Showing papers on "Mortar published in 1988"
TL;DR: In this article, the results of corrosion rate and simultaneous electrical resistance values of rebars in mortar fabricated with six different types of cements are given and the relation between those values is presented.
352 citations
TL;DR: In this paper, a method of test for bond should reflect a typical in-service stress state yet also be sensitive to variation in the strength of the bond, and a slant shear test was found to be the most appropriate.
Abstract: When new concrete is placed next to old concrete, attempts are usually made to bond the two concretes together: ofen a cement paste or mortar joint is used, as in masonry. The service stress states in bonds can vary tremendously so no single test method can replicate all these states. A method of test for bond should reflect a typical in-service stress state yet also be sensitive to variation in the strength of the bond. Four tests were evaluated, and a slant shear test was found to be the most appropriate. The effects of various parameters were evaluated theoretically with the finite element and/or experimentally. A bond material with a modulus of elasticity similar to the adjacent concrete was found to be desirable, as was consistency in the bond material properties. Thick bond layers were found to reduce bond strength considerably and copolymer polyvinyl acetate was found to be a poor bonding agent over a wide range of curing conditions and mortar mix designs.
159 citations
TL;DR: In this paper, the corrosion mechanism of steel in concrete and the so-called threshold chloride content are discussed based on the results obtained by electrochemical measurement, pore solution analysis, and scanning electron microscopy (SEM) observation.
Abstract: The corrosion mechanism of steel in concrete and the so-called threshold chloride content are discussed based on the results obtained by electrochemical measurement, pore solution analysis, and scanning electron microscopy (SEM) observation. It is shown that mortar (or concrete) provides better protection to steel than alkaline solutions. One of the protective mechanisms provided by mortar is found to be the pH control action of calcium hydroxide crystals located at the steel-mortar interface. For the protective mechanisms provided by mortar to operate, adhesion between the steel and the mortar is necessary and formation of voids at the steel-mortar interface is essential for active corrosion to start. The critical threshold chloride content is not determined simply by a parameter of the pore solution such as [Cl−]/[OH−] ratio; it is shown that the threshold value depends on the steel-mortar interface conditions.
146 citations
TL;DR: In this article, a permeability cell for measuring the permeability of mortar and concrete to gas is described, and the problems encountered and overcome during the development of the cell are discussed.
Abstract: Synopsis A permeability cell for measuring the permeability of mortar and concrete to gas is described. The problems encountered and overcome during the development of the cell are discussed. The cell is designed to test 25 mm diameter mortar samples but can also be used for 50mm diameter concrete specimens. Specimens of heights between 10 and 50mm can be tested. Measurements using the new cell are highly repeatable and reproducible. The cell is very sensitive to the influence of water/cement ratio, age and replacement of cement by pulverized-fuel ash. It can be used to obtain permeability profiles through the depth of a concrete element in order to evaluate the influence of different curing conditions or curing compounds.
139 citations
TL;DR: In this article, the effects of chemical attack on portland cement mortar from internal and external sulfate sources were compared with respect to expansion and strength development and substantial differences exist between the two types of sulfate attack.
125 citations
TL;DR: A galvanostatic pulse technique was used to study corrosion of steel in mortar immersed in simulated sea water and steel exposed to 03 M NaOH + 06 M NaCl, both as aqueous solution and set with agar gel as discussed by the authors.
114 citations
Patent•
14 Nov 1988
TL;DR: A hydraulic cement is formed from a Class C fly ash, an alkali metal activator, and citric acid as mentioned in this paper, which is particularly useful in producing mortar and concrete compositions that achieve high strength in a short time.
Abstract: A hydraulic cement is formed from a Class C fly ash, an alkali metal activator, and citric acid. Mortar and concrete compositions can be prepared with this hydraulic cement. The cement is particularly useful in producing mortar and concrete compositions that achieve high strengths in a short time, in particular, a mortar having a strength of at least 2500 psi in 24 hours, when cured at room temperature.
68 citations
Patent•
28 Apr 1988TL;DR: In this paper, the authors described different types of concrete compositions, i.e., mortar, structured concrete, precast concrete, and oilfield cement, comprising 0.01-0.9% (wt/wt) welan gum.
Abstract: Cement compositions, i.e., mortar, structured concrete, pre-cast concrete, and oilfield cement, comprising 0.01-0.9% (wt/wt) welan gum are described.
62 citations
Patent•
19 Apr 1988
TL;DR: In this paper, a mortar collecting device adapted to be located adjacent a wall surface of a masonry or brick wall under construction and collect excess mortar extruded from between rows of masonry during construction of the wall is described.
Abstract: A mortar collecting device adapted to be located adjacent a wall surface of a masonry or brick wall under construction and collect excess mortar extruded from between rows of masonry during construction of the wall Such mortar collecting devices each posses an upper surface means adapted to collect mortar but repel moisture in the form of water droplets which falls on such surface means Repulsion of water is accomplished by providing an upper surface means having an inclined portion sufficiently inclined to the horizontal when such device is in mortar collecting position so as to cause moisture to slide off, but being insufficiently inclined so as to cause mortar to slide off Alternatively the mortar collecting device may have a plurality of passageway means extending vertically therethrough of dimensions sufficient to allow moisture to pass therethrough, but of dimensions insufficient to allow mortar to pass therethrough
62 citations
TL;DR: An analytical study of hydrochloric acid attack on cement mortar prisms is done in this paper, where 4×4×16 cm morter prism specimens (cement sand ratio 1:3) were made.
55 citations
Patent•
09 Jun 1988TL;DR: In this article, a method of installing facing bricks on the surface of an outer building wall including, as a first step, the attachment to the wall of chicken wire provided with parallel ridge configurations is described.
Abstract: A method of installing facing bricks on the surface of an outer building wall including, as a first step, the attachment to the wall of chicken wire provided with parallel ridge configurations. These configurations are positioned to form horizontal barriers in the chicken wire which are spaced far enough apart to receive the facing bricks between them. The bricks are buttered on one side with mortar, then pressed into position between the barriers with their lower edges adjacent the lower of the two flanking barriers. When the mortar sets, grout is applied to the spaces between the bricks to embed the ridge configurations in the chicken wire. The result is a veneered wall having the bricks fastened to the wall surface with mortar and integrated into a cohesive veneer skin, along with the mortar, chicken wire and grout. Thus, if one or more of the bricks breaks away from the wall through loss of the mortar bond between the bricks and the wall, the chicken wire will hold them in position and prevent them from falling and harming or damaging persons or property below.
TL;DR: In this paper, the steady state diffusion of chlorides through cement pastes was investigated and the relationship between the electrical resistivity and diffusivity of paste, mortar, and concrete was investigated.
Abstract: Chlorides are currently the main culprit in the deterioration of concrete structures in most parts of North America and Europe. During the last few years the authors have investigated the following properties: (i) the steady state diffusion of chlorides through cement pastes; (ii) penetration of chlorides into mortar and concrete; (iii) the binding of chlorides in the paste phase; (iv) the threshold value of chlorides below which corrosion of reinforcement is unlikely to occur; and (v)the relationship between the electrical resistivity and diffusivity of paste, mortar, and concrete. The variables investigated include water/cement ratio, cement type, curing conditions, effects of admixtures, and pozzolanic additions and the cover depth.
Patent•
09 Aug 1988
TL;DR: In this paper, a masonry structure is made by setting up a prefabricated wire support structure having the shape of the structure to be made, assembling a first row of bricks on the lowermost horizontal section thereof, masking a plurality of bricks of that row with an open top removable mortar molding form which is placed around the bricks and covering the tops of the bricks by filling the form with mortar and leveling it to provide a mortar filling layer between adjacent bricks of the run and a continuous mortar layer above the bricks.
Abstract: A masonry structure is made by setting up a prefabricated wire support structure having the shape of the structure to be made, assembling a first row of bricks on the lowermost horizontal section thereof, masking a plurality of brick of that row with an open top removable mortar molding form which is placed around a plurality of bricks and covering the tops of the bricks by filling the form with mortar and leveling it to provide a mortar filling layer between adjacent bricks of the run and a continuous mortar layer above the bricks.
Patent•
18 Jan 1988
TL;DR: In this article, the amount of water added to a concrete charge is regulated subject to the weight difference of the sand sample prior to and after drying, and this sand sample is dried.
Abstract: The invention relates to a method and apparatus for preparing concrete mortar. In order to regulate the moisture content of the concrete mortar a sand sample is taken of the sand used. This sand sample is dried. The amount of water added to a concrete charge is regulated subject to the weight difference of the sand sample prior to and after drying.
TL;DR: In this article, the effect of ice formation on the elastic moduli of cement paste and mortar is analyzed using a modified direct method which is based on both micromechanical and classical elasticity theory.
TL;DR: In this article, the influence of steel fibres on the free shrinkage of cement-based matrices was investigated and the results indicated that fibres restrain the shrinkage to a significant extent, resulting in reductions of up to 40%.
Abstract: The paper presents results of an experimental investigation on the influence of steel fibres on the free shrinkage of cement-based matrices. Shrinkage tests were carried out on cement paste, mortar and two types of concrete mixes for a period of up to 520 days. Melt extract, crimped and hooked steel fibres were used for reinforcement at volume fractions ranging between 1 and 3%. The results indicate that fibres restrain the shrinkage of the various cement matrices to a significant extent, resulting in reductions of up to 40%. Crimped fibres are the most efficient in providing shrinkage restraint. The paper also presents a theoretical expression and an empirical expression which can be used to predict shrinkage strains of steel fibre reinforced cement matrices. The analysis requires a knowledge of the values of coefficient of friction, μ, at the fibre-matrix interface, which are also derived in this paper. The μ values for steel fibres in normal concrete, mortar and cement paste range between 0.07 and 0.12.
TL;DR: In this article, a test on mortar bars correlates with service performance of the aggregates and, compared with the conventional mortar bar test, an acceleration factor of about 30 is achieved.
Journal Article•
TL;DR: Etude experimentale, par porosimetrie au mercure, montrant la reduction de porosite avec l'adjonction de granulat fin this paper.
Abstract: Etude experimentale, par porosimetrie au mercure, montrant la reduction de porosite avec l'adjonction de granulat fin
TL;DR: In this paper, the influence of temperature and w/c ratio on the initial and final times of setting for different mortar mixes were examined and the results showed that the times of the setting decreased with an increase in temperature and/or a decrease in w /c ratio.
TL;DR: In this paper, Mortar and concrete cubes have been immersed in a channel containing a 3% solution of continuously flowing sulphuric acid for up to 81 days, and the effect of polyvinyl alcohol (PVA) was to preserve the integrity of the cubes, and possibly slow down the rate of acid attack.
Abstract: Synopsis Mortar and concrete cubes have been immersed in a channel containing a 3% solution of continuously flowing sulphuric acid. The cementitious materials examined were: ordinary Portland cement containing polyvinyl alcohol (PVA) and pulverized-fuel ash; sulphate-resisting Portland cement, and a proprietary dense mortar. The change in weight with time of each cube was measured for up to 81 days. The effect of the PVA was to preserve the integrity of the cubes, and possibly slow down the rate of acid attack. The rate of acid attack on the SRPC concretes was similar to that on OPC concretes. The dense mortar had much improved resistance to sulphuric acid attack, and the improvement was enhanced with increased volume fraction of aggregate.
TL;DR: In this paper, the authors evaluated current methods for the prediction of the safe shelf life of gun and mortar propellants and achieved this in a four part approach based on the current picture of the chemical stabili...
Abstract: Current methods for the prediction of the safe shelf life of gun and mortar propellants are evaluated. This is achieved in a four part approach. Firstly, the current picture of the chemical stabili...
01 Jan 1988
TL;DR: Alkali activation is a chemical activation of slag with alkali hydroxide, non-silicic salt of weak acids and silicic salts as discussed by the authors. But it has not been applied to ground slag.
Abstract: Alkali activation is a chemical activation of slag with alkali hydroxide, non-silicic salts of weak acids and silicic salts. In the experiments reported on water-glass, sodium hydroxide and sodium carbonate have been used as activators of slag from Oxeloesund in Sweden and from Nowa Huta in Poland. The fineness of the ground slag and the quantity of activator added have been varied. The influence on the setting time, compressive strength, dynamic modulus of elasticity, flexural strength, porosity, shrinkage and microstructure have been studied. Specimens of slag mortar have been either cured in air at 80% RH at a temperature of +20 degrees centigrade or have been steamcured at different temperatures and for different lengths of time. The properties of the alkali-activated mortars have been compared with the properties of ordinary Portland cement mortar.
TL;DR: The diffusion of chloride ions through cement pastes and mortars with and without polymers was studied in this article, showing that the diffusion in the portland cement paste matrix of the mortar was greater than that of the diffusion of the paste of similar w/c ratio.
TL;DR: The microstructure of mortars from three Egyptian pyramids, Meidum 2600 BC, Cheops 2500 BC and Unas 2250 BC, was examined by optical and electron microscopy and X-ray diffraction as discussed by the authors.
Patent•
30 Nov 1988
TL;DR: In this paper, a strippable paint on the inner surface of a mold is applied to a concrete or a mortar to create a barrier, and then the mold is removed from the cured concrete or mortar.
Abstract: A protective layer is formed on concrete or mortar by coating a strippable paint on the inner surface of a mold, to form a strippable membrane. A transferring layer is then formed on the strippable membrane, and concrete or mortar is placed in the mold having the strippable membrane and the transferring layer. The concrete or mortar is cured in the mold. Then, the mold is removed from the cured concrete or mortar, thereby allowing the strippable membrane to transfer onto the surface of the cured concrete or mortar.
TL;DR: In this paper, the presence of chlorides and carbonation of the concrete cover are the two main causes of corrosion of reinforcement, and that the simultaneous occurrence of both chlorides, carbonation is expected to increase the likelihood of corrosion This likelihood may be quantified and monitored through the use of electrochemical techniques.
Abstract: Synopsis It is well known and accepted that the presence of chlorides and carbonation of the concrete cover are the two main causes of corrosion of reinforcement, and that the simultaneous occurrence of both chlorides and carbonation is expected to increase the likelihood of corrosion This likelihood may be quantified and monitored through the use of electrochemical techniques Polarization resistance and electrochemical impedance measurements on rebars embedded in carbonated mortar containing chlorides have been carried out and the results indicate that these techniques not only allow the extent of corrosion to be estimated but also give information about the effect of the variables on the corrosion process
01 Dec 1988
TL;DR: In this paper, a rapid method of assessing the ultimate shear strength of reinforced concrete beams containing both stirrups and fibers as shear reinforcement is suggested, and a good correlation has been obtained between observed test values and the predictions using the method suggested in this paper.
Abstract: A total of 24 tests have been carried out to investigate the shear resistance of rectangular mortar beams reinforced with three combinations of steel fibers and conventional stirrups; the tests have also been designed to study the effect of partial replacement of cement by pulverized fuel ash (PFA). The experiments have demonstrated the advantages of combining steel fibers and stirrups for shear reinforcement. The partial replacement of cement by PFA results in improved workability and higher long term strengths. Based on the test observations, a rapid method of assessing the ultimate shear strength of reinforced concrete beams containing both stirrups and fibers as shear reinforcement is suggested. Good correlation has been obtained between observed test values and the predictions using the method suggested in this paper.
TL;DR: In this paper, a comprehensive test program on the behavior of high-strength mortar under different conditions has been performed by studying the propagation of ultrasonic waves (compressional and shear) through 2-in. (0.051 m) cubes.
Abstract: A comprehensive test program on the behavior of high-strength mortar under different conditions has been performed by studying the propagation of ultrasonic waves (compressional and shear) through 2-in. (0.051 m) cubes. The increase of the ultrasonic wave velocities was monitored as a function of time. The attenuation of the ultrasonic waves under different conditions was analyzed. Special emphasis was given to the study of the effect of cracking on the ultrasonic velocities and attenuation of the mortar, including the development of anisotropic behavior once cracking had developed. The healing of the cracks over time was also analyzed, and it was shown that a substantial degree of healing can occur. The effects of changes in relative humidity and subzero temperatures on the seismic wave velocities were studied in detail.