Showing papers on "Cement published in 1970"

The chemistry of cement and concrete

Abstract: The chemistry of cement and concrete , The chemistry of cement and concrete , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Corrosion and Corrosion Inhibition of Reinforcing Steel: II. Embedded In Concrete

Abstract: Reinforcing steel, whether embedded in Portland concrete or Portland cement-blast furnace slag concrete and mixed with distilled or tap water, becomes passivated. On the other hand, when the concrete is mixed with sea water, the steel corrodes severely, and when Helwan mineral water is used for mixing, a borderline condition is obtained. Portland cement-blast furnace slag concrete had poorer corrosion resistance compared with ordinary Portland cement concrete.Steel passivity is not impaired when Portland cement concrete or Portland cement-blast furnace slag concrete is admixed with up to 8% of sulphates. However, when cement extract is used, the passivity is impaired when as little as 0·2% of sodium sulphate is added.Additions of some anodic inhibitors such as benzoate, chromate, nitrite, phosphate and stearate to a corrosive concrete medium are efficient in preventing the corrosion of reinforcing steel. The critical concentration for inhibition is higher in the case of Portland cement-blast furna...

Repair and reattachment in the balanidae as related to their cementing mechanism

Abstract: Barnacles, which become partially or totally detached from their substratum in a natural environment, produce a secondary cement secretion. Laboratory experiments demonstrate that the secondary cement can successfully reattach the barnacle to a new substratum. Similar secondary secretion was found at the site of minor injuries to the barnacle basis. The secondary cement usually has a looser, more cavernous structure than the primary cement, but both secretions have similar staining characteristics. Microscope preparations indicate that occasionally barnacles are capable of developing new secondary cement ducts leading into the injured or detached areas to secrete secondary cement. In most cases, however, the existing primary cement duct network is used for the secondary secretion. This is possible only because most of the once used ducts are not plugged by hardened cement, in spite of the fact that the cement can harden inside the ducts. Chemical analysis suggests that the cement is an organic biopolymer and indications are that the cement hardening is initiated inside the organism. A unique flushing mechanism seems to be responsible for keeping the cement ducts open and ready for reuse. A nonhardening flushing fluid forces the still liquid cement out of the ducts. The cement hardens outside the duct openings sealing the flushing fluid inside the duct network. In case of detachment or injury. the cement seal breaks; the flushing fluid drains out leaving the duct open for the secondary cement secretion. The vesicles in conjunction with the main channel control the flow of the flushing fluid and the cement. The permeable wall of the main channel portion inside the vesicle reduces the convection and diffusion between the vesicle and the main channel, thus bypassing of vesicles and duct networks not affected by detachment is possible. The wall of the main channel inside the vesicle is also collapsible, thus acting as checkvalve when the vesicle is under pressure and allowing the cement to be pumped only into the ducts toward the secretory orifices.

An evaluation of a carboxylate adhesive cement.

Abstract: Properties of a zinc phosphate and a carboxylate cement were measured and compared. Solubility, setting time, film thickness, and pH were similar, and tensile strengths were in the same range. The carboxylate cement was distinctly superior in its adhesion to both enamel and dentin under tensile loading, but little difference was observed when both cements were evaluated by measuring the tensile force needed to remove Class I inlays.

Method for forming foamed concrete structures

Abstract: CELLULAR CONCRETE STRUCTURES ARE MADE BY ADMIXING WATER AND CEMENT UNDER CONDITIONS SUFFICIENT TO PRODUCE A HIGH DEGREE OF HYDRATION OF THE CEMENT PARTICLES, FOLLOWED BY THE INTRODUCTION OF A FOAM FORMED UNDER PRESSURE FROM A MIXTURE OF WATER, AIR, FOAMING AGENT AND CHLORIDE ACCELERATOR. THE FOAM MIXTURE AND CEMENT ADMIXTURE ARE BLENDED TO A SUBSTANTIALLY HOMOGENEOUS, FOAMED CEMENT SLURRY, WHICH IS CAST INTO A MOLD AND CURED TO FORM A LIGHTWEIGHT CELLULAR CONCRETE STRUCTURE. IN THE STRUCTURE, THE VOIDS ARE RELATIVELY SPHERICAL IN SHAPE AND HAVE AN AVERATE DIAMETER OF ABOUT 0.05 TO 0.050 INCH. THE FOAMING AGENT AND CURE ACCELERATOR ARE CONCENTRATED AT THE SURFACE OF THE CONCRETE MATRIX ABOUT THE VOIDS, AND THE STRUCTURE HAS A UNIFORM DENSITY OF ABOUT 25 TO 75 POUNDS PER CUBIC FOOT.

Glass Fibre Reinforced Cement and Gypsum Products

Abstract: Glass fibre reinforced cements and gypsum plaster provide examples of composite materials where both the components are brittle and the matrix phase fails at a much lower strain than the fibre. Porosities of the order of 30% or more are usually present in these matrices. The interfacial bond that develops between the fibre and the matrix is very discontinuous and irregular. The dispersion of glass fibre in the matrix is not easy. When chopped multifilament strands are distributed in the matrix by a spraying process, the tensile and flexural strength of the composite material produced from gypsum plaster reach maximum values around 10% by volume of fibre addition. Beyond the elastic limit, the composite material exhibits a quasi-plastic behaviour until it fails by fibre pull-out. Fire resistance and impact strength of plaster are greatly improved by fibre incorporation. Glass fibres now available commercially are not durable in the alkaline medium present in hydrating Portland cements. Experimental fibres produced from more alkali-resistant glasses are being studied for their suitability in reinforcing cements and concrete. It can be foreseen that given a durable glass, the composite material will have pronounced advantages over existing sheet materials in respect of impact strength and resistance to cracking, tensile and bending strength and fire resistance.

Mechanism of seawater attack on cement pastes

Abstract: TYPE I (WHITE), II, AND V (ZERO TRICALCIUM ALUMINATE) CEMENT PASTES OF WATER-CEMENT RATIOS OF 0.3 AND 0.5 WERE IMMERSED IN SEAWATER AND SOLUTIONS OF SODIUM AND MAGNESIUM SULFATES. THE ATTACK ON THE CEMENT PASTES WAS INTERPRETED IN TERMS OF KINDS, AMOUNTS, AND LOCATION OF THE REACTION PRODUCTS IN THE PASTES. X-RAY DIFFRACTION AND DIFFERENTIAL THERMAL ANALYSIS WERE USED IN STUDYING THE SPECIMENS. ETTRINGITE IN TYPE I CEMENT PASTES PRECIPITATED AS CRYSTALS. GROWTH OF THESE IN CONFINED SITES CAUSED EXPANSION. THE ETTRINGITE IN TYPE V CEMENT PASTES PRECIPITATED AND PERSISTED AS A GEL. SINCE THERE WAS NO CRYSTAL GROWTH, EXPANSION DID NOT OCCUR. THE ROLE OF CHLOROALUMINATE, BRUCITE, AND GYPSUM IS DISCUSSED. /AUTHOR/

Hydraulic cementitious compositions reinforced with fibrillated plastic film

Abstract: CONCRETE, MORTAR, CEMENT OR PLASTER OF PARIS ARE REINFORCED TO PROVIDE PRODUCTS OF IMPROVED BENDING STRENGTH BY ADDITION OF UP TO 2% BY WEIGHT OF FIBRILLATED POLYPROPYLENE FILM TO THE MASS PRIOR TO OR DURING MIXING

A mercury porosimetry study of the porosity in portland cement

Abstract: THE PORE SIZE DISTRIBUTIONS OF TWO SERIES OF CEMENT PASTES PREPARED AT WATER-CEMENT RATIOS 0.4 & 0.6 WERE DETERMINED AS FUNCTIONS OF AGE, USING MERCURY POROSIMETRY. THE CONTACT ANGLE OF MERCURY ON THOROUGHLY DRIED PASTE WAS MEASURED AS 117 DEGREES; FOR P-DRIED PASTE IT WAS FOUND TO BE 130 DEGREES. IT WAS FOUND THAT MUCH OF THE PORE SPACE PRESENT AT ALL AGES OCCURRED IN PORES BETWEEN 0.1 AND 0.01UM; THAT IS, IN BETWEEN THE CONVENTIONAL CONCEPTS OF CAPILLARY AND GEL PORE DIAMETERS. IT WAS FURTHER OBSERVED THAT PORE VOLUME LEFT UNINTRUDED BY MERCURY AT 15,000 PSI WAS SIGNIFICANTLY LESS THAN THE 28 PERCENT BY VOLUME THAT SHOULD BE PRESENT IN MATURE PASTES ACCORDING TO CURRENTLY ACCEPTED IDEAS OF THE NATURE OF CEMENT GEL. ON THE BASIS OF THESE OBSERVATIONS AND DIRECT EXAMINATION OF FRACTURE SURFACES OF CEMENT PASTE, IT WAS CONCLUDED THAT MOST OF THE SPACE PRESENT IS NEITHER CONVENTIONAL CAPILLARY NOR CONVENTIONAL GEL SPACE BUT MERELY SPACE BETWEEN FINE INDIVIDUAL PARTICLES OF CEMENT HYDRATION PRODUCTS. /AUTHOR/

Lightweight cements for oil wells

Abstract: DISCLOSED HEREIN IS A LIGHWEIGHT CEMENT WHICH UTILIZES SMALL CENOSPHERES PRIMARLY CONSISTING OF SILICA-ALUMINA. THIS MATERIAL KNOWN AS FLOAT ASH IS ESSENTIALLY THAT PORTION OF FLY ASH THAT FLOATS ON WATER AND HAS SPECIFIC GRAVITY AROUND 0.7. THE LIGHTNESS OF FLOAT ASH AND ITS INHERENT COMPRESSIVE STRENGTH MAKE IT DESIRABLE AS AN INGREDIENT FOR DECREASING THE WEIGHT AND IMPROVING THE STRENGTH OF OIL WELL CEMENTS.

Cement additive comprising calcium sulfo-aluminate, an organic adhesive, a foaming agent, and a dispersing agent

Abstract: A cement additive consisting of 100 parts by weight of a mineral consisting mainly of calcium sulfo-aluminate, which forms ettringite having a high content of sulfate through hydration, 0.1 to 2.0 parts by weight of an organic adhesive, 0.005 to 0.5 part by weight of a blowing agent and 1.0 to 6.0 parts by weight of a dispersing agent is suitable for grout. This cement additive is preferred to be added with 0.5 to 10.0 parts by weight of an accelerating agent.

Shrinkage and creep of concrete as affected by the fineness of Portland cement

Abstract: Synopsis Tests are reported on the shrinkage and creep of concrete made with Portland cement of three different grades of fineness, but of similar composition except for gypsum content. The programme comprised tests of unrestrained shrinkage, restrained shrinkage and cracking by a ring test, and creep over periods up to four-and-a-half years. The results indicate that there is an increase of unrestrained shrinkage and creep with finer cement but that, owing to the higher strength, there is no tendency for undesirably rapid shrinkage cracking to occur.

Method of making light-weight concrete aggregate

Abstract: An aggregate for making high-strength, light-weight concrete, the aggregate being constituted by shaped glass, asbestos, cement, metal or plastic elements whose surfaces are fluted and otherwise treated to improve the adhesion of the aggregate to the concrete matrix and which can be made hollow to effect a significant decrease in weight.

Dental Silicate Cements: X. The Precipitation Reaction

Abstract: The precipitation of ions during the setting and hardening of cements has been studied by extraction of soluble materials at different stages during the aging process, followed by chemical analysis. Cement formation arises from precipitation of aluminum, zinc, and calcium phosphates in conjunction with a siliceous gel phase.

Shrinkage compensating cement

Abstract: A shrinkage compensating cement which includes a composition of Portland cement and a reactive compound which expand upon contact with water. The reactive compound is coated with an alkali soluble, water insoluble material in order to delay the time within which the reactive compound will expand. Quicklime or Plaster of Paris are examples of reactive compounds which may be used.

Properties of cements mixed from liquids with altered water content

Abstract: The water content of the liquids of silicate, zinc phosphate, and silicophosphate cements was altered within the range of plus 10 to minus 10 per cent. Tests were run on the cements mixed from these liquids and the results of these tests compared with data obtained by testing cements mixed from the unaltered liquids. The following observations are made: 1. The setting times of zinc phosphate and silicophosphate cements are increased with increases in water of the liquids whereas the setting time of silicate cements is increased by a decrease in the water content of these liquids. 2. Cements mixed with liquids having altered water content have reduced physical properties, such as a marked reduction in abrasion resistance and increased solubility. 3. The results of the investigation emphasize protection of cement liquids from alteration in water content in order to maintain maximum physical properties of the cement mixes.

Electrode joint cement

Abstract: A high temperature cement, comprising elemental powders of boron and a transition metal and a carbonizable binder, is provided for joining sections of a carbonaceous electric-furnace electrode column. The cement is initially heated to between about 90* C. and 130* C. to thermoset the carbonizable binder and then the temperature is elevated to above 1,000* C. to react the transition metal with the boron to form a strong cemented bond having excellent thermal and electrical properties.

Quick setting and quick hardening cement and method for producing the same

Abstract: A QUICK SETTING AND QUICK HARDENING CEMENT AND A METHOD FOR PRODUCING THE CEMENT IS DISCLOSED. THE CEMENT CONTAINS ALUMINOUS CEMENT, LIME OR LIME CONTAINING MATERIAL, PORTLAND CEMENT, AND A KETOCARBOXYLIC ACID OR ITS SALT AS A CHELATING AGENT. THE CHELATING AGENT FORMS A COMPLEX SELECTIVELY WITH CA ION IN THE ALKALINE STATE AND AFTER A CERTAIN PERIOD, THE COMPLEX WILL DECOMPOSE OR DECREASE. THEREFORE, THE TIME TO BEGIN SETTING CAN BE CONTROLLED TO 1-90 MINUTES AND SUFFICIENT HARDENING TAKES PLACE IN A SHORT TIME.

Model for Strength of Brittle Materials Built up of Particles Joined at Points of Contact

Abstract: Theoretical analysis of the strength of materials consisting of particles joined along contact areas small in relation to particle size resulted in the model where p denotes strength, D particle size, γ surface energy, d linear extent of the contact area, E modulus of elasticity for the particles, and θ porosity. The first factor has the same form as the Griffith model except that particle size is substituted for crack size; it shows that strength increases inversely with the square root of particle size. The model can be used as a guide in the design of materials such as mortars with low cement content, sand-lime bricks, soil stabilizers, and sintered products. The strengths of mortars made from finely ground quartz and cement and cured at high temperatures were 4 to 40 times higher than those of normal mortars with the same cement/water ratio.

Epoxy hydraulic cement composition

Abstract: THE INVENTION RELATES TO A HYDRAULIC CEMENT COMPOSITION WHICH HAS ADMIXED THEREIN AN AQUEOUS EPOXY EMULSION COMPOSITION OF AN EPOXY RESIN AND AN EMULSIFYING AND CURING AGENT FOR THE RESIN IN AMOUNT SUFFICIENT TO ENHANCE THE PROPERTIES AND MOST NOTABLY THE TENSILE, FLEXURAL AND COMPRESSIVE STRENGTH OF THE CEMENT, WHEN THE CEMENT IS CURED. THE EMULSIFYING AND CURING AGENT USED IS OF A PARTICULAR KIND, NAMELY, A REACTION PRODUCT OF A PRIMARY OR SECONDARY AMINE WITH A DIGLYCIDYL ETHER OF A POLYGLYCOL. SUCH CURING AGENTS ARE DISCLOSED IN MY COPENDING APPLICATIONS SER. NO. 873,501, FILED NOV. 3, 1969, NOW ABANDONED AND SER. NO. 53,010, A CONTINUATION THEREOF, FILED JULY 7, 1970.

Sulfuric Acid Attack on Concrete Sewer Pipe

Abstract: Research was performed to determine if selected surface treatments would react chemically with the portland cement and increase the resistance of a mortar to sulfuric acid attack. Four parameters were investigated: (1) Portland cement type; (2) water/cement ratio; (3) sulfuric acid concentration; and (4) chemical surface treatment. The laboratory tests did not produce a desired solution for the problem of sulfuric acid attack on portland cement mortar. However, the experience in the laboratory did lead to the following conclusions: (1) Magnesium silicofluoride, sodium silicate, potassium silicate, and sodium alginate do not benefit the resistance of portland cement mortar to sulfuric acid attack; (2) even weak sulfuric acid solutions caused deterioration of both treated and untreated mortars; (3) varying the constituents of mortar produced from either Type I or Type II cement do not prevent failure due to sulfuric acid attack; and (4) sulfuric acid attack on portland cement mortar is a surface phenomenon and does not affect the structural integrity of the interior of the mortar specimens.

Cement raw mix control apparatus and programming

Abstract: A system including computer apparatus and programming automatically controls the proportioning of raw materials fed to a kiln-producing cement clinker, the automatic control depending upon the analytical values of the various oxides of the raw materials, the result being a raw mix composition of optimum uniformity.

Non-hardenable, high-density fill composition and process for making same

Abstract: An improved non-hardenable, high-density composition especially useful as a backfill material for high-voltage cable installation along with a method for making and using the composition is disclosed. The composition is characterized as an admixture of particulate materials, such as sand, gravel, and crushed stone aggregate, a filler such as portland cement, with or without pulverized limestone, clay, etc. and a lubricant. A quantity of water sufficient to give the admixture good workability can be added in a manner which prevents the cement from hardening. The improved composition is useful as ship ballast in addition to its use in construction as a backfill material for pipes, cables, tunnel liners or the like.

Composition for eliminating efflorescence in portland cement products

Abstract: A composition comprising polyvinyl alcohol characterized by high-molecular weight and viscosity and very low solubility of insoluble in water, mixed with barium hydroxide or barium oxide, and added to Portland cement in the proportion ranging from 3/4 to 5 percent of the alcohol to 100 percent of the cement, effective to prevent bleeding of salts out of the cement and thereby markedly lessen or eliminate efflorescence in Portland cement products.

Reinforcement of Cements and Gypsum Plaster by Glass Fibres.

Abstract: : Inorganic building materials such as cement and plaster posses adequate compressive strength but their inherent weakness in tension and against impact seldom permits effective utilisation of their high compressive strength in structural applications Commercially available glass fibers (eg E-fibers) can successfully reinforce gypsum plaster and that composites made by using a suitable fabrication technique possess sufficient strength and durability to be considered for load-bearing applications Regarding the reinforcement of cements and concrete, E-glass fibers are very seriously damaged by Portland cements; but certain glass fibers having compositions in the Na2O-SiO2-ZrO2 system may possess adequate alkali resistance to be suitable for reinforcing such cements The present paper describes results in this area (Author)

Cement having improved color

Abstract: COLORED CEMENTS HAVING IMPROVED COLOR AND REDUCED EFFORESCENCE ARE PREPARED BY ADHERING TO A PORTION OF THE SURFACE OF A MAJORITY OF THE UNSET CEMENT PARTICLES A SURFACE-TENSION REDUCING AGENT AND/OR A DISPERSANT WHICH EFFECTS DISPERSION BY ESTABLISHING A COMMON CHARGE ON EACH OF THE CEMENT PARTICLES WITHOUT SUBSTANTIAL REDUCTION IN THE SIZE OF THE PARTICLES PREFERABLY, THE ORGANIC MATTER IA ADHERED TO THE CEMENT PARTICLES BY IMPINGING A STREAM OF ONE OF THE PARTICLES ON A STREAM OF THE OTHER AND PREFERABLY BOTH A SURFACE-TENSION REDUCING AGENT AND A DISPERSANT ARE UTILIZED

Shear strengths of fissures in ledge rock before and after grouting

Abstract: 1. Cement grouting of fissured ledge rocks leads to a marked reduction in slip deformation due to an inclined load. The effect of cementation is most marked in badly fractured rocks, the slip of which in the natural state is characterized by an elongated horizontal-displacement graph. 2. Cement grouting leads to an increase in the shear strength of hard rocks. Cementation is most effective in badly fractured rocks without fine earth filling, owing to the efficient filling of the cracks by the cement solution. (We must, however, remember that such conditions are not always found in natural rock masses.) 3. The use of cement solutions based on dispersed cement (colloidal cement or dry-vibromilled cement) permits cement grouting to be more effective than with ordinary cement. 4. The presence of badly broken sections in a rock foundation is not necessarily a reason for reduced slip resistance parameters or for removal of much of the rock, and in such cases we should always consider whether it is advantageous to use cement grouting to improve the quality of the rock.