Showing papers on "Mortar published in 1986"

The influence of contaminating (fossil) carbonate and the variations of delta (super 13) C in mortar dating.

Abstract: The influence of the aggregate in mortar dating is examined. Sample activity as well as isotopic fractionation approach the expected values at lower yields of the preparation reaction of the counting gas. Good results are obtained at low fossil carbonate concentration. 813C cannot give information about this concentration but preliminary visual and chemical analysis of the mortar makes prediction of sample validity possible. INTRODUCTION It is well known that 14C dating does not date archaeologic events but only the materials found in an archaeologic context. Thus, there may be an important interval between the age of the material and the archaeologic event. A good example of this is 14C dating wooden beams used in construction. The 14C dated tree rings can easily be a century older than the building, itself. This problem becomes even more severe if we consider re-use of material. This problem can be avoided by using mortar as a dating material. Traditionally mortars were made essentially of lime and sand. Different limes were used, quicklime and hydraulic lime. Quicklime (CaO) is obtained by burning (CaCO3) over a fire at ca 1000°C. When water is added it forms Ca(OH)2 and hardens by absorption of atmospheric CO2. Hydraulic lime is obtained by burning argillaceous limestone. It contains aluminates and silicates which harden with water. Younger mortars tend to be more hydraulic than older mortars. The hydraulic index framed by Leduc and Chenu (1912) provides a useful parameter to classify mortars. This index is defined as Al203 + Fe203 + S102 soluble CaO + MgO This is, in fact, the ratio between the clay and the lime fractions. Fat limes have values up to 0.1; values > 0.5 indicate that the material is cement rather than mortar. In between are mortars which are more or less hydraulic. Besides lime, mortars also contain sand and aggregate which are used as charge. Their purpose is to enlarge the volume of the mortar and to avoid cracks. Several laboratories have been working on mortar dating since 1964. Some obtained very good results (Delibrias & Labeyrie, 1965); others obtained dates that were far too old (Stuiver & Smith, 1965). In summary, we can say that, theoretically, mortars containing lime ought to be 14C datable since hardening time is short compared to the half-life of 14C. How-

Compressive Strength of Concrete Masonry Prisms

Abstract: Experimental tests on prisms and constituent materials (mortar, grout, and hollow-core concrete blocks) are used to calibrate linearly elastic finite element models for hollow and grouted concrete ma­ sonry prisms. These finite element models are then used to develop simplified relationships which closely predict the compressive strengths and failure modes of prisms.

Strength development of blended blast-furnace slag-cement mortars

Abstract: Blast‐furnace slags cooled at different rates were used to study the effect of fineness, mixing method and content of slag on the strength development of blended‐slag mortar. Activator and curing temperature were used to activate the early strength. The microstructure of blended‐slag paste was also investigated in this study to explain the strengthen effect.

Isotopic fractionation of carbon during CO (sub 2) absorption by mortar.

Abstract: Recent studies comparing dates from the carbon content of mortars with dendrochronologic dates for the same material have shown considerable inconsistencies related to mortar type (Van Strydonck et al, 1985). Even after the best possible removal of “dead” calcite, some mortars are unsuitable for dating. We describe here our experimental study of carbon isotope fractionation during the manufacture and hardening of mortars. Preliminary experiments established overall uptake of CO2 from the air. We then measured isotopic ratios in identical mortars at different hardening times.

Compression Behavior of Concrete Masonry Prisms

Abstract: An analytical investigation using a three‐dimensional finite element model was conducted to study the complex behavior of hollow block prisms under axial compression. Detailed stress distributions in different directions were determined which help in understanding the composite behavior and failure mechanism of both face shell and fully‐bedded mortared prisms. The effects of type of mortar bedding, mortar deformational characteristics, block size, heightto‐thickness ratio, number of mortar joints, and stiffness of bearing plates on the behavior of axially loaded prisms were studied. The results show that the most significant parameters are the type of mortar bedding, the prism geometry, and the stiffness of bearing plates. Recommendations for the determination of masonry compressive strength and evaluations of code provisions for the testing of concrete masonry prisms are presented.

Extraordinary effects of mortar-and-pestle grinding on microstructure of sintered alumina gel

Abstract: The use of the mortar and pestle in the laboratory dates back to the earliest attempts to understand and use the materials around us. Even now, it is difficult to imagine an alternative to crushing and grinding for the preparation of many samples. Traditionally, mortar-and-pestle mixing or grinding has been held to be a relatively mild and controlled process, although it was recognized that the grinding of materials harder than the material of the mortar and pestle would result in some contamination. Thus, good practice forbade grinding of, for example, mullite and alumina in agate mortars. That this technique is not so innocuous was demonstrated by Dachille and Roy1 with respect to the stresses generated. They showed that phases usually obtained only at 10–20 kbar can be obtained metastably by simple grinding in a laboratory mortar. There are numerous examples of solid–state phase transformations being produced by prolonged or intense comminution2, two of the best–documented cases of stress/shear–induced transformation being the conversion of calcite to aragonite1, and of quartz to amorphous silica3,4, both by prolonged grinding in a laboratory mortar and pestle. Here we show that the very small amounts of material generated by the wear of mortar and pestle surfaces by even mild grinding can also have substantial effects on the micro-structure and transformation kinetics of certain ceramic systems so treated.

Fracture of Concrete Subjected to Impact Loading

Abstract: To evaluate the response of concrete structures subjected to impact or impulsive loading, it is essential to know how cracks propagate under such dynamic loading conditions. Single-edge notched beams were subjected to varying rates of loading to establish the stress intensity factor K1 versus crack velocity V relationship for mortar and concrete. Impact tests were performed using a modified instrumented Charpy test system. During loading, the rate of crack growth was obtained using special brittle Krak gages. Results indicate the following: (1) For a given strain rate the extent of pre-peak crack growth is larger for concrete than for mortar, and the amount of pre-peak crack growth decreases with increase in strain-rate. (2) Decrease in pre-peak nonlinearity at higher strain rates is probably caused by the decrease in amount of slow (pre-peak) crack growth. Hence, the linear-elastic fracture mechanics (LEFM) approach at high rates may be valid. (3) To obtain realistic size independent value of stress intensity factor, slow crack growth should be included in the calculation for cement composites. (4) The relationship between log K1 and log V is nonlinear especially at the higher rates of loading, for both mortar and concrete.

Adhesion of Polymer-Modified Mortars to Ordinary Cement Mortar by Different Test Methods

Abstract: This paper deals with the adhesion or bond strength of polymer-modified mortars to ordinary cement mortar, which is tested by different methods, and the effects of polymer types and polymer-cement ratio on the adhesion. Polymer-modified mortars using a commercial styrene-butadiene rubber (SBR) latex, ethylene-vinyl acetate (EVA) emulsion and polyacrylic ester (PAE) emulsion are prepared with various polymer-cement ratios, and tested for adhesions in tension, flexure and compressive shear. Substrate used is a mortar with a ratio of cement to standard sand 1:2. The test results obtained are summarized as follows: (1) The adhesions in tension, flexure and direct compressive shear of the polymer-modified mortars increase with a raise in the polymer-cement ratio regardless of the types of polymers and specimens. (2) The adhesion in slant (indirect) compressive shear of the polymer-modified mortars reaches the maximum at a polymer-cement ratio of about 5%. (3) The failure mode distribution of the polymer-modified mortars remarkably depends on the test methods and polymer-cement ratio. (4) The adhesion test methods which can successfully reproduce service conditions in the practical applications of the polymer-modified mortars are recommended.

Use of grout-filled sausages in coastal structures

Abstract: An alternative to rubble mound construction, with or without precast concrete armor units, is recommended which comprises flexible membranes filled with cement mortar in situ. The placement of these for greatest stability is suggested by maximizing surface contact of sausage type units. Results of tests to derive an economical mortar mix are described. Construction details are outlined together with comparative costs for a marina breakwater.

Compression creep behaviour of steel fibre reinforced cement composites

Abstract: The paper presents the results of an experimental investigation to determine the influence of steel fibre reinforcement on the creep of cement matrices under compression. Creep tests were carried out at a number of applied stress-strength ratios ranging between 0.3 to 0.9. Melt extract and hooked steel fibres were used at volume fractions ranging between 0 and 3% by volume of a mix. Three types of cement matrices were used namely cement paste, mortar and two mix proportions of concrete.

Effects of Ground Granulated Blast-Furnace Slags on Some Properties of Pastes, Mortars, and Concretes

Abstract: Tests were performed under separate contracts at different times for three manufacturers of ground granulated blast-furnace slag to determine the performance of their products with portland cement. Physical tests were performed on pastes, mortars, and concretes to determine both freshly mixed and hardened properties. The effects of gypsum addition, fineness of slag, and levels of replacement in cement-slag combinations were evaluated. Physical tests performed on pastes and mortars included time of setting, compressive strength, and volume stability. In the mortar compressive strength series, various curing regimens were evaluated with respect to strength development. Included were normal moist curing at 23°C (73°F) and 4.4°C (40°F) and 100% relative humidity, and accelerated atmospheric curing [71°C (160°F)] and 100% relative humidity. Tests conducted on concretes containing slag included compressive strength, freeze-thaw durability, and resistance to deicer chemicals (scaling). Measurements of air-void systems of hardened concretes were made. Results generally show that use of slag can be beneficial without resulting in significant technical problems or adverse construction problems.

Deterioration of brick masonry caused bi acid rain

Abstract: The effect of acid rain on bricks and mortar is considered for bridge, the main reaction is the dissolution of the glassy phase; for lime-containing mortars, the acid dissolution of the carbonated lime. The overall deterioration is mainly due to the mechanical effect of the recrystallisation of solubles salts. Photographs, references.

Strength Development of Blended Blast Furnace Slag Cement Mortars

Abstract: Blast‐furnace slags cooled at different rates were used to study the effect of fineness, mixing method and content of slag on the strength development of blended‐slag mortar. Activator and curing temperature were used to activate the early strength. The microstructure of blended‐slag paste was also investigated in this study to explain the strengthen effect.

Testing of Bond Between Fresh and Hardened Concrete

Abstract: The bond between fresh and hardened concrete can be subjected to various stress states depending on the application and service conditions. Four test methods, reflecting different stress states at the bond between the fresh and hardened concrete, are evaluated. The four methods are a slant shear test, an indirect tension test and two different flexure tests. The slant shear test is shown to be consistent and the most sensitive test in showing the strength of the bond, and was used to evaluate the effect of the following parameters on that strength: (1) the water cement ratio of a portland cement mortar; (2) the thickness of the bond layer; (3) the effect of various curing conditions; (4) the effect of wetting the surface of the hardened concrete before application of the portland cement mortar bonding agent; and (5) the effect of delay between mixing a copolymer Polyvinyl acetate (PVA) bonding agent, and its application to hardened concrete.

Process for the manufacuture of stratified pieces such as roof tiles and wall tiles

Abstract: A process for manufacturing stratified pieces, such as roof tiles and wall tiles, by sucessive and independent extrusion of mortars or concretes. In the process mortar is deposited on a limited part of the molds. The mortar is extruded and compacted, and some mortar is dislodged from cross strips in each zone of contact between two consecutive molds. Thereafter, complete sheets of mortar are shaped on the first layers, filling both the emptied cross strips and the limited sides, and lastly the thicknesses of the pieces are cut in their entirety in a vertical transversal plane at each zone of contact of the molds to form multiple layer tiles having homogeneous facing surfaces.

Building blocks and their method of manufacture

Abstract: A construction element made up of three attached layers, the central layer of which is made of insulating material whilst the outer layers are load-bearing. The central layer S1 is a solid made of insulating material prepared in advance whilst the layers located on either side are made of mortar of cement and fine sand cast against the insulating solid. Application to the building of walls and surfaces.

Process for producing mortar and method for applying the same

Abstract: A process for producing a cement composition such as concrete, mortar, or the like widely used in the field of civil engineering, building, etc. and a method for applying it. In preparing mortar or the like, cement, small blocks of and, if necessary, aggregates such as sand, gravel, etc. are mixed to cause hydration reaction. Ice blocks are used in place of water to be mixed with cement, aggregates, etc. at a low water-to-cement ratio to thereby prepare a macroscopically uniform system of a pseudo solid phase which is wetted with a small amount of molten water formed on the surface of the ice block. The ice blocks gradually melt to form a homogeneous mixture prior to the application of the mortar.

Method of producing and applying mortar

Abstract: A method of producing and applying a cement-containing composition such as a concrete and mortar broadly used in civil, construction and various other fields is disclosed. To prepare the mortar or the like, a hydration reaction of cement and water is caused in the presence, if necessary, of aggregate such as sand or gravel. According to the present invention, small ice masses are used in lieu of water. That is, cement, aggregate and small ice masses are mixed and kneaded together in a low water-cement ratio and in a quasisolid state wetted by a small quantity of water resulting on the surfaces of the small ice masses from the melting thereof into a macroscopically homogeneous system. Subsequently, gradual transition of this system into a homogeneous mixture with the melting of the small ice masses is caused. The ice masses are entirely melted until the instant of charging of the composition thus prepared.

Factors influencing electrode potential of steel in concrete

Abstract: An investigation of the rusting of steel wire in concrete and mortar is reported. Steel corrosion was monitored using electrode potential measurements, and five experimental parameters were controlled: cement type, mortar porosity, mortar cover thickness, mortar cracking, and carbonation thickness. Measurements were made by connecting the reference electrode to three locations on each face of every reinforced mortar parallelepiped sample. The results showed that the mean value of the electrode potential for a sample is correlated with the degree of rusting of the steel, although the location of the measurement does have some effect on the recorded electrode potential. Cracking of the mortar has also been shown to influence the electrode potential.

Effects of Cellulose Ether on Bond Between Matrix and Aggregate in Concrete

Abstract: The influence of cellulose ether on the strength of mortar and on the anisotropy of concrete are discussed by obtaining relationships between cement-void ratio and compressive strength and by comparing two tensile strengths in the casting direction and direction perpendicular to the casting. — It may be stated that the strength of mortar is little influenced by both cellulose ether and/ or defoamer and the addition of cellulose ether improves bond strength between cement matrix and aggregate by decreasing defect under aggregate due to bleeding.

Construction material, process for the production thereof and use thereof

Abstract: A construction material consists of a set and/or puzzolanically hardened mixture, containing 70 to 95% by weight of sulphite-containing flue-gas desulphurisation product from dry and/or quasi-dry processes, 5 to 30% of fly ash, if appropriate additionally up to 15% by weight, based on the mixture, of a hardening agent and, if desired, additionally up to 3% by weight of further additives and auxiliaries. It is preferably used in the form of subsequently ground briquettes, pellets, mechanically compacted blocks, extruded material or cast pasty materials. It may be used as construction material, in particular as mineral concrete, for foundation layers of buildings, car parks, cycle tracks, as filling material in civil engineering and earthwork, as filler in dam construction and dyke construction and as aggregate for mining mortar and, with or without aggregate, as mining mortar.

Grain for construction material

Abstract: Disclosed is an improved granular material used for forming construction materials such as concrete and mortar. The grain material comprises a main material of fly ash or slug powder and reinforcing fibers. The reinforcing fibers are mixed with the main material together with a binder to form a grain body such that the reinforcing fibers project outward from the surface of the grain body. The reinforcing fibers mixed in this fashion permit increasing the bonding strength between the grain and the binder such as cement so as to improve the mechanical strength of the resultant construction material.

Method of mounting a metal band about a cover plate

Abstract: A metal band is mounted about the periphery of a cover plate, particularly a ceramic sliding plate for use with a sliding gate nozzle for controlling the discharge of molten metal from a vessel, such that the cover plate can be mounted on a supporting frame by means of releasable clamps acting on the metal band. The peripheral surface of the cover plate is covered with a layer of thermally setting mortar, and a heated steel ring is positioned around the mortar layer. The steel ring is cooled, such that the steel ring shrinks about the mortar layer, while the mortar layer is heated and thereby set, such that the cooled steel ring is bonded about the peripheral surface by the mortar layer. Alternatively, the cover plate may be positioned within a mold having a peripheral rim such that there is defined between the mold rim and the peripheral surface a space surrounding the peripheral surface. This space may be filled with a molten non-ferrous metal or gray cast iron which is solidified, thereby forming a band fixed to the peripheral surface.

Adhesion Forces of Polymer Modified Concrete and Plain Concrete to Steel in Moulds and in Reinforced Concretes

Abstract: The paper discusses types and conditions of adhesion forces of polymer modified concrete and plain concrete to steel occurring in moulds and in reinforced concretes. Particular attention was paid to hydroxyls -OH, present in the concrete and evoking forces of specific adhesion. The author reports the test results on adhesion and abhesion to steel of the cement and vinyl-maleic modified mortar.