CONCRETE

[:ru]Чекнаворян А. А.[:en]Jeknavorian, A. A.[:] [:ru]канд. техн. наук, ст. научный сотрудник, компания W.R. Grace & Co, Кембридж, штат Массачусетс, США[:en]PhD, Research Fellow, W.R. Grace & Co, Cambridge, MA, USA[:]

Alitinform №4-5 (26) 2012 г. 52-63 p.

Abstract

Chemical admixtures have long been known for the beneficial role they play in improving the engineering properties of concrete and mortar mixtures. Looking back over the recent decades, the use of air entraining agents and superplasticizers can be considered among the major influences that have allowed the extending of the use of concrete to many diverse applications. ACI 212.3R reports that chemical admixtures provide numerous benefits to concrete mixtures such as increasing compressive and flexural strengths at all ages, increasing durability through reduction in permeability, inhibiting corrosion of steel reinforcement, reducing shrinkage, altering setting and hardening rates, and increasing the slump and flow characteristics — all of which contribute to cost reductions associated with materials and placing, and increasing the service life of concrete.
This discussion concerns the current and future needs of the concrete industry and how either available or future admixture technologies can have a favorable impact. Special attention is paid to the class of superplasticizers known as polycarboxylates as this highly flexible technology has already provided great value to the concrete industry, most notably the production and placement of self-consolidating concrete (SCC). Complementing the introduction of new chemical admixture technologies is the need for applicable standards that both protect and guide users as well as facilitate commercialization.

Key words:

self-consolidating concrete; high range water reducers; superplasticizers; polycarboxylates; cement-admixture interaction; supplementary cementitious materials; pervious concrete