Mechanisms of autogenous shrinkage of alkali-activated fly ash-slag pastes cured at ambient temperature within 24 h

Internal curing of alkali-activated fly ash-slag pastes using superabsorbent polymer

“…10a. With 0.3% SAP addition, the increase of slag content from 15% to 30% leads to a greater shrinkage at 48 h, which is in good agreement with the previous research of AAFS pastes [44]. The maximum shrinkage discrepancy between G15 and G30 is about 1500  (see Fig.…”

“…It is more preferable compared to volumetric measurements, in which the volume change is determined, because the factors such as thermal dilation and setting time are included in the slab test for a more realistic material behaviour [43]. Fang et al [44] compared the contact and non-contact methods of linear measurements and concluded that the non-contact method using laser sensors is more suitable as it enables the determination of autogenous shrinkage from the initiation status with a stable and accurate result. An autogenous measuring apparatus consisting of a 70 × 70 × 70 mm inner size PVC mould with sealed cover and a plastic envelope with two reflecting plates.…”

“…It was then sealed and placed in the chamber with steady environment (20 ºC and 40% RH). Once the autogenous shrinkage takes place in paste samples, a force could be induced, which drags the reflecting plates in the horizontal direction [44]. The autogenous shrinkage corresponding to the horizontal movement of reflection plates was then measured using laser sensors.…”

“…The autogenous shrinkage corresponding to the horizontal movement of reflection plates was then measured using laser sensors. The data were automatically logged on a computer for 48 h with a time interval of 0.2 s. For each mixture, three duplicated autogenous shrinkage tests were carried out and an averaged value was taken to reduce random errors [44].…”

“…8. Regarding basic construction purposes and corrosion protection of concrete reinforcement, the compressive strength of concrete at 28 d should exceed 28 MPa and 35 MPa respectively according to ACI 318M-05 [44,46].…”