Admixtures ― present and future trends

This review article was first presented as a paper at the 14th annual convention of the institute of concrete technology, 23-25th April, 1986. Trends are divided into commercial and technical, the former being analysed mainly up to the present and the latter using past developments to extrapolate possible trends in the future. Admixture usage/value figures derived from the cement admixtures association's statistical returns for the 12 month period up to June 1985 have been analysed and compared with a similar period from five years previously. UK trends are adjudged indicative of the world scene. Technically and in general the present trend is to replace natural products with synthesized materials and the production of complex admixtures with two or more active constituents with either a dual function or increased effectiveness. Two examples are combined air entrainer/water-reducing plasticisers (major) used in pavement quality concrete and economic superplasticisers (minor) consisting of blends of modified lignosulphonate (mls) and sulphonated naphthalene formaldehyde condensates (snf). For the commercial future it is likely that admixture development will be part of an overall concrete development taking account of cement change, alternative hydraulic binders and changing practices. Potential future technical trends are discussed under the main headings air entraining admixtures, mortar plasticisers and waterproofers and changes in usage. Other suggested future developments briefly discussed are plasticisers and superplasticisers with more efficient action, more efficient non-chloride accelerators, emphasis on calcium rather than sodium salts for use as admixtures in response to problems with alkali-aggregate reaction, increasing use of synthetic surfactants as air entrainers, special admixtures to increase the cohesiveness of concrete or grout placed under water, investigation of admixtures with composite materials comprising opc and alternative hydraulic binders eg pfa, ggbfs and fume, water reducing/accelerating/retarding admixtures and air entraining admixtures.