Showing papers in "Journal of Materials in Civil Engineering in 1990"
TL;DR: In this article, experiments were performed to determine the coefficient of friction between concrete and steel and the nominal normal stress varied from 1 P.S.I. to 68,000 P.I., with an average value of 0.47.
Abstract: Experiments were performed to determine the coefficient of friction between concrete and steel. The nominal normal stress varied from 1 P.S.I. to 68,000 P.S.I. The coefficient of friction was found to be nearly constant with an average value of 0.47.
221 citations
TL;DR: In this paper, the feasibility of using shell and fiber ash as a construction material was studied and the experimental results indicated that no significant effects of ash addition on the segregation, shrinkage, water absorption, density, and soundness of cement.
Abstract: The palm‐oil industry produces large amounts of solid wastes. Shell and fiber wastes are used extensively as fuel for steam production in palm‐oil mills. After combustion, a large quantity of ash is produced and creates problems of disposal. The feasibility of using the shell and fiber ash as a construction material is studied. The material differs from PFA from coal‐fired power plants in that it has a higher content of residual organic, a higher alkali content, is coarser. The experimental results indicate that no significant effects of ash addition on the segregation, shrinkage, water absorption, density, and soundness of cement. The workability of concrete blended with the shell and fiber ash is good, and setting times are well within the requirements of both American and British standards. The shell and fiber ash is only weakly pozzolanic, the decrease in compressive strength of concrete is almost proportional to the amount of ash in the blended cement, except when only 10% ash is used. The results sh...
151 citations
TL;DR: In this article, a multicutting technique is introduced to determine the extension of the fracture process zone together with the conventional compliance method, and a new compliance curve is established from a damaged specimen during multicuttting and compared with the compliance-calibration curve.
Abstract: A multicutting technique is introduced, which can be used to determine the extension of the fracture‐process zone together with the conventional compliance method. A new compliance curve is established from a damaged specimen during multicutting and compared with the compliance‐calibration curve. From the comparison of these two compliance curves the extension of the fracture‐process zone can be estimated. Experimental results of wedge‐opening loaded specimens with a ligament length of 110 mm show that the length of the fracture‐process zone in mortar varies from around 43 mm to 12 mm while the crack is approaching to the boundary. A relation between the length of the fracture‐process zone and the shape of the Kr‐curve is established.
65 citations
TL;DR: In this paper, the authors combine the model for foam creep with the standard analysis of deflection of a sandwich beam to develop an expression for the creep of a beam with a polymer foam core.
Abstract: Polymer foam‐core sandwich panels are increasingly being considered for load‐bearing components in buildings. In addition to offering a high stiffness per unit weight, such panels give excellent thermal insulation and may be easily mass‐produced. But polymers creep at room temperature, limiting their use in structural applications. In this paper we model the creep of sandwich beams with linear viscoelastic polymer foam cores. A previous study indicated that the creep of a polymer foam can be described knowing the creep response of the solid from which it is made and the relative density of the foam. In this study, we combine the model for foam creep with the standard analysis of deflection of a sandwich beam to develop an expression for the creep of a sandwich beam with a polymer foam core. The results are compared with data from a series of tests on sandwich beams with aluminum faces and rigid polyurethane foam cores. The model gives a good description of their behavior at loading times up to 1,200 hours...
39 citations
TL;DR: In this paper, the in-plane shear modulus and the shear strength of pultruded glass fiber reinforced plastic (FRP) materials were measured using the Iosipescu shear test method.
Abstract: The in‐plane shear modulus and the in‐plane shear strength of pultruded glass fiber reinforced plastic (FRP) materials were measured using the Iosipescu shear test method. Material specimens, in coupon form, were cut from the webs and flanges of commercially produced polyester and vinylester wide‐flange pultruded beams. The experimental testing procedure is described, and data reduction methods needed to define the shear modulus and the shear strength from the nonlinear stress‐strain curves are discussed. A new method to obtain the in‐plane shear modulus directly from load‐displacement data is proposed. Shear modulus predictions using the proposed method are compared with those obtained from the stress‐strain data.
33 citations
TL;DR: In this paper, the authors show that residue obtained from the incineration of dewatered sludge in a brick-making kiln is suitable for making coarse aggregate for the production of light concrete.
Abstract: Sludge is a by‐product of municipal wastewater treatment. Its disposal problems could be drastically reduced if sludge could be converted for economical uses as substitute materials. Dewatered sludge, after incineration at a high temperature, yields a hard and porous mass with low unit weight. This hardened mass of incinerated‐sludge residue can be broken down into smaller sizes that when graded in suitable proportions, manifest the basic attributes required of lightweight aggregate. When used as coarse aggregate in concrete, experimental results show that the resulting concrete satisfies the physical requirements of lightweight concrete in terms of unit weight, strength, and potential heat‐insulating properties, thus indicating that incinerated sludge residue could be a likely source of suitable lightweight aggregate. Results of the present study show that residue obtained from the incineration of dewatered sludge in a brick‐making kiln is suitable for making coarse aggregate for the production of lightw...
32 citations
TL;DR: In this paper, the authors dealt with the shear transfer problem across an initially uncracked plane, in concrete containing short and discrete steel fibers, and provided some experimental evidence.
Abstract: The study reported in this paper deals with the shear transfer problem across an initially uncracked plane, in concrete containing short and discrete steel fibers. An attempt has been made to predict rationally the shear transfer behavior of reinforced fiber concrete and to provide some experimental evidence. Within the scope of the study, the conclusion that can be drawn include: 1) The strength and deformation characteristics of reinforced concrete across an initially uncracked plane can be enhanced by the use of discrete steel fibers in the concrete mix; Modification to the softened truss model gives good prediction of the strength as well as the load-deformation response of an initially uncracked plane in reinforced fiber concrete represented by a push-off specimen.
29 citations
TL;DR: The long-term compressive strength of silica-fume concrete concretes has been recently questioned by some researchers as discussed by the authors, who reported the results of data on 4- to 6-year-old cores obtained from well-documented field experiments where both silica•fume and nonsilica•mixtures were used.
Abstract: The long‐term compressive strength of silica‐fume concrete has been recently questioned by some researchers. This paper reports the results of compressive strength data on 4‐ to 6‐year‐old cores obtained from well‐documented field experiments where both silica‐fume and nonsilica‐fume concrete mixtures were used. All concretes were exposed to freeze/thaw and thawing cycles and heavy deicing salt applications. The 1988 core results clearly show that the silica‐fume field concretes have not experienced any strength loss, compared to the nonsilica‐fume concretes. Moreover, the compressive strength results obtained on concrete cores taken after a 4‐year period from an experimental column built with a very high‐strength concrete also confirmed that there was no tendency for strength loss in silica‐fume concretes.
27 citations
TL;DR: In this paper, a systematic approach to the study of durability of building materials is attempted with reference to porous materials in an aggressive environment, and the service lives of these materials strongly de...
Abstract: A systematic approach to the study of durability of building materials is attempted with reference to porous materials in an aggressive environment. The service lives of these materials strongly de...
22 citations
TL;DR: In this paper, the authors contribute to the knowledge of active additions, which can be added to Portland cement to give it properties that improve its performance behavior using X-ray diffraction (XRD).
Abstract: This paper contributes to the knowledge of materials known as active additions, which can be added to Portland cement to give it properties that improve its performance behavior. This knowledge is obtained by X‐ray diffraction (XRD), which in a few minutes gives a spectrum by which the crystalline phases can be identified by its peaks, as well as some information concerning noncrystalline constituents, from the position and form of the diffuse band. According to these data, the type of addition can be analyzed and from here, the activity or lack thereof, of the added material. Active additions can modify properties of cement, increasing or decreasing its durability. The identification of active additions results in improved behavior.
20 citations
TL;DR: The authors analyzes the dynamic processes and the development of thermal and moisture fields during the test, and shows that changes in the moisture field increase as the ratio of the vapor diffusivity to the hydraulic modulus of the material decreases.
Abstract: Thermal conductivity measurements are based on temperature gradients within the tested material. When testing nonsaturated moist porous materials, this gradient causes redistribution of the enclosed moisture and, as a result, the apparent (measured) conductivity is smaller than the actual one. This paper analyzes the dynamic processes and the development of thermal and moisture fields during the test, and shows that changes in the moisture field increase as the ratio of the vapor diffusivity to the hydraulic modulus of the material decreases. It shows, however, that for a wide range of concretes (dry density between 340 and 2,240kg/m3), tested under a commonly used temperature gradient (of about 3–5° C/cm), moisture changes may reach a significant fraction of a percent only when this ratio is smaller than 1.0 mN/gr as may be the case for some highly hydrophobic thermal plasters. This paper suggests a procedure for estimating the dependence of the actual moist thermal conductivity on the moisture content b...
TL;DR: In this paper, an investigation was conducted to evaluate the effectiveness of surface coatings as carbon dioxide barriers, and it was found that the coating effectiveness depends not only on the coating material but also on its mode of application and the conditions of its concrete substrate.
Abstract: The deterioration of reinforced concrete structures resulting from reinforcement corrosion is a worldwide concern. One significant part of repair solutions is to coat the concrete surface to inhibit the ingress of penetrating substances such as carbon dioxide and water. An investigation was conducted to evaluate the effectiveness of surface coatings as carbon dioxide barriers. It was found that the coating effectiveness depends not only on the coating material but also on its mode of application and the conditions of its concrete substrate. The minimum required effectiveness of a coating depends on job requirements, and in its specification, the influence of the coating on the moisture condition of the substrate has to be taken into account.
TL;DR: An experimental investigation into fracture of autoclaved aerated concrete (AAC), a lightweight building material, is presented in this paper, where the authors indicate that AAC is a softening material, and the fracture process can be considered as a steady degradation of the composite structure consisting of a microporous matrix and artificially induced air pores.
Abstract: An experimental investigation into fracture of autoclaved aerated concrete (AAC), a lightweight building material, is presented. The experiments indicate that AAC is a softening material, and the fracture process can be considered as a steady degradation of the composite structure consisting of a microporous matrix and artificially induced air pores. In terms of fracture mechanisms, there exists a similarity between AAC and structural concrete, and the fracture process can be described by the fictitious crack model that is used for concrete. Fracture properties such as the specific fracture energy, GF, depend on the specimen geometry, i.e., GF increases with increased fracture ligament length and specimen thickness. The softening diagram of AAC is numerically evaluated through data fit of numerical and experimental force versus deformation curves of the specimen. The characteristic length, lch, is proposed to be a material parameter to assess the quality of AAC regarding fracture. The fracture properties ...
TL;DR: In this article, a methodology for permanent deformation characterization of asphalt paving materials is presented. But the main objective is to develop a methodology to characterize the rutting potential of asphalt mixtures that can be easily implementable at highway agencies.
Abstract: Rutting is one of the major modes of distress in flexible pavements. It is caused by plastic deformation that can occur in any of pavement layers. Historically, rutting of asphalt concrete has been considered a mix design and/or construction problem. Furthermore, current methods of mix design are independent from pavement thickness design procedures. The focus of this paper is on permanent deformation of asphalt concrete layer. The primary objective is to develop a methodology for characterization of rutting potential of asphalt mixtures that can be easily implementable at state highway agencies. Permanent deformation characterization procedures are to be based upon parameters that can be integrated into mechanistic pavement design procedures. A mechanistic methodology is developed for permanent deformation characterization of asphalt paving materials. Rheological properties of hot mix asphalt (HMA) are thoroughly studied by means of a simple creep test that is originally developed by Shell researchers. Procedures are developed in order to account for nonlinear, viscoelastic, and viscoplastic deformation components of HMA. Results indicate that structural arrangement of pavement layers has a significant influence on rutting performance of the HMA layer. Findings of this study can be easily implemented in an integrated mix-thickness design procedure.
TL;DR: In this paper, the concentration of free hydroxyl ions in pore solutions of mortars is studied, and the effects of hot environment on these ions are reported; the influence of fly-ash addition is observed and discussed.
Abstract: The concentration of free hydroxyl ions in pore solutions of mortars is studied, and the effects of hot environment on these ions are reported. The influence of fly‐ash addition is observed and discussed. Fog curing decreases free OH- ions in cement mortar. Fly‐ash mortar retains free OH- ions more satisfactorily. A further decrease in OH- concentration is observed as a consequence of exposure to hot environment. Initially well‐cured fly‐ash/cement mortar performs better in this respect than cement mortar. The ratio of Cl- to OH- in mortars that include Cl- ions increases sharply as a result of hot environment. Fly‐ash inclusion is also beneficial in this situation. Nevertheless a large increase in the Cl-‐to‐OH- ratio is still recorded as a result of hot weather application. The results of this study indicate the importance of applying a suitable curing regime when the concrete contains fly‐ash and/or is exposed to hot weather. The results are relevant to studies concerned with corrosion protection of st...
TL;DR: In this paper, the physical, chemical, and microstructural characteristics of a type K cement to which up to 10% of a silica fume and a superplasticizer are added.
Abstract: Type K cement belongs to a special class known as shrinkage‐compensating cement. A literature survey reveals that very little research has been conducted on the performance of this type of cement when additives are used with it. The writer studies the physical, chemical, and microstructural characteristics of a type K cement to which up to 10% of a silica fume and a superplasticizer are added. Several techniques, such as conduction calorimetry, X‐ray diffraction, thermal analysis, and SEM/EDXA are used for this investigation. It is demonstrated that significant strength increase can be obtained through the use of additives in type K cement. Changes in rheological properties, however, can result from such additions. Adjustments in the amount of sulphate and aluminate components may lead to better control of setting and viscosity in this cement.
TL;DR: In this paper, a simple method to optimize the level of cement replacement by fly ash in concrete and concrete is proposed based on flow-table tests, where the lines representing water content of the mixes and the logarithm of the number of drops are called flow lines.
Abstract: A simple method to optimize the level of cement replacement by fly ash in cement—fly‐ash mortar and concrete is proposed. The method is based on flow‐table tests. In this test, for any specific level of flow a decrease in water content of the mix increases the number of drops. The lines representing water content of the mixes and the logarithm of the number of drops are called flow lines. As the replacement of cement by fly ash is increased in any mix, there is a progressive reduction in water requirement to cause some percentage flow. The slopes of the flow lines gradually decrease with increasing fly‐ash content. Normalization water content, w, of the flow lines, with respect to water content corresponding to 25 drops, w25, leads to collapse of the flow lines into a unique line. This establishes a functional relationship between w/w25 and the number of drops. Using this relationship, the flow line of any mix can be predicted if the value of number of drops for any arbitrary water content is known. This ...
TL;DR: In this paper, a failure criterion that can represent the cracking and crushing is proposed, which involves three independent material parameters: tensile, compressive, and biaxial compressive strength.
Abstract: It is well known that concrete will fail in the form of cracking or crushing for the uniaxial tension or compression. However, it would be difficult to classify and define precisely the failure form for the multiaxial stress state with tension and compression. In this paper, a suggestion about the identification of cracking and crushing failure is given based on the macroscopical failure phenomenon of concrete. The failure criterion that can represent the cracking and crushing is also proposed. The present failure criterion involves three independent material parameters. They may be determined by the uniaxial tensile and compressive as well as equal biaxial compressive strengths. The comparisons between the failure criterion and both the experimental data and the theory suggested previously are made in biaxial, triaxial, and octahedral planes. These comparisons show that the present failure theory is able to predict the characteristics of failure and is available for both biaxial and triaxial stress state...
TL;DR: In this article, both circular and square cross sections are tested as individual elements, and in clusters, and the effect of temperature variation on energy absorption is rated according to a thermal index.
Abstract: Energy dissipation characteristics of rubber elements are discussed as a function of material, geometry, temperature, and grouping effects. Static and dynamic energy absorption of particular rubber compounds is quantified. Compounds studied include natural rubber, butadiene, ethylene-propylene, butyl, neoprene, and a proprietary elastomer. Both circular and square cross sections are tested as individual elements, and in clusters. Photographic sequences of static and dynamic tests show deformed shapes of cross sections. While circular cylinders deform in a stable manner during impact, individual and clustered square cylinders are susceptible to buckling and absorb energy that varies with the impact angle. Web stiffeners substantially increase energy-absorbing capabilities of circular cylinders but add complexity to the manufacturing process and reduce reliability under load. Influence of temperature variation on energy absorption capabilities for various rubber compounds is rated according to a thermal index.
TL;DR: In this article, the effect of CO2 on cement-silica blends depends on the type of silica used and on the curing period, and it was confirmed that high early (seven-day) strength mixes are more durable in a static CO2 atmosphere and have higher ultimate strength.
Abstract: Thermal oil‐well cement blends containing 40% silica in the form of fume, flour, and sand exhibit changes in their compressive strength and water permeability when cured in a static CO2 atmosphere. The magnitude of the effect of CO2 on cement‐silica blends depends on the type of silica used and on the curing period. It has been confirmed that high early (seven‐day) strength mixes are more durable in a static CO2 atmosphere and have higher ultimate strengths. Water permeability is affected only at early ages of up to 28 days. In a CO2 atmosphere, permeability is reduced slightly for blends with silica flour and with silica fume and sand; values are increased markedly for fume and fume‐flour mixes. The differences in these engineering properties are explained in terms of competition for calcium hydroxide between carbonation and pozzolanic reactions, and types and amounts of calcium carbonates formed. Products formed hydrothermally (7 days at 230° C and 2.75 MPa) from partially or fully hydrated cement‐silic...