The use of electrical impedance spectroscopy for monitoring the hydration products of Portland cement mortars with high percentage of pozzolans

In this paper, mortars and pastes containing large replacement of pozzolan were studied by mechanical strength, thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), mercury intrusion porosimetry (MIP) and electrical impedance spectroscopy (EIS). The effect of metakaolin (35%) and fly ash (60%) was evaluated and compared with an inert mineral addition (andalusite). The portlandite content was measured, finding that the pozzolanic reaction produced cementing systems with all portlandite fixed. The EIS measurements were analyzed by the equivalent electrical circuit (EEC) method. An EEC with three branches in parallel was applied. The dc resistance was related to the degree of hydration and allowed us to characterize plain and blended mortars. A constant phase element (CPE) quantified the electrical properties of the hydration products located in the solid¿solution interface and was useful to distinguish the role of inert and pozzolanic admixtures present in the cement matrix.The authors thank the Universitat Politecnica de Valencia (UPV, Vicerrectorado de Investigacion) for its support (project PAID-05-09 ref 4302) and Debra Westall (UPV) for revising the manuscript.Cruz González, JM.; Fita Fernández, IC.; Soriano Martinez, L.; Paya Bernabeu, JJ.; Borrachero Rosado, MV. (2013). The use of electrical impedance spectroscopy for monitoring the hydration products of Portland cement mortars with high percentage of pozzolans. Cement and Concrete Research. 50:51-61. doi:10.1016/j.cemconres.2013.03.019S51615

Influence of paste thickness on the coated aggregates on properties of high-density sulphoaluminate cement concrete

An improved method for the densified mixture design algorithm and Fuller curve were used to design high-density sulphoaluminate cement concrete (HDSC). The performance of HDSC is significantly influenced by the paste thickness on the coated aggregates. Sulphoaluminate cement concrete mixtures containing aggregates coated with 3 different paste thickness of t=10μm, 20μm, and 30μm and water-binder ratios (W/B) of 0.25, 0.30 and 0.35 were prepared. The results of experiments show that paste thickness on the coated aggregates significantly influences the mechanical properties and durability of HDSC. With the increase of paste thickness, the compressive strength is increased, but the electrical resistivity is decreased, particularly at the early ages of 1 and 3 days. The sulfate corrosion resistance coefficients of HDSC are larger than 1.0, the total porosity can be less than 7%, and the micropore (i.e. with pore size less than 20nm) can be larger than 70%

Applications of high-performance concrete

Peer reviewed: NoNRC publication: Ye