Aggregate reactivity test

A recently developed technology takes a different approach to solving the stress problem (14). Rather than chemically plasticizing the sulphur, non-reactive additives are used to holistically plasticize the sulphur concrete mix. In essence these additives are lubricants which operate at the sulphur/aggregate interface to allow slippage and stress relief without disruption and cracking. The apparent permanency of this plasticization approach has been demonstrated by extensive testing over a four year period. 

Benzylquininium chloride has been studied as a catalyst for the asymmetric Michael reaction. Reaction of amidoma-lonate (5) and chalcone (4) with catalytic base and a variety of chiral, nonracemic ammonium salts in the absence of solvent produced (6) in yields of 41-68% and 20-68% ee (eq 2). The quinine-derived salt (1) was of intermediate effectiveness (38% ee, 47% yield) when compared to ephedrine-based catalysts. Although (1) was not specifically tested with regard to solvation effects, it is suggested that increased aggregation of reactive species under solid-liquid PTC conditions leads to enhanced organization and selec-... 

The simplest, and one of the most remarkable, new enzyme mimics has emerged from a piece of lateral thinking by Menger and Fei. [9] No synthesis is involved. These authors simply mixed long-chain carboxylic acids, amines, alcohols and alkylimidazoles, of the sort known to form aggregates, and eventually micelles, in aqueous solution then screened large numbers of such mixtures for catalytic activity. The test reaction was the hydrolysis of the reactive ester 9 (X = O), which is easily followed above pH 7 by the release of the p-nitrophenolate chromophore. Some of the mixtures used effected the hydrolysis of 9 (X = O) at rates too fast to measure manually. Remarkably this was also true in the presence of a single component when this was the hexadecanoate anion, and this system also effects the hydrolysis of the p-nitroanilide (9, X = NH). 

At this stage it should seldom be necessary to return to selective testing. Sometimes it happens that an otherwise adequate catalyst cannot be suitably aggregated in full production, fails after too few cycles of reactivation owing to loss of an essential but irreplaceable component, or cannot be reactivated speedily. Then, if exploratory and selective testing has been properly weighted, alternative catalysts will be available. 

Limestones generally do not contain sufficient reactive silica or silicates to cause expansion, and damaging alkali-carbonate reaction has rarely been reported. The reactions involving carbonate rocks can be either expansive or non-expansive and are more likely to occur when the limestone contains appreciable quantities of dolomite and clay minerals [8.1]. ASTM C586 [8.8] gives a test method for determining the potential alkali reactivity of carbonate rock aggregates. 

ASTM C586-92 Test method for potential alkali-reactivity of carbonate rocks for concrete aggregates (rock cylinder method) , 1992. 

Turriziani [60] points out that the limit values used to classify the particular types of aggregate relate only to the American materials. It has been underlined by Lea [98] that the results of tests for some expanding aggregates allow to classify them as the non-reactive ones and there are the inverse cases too. Sorrentino et al. [108] found that the classification of aggregate to any reactivity class (Fig. 6.33) is more... 

Bryan GC, Scudder J (1952) Dextran and pneumococcus polysaccharide cross-reactivity in skin tests and serum precipitin tests. Ann NY Acad Sci 55 477-478 Bygdeman S, Eliasson R (1967) Effect of dextrans on platelet adhesiveness and aggregation. Scand J Clin Lab Invest 20 17-23... 

Monomers which produce polymers with the desired polymer interaction parameter are now selected for possible testing as lens materials. Formulations of those monomers with the appropriate amount of ctosslinker and ctosslinking are identified by estimating modulus of elasticity that a reaction product would possess using a Monte Carlo method developed by Xu and Mark (28). Potential formulations to make the lens are further refined by comparison of reactivity ratios between prospective monomers. The potential for a mixture of monomers to form a desired copolymer is estimated fiom the AUrey-Price, Q-e scheme (29) for radical-monomer reactivity. If the reactivity ratios ofthe monomers in a formulation are close in numerical value, the polymer is projected to be truly random and it may form a functional lens. These formulations are accepted. If the reactivity ratios are very different the monomers will react in block fashion. A block copolymer is prone to be hazy because the blocks in the copolymer can aggregate and create sharp changes in index of refraction in a lens. These formulations are rejected. 

From the tensile tests presented, it appeared that the nanocomposites made by alkyl silane-functionalized sepiolite give the best mechanical performances, in particular for what concerns the yield stress. In fact, the sepiolite surface fimctionalization by silane is a reactive treatment, which decreases the interparticle aggregation (improved dispersion) and, at the same time, increases the matrix-filler interactions. The addition of fimc-tionalized polymers is, instead, a nonreactive surface treatment. It leads to a decrease of the particle-particle interaction but can also reduce the matrix-particle interaction, which leads to lower yield stress and ultimate tensile stress. 

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