Showing papers on "Durability published in 1985"

The effect of deicing salt on aggregate durability

Abstract: Since 1962, the Iowa DOT has been using the methods of rapid freezing in air and thawing in water to evaluate coarse aggregate durability in concrete. Earlier research had shown that the aggregate pore system was a major factor in susceptibility to D-cracking rapid deterioration. There are cases in which service records indicate that on heavily salted primary roads, concrete containing certain aggregates show rapid deterioration while the same aggregates show relatively good performance on secondary roads with limited use of deicing salt. A fivecycle salt treatment of the coarse aggregate before durability testing has yielded durability factors that correlate with aggregate service records on heavily salted primary pavements. X-ray fluorescence analyses have shown that sulfur contents correlate well with aggregate durabilities with higher sulfur contents that produce poor durability. Trial additives affecting the salt treatment durabilities would indicate that one factor in the rapid deterioration mechanism is an adverse chemical reaction. The objective of the current research is to develop a simple method of determining aggregate susceptibility to salt-related deterioration. This method of evaluation includes analyses of both the pore system and chemical composition.

Durability of building materials: Durability research in the United States and the influence of RILEM on durability research

Abstract: This paper is based on the text of a talk given at a RILEM Seminar on Durability of Building Materials. It reviews some of the recent non-proprietary research on the durability of building materials carried out in the US. It also reviews activities in RILEM which have stimulated the generation or dissemination of knowledge on durability of building materials. The paper emphasizes the need for international collaboration in durability research.

Durability predictions of adhesively bonded composite structures using accelerated characterization methods

Abstract: The utilization of adhesive bonding for composite structures is briefly assessed. The need for a method to determine damage initiation and propagation for such joints is outlined. Methods currently in use to analyze both adhesive joints and fiber reinforced plastics is mentioned and it is indicated that all methods require the input of the mechanical properties of the polymeric adhesive and composite matrix material. The mechanical properties of polymers are indicated to be viscoelastic and sensitive to environmental effects. A method to analytically characterize environmentally dependent linear and nonlinear viscoelastic properties is given. It is indicated that the methodology can be used to extrapolate short term data to long term design lifetimes. That is, the method can be used for long term durability predictions.

The durability of steel in concrete

Abstract: In a joint research programme, BRE and Aston University are studying the basic processes of corrosion in reinforced concrete. This will provide essential knowledge for predicting long‐term durability and performance of reinforced concrete and for the assessment of repair work.

Stochastic Modeling of Building Materials Performance in Durability

Abstract: The scatter in observed service life of buildings and structures is very high. Designing an optimal structure in relation to the durability is therefore not easy. In this paper, the use of a probabilistic approach is explored as a possible means of addressing service life prediction problems. Essentially the same techniques are used as those which have been proven to be successful as a design tool for ultimate and serviceability limit states without deterioration effects. As an example, an outdoor gallery slab, made of reinforced concrete, is analyzed for the limit state of corrosion of the reinforcement. The analysis provides insight into the relative importance of parameters involved. Furthermore, a cost optimisation is performed including building costs and expected maintenance and repair costs.

Relative Durability of Shale -- A Suggested Rating System

Abstract: The inability to predict the degradation tendencies of shale ha re sulted in numerous failures of projects where shale was used as a construc tion material. Because shale does not fit neatly into either a soil category or a rock category, the tests that are cocznonly used to classify soil or rock are in many instances not totally suitable for classifying shale as to its long—term behavior properties. Thus, special classification tests of shale types has becane necessary. The durability or shale relates to how weil it can withstand its changing environment and still retain its initial proper ties. Strength, expanaion characteristics, and pereabflity play a part in the durability of a shale. A good classification system would incorporate in sane manner these parameters to reflect the short-term and long-term durability of the shale. A new method of predicting shale durability has been developed based upon an analysis or a battery of index tests. Using multiple regression techniques, six tests have been shown to reflect the overall durability of shale. One of these tests is a new modification of the slake durability index test. These tests have been incorporated into a simple linear equation which can be used to obtain a durability rating on a scale of 0 to 100 for a particular shale.

Sand blast carving method

Abstract: PURPOSE:To withstand a sand blast even with a thin film and obtain easy release and safety by screen-printing with a specific-mesh plain gauge on a surface protective film of a solution made of water dispersion acrylic polyvinyl alcohol resin and a release agent then drying it CONSTITUTION:About 03-30ptswt of a solution of polyvinyl alcohol resin with polymerization degree of about 300-2,000 solved in water is mixed with about 100ptswt of colloidal dispersion of water dispersion acrylic resin or acrylic resin and further a release agent is added Next, screen printing is performed by passing a screen-printing water dispersion solution through a 50- 250-mesh plain gauze onto an inorganic surface, eg, metal, stone, plaster, or a plate, furthermore, a surface protective film is formed which withstands a sand blast after the film is dried and is capable of re-peeling off as required after a sand blast The work environment on occupational safety and health against poison and fire is improved and the durability of the printing positive and plain gauze can be improved

A Laboratory Study of the Effectiveness of Various Admixtures on the Attenuation of Moisture Damage Upon Various Foamed Asphalt Mixtures

Abstract: Durability characteristics of certain foamed asphalt mixtures were established during this laboratory investigation. Durability was characterized by a water sensitivity test and cyclic freezing and thawing. The various foamed asphalt mixtures were evaluated for durability after the mixtures had been compacted into 10.16-cm (4.00-in.) diameter by approximately 6.35-cm (2.50-in.) high specimens, and cured. Durability effects of different variables were determined in this laboratory study. These variables were foamed asphalt content (two levels for water sensitivity section, one level for freeze-thaw section), aggregate (three types, used in both sections), additives (three types, plus a set without additives), and additive content (two levels for each additive in the water sensitivity section, one level for each additive in the freeze-thaw section). One asphalt type, one mixing and testing temperature, one set of curing conditions, and one moisture content per aggregate were used. Resilient modulus and modified Marshall stability tests were used to monitor durability characteristics of the mix in the water sensitivity section. Durability in the freezing and thawing section was monitored by pulse-velocity, resilient modulus, and modified Marshall stability tests. When lime was used as an additive, durability, strength, and longevity of the foamed asphalt mixtures were substantially improved. The improvement achieved with the addition of lime was such that a material generally less suitable for bituminous mix, such as outwash sand or pit-run gravel, may rival a material more suitable for bituminous pavement mix such as crushed limestone. During this study there were similar rates of decline per freeze-thaw cycle for pulse-velocity and modified Marshall stability. Pulse-velocity, a nondestructive test, appears to be related to the destructive modified Marshall stability method. There seemed to be a good reproducibility of pulse-velocity values among similar specimens.

Study on Surface Durability of Laser-hardened Steel Roller

Abstract: Laser-hardened S45C, SNCM439 and SMnC443H steel rollers and induction-hardened S45C steel rollers were tested using a sliding-rolling contact fatigue testing machine, and the surface durability and surface failure were investigated. The experimental results were discussed in terms of an amplitude of ratio of reversing orthogonal shear stress to hardness. The machanism of spalling failure of laser-hardened rollers was made clear, and it was recognized that the surface durability of a laser-hardened roller was possibly equal to or higher than that of an induction-hardened roller.

Durability of Reinforced Concrete Structures in Marine Environment

Abstract: This report presents the result of the investigation of corrosion of reinforced steel and concrete deterioration.

Durability of concrete

Abstract: The durability of concrete is obviously a complex topic. This paper deals with an overview in four parts: The first part consists of durability as affected by more than 200 individual separate items involved in its constituent materials; the effect of practical matters in preparing and handling concrete aggregates; cement storage and handling and construction techniques; the physical properties of the hardened concrete; nature of exposure of the concrete; and finally the types of loading to which concrete is exposed. Second, examples of durability of nonstructural exposed concrete are given in terms of resistance to freeze-thaw forces in relation to air-void characteristics of normal concrete. Third, an example of nondurable, load bearing structural concrete is illustrated along with the causes of distress and method of repair. Finally, a recent example of a high strength structural concrete bridge deck containing a superplasticizer is presented in terms of its durability characteristics. Detailed data on each of these four classifications has been referenced to facilitate a more in-depth study by those parties who may have an interest in one or more of those topics.

Double-Layer Valve Seat Inserts for Passenger Car Diesel Engines

Abstract: A new double-layer valve seat insert has been developed for use in high performance diesel engine of passenger car. The seat layer is composed of a sintered alloy of a high wear resistance and a high heat resistance. The base layer is composed of a sintered alloy of a higher heat resistance than that of the seat layer. This double-layer valve seat insert was proven to have good wear resistance and heat resistance in a durability test on the diesel engine with a turbocharger system.