Abstract
Crystalline admixtures are employed for waterproofing concrete. This type of admixtures can affect the early age performance of cement-based mixes. The electrical resistance properties of cement have been related to the initial setting time and to the hydration development. This paper proposes a system for remote monitoring of the initial setting time and the first days of the hardening of cement-based mortars to evaluate the effect of the incorporation of crystalline admixtures. The electrical resistance results have been confirmed by other characterization techniques such as thermogravimetric analysis and compressive strength measurements. From the electrical resistance monitoring it has been observed that the incorporation of crystalline admixtures causes a delay in the initial setting time and hydration processes. The measurements also allow to evaluate the influence of the amount of admixture used; thus, being very useful as a tool to define the optimum admixture dosage to be used.
Highlights
Crystalline admixtures (CAs) are proposed as an effective alternative for waterproofing concrete when watertight conditions are needed [1]
The full waterproofing effect of concrete prepared with a crystalline admixture has been reported to occur several days after casting [5]
No studies have been found in the literature to evaluate the effect that this delay in the hydration processes may have on the properties of the fresh state of the mix or on the mechanical strength of the concrete
Summary
Crystalline admixtures (CAs) are proposed as an effective alternative for waterproofing concrete when watertight conditions are needed [1]. Oliveira et al [9] studied the performance of crystalline admixtures during the early age when added to cement pastes They reported a retard on the hydration processes when CA added to cementitious mixes, more significant with the increment in CA dosage. Yousuf et al [24] proposes monitoring electrical resistivity of cement pastes for evaluating the setting and hardening behavior of cement pastes incorporating different types of additives using a non-contact method for the resistivity measurements, with continuous automatic data recording using a computer. In the present study the continuous monitoring of the electrical resistance of mortars containing different amounts of crystalline admixtures is proposed as method for evaluating the effect of the additives on the setting and hardening processes. The proposed system can be used as a tool for assessing the quality of cementitious mixes from an early age as well as for optimizing the dosage of additives that, when incorporated in the mix, may affect its behavior in the fresh state
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