The rheological, fresh and strength effects of cold-bonded geopolymer made with metakaolin and slag for grouting

Abstract

A potential use of cold-bonded geopolymer stabilizers made with metakaolin and slag for grouting in ground enhancement was aimed to experimentally research in this article. The rheological, fresh and strength performances of the cement (PC)-based grouts with the stabilizers of metakaolin (MK), slag (SL), cold-bonded geopolymerized metakaolin (GMK), cold-bonded geopolymerized slag (GSL) and cold-bonded geopolymerized slag with metakaolin (GSL + MK) were investigated for this purpose. At a wide range of stabilizer replacement (0%–100%) and the common ratio of water/binder = 1, the rheometer tests were conducted for the rheology of grouts, while the testings of mini-slump, Marsh flow time, bleeding and setting time were carried out for the fresh characteristics. Using the proper replacements from the flow properties, the unconfined compressive strength (UCS) tests and ultrasonic pulse velocity (UPV) tests were performed for the strength quality (7-day, 28-day) of grout specimens. The failure patterns of UCS specimens were also examined. From the experimental work, the rheology of grout mixtures indicated: i) the dilatant behavior mostly, similar to PC, and ii) a good rheology for the low rates of MK(10%–20%) and GMK(10%–40%), and all rates of SL, GSL and GSL + MK, due to a well trend of the shear stress, apparent viscosity, yield stress and plastic viscosity with PC. The fresh tests due to the mini-slump and Marsh flow time also demonstrated a good workability (flow time = 8 s-35 s) for the favorable replacements of rheology. However, the bleeding capacity of PC was increased by SL, GSL and GSL + MK beyond the rate of 30%, while positively reduced (<10%) by MK and GMK. Except GMK, the trend of this effect was approximately similar for the setting time within a normally length of time (4hr-24hr). Hence, overall from the rheological and fresh effects, the low replacements of stabilizers (0%–30%) were rationally proposed for the flow issues of grouting. From the strength tests (0%–30%), all UCS responses (2.6 MPa-6.5 MPa at 7-day, 5.5 MPa-10.2 MPa at 28-day) were satisfied with the performance criterion of the bearing capacity for grouting (>0.4 MPa). Together with the flowability, this relatively encouraged the employment of the cold-bonded stabilizers. The additions MK, SL and GSL + MK at the dosage of 10% performed the best UCS responses (28-day). Besides, the GSL at 30% was favorable together with the GSL + MK. The UCS trends were mostly confirmed by UPV performances. The failure planes mostly occurred in axially splitting that was not correlated with the stabilizer types and dosage rates. From the evidences of flow and strength effects in the study, the contributions of GMK, GSL and GSL+ MK in low replacements from the potential of cold bonding geopolymerization are promising for grouting.