Experimental evaluation of a new phosphonate-based superplasticizer for concrete

The paper deals with the effectiveness of an innovative phosphonate-based superplasticizer (PHN) for ready mixed concrete. Concrete specimens were manufactured by considering a constant initial workability, equal to 220 mm slump at the end of the mixing procedure. Workability was measured at 0, 30 and 60 minutes to evaluate the workability retention performances of the innovative superplasticizer. Compressive tests at 1, 7 and 28 days were carried out to evaluate the influence of the superplasticizer on concrete setting and hardening. The concrete mixtures were designed by considering 13 different cements to assess the superplasticizer-cement compatibility. The PHN-based admixture showed a better performance in terms of water reduction and workability retention with respect to NapthaleneSulphonate (NSF)-based admixtures; however a higher dosage of PNH with respect to PolyCarboxylate Ethers (PCEs) was needed to get the same initial fluidity. Poorer 1-day compressive strength was measured for PHN with respect to both NSF and PCEs, but higher 7-day and 28-day compressive strengths were observed in all cases. The experimental data indicate an overall better compatibility with different cement types of the PHN-based admixture compared to the NSF and PCE superplasticizers. Keywords: cement-superplasticizer compatibility, superplasticizers, phosphonate based admixtures