Mortars Creep

Aggregate elasticity modulus is 50.0 Gpa Poisson s ratio is 0.2 Creep is 0 volume ratio is 0.46. Determine the mortar creep by inversion calculation. Inversion result and numerical result are list in Table 2 and Figure 4. 

C 1181 Standard Test Method for Creep of Concrete in Compression C 531 Standard Test Method for Linear Shrinkage and Coefficient of Thermal Expansion of Chemical Resistant Mortars, Grouts, and Monolithic Surfaces... 

In general, at low latex dosage levels, the creep strain and creep coefficient of latex modified concrete and mortar are considerably smaller than those of ordinary cement cement, mortar and concrete [94, 98]. The low creep is probably due to the low polymer content which may not affect the elasticity, but increases the strength by improving the binding capacity of the matrix as well as providing better hydration through water retention in the mortar and concrete. The coefficient of thermal expansion at about 9-10 x 10 is very similar to that of concrete, which is 10 x 10 6 [87, 94, 99]. 

Methyl 4,6-O-benzyIidene-a-D-aItropyranoside. Triturate 4.0 g (0.015 mol) of the foregoing anhydro derivative in a mortar with a solution of 5 g of potassium hydroxide dissolved in 140 ml of water. Transfer the suspension to a round-bottomed flask and heat the mixture under reflux until all the solid has dissolved (about 28 hours). During this period solid material tends to creep up the inside of the flask surface shake periodically to re-suspend material. Remove the trace of insoluble matter which remains and neutralise the cooled filtrate with carbon dioxide (use phenophthalein as an indicator). Extract the solution with five 25 ml portions of dichloromethane, wash the combined extracts with a little cold water, dry over anhydrous sodium sulphate and remove the solvent under reduced pressure (rotary evaporator). Crystallise the syrup by scratching a small portion on a watch glass with ether stir the bulk syrup with ether and the seed crystals. Filter off and recrystallise the product from a small quantity of methanol to obtain 3.5 g (83%) of methyl 4,6-0-benzylidene-oc-D-altropyranoside, m.p. 174 °C, [a]D°+115° (c2 in CHCI3). 

Potassium Bromide. Combine all the mother liquors, evaporate in a porcelain dish until a pasty mass is obtained, mix this thoroughly with 5 grams of powdered charcoal, and dry the hi ass completely. Pulverize the dry mixture in a mortar and heat it to redness, for 20 minutes, in an iron crucible surrounded by an asbestos mantle. Extract the product with 60 cc. of hot water, filter, wash the residue and filter with an additional 15 cc. of hot water, and evaporate the solution to dryness to obtain potassium bromide. The solution of potassium bromide creeps. If it has to be set away over night the vessel containing it should be placed in a clean large dish to catch any of the salt that creeps over the edge of the smaller vessel. 

Up till now there is only few safe knowledge about stress-induced deformations (E-modulus, creep) and stress-independent deformations (shrinkage, swelling, temperature-expansion). But due to long experiences with other mortars containing polymers (e.g. lightweight mortars with expanded polystyrene as aggregate, polymer modified cement mortars PCC), basic problems are not to be expected. 

KEY WORDS citric acid, gypsum, mechanical properties, mechanism of sel retardation, microstnicture of retarded gypsum mortars, texture index, strength, creep properties... 

Conflicting data exist on the creep behavior of latex-modified mortar and concrete. The creep characteristics of SBR- and PAE-modified concretes reported by Ohamal l are represented in Fig. 4.40. Like ordinary cement concrete, the relationships between loading time (t) and creep strain (ec) or creep coefficient (< )) (i.e., creq) strain/elastic strain ratio) of the latex-modified concretes fit approximately the expression ... 

By contrast, SolomatovI " found that the creep deformation in flexure of poly(vinyl acetate-dibutyl maleate)-modified mortar was several times larger than that of unmodified concrete at 20°C, and its catastrophic deformation occurred at 50°C since the polymer developed a high plasticity above its glass transition temperature. 

ABSTRACT It is very important to determine the thermal and mechanical parameters of mortar and concrete in mesoscopic simulation. In this paper, on the basis of the Mori-Tanaka formula of mesoscopic mechanics and the concrete is treated as a two-phase composite material constituted by aggregates and mortar, the inversion of coefficient of thermal expansion, autogenous shrinkage, elastic modulus and creep were studied. This paper proposed some inversion formulas regarding these four mechanical parameters of mortar in concrete. The accuracy of these formulas was verified by FEM numerical test and demonstrated by some examples. 

Until now, much research work has been done on the prediction of composite material coefficient of thermal expansion and elastic modulus by forefathers, and many prediction methods have been developed such as the sparse method (Guanhn Shen, et al. 2006), the Self-Consistent Method (Hill R.A. 1965), the Mori-Tanaka method (Mori T, Tanaka K. 1973) and so on. However, none of these formulas take into account the parameters variation with concrete age, and there is little research on the autogenous shrinkage and creep. In the mesoscopic simulation of concrete, thermal and mechanical parameters of mortar and aggregate (coefficient of thermal expansion, autogenous shrinkage, elasticity modulus, creep, strength) are important input parameters. In fact, there is abundant of test data on concrete, but much less data on mortar while it is one of the important components. Also parameter inversion is an essential method to obtain the data, but there are few studies on this so far. 

Concrete is treated as a two-phase composite material constituted by aggregate and mortar. This paper provides the inversion formulas of several vital thermal and mechanical parameters of mortar by Mori-Tanaka theory in meso-mechanics. With these formulas, the mortar coefficient of thermal expansion, autogenous shrinkage curve, elasticity modulus curve and creep curve can be determined conveniently. However, this paper takes no consideration of the influence of interface between aggregate and mortar. Thus further studies are needed to be done to show the effect of this factor. 

The superposition approach can be used to produce a constitutive equation which expresses the creep compliance (Ca) of the adhesive in terms of a reference creep compliance (O and shift factors for stress (a ), temperature (at) and resin content (Cv) such that Ca = Cr X a X Ut X Oy X f". The method has been used by Dharmarajan et al. (30) to characterise the creep behaviour of epoxy, polyester and acrylic mortars in the form of prism specimens under 3 point loading. From relatively short-term tests, strain v. time curves such... 

Fig. 6.6. Compressive creep strains in repair mortars, (a) Polymethyl methacrylate mortar, (ft) Polyvinyl acetate modihed mortar, (c) Magnesium phosphate modified mortar, d) Flowing concrete.

The impregnation of hardened concrete or mortar with polymers increases the strength of the material signifieantly forrrfold increases are not rmcommoa At the same time the material attains a more brittle character. The creep of the material is also reduced... 

In hardened cement-based composites the transportation of liquids and gases through pore and microcrack systems plays a very important role in many processes, such as hydration of Portland cement, pozzolane effects of microfillers, carbonation, corrosion of cement paste and reinforcement due to reaction with external agents, shrinkage and creep, etc. These processes are partly described in respective Sections 4.1, 4.3, 6.5 and 11.5. Only basic information is reiterated below concerning the flow of liquids and gases through concretes and mortars. 

The need for a building material with high strength and durability afforded the development of Polymer Mortars (PM). PM show, in general, high mechanical, chemical and durability properties however, they also exhibit great sensitivity to high temperatures and creep phenomena, and mainly, deficient behaviour under fire (Ribeiro et al., 2004, 2008 Tavares et al., 2002). 

Walton and Majumdar [122] studied the tensile creep of Kevlar fibres and the bending creep of cementitious composites made with these fibres (2.4% by volume of short random 2-dimensionally dispersed fibres). The creep coefficients of the aramid fibres themselves were found to be smaller than those of other synthetic fibres (polyethylene, polyvinylchloride and polycarbonate). The creep of the composite was of the same order of magnitude as that expected in a plain mortar matrix. 

The CIC tests were conducted using a sample size similar to the SCSS test samples except for the sample OD. The brick sample size used for the creep in compression tests were the same as those used in the SCSS tests. The brick/mortar composite samples were also the same as those used in the SCSS tests. The creep samples were subjected to a constant compressive load of 0.689 MPa (100 psi). The heatup rate of the CIC samples was set at 1.8°F/min (l°C/min)... 

Figures 30, 31, and 32 show the creep behavior of the brick-only, mortar-only, and brick/mortar composite samples at 816°C (1500°F), 1094°C (2000°F), and 1372°C (2500°F), respectively. At all three temperatures the brick-only and brick/mortar composite samples exhibit insignificant creep. The mortar-only samples (no confinement) exhibit relatively considerable creep response. The creep tests also confirm that unconfined mortar tests do not replicate the true confined behavior of the mortar in the mortar joint.

Figure 30 Comparisons of creep curves at 816°C of silica KD composite, mortar-only, and brick-only.

Figures 38 through 40 show the creep deformations of silica KN composity, mortar-only and brick-only.

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