Showing papers on "Mortar published in 1991"

Rheology of fresh cement and concrete

Abstract: Cement-based materials are of enormous technological importance and their satisfactory performance depends on being able to transport and mould them in the freshly mixed state. This article describes the rheology of fresh cement, mortar, concrete and related products in the context of practical situations, and deals with testing and measurement, together with the main features of their behaviour. It explores the links between rheology and technology, and identifies areas where these are weak and could benefit from further experimental and computational effort.

Bond-Slip Mechanisms of Steel Fibers in Concrete

Abstract: A comprehensive experimental program on pullout and pullthorugh tests of steel fibers from a cement-based matrix is described. Emphasis is placed on the accurate measurements of the pullout load versus end-slip response. Parameters included 3 different type of fibers, three different mortar matrixes with low medium, and high strengths, one cement-based slurry matrix, and additives such as latex, fly ash, and microsilica. The medium from which the fiber was pulled out included a control mortar mix without fibers, mortar mixes with 1, 2, and 3 % fibers by volume, and a SIFCON matrix containing about 11 % fibers by volume. For smooth fibers, 5 different diameters and 3 different embedment lengths were investigated. Experimental pullout load versus slip curves are needed to derive typical bond shear stress versus slip curves considered to be a property of the interface.

The rheology of fresh mortar

Abstract: The effects of mixing procedure, testing procedure and relative proportions of constituent materials on the rheology of fresh mortar, as measured by the ViscoCorder, have been studied. Mortar shows...

Reduction in Mortar and Concrete Expansion with Reactive Aggregates Due to Alkali Leaching

Abstract: Mortar bar expansion tests for evaluating alkali-silica reactive aggregates are not always reliable. Containers with efficient wick systems may cause excessive leaching of alkalies out of mortar bars, thus reducing the expansion. This problem has become more apparent since the introduction in 1987 of a new recommended container for the ASTM C 227 mortar bar test. It is believed that the use of this container can result in deleteriously expansive aggregates appearing to be innocuous in laboratory testing. Similar effects were found with concrete prisms made with alkali-carbonate reactive aggregate. If laboratory expansion tests are to be reliable, it is necessary to calibrate the severity of the storage condition by conducting calibration tests with known alkali-reactive aggregates as reference materials. The use of Pyrex glass is not satisfactory for calibrating storage conditions because it contributes alkalies to the reaction.

Enhanced cement mixed with selected aggregates

Abstract: A cement enhanced to obtain a self-smoothing, self-levelling, non-shrinking mortar or concrete, consisting of an artificial cement mixed with additives, including at least a combination of a plasticizing agent included in a proportion of between 0.5 and 4% of the weight of the artificial cement and an expanding agent included in a proportion of between 0.000001 and 0.00099% of the weight of the artificial cement, and mortar or concrete obtained with the enhanced binder, mixed with a filler consisting of aggregates with a selected particle size.

Latex-modified carbon fiber reinforced mortar

Abstract: Effects of latex modification on performance characteristics of carbon fiber reinforced mortars incorporating silica fume were investigated. Two styrene butadiene latexes were considered in this investigation. Latex modification was observed to enhance the bonding of cementitious matrixes to carbon fibers. Latex-modified fibrous cement composites, when compared with the unmodified ones, also had reduced water absorption and drying shrinkage movements, and increased flexural toughness. The desirable flexural strength and impact resistance of carbon fiber reinforced mortar were not much influenced by latex modifications, and the presence of latex led to some reductions in the compressive strength of the composite material. Latex modification of carbon fiber reinforced mortar led to higher frost resistance and significantly improved resistnace to acid attack.

Fly ash in concrete : properties and performance : report of technical committee 67-FAB, use of fly ash in building, RILEM (The International Union of Testing and Research laboratories for Materials and Structures

Abstract: Preface. Introduction. Characterization of fly ash. Origin of coal and burning conditions. Properties of fly ash. Fresh mortar and concrete with fly ash. Properties of freshly mixed mortar and concrete. Admixtures and air content. Setting. Plastic shrinkage. Hardened mortar and concrete with fly ash. Hydration and strength. Deformations. Frost resistance. Chemical resistance. Carbonation. Chloride attack on steel reinforcement. Electrical resistivity. Other uses of fly ash. Cement. Binders with fly ash. Precast concrete. Bricks and blocks. Lightweight aggregates. Fly ash in road construction. Fly ash in soil stabilization. Fly as asphalt-filler. Fly ash as fill. Waste neutralizaton and stabilization. References. Appendix. RILEM Recommendations: Fly ash in concrete - Test methods. Index.

Durability of fiber reinforced mortar

Abstract: The durability properties fo 4 types of fiber reinforced cement composites are compared. The 4 composites are conventional steel, polypropylene, glass fiber reinforced mortar, and slurry-infiltrated fiber concrete (SIFCON). Study results indicate that polypropylene fiber reinforced mortar has the best overall durability, while glass fiber reinforced mortar shows the poorest overall performance. Steel fiber reinforced mortar showed noticeable reduction in flexural strength and a dramatic reduction in toughness. For SIFCON, the reductions in both strength and toughness were moderate. A prediction model for the long-term deterioration of steel fiber reinforced mortar is proposed, and a sample analysis is performed. The results of the analysis are discussed.

Tensile failure mechanisms in synthetic fibre-reinforced mortar

Abstract: The ultimate tensile behaviour of fibre-reinforced cementitious composites is closely related to its failure mechanisms which in turn are dependent on reinforcement parameters such as fibre characteristics and the fibre/matrix interface properties. Based on the direct tensile tests of mortar specimens reinforced with various synthetic fibres, this paper attempts to explain such relationships and to indicate directions towards more effective fibre reinforcement.

Method for producing a replicated stone surface

Abstract: A method for producing a replicated stone surface comprising the steps of preparing a polymer mortar, coating a substrate with the polymer mortar, leveling the polymer mortar to a substantially even thickness, creating a textured surface on the polymer mortar, applying a hydrophobic release agent to the surface of polymer mortar, displacing portions of the polymer mortar by pressing a patterned tool on the surface of the polymer mortar to form the plurality of simulated stones with raised peripheral edges and intervening simulated grout lines, allowing the polymer mortar to cure, applying a pigment to the surface of the plurality of simulated stones and simulated intervening grout lines, buffing the surface of the plurality of simulated stones and simulated intervening grout lines to impregnate the pores thereof with the pigment, abrading the surface of the plurality of simulated stones to create a weathered appearance and sealing the surface of the plurality of simulated stones and simulated intervening grout lines with a sealer to protect the replicated stone surface.

Attenuation and dispersion of elastic waves in multi-phase materials

Abstract: The attenuation and dispersion of elastic waves in multi-phase materials such as granite, cement, mortar and concrete have been evaluated by the point-source/point-receiver technique with glass capillary breaking as an ideal source and a calibrated pin-type transducer as an ideal detector. The magnitude and phase spectrum from the Fourier analysis of the velocity signal gave attenuation and dispersion of the materials respectively, and the frequency dependence was also obtained in a single experiment. The sequence for attenuation was mortar, cement, granite and concrete; however, that for dispersion was cement, mortar, granite and concrete in increasing order. The difference in resonant frequency spectra of mortar and concrete blocks was explained in terms of the measured attenuation and dispersion.

Latex modified mortar and concrete

Abstract: A modified mortar or concrete composition in which a polymeric binding material is combined with sand, cement, and fine fillers. Use of the higher than previously considered functional ratio of latex binding material to cement permits the resulting mortar or concrete composition to increase the percentage of fine fillers, and reduces the amount of voids as a result of less water loss. The latex material partially fills the voids becoming a part of the structure of the system. This leads to a higher degree of flexibility and coherence of the system.

Leaching Tests for Concrete Containing Fly ASH - Evaluation and Mechanism

Abstract: Summary Various leaching tests were carried out with mortar mixtures containing fly ash. Mortar specimens using one bituminous coal fly ash and one fly ash from municipal waste incineration were prepared. The results of the leaching tests were compared and classified. In addition, diffusion rates for certain elements were determined by means of tank tests with mortar specimens.

A rapid autoclave mortar bar method to determine the potential alkali-silica reactivity of st. lawrence lowlands carbonate aggregates (quebec, canada)

Abstract: The paper discusses the efficiency of the proposed autoclave mortar bar tests for evaluation of the potential alkali reactivity of the limestone and dolostone concrete aggregates exploited in the St Lawrence Lowlands. The influence of various parameters on the test results and the accuracy of the method were evaluated. Forty carbonate aggregates were then tested by the method and sampled along the St Lawrence Lowlands. Expansion limits are suggested based on the behavior of the aggregates under standard testing conditions and on field performance. The reaction products developed in the mortar bars during the test, as observed under the scanning electron microscope, were also investigated.

Method for lining a pipe with a cement mortar

Abstract: An improved method for lining a section of pipe with a cement mortar. After a wet cement mortar has been applied to a cleaned interior surface of a pipe, carbon dioxide is introduced into the freshly lined section of the pipe in such quantity that a crust of calcium carbonate will be formed on the surface of the wet cement mortar lining as the carbon dioxide reacts with calcium compounds of the wet cement mortar in a relatively short period of time. This crust is provided to tolerate a low-velocity flow of water to protect the underlying mortar from scouring until the normal hardening of the underlying mortar through hydration can take place so as to substantially reduce the out-of-service time of the section of pipe which is being lined.

Microcrack propagation study of concrete under compression

Abstract: The propagation of microcracks in concrete under compression is studied by the finite element method. To this end, concrete is modeled as a two‐phase composite, consisting of a mortar matrix and aggregate inclusions. Two distinct types of microcrack (mortar crack and bond crack) are considered. To reflect the current stage of development, the principle of nonlinear fracture mechanics and the joint finite elements coupled with the generalized plasticity concept are incorporated into the present analyses. The numerical results thus obtained indicate that the stress state has a very significant influence on the development of mortar cracks; much less influence on the propagation of bond cracks is seen. Combined with well‐known experimental results then, the present study concludes that the deformation of a concrete specimen before peak load should be more uniform than its postpeak deformation and that the hardening behavior of a concrete specimen should be less influenced by loading conditions than the softe...

Improved cement and polyolefin lined product

Abstract: Iron pipe and other hollow articles are lined with a cementitious mortar containing a quantity of polymer particles and the pipe is rotated about its axis so as to stratify the mortar and develop a polymer rich inner surface that is subsequently cured, dried and heated to the polymer fusion temperature and then coated with a continuous layer of pure polymer.

Cement based mortar compositions having elastomeric properties, and method of manufacture

Abstract: Elastomeric cement based mortars and grouts are provided by adding acrylic polymer dispersion. Such compositions may be utilized on substrates which are subject to vibration and deflection, and are capable of recovering from deformation resulting from an elongation of greater than 30 percent. The elastomeric cement based mortars and grouts of the present invention are particularly suitable for setting and grouting tiles, for crack suppression membranes, for tile installation, for stuccos, for floor leveling, and for patching mortars.

Mortar and concrete to be processed by wet spraying and method of production of mortar and concrete

Abstract: The invention relates to concrete and mortar for the wet-spraying process, whose setting time is extended and, for example, retarded to such an extent that it can be supplied from a ready-mixed concrete works to the building site and remains processable at the latter for up to 2 days, but can be caused at any time to stiffen immediately, to set and to harden quickly by addition of a setting accelerator, in particular an accelerator based on potassium aluminate.

Mortar securing building brick

Abstract: A building brick includes a through-extending bore of a trapezoidal cross-sectional configuration to ease removal of a building brick from a mold during fabrication. The central bore permits the stacking of the building bricks to include the bottom wall in downward orientation to accommodate a greater quantity of mortar at the base portion thereof for a stable mortar configuration in use. A further embodiment of the invention includes the bottom wall of a concave configuration to assist in the positioning of mortar between adjacent building bricks, as well as a further embodiment including a forward wall flange extending downwardly relative to the concave surface and a second end wall flange to assist in the positioning of mortar between adjacent bricks to secure the mortar in a semi-solid state.

Contribution of calcium from limestone and mortar to the decay of granite walling

Abstract: Summary An hypothesis for the decay of granite in association with sources of Ca in an urban environment is developed. This hypothesis was applied to granite decay in association with limestone decorative features on a facade, and to granite decay in association with mortar joints. The hypothesis was tested by quantitatively comparing the soluble salt content in two facades, one with, the other without, limestone features.

Hopper for dispensing cement or mortar

Abstract: A hopper dispenses cement or mortar into the space between side by side paving bricks. The hopper is a self supporting container. The container has opposing container sides converging downwardly to an elongated opening. This elongated opening extends for most of the length of the container. The opening has just below it a spaced pair of thin parallel guides for guiding the cement or mortar into the space between the paving bricks.

Pumice containing composition

Abstract: A composition for forming a waterproof, high strength, hard material having good insulation properties, comprising a mixture of crushed pumice and type S mortar, and preferably refractory additives or fillers, which forms the hard material upon the addition of water and after allowing the mixture to cure. The material has superior insulation properties to conventional compositions formed using portland cement instead of type S mortar.