Showing papers on "Mortar published in 1992"

Effect of composition, environmental factors and cement-lime mortar coating on concrete carbonation

Abstract: The paper describes the physicochemical processes of concrete carbonation and presents a simple mathematical model for the evolution of carbonation in time, applicable under constant relative humidity higher than 50%. The model is based on fundamental principles of chemical reaction engineering, and uses as parameters the ambient concentration of CO2, the molar concentratrations of the carbonatable constituents, Ca(OH)2 and CSH, in the concrete volume, and the effective diffusivity of CO2 in carbonated concrete. The latter is given by an empirical function of the porosity of hardened cement paste and of relative humidity, derived from laboratory diffusion tests. The validity of the model for OPC or pozzolanic cement concretes and mortars is demonstrated by comparison of its predictions with accelerated carbonation test results obtained in an environment of controlled CO2 concentration, humidity and temperature. The mathematical model is extended to cover the case of carbonation of the coating-concrete system, for concrete coated with a cement-lime mortar finish, applied either almost immediately after the end of concrete curing or with a delay of a certain time. Parametric studies are performed to show how the evolution of carbonation depth with time is affected by cement and concrete composition (water/cement or aggregate/cement ratio, percentage OPC or aggregate replacement by a pozzolan), environmental factors (relative humidity, ambient concentration of CO2), the presence and the time of application of a lime-cement mortar coating and its composition (water/cement, aggregate/cement and lime/cement ratios of the mortar, percentage OPC or aggregate replacement by a pozzolan).

Polymer concrete and polymer mortar using resins based on recycled poly(ethylene terephthalate)

Abstract: Fundamental properties of polymer concrete (PC) and polymer mortar (PM) made from unsaturated polyester resins based on recycled poly(ethylene terephthalate), PET, are described. Mechanical properties investigated include strength, modulus of elasticity, ductility index, Poisson's ratio, coefficient of thermal expansion, shrinkage, and exotherm. Durability properties include chemical resistance, water absorption, sand-blast resistance, and thermal cycles of thin overlays on portland cement concrete slabs. Resins based on recycled PET offer the possibility of a lower source cost for forming useful PC and PM (PC/PM) based products. The recycling of PET in PC and PM would also help alleviate an environmental problem and save energy.

Radiocarbon Dating of Lime Fractions and Organic Material from Buildings

Abstract: We have dated carbonate fractions and organic material from different types of mortar from two sites in Belgium. We demonstrate the difficulties in obtaining good dates from carbonate samples. We also discuss the need for new types of dating material when the mortar comes from contaminated and disturbed sites, where even charcoal can yield aberrant results.

The influence of mixing on the microstructure of the cement paste/aggregate interfacial zone and on the strength of mortar

Abstract: The influence of mixing on the microstructure of the cement paste/aggregate bond has been investigated Back-scattered electron microscopy was used in conjunction with quantitative image analysis to examine the microstructure of the interface between limestone aggregate and the cement matrix in a series of mortars The distribution of porosity and anhydrous material along the paste/aggregate interface was shown to be dependent upon the relative abundance of water at the aggregate surface during mixing Improvements in the interfacial microstructure were shown to correlate with improvements in strength and fracture properties The interfacial zones seen in the limestone mortars were compared with a model interfacial system A new classification system for two types of interfacial regions in mortar is proposed

Evaluation of Pozzolanic Activity of Rice Husk Ash

Abstract: The changes in physical and chemical properties of RHA (rice husk ash) fired at several temperatures from 400 deg C to 800 deg C at 50 deg C increments were studied. The effect of RHA on properties of mortar such as strength, drying shrinkages, resistance to acid attack, freeze thaw resistance and carbonation was also determined. It was found that the compressive strength of RHA blended mortar with respect to that of plain mortar corresponded to the variation in conductivity. The RHA in mortar improved resistance to acid attack and developed the same degree of resistance to freeze-thaw action as that with the use of silica fume, while it increased the drying shrinkage.

High-performance mortar, concretes obtained from this mortar and the elements produced from this mortar or concrete

Abstract: Mortar of very high performance. This mortar is obtained by mixing with water a mixture which comprises a Portland cement, a vitreous microsilica obtained as byproduct in the zirconium industry, a superplasticising agent and/or a wetting agent, a quarry sand, optionally other adjuvants, in the proportions shown. The invention makes it possible in particular to obtain mortars which have a crushing strength of the order of 250 MPa and to prepare concrete of very high performance.

High tg polymer and redispersible powder for use in hydraulic portland cement mortar and concrete

Abstract: Polymers with a high glass transition temperature are used in cement additives to produce a portland cement mortar or concrete that does not have the initial stickiness typical of prior art polymer-modified portland cement compositions and does not form a crust on the surface when exposed to air drying, thus improving the working time of the mix. This simplifies equipment cleaning and permits the use of transit mixers for field applications of polymer-modified concrete. The properties of the mortar and concrete modified with these materials, both in the plastic and hardened state, are equivalent or superior to those of the currently available products which use film-forming materials. Within the scope of this invention are a redispersible powdered cement additive, a redispersible polymer powder and a ready-to-use portland cement composition, as well as related processes.

The ‘pessimum’ effect in an accelerated mortar bar test using 1M NaOH solution at 80°C

Abstract: Highly reactive opal was incorporated in mortar bars (25 mm × 25 mm × 285 mm) in proportions of 0, 5, 10, 30 and 50% of total aggregate content, and their expansion was measured for up to 3 weeks under storage conditions of 1 M NaOH at 80°C. Maximum expansion occurred when the aggregate contained 5% opal, and increasing the amount of opal caused decreasing expansions, i.e. a ‘pessimum’ effect was observed at 5% opal content. Although this effect can be explained in the standard mortar bar tests (ASTM C227 and Australian Standard AS 1141-38) on the basis of limited alkali contents in the mortar bars, it cannot be explained on this basis in the accelerated test because of large amounts of alkali available to the mortar bars. An explanation for the occurrence of the ‘pessimum’ effect in the accelerated test has been provided based on the formation of a barrier to the penetration of NaOH in the outer skin of the mortar bars containing opal contents much larger than the ‘pessimum’ proportion.

Relative importance of deleterious reactions in concrete: formation of AAR products and secondary ettringi te

Abstract: Aggregates, varying in alkali reactivity, were used for making mortar bars and concrete prisms, employing the same Portland cement Measurement of length changes of the specimens was carried out under various storage conditions and for different lengths of time Scanning electron microscopy of the specimens and energy-dispersive X-ray analysis of the products formed in them has shown that alkali-aggregate reaction (AAR) products develop first and much faster than ‘secondary’ ettringite (mat-form, filling cracks) associated with some deteriorated steam-cured concrete elements The expansion and cracking due to AAR was more rapid and extensive at higher temperature (80°C) than at lower temperature (40°C) Mat-forms of ettringite developed only after prolonged storage of the specimens in a fogroom, and the amount was larger in the specimens initially treated at 80°C, mainly because more AAR expansion and cracking occurred at the higher temperature, but also because the higher initial temperature caused large

Drainage enhancer for double seepage drains

Abstract: A device for improving the drainage through, and structural integrity of, a mortar bed of a shower floor. The device encircles a neck portion of a drain in the shower floor. The device is positioned between the mortar bed and drainage weep holes formed in the drain so that practically any water seepage through the mortar bed must pass through the device before entering the weep holes. The device has a greater porosity than that of the mortar bed and provides a larger drainage surface area of the mortar bed than that of the weep holes alone.

Building material made from waste paper and method for producing the same

Abstract: A slurry composed of paper fibers, water, and cement that can then be used for a variety of construction applications is prepared. After draining the majority of the water, the slurry may be molded into blocks, sheets, or any other desired shape to be used as a construction material, or it can be sprayed onto wire shapes to form custom structures. The slurry product can be used as a mortar in conjunction with building blocks that have been made from the slurry, and it can be used as a plaster when mixed with conventional cement and sand mortar. The slurry can also be poured into forms in the same manner as concrete to form blocks for construction applications.

The mechanical and drying shrinkage properties of cement mortars containing carbide lime waste

Abstract: The present study investigates the possibility of utilizing carbide lime waste, obtained from the generation of acetylene from calcium carbide, as a mineral filler material in various cement mortar mixes. The physical and chemical analysis of the waste were studied. Five mortar mixes containing various contents of carbide lime waste were prepared, tested, and compared with one control mix, to investigate the influence of the waste material on both fresh and hardened properties of mortars. The properties discussed were density, compressive strength, splitting tensile strength, flexural strength, and drying shrinkage. The strength and drying shrinkage values were determined at 3, 7 and 28 d, respectively. The results revealed that addition of carbide lime waste generally caused a reduction in both strength properties and density when compared with the control mix, in spite of the small influence on the drying shrinkage of some of the mortar mixes. However, the results obtained satisfy the minimum requirements of strength specified by British Standards, and hence it can be concluded that the material can readily be used for masonry mortar cement.

Cement paste mixer and method for producing mortar and concrete

Abstract: There is provided in a pressure feed pipe for feeding cement paste under pressure a wall panel assembly formed of a plurality of wall panels having collision surfaces and through holes and arranged at predetermined intervals. High-strength or superhigh-strength mortar or concrete is produced by kneading a designed amount of binder material comprising cement or cement and a pozzolan material together with a predetermined amount of water, passing this cement paste through the abovementioned pressure feed pipe to crush the cement balls contained in the cement paste and thus to homogenize the paste, and kneading the thus homogenized cement paste together with fine aggregate or fine and coarse aggregates.

Preliminary Analysis of the Masonry of the Hagia Sophia Basilica, Istanbul

Abstract: Specimens of brick and mortar taken from the Hagia Sophia Basilica in Istanbul, Turkey, are being analyzed as part of an investigation of the construction history and present state of structural stability of the building. The analysis, covering both chemical composition and physical properties, involves a suite of instrumental methods including quantitative X-ray diffraction, thermal analysis, and automated image analysis of polished sections under SEM. These conventional methods are being supplemented by neutron diffraction and neutron and Xray small angle scattering. Preliminary results suggest the presence of cementitious materials including plombierite and tetracalcium aluminum carbonate in the mortar as well as calcium carbonate. The mortar contains significant amount of brick dust and also large chunks of brick as coarse aggregate. Given the pozzolanic nature of brick dust, it is possible that the mortar is actually not a conventional carbonated lime material, but rather a proto-concrete. The type of masonry construction involving very wide mortar joints, comparable to the width of the bricks, suggests that the Byzantine architects took advantage of this property of the mortar. This sophisticated materials technology may help to explain how the Basilica was constructed in such a short time period, and also to allow us to understand and model subsequent structural problems, including major deformations of the main piers. Also, the feasibility of dating by radiocarbon and thermoluminescence methods is being investigated to determine which parts of the elaborate buttress system are the original Byzantine structure as opposed to later Ottoman additions.

Mortar composition and extrusion gun

Abstract: A mortar extrusion gun includes a refillable and cleanable mortar supply tube possessing a first end terminating in a forwardly and radially inwardly extending flange surrounding a mortar ejection aperture and a second opposite open end A conical spout includes a tip provided with a mortar outlet aperture and a base possessing a mortar inlet aperture surrounded by a radially outwardly extending flange Preferably, a set of spouts possessing various different dimensions are provided for selective use under different working conditions In an assembled condition, the spout is inserted through the supply tube and ejection aperture such that the inwardly and outwardly extending flanges abut in sealing relation, supporting the spout at the first end of the supply tube After the supply tube is filled with mortar, a packing disk is inserted into the open end of the supply tube, and the supply tube and spout assembly is inserted into a slightly modified conventional caulking gun Various disclosed embodiments of the packing disk possess different profile configurations and may include pressure relief vent apertures or cracks to diminish separation of water from the mortar within the supply tube and resultant clogging of the gun Various mortar compositions suitable for pressure application and dependent upon mortar joint width are disclosed The mortar extrusion gun is intended for use in precisely, completely, and rapidly applying mortar to joints during construction and repair of masonry structures

Strip of reinforcing fibres

Abstract: A strip for reinforcing fibres for mixing into mortar, concrete or asphalt. The fibres are glued together side by side by means of a glue that dissolves or melts or otherwise looses its binding ability when mixed in such material. Glue is only laid on one side of the strip instead of dipping and wiping-off. This reduces the danger of compression into lumps during transport and storage of the bags filled with such strips, and combines the use of less glue.

Process of manufacturing of sprayable concrete and morton by using an additive

Abstract: Additives for air-placed concrete or mortar, which contain a silica sol or consists thereof, lead to a marked decrease in dust evolution and recoil in the processing of the air-placed concrete or mortar by the dry or wet process. When processing the air-placed concrete or mortar, this additive is preferably added during spraying, for example in the spray nozzle.

Method of field casted pile forming with ash cement slurry wall protecting

Abstract: The present invention relates to a piling method by pouring powdered coal ash cement wall-protection mortar. Said invention uses the long-screw driller to drill hole to the designed depth, and at the same time of lifting drilling rod the powdered coal ash cement wall-protection mortar is injected into the hole at low pressure through the mortar outlet of drill bit. When the wall-protection mortar is reached to the position where there is no caving hale, the drill rod is drawn out and the reinforcing cage is placed, and then the conduit is put in, and the mixed concrete is poured from hole bottom into the hole through the conduit. Pouring the concrete while pulling the conduit until the mouth of hole is reached. It can ensure the quality of finished pilereduce cost, raise loading capacity and reduce contamination.

Mechanical properties of materials used in concrete blockwork construction

Abstract: This experimental investigation is intended to study and determine the difference in strength of unfilled and filled concrete block specimens compressed in two orthogonal directions. It also studies the effects of using different concrete infill mixes on the block compressive and splitting strengths, and the mechanical properties of the materials used in blockwork masonry construction. The materials involved were the concrete block, concrete infill and mortar; one type of concrete block, three mixes of concrete infill and three types of mortar were used. The characteristics studied were the stress versus strain curves, the modulus of elasticity, the Poisson ratio, the block compressive strength and the splitting strength, the shrinkage after 28 days, the cohesive bond between the block and concrete infill, and the shear strength. The Paper gives values and relations to determine the above characteristics and also compares them with some standardized ones.

Strength of mortar made with cement containing rice husk ash and cured in sodium sulphate solution

Abstract: This study researched the benefits of using waste husk from rice production. The mortars were prepared by substituting cement with husk at 10, 20, and 30 % by weight. The mortars were stored in sodium sulphate solution until testing date after the initial 28 days curing in water. Compressive and flexural strength tests were carried out on the mortar specimens at 4, 8, and 12 week periods of storing in solution. It was observed that durability and strength of mortars increased by using rice husk ash.