Influence of superplasticizers on the evolution of ultrasonic P-wave velocity through cement pastes at early age

Abstract

The paper discusses a possibility of using an ultrasonic wave transmission method to study the influence of superplasticizers on the formation of structure of cement pastes at early ages. When compared to mixtures without additives, lower P-wave velocity was found through superplasticized cement pastes, indicating that superplasticizers prevent formation of a solid network frame. Comparing to sulfonate naphthalene-formaldehyde superplasticizers, polycarboxylate ether (PCE) admixtures retarded the solid network frame development more intensively, resulting in a plateau on a P-wave velocity curve during the setting period. The length of the plateau is proportional to the dosage of the PCE and inversely proportional to the specific surface area of the hydration products developed, proving that the specific surface area of a solid phase affects the performance of the PCEs. Validation of ultrasonic results was determined on the basis of the temperature evolution of the material in time.

Influence of high mixing intensity on rheology, hydration, and microstructure of fresh state cement paste

“…Interestingly, the delaying effect of superplasticizers was compensated by increasing the final mixing speed (compare Figures 16 (a), (b), and (c)). Retardation of cement hydration due to superplasticizers has been commonly reported, and could be due to adsorption of the polymer molecules of the superplasticizer onto cement particles inhibiting subsequent topochemical reactions from occurring [50,[55][56][57][58][59] and/or an increase in the time needed to reach the percolation threshold due to the particles being initially dispersed further apart from the superplasticizer [53]. It was seen that the apparent viscosity of the 045_SP mixture was lower than of the 045 mixture (see Figure 5) at all the sample preparation mixing speeds that were used in this research.…”

The Role of Titanium Dioxide on the Hydration of Portland Cement: A Combined NMR and Ultrasonic Study

“…This period lasted for up to ~300 h of hydration for the TiO 2 -containing samples (between lines C and D) and up to ~ 700 h for the reference sample (between lines C and E). The data show a nonlinear behavior for the TiO 2 -containing specimens and a linear behavior for the reference sample, a characteristic of adding fine aggregates to cement [ 66 , 67 , 68 , 69 , 70 ]. The addition of fine aggregates accelerates the evolution of the microstructure [ 51 ].…”

Relation between ultrasound measurements and phase evolution in accelerated cementitious matrices

“…Kinetics Phase evolution [1,12,14,15] • • • [2][3][4][5][6][7][8][9][10]13] • • [11] • • • [16] • • • [17] • •…”

“…Several ultrasound techniques have been used to evaluate the setting process [1][2][3], mechanical strength [4,5], porosity [6][7][8][9], permeability [6][7][8][9] and durability [10,11] of pastes, mortars and concrete during the past years. The influence of different superplasticizers and additions on early strength development has been analyzed by [12][13][14][15].…”