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ASTM Types I and V Portland cements were hydrated up to 28 days in the presence of 0.3%and 0.6% sulfonated melamine formaldehyde (SMF), at a water/cement ratio of 0.35.Hydration was studied by conduction calorimetric and thermogravimetric analyses. Theamount of Ca(0 Hh produced, compressive strength and porosity l!'ere determined after 1, 3,7 and 28 days of curing. The compressive strengths of all samples increased with the age ofcuring. In the period studied the values decreased in the order: Type I cement(reference) = Type I cement + SMF> Type V cement (reference) ~ Type V cement + SMF.The superplasticizer addition retarded the development of heat in the cements, but moreseverely in Type V cements. Porosities were generally higher for samples with 100vercompressive strengths. In the presence of 0.6% SMF, the early lOll' strengths in Type Vcement mixtures could be attributed to lower degrees of hvdration. At later ages, themicrostructure rather than the degree of hydration determined the strength development.However, incorporation of 0.3%SMF in Type V cement did not affect its strength development.

Six phosphonates, comprising the three acids aminotri(methylenephosphonic acid) (ATMP), 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and diethylenetriaminepenta-(methylenephosphonic acid) (DTPMP) and their corresponding sodium salts Na5ATMP, Na4HEDP and Na6DTPMP, were added to Portland cement in dosages ranging from 0.03 to 0.09%, at a constant water/cement ratio of 0.35 and their conduction calorimetric behaviour was investigated up to 72 h. The induction period, the time to attain the maximum heat effect and the integral heat developed at different times were determined. All phosphonates increased the induction period, from about 3 h to greater than 72 h, with respect to the reference cement with an induction period of 2 h. The acid phosphonates were more effective retarders than their corresponding salts. At a concentration of 0.05% the induction period extended from 10.1 to 21.1 h with the acids and only from 4.1 to 16.2 h with the salts. DTPMP was the most effective retarder among all the phosphonates, a concentration of 0.05% producing an induction period of 21.1 h and an exothermic inflection at 42.4 h compared with values of 2.2 and 7.9 h, respectively, for the reference. The corresponding salt (Na6DTPMP) was the most efficient of all the salt retarders. At a concentration of 0.05%, the induction period was extended to 16.2 h and the exothermal inflection to 31.4 h. In most instances the degree of extension of the induction period increased with the dosage of retarder. Phosphonates appear to be much more efficient retarders than many other retarders used in concrete practice.

The preparation of this book was undertaken with the aim of integrating the chemistry and application of concrete superplasticizers, in a way, it is hoped, that will be relevant to conrete engineers and technologists, and useful to researchers and students. The book is divided into 14 chapters. Each chapter contains a list of important references that should serve as a useful guide to obtain further information. The first chapter, an introduction to concrete science, is included to describe the most recent concepts so that the informatin presented in subsequent chapters can be easily followed and appreciated. (A)

The hydration stoichiometry, products and kinetics of dicalcium silicate are summarized. Hydration takes a similar course to tricalcium silicate, but at a much slower rate. The differences and similarities between the two compounds are identified and discussed, and future research needs identified.

Many aspects of the action of calcium chloride in concrete are ambiguous, controversial, or incompletely understood. Examples include: (a) the restrictive definition of calcium chloride as an accelerator; (b) the lack of clarity in prescribing the dosage for practical applications; (c) the classification of calcium chloride as an antifreezing agent; (d) the misconception regarding corrosion of reinforcement in the presence of CaCl2; (e) the divergence of opinion on the mechanism of action; and (f) incomplete understanding of the changes in the intrinsic properties of cement containing calcium chloride. This paper attempts to deal with these aspects citing typical examples.

Normal Portland cement, low C[3]A cement, tricalcium silicate, and C[3]A-gypsum mixtures are hydrated in the presence of 0,0.8,1.5 and 3.0% CaC1[2] for 1,3,7,14 and 28 days and the amounts of extractable chloride determined by applying a pressure of 80000 lb (449 MPa) or by treating the pastes with excess water. At early periods of hydration both methods yielded similar values for immobilized chloride. The amount of free chloride in the pore solution increased as the dosage of initially added chloride was increased. The C[3]A-gypsum mixture immobilized much higher amounts of chloride than did the C[3]S phase. Normal Portland cement had lower amounts of free chloride than low C[3]A cement.

A study was designed to assess the merits of polymer addition to superplasticized cement paste, mortar and concrete. Three superplasticizers - a sulfonated melamine formaldehyde, a sulfonated naphthalene formaldehyde and a commercial superplasticizer were used in combination with experimental polymers. Polymer and super-plasticizer dosages ranged from 0-15% and 0-0,3% respectively. The effect of binary admixture systems - (superplasticizer and polymer) - on the physico-mechanical properties of the cementitious systems was determined. Properties investigated included the following; slump retention, setting time, compressive strength, flexural strength, surface area, porosity and density. Compatibility of the polymers with the superplasticizer was assessed with respect to the influence of the individual admixtures on the properties of the various systems. Synergistic effects were observed for one polymer, the results of which are discussed in detail., Proc. 3rd Int. Conf on Superplasticizers and Other Chemical Admixtures in Concrete: 1989, Ottawa, Ont. Canada