Study the Mechanical Properties of Geopolymer under Different Curing Conditions

Abstract

The geopolymer is an environmentally friendly and high-performance material. Nowadays, how to improve the degree of the geopolymer’s reaction and enhance its mechanical properties has become a hot topic. This study used orthogonal tests to design the precursor mixing ratio, considering GGBS content (A), water/binder ratio (B), and alkaline activator modulus (C). The fly ash (FA) ground granulated blast furnace slag (GGBS)-based geopolymers were cured under two standard curing conditions: 40 °C under water and 40 °C in the oven. Then, the influence of these factors on the mechanical properties of geopolymers under different curing conditions was summarized. The contribution of each factor was ranked, which was used to find out the most sensitive factors affecting the mechanical properties. Taking the 7 days and 28 days of compressive strength and flexural strength of the geopolymer specimens as the evaluation criteria, the optimum ratio method for preparing geopolymers was obtained. Then, the prediction model of compressive strength under different curing conditions was established. SEM and XRD were used to analyze the microstructure and hydration products of the samples. The test results showed that the optimum ratio of FA-based geopolymers varied under different curing conditions. The GGBS content was the key factor in determining the mechanical properties. The heat curing condition was the best curing condition, the 28-day compressive strength could reach 76.3 MPa, and the 28-day flexural strength could reach 7.4 MPa. The prediction models established for compressive strength under different curing conditions had high accuracy. The specimens under the best curing conditions exhibited a dense internal microstructure and the presence of C-S-H gels, C-A-S-H gels, and N-A-S-H gels.

Effects of Rest Time and Curing Regime on Short- and Long-Term Strength of Class C Fly Ash-Based Alkali-Activated Mortars

“…Figure 12 shows the results of the XRD measurements conducted on the raw FAs and paste powder from each mixture cured in ambient conditions for one day. The main crystal phases present in the FA37 sample were anatase (hereinafter, A), periclase (hereinafter, P), quartz (hereinafter, Q), gehlenite (hereinafter, G), and hatrurite (hereinafter, H), while those in the FA21 sample were A, Q, G, and P, and these were analyzed based on the findings of previous studies [44][45][46][47][48]. The presence of a crystal was mainly due to its addition as an internal component for crystal-phase quantification purposes (Table 5).…”

Fabrication of porous geopolymers utilizing aluminum wastes as foaming agent

“…Curing at higher temperatures, leads to a decrease in porosity in geopolymers [19]. Liu et al showed that curing at 40℃ demonstrated the best mechanical properties, with dense microstructures [20]. Yilmaz et al reported that curing times were more effective than curing temperatures in terms of porosity values, which decreased as the curing times increased [21].…”

Potential Role of GGBS and ACBFS Blast Furnace Slag at 90 Days for Application in Rigid Concrete Pavements

“…In addition, the pore structure of the concrete was changed, and the volume of capillaries larger than 0.05 µm was reduced [26]. Moreover, GGBS plays an important role in filling voids between raw materials and reducing porosity so as to increase the compactness of concrete [27,28]. Adding GGBS decreases the permeability and increases the chemical stability of selfconsolidating concrete (SCC) due to the reaction of blast furnace slag with excess soluble calcium hydroxide [29,30], while ACBFS aggregates affect the flexural strength, but they improve other properties, such as the compressive strength and drying shrinkage [31].…”