Journal of Materials in Civil Engineering

This paper presents experimental work conducted to investigate the possibility of using unconfined compressive strength (UCS) of soil-cement as a credible indicator of durability. The UCS is determined for specimens subjected to cycles of the standard freeze-thaw durability test but not brushed, which eliminates a major source of variation and produces more consistent results. The measured strength will be termed the residual UCS. The work in this paper complements previous work done on wet-dry durability test specimens. UCS could also be determined for the specimens cured for 7 days without subjecting it to the alternating cycles, and this will be termed UCS. The data in this paper show strong correlation between percent mass loss from the standard freeze-thaw durability test and either residual UCS or UCS. The use of UCS, pending enough data, could also expedite the results and reduce the duration of the test from about 40 to 7 days.

The present paper studies the static and dynamic properties of cementitious thin sheets reinforced with discontinuous fiber reinforcement by direct tension test and impact test. The thin sheet specimens are fabricated by the extrusion technique so that the majority of fibers can be aligned into a unified direction. Two kinds of fibers are investigated: (1) polyvinyl alcohol fibers; and (2) glass fibers. It is found that glass fibers are more effective in improving the tensile strength and impact properties of specimens, while polyvinyl alcohol fibers can greatly increase the tensile strain and toughness of specimens. When using these two fibers together, both the static and dynamic properties of specimens can significantly be improved, especially the impact toughness. The influences of high dosages of ground blast furnace slag and silica fume in the mixture are also investigated. The optimum mixing ratios of these mineral admixtures are proposed based on the static and dynamic testing results.

Although structural light-weight concrete has enjoyed frequent application in Europe and the United States since the 1950s, it has not been used at all in Turkey despite abundant and economical sources of natural light-weight aggregates. The reason for this reluctance is lack of confidence and technical ignorance. In order to allay, to some extent, the fear in the construction sector of using pumice as a concrete aggregate, composite reinforced concrete (CRC) is suggested. The CRC element consists of two layers, the lower being cast as normal-weight concrete (NWC) and the upper as a layer of light-weight concrete (LWC), both of which are placed in the fresh phase, the LWC overlying the NWC. Hence, bond strength will be close to that in normal reinforced concrete elements, which is important for Turkey, where usage of plain steel reinforcement bars is still common. The depth of the LWC layer will be greater than that of the NWC layer. Because of the widespread practice of ready-mixed concrete suppliers, it is practicable for some mixers to carry LWC while others handle NWC. In this study, theoretical ultimate strength analysis of such a CRC element is done and its mechanical behavior is experimentally investigated by subjecting many prototype CRC elements to bending in a conventional four-point loading-frame setup. It is observed that the CRC elements behave similar to normal reinforced concrete elements with the advantage of reduction in dead weight.

The material's volumetric-flow rate (MVR) (cm³/10 min) through a predefined die under conditions of constant temperature and stress has been used for obtaining unified curves of fundamental rheological properties such as |G*|, G″, and |G*|/sin δ versus frequency in the case of six unmodified asphalts. It has been shown that there is a theoretical basis for the unification and that the unified curves have far-reaching implications. Because MVR is so simple to determine quite accurately on a relatively inexpensive, easy-to-use flow measurement device, this parameter can be generated on paving sites or at refineries, rather than in research laboratories as is the case with fundamental rheological parameters. The MVR can then be used as an excellent indicator of the fundamental rheological parameters through the use of the unified curves.

This paper reports on the results of experimental studies on the durability of intumescent coating for steel frames. Intumescent coatings are fireproof materials that provide the thermal insulation of steel structures. They start to foam when the surface temperature reaches about 300°C by heating and form a layer of carbonaceous char 25 to 50 times thicker than at room temperature. However, their durability or long-term fireproofing is not clear. Preliminary accelerated tests and small-scale heat tests were conducted, and it was found that water is the principal environmental factor that affects the durability of intumescent coatings. Another series of accelerated tests and exposure tests was then performed mainly for water resistance. The fire resistance of specimens after degradation was verified in full-scale heat tests. As a result of these tests, a new testing method was proposed for evaluating the durability of intumescent coatings by considering the high-temperature and high-humidity weather conditions of Japan.

A better understanding of the bond behavior, which is one of the main behavioral aspects of reinforced concrete structures, is needed for fiber-reinforced plastic reinforcing bars, because tests have shown that the bond is different from that of steel reinforcing bars and varies with the type of reinforcing bar as well. In this paper results from bond tests performed on commercially available glass fiber-reinforced plastic (GFRP) reinforcing bars are presented and discussed. The experimental bond-slip curves have been obtained and some information about bond mechanisms have been derived. Furthermore, values of the elastic modulus and the tensile strength of the reinforcing bars have been measured. Finally, a numerical procedure for the identification of the constitutive bond stress-slip relationship, based on the experimental results, is presented.

Stabilized rammed earth offers a low energy durable alternative to conventional building materials, such as masonry and processed timber, for low-rise residential projects. To date, rammed earth construction has mainly been used in the developing world, particularly Africa and Asia. Despite recent applications in Australia and the United States, further development of rammed earth in these countries has been hindered by a lack of data on important aspects of material performance. In this paper, work undertaken to assess bond of rebars embedded in rammed earth is described. A variety of cement-stabilized rammed earth pullout test samples were fabricated with deformed, galvanized deformed, plain, and stainless steel rebar. Pullout bond resistance is shown to be a function of rammed earth compressive strength, rebar type, embedment length, and the method of specimen preparation.

Temperature is one of the most important factors affecting the design and performance of pavement. Temperature variations within the pavement structure contribute in many different ways to distress and possible failure of that structure. The structural performance of pavements is highly dependent on temperatures to which these pavements are exposed. Under loading conditions, the pavement temperature is a major factor affecting the deformation response of bituminous structures. The load-spreading characteristics depend on the moduli of temperature-sensitive layers whose strength is significantly reduced by increased temperature. Variations of temperature across pavement depth must be considered in the back-calculation of flexible pavement layer moduli. This paper presents the results of a comprehensive study that was carried out to explore trends of temperature variation in an arid environment and their implications on the moduli of flexible pavements. Temperature correction factors and resilient modulus estimation equations from basic material physical properties were developed using statistical procedures to a high degree of reliability.

The volume of waste polymer being produced continues to rise. Disposal is difficult and waste exceeds acceptable levels. The purpose of this research is to examine the possibility of incorporating waste polymer into bitumen as a modifier. The aim was to find recycled polymer modified binders that would be similar to proven modified binders or that would augment the properties of 100 penetration grade bitumen. A wide range of recycled polymers were tested, including polyethylenes, polypropylenes, polyetherpolyurethane, ground rubber, and truck tire rubber. Tests included viscosity, penetration, softening point, aging, and rheology. Stiffness tests on samples of bituminous mixes made using a selection of binders also formed part of the research program. Although stability problems were evident with some recycled modified bitumen, some cases were found to be successful. The blend with 3% low density polyethylene substituted for 1% styrene butadiene styrene had similar properties to that of Polyflex 75, although it had lower stiffness. The most impressive was a combination of low density polyethylene, bitumen, and ethyl vinyl acetate.