Sodium lignosulfonate and naphthalene and melamine sulfonate formaldehyde condensates, dissolved in lime water, are adsorbed on C4AHU and C&i6. When dissolved in dimethylsulfoxide the same admixtures are adsorbed on CsAHIJ but, apparently, not on C3AHa. The adsorption isotherms of the two polycondensates are very similar but different from those of lignosulfonate. This fact can be attributed to the considerable structural difference between the synthetic admixtures and the lignine derivative. The particle zeta potential is modified by the presence of the admixtures, minimum additions of which are enough to bring the zeta potential to negative constant values. Nevertheless, the values of the potential cannot be correlated with the viscosity of the aluminate hydrate pastes, since the viscosity first increases and then decreases as the admixture increases. This behavior can be explained by a bridging effect among the particles, which overcomes the repulsive effect due to zeta potential.

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A methodological approach, based on some innovative reactivity parameters such as the threshold alkali level (TAL) of aggregates and the tolerable driving force (Delta(tol)) of the deleterious expansive process associated with alkali-silica reaction (ASR), is proposed in order to assess the alkali-reactivity of aggregates and compare the effectiveness of different types of ASR inhibitors (low-alkali Portland cements, lithium compounds, and blended cements manufactured with active mineral additions). The effectiveness of the ASR inhibitors, expressed in terms of Delta(tol), is related to the naturally available alkali content of concrete and the TAL of the aggregate used in the concrete mix. The potential minimum contribution of alkalis (L (im)) by a given ASR inhibitor to the concrete mix is proposed as a specific efficacy parameter. The relationships between the effective dose levels of mineral additions or lithium compounds and the efficacy parameters Delta(tol) and L (im) have also been identified. The test procedures for the experimental determination of such parameters are described and some methodology applications to published ASR expansion data are reported

The effectiveness of blended cements (three pozzolanic cements -two with natural pozzolana and one with coal fly ash -and one blast-furnace cement) in counteracting alkali-silica reaction (ASR) was assessed by using both the ASTM C1567 accelerated mortar bar expansion test and the accelerated concrete prism expansion test at 38°C and 100% RH. A low-alkali Portland cement was also tested as ASR inhibitor. The results of the mortar and concrete expansion tests were analyzed through a kinetic-based model (KAMJ model) to evaluate the expansion rate constant, k, and the Avrami exponent M. These two kinetic parameters were taken as efficacy parameters for each type of inhibitor. The results of the concrete prism expansion tests were also analyzed through an innovative methodological approach and a third efficacy parameter, such as the potential minimum alkali contribution by the inhibitor to concrete (L im ), was evaluated. It was found that the values of ln(k) mb =-6.0 for mortar bars and ln(k) cp = -7.7 for concrete prisms were appropriate efficacy criteria for discriminating between deleteriously expansive and non-deleteriously expansive mortar or concrete mixes, respectively. In the case of concrete mixes, a good relationship between the efficacy parameter L im and the kinetic parameter M cp was found, thus demonstrating the suitability of M cp as a criterion for ranking not expansive concrete mixes. With respect to the kinetic parameters ln(k) cp and M cp , the efficacy parameter L im appears to be of greater technological interest, the last being strictly related to the composition of the concrete mix.

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