Polycarboxylates (PCEs) currently dominate the global superplasticizer market. Among them, HPEG and IPEG PCEs have attained a prominent position as they present the most cost-effective PCEs known at present. Recently, novel vinyl ether PCEs designated as EPEG and GPEG PCEs were introduced, thus broadening the family of VPEG PCEs, and their overall performance is still evaluated. Well documented are now the advantages of novel phosphated comb polymers which can significantly reduce the stickiness of concrete e.g. in UHPC. In spite of many attempts, so far no overall cost-effective clay tolerant superplasticizer has been identified, the challenge being that such a structure must include side chains that however do not contain polyethylene glycol/polypropylene glycol (PEG/PPG) or polyamines. Fortunately, for calcined clay blended cements, HPEG PCEs of specific molecular design as well as zwitterionic (amphoteric) PCEs have proven to be highly effective. Moreover, AAS binder systems were successfully fluidized with APEG or HPEG PCEs exhibiting particularly short side chains (nEO < 10). This review underlines the critical role that innovation in chemical admixtures will play in the future to facilitate a successful migration to low-carbon binders.

This paper provides a brief overview of a project comprising several parts, carried out in collaboration with Jim Wight and a number of graduate students over a period of about fifteen years, starting in the mid 1980’s. The project focused on the effects the addition of fibers can have on the performance of reinforced concrete joints. Lessons learned from early “non-success” and subsequent successes achieved are described. Although details of the effects of fiber reinforcement on the joint behavior under monotonic and cyclic loading such as load carrying capacity, hysteretic moment-rotation response, strength and stiffness degradation, shear resisting mechanisms, and absorbed energy are left to the references cited, a key observation related to the hysteretic energy dissipated is emphasized. It is observed in particular that not all fibers provide equal benefits and the fiber reinforcing parameters must be carefully selected in order to achieve superior results. Two important factors are further stressed: the need to achieve a fiber reinforced concrete composite that is strain hardening in tension (thus likely in shear as well), and the need to develop a postcracking resistance that remains significant even when crack widths exceed the millimeter range.