameters are obtained from independent laboratory test for the sand/bentonite (materials 6 and 8), from the literature for the other materials there is no back-estimation from the calculation results or calibration involved. 

Over 90 per cent of recently constructed plants have concrete floors. The types of finishes for this concrete base flooring are listed in Table 8-2, making possible a selection of one or a combination of materials for chemical plant flooring requirements. In many cases where new chemicals are being handled, laboratory tests will have to be run to select suitable flooring finishes. 

Laboratory tests of stationary diffusion of chloride ions in cementitious systems have been conducted since the 1970s for purposes of research and classification of different concrete compositions [5]. 

R. B. Polder, Laboratory testing of five concrete types for durability in a marine environment , Proc. Fourth Int. Symp. on Corrosion of Reinforcement in Concrete Construction,... 

The apparent diffusion coefficient, obtained from real structures or laboratory tests, is often also used as the parameter that describes the resistance of concrete to chloride penetration, e. g. when performances of different materials are compared. The lower D,pp is, the higher the resistance to chloride penetration is. It should, however, be observed that, while the diffusion coefficient obtained from pure (steady-state) diffusion tests can be considered as a property of the concrete, the apparent diffusion coefficient obtained from real stractures also depends on... 

Alkanolamine-hased inhibitors have been tested in similar conditions. For ongoing chloride-induced corrosion with a chloride level of about 1-2 % by mass of cement, in mortar specimens no reduction in corrosion rate was found (Figure 13.6) except at low chloride concentrations. This is confirmed by two other studies [1,11,14] pre-corroded rebars in mortar (w/c 0.75, cover thickness 25 mm) did not show any detectable effect on the corrosion rate of embedded steel once active corrosion had been initiated, despite the fact that the specimens had low cover and porous mortar [14]. It seems that for penetrating or migrating inhibitors the favourable effects found in solution do not occur when applied to hardened mortar or concrete laboratory specimens with ongoing steel corrosion. It is thus necessary to look for information regarding the transport of inhibitor blends in mortar or concrete. 

Titanium activated with oxides of different metals, in particular mthenium or iridium, used in the form of mesh, wire or strip, is the most reliable and widely used type of anode [51]. It has good mechanical properties and can easily be adapted to the entire surface of the structure in order to obtain a good distribution of current It is usually coated with an overlay of mortar but can also be embedded directly into the concrete. It can dehver current densities up to 100 mA/m over long periods, with short-term maximum levels of even 300-400 mA/m. Laboratory tests and field experience indicate that the service hfe can range from 20 to over 100 y (if the quahty of concrete and overlay are adequate). 

There has been some controversy about electro-osmosis. No evidence of its occurrence has been found in early laboratory tests or during testing of cores in a realkalisation demonstration project [24,84,85]. On the other hand, recent laboratory experiments by Andrade and co-workers [86,87] have confirmed the occurrence of electro-osmosis, supporting previous observations by BanfiU [80,88]. Electro-osmotic flow was observed in carbonated concrete, while it was not observed in uncarbonated concrete. Full understanding of the mechanism and the controlling factors in terms of practical characteristics of structures needs further study. 

Durability. Electrochemical realkalisation has been appUed for over ten years, mainly to structures made with Portland cement concrete. Although well-documented case studies are rare, those available show that the corrosion protection obtained is durable [93]. Laboratory tests followed over several years support the dur-abiUty of the effect on reinforcement corrosion, as long as sufficient electrical charge has been applied [89,90]. As noted above, the amount of charge needed may depend on the cement type. 

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%... 

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