Preparation and characterization of a novel prepacked aggregate geopolymer: A feasibility study

A novel prepacked aggregate geopolymer (PAG) is prepared for the first time in this study, which has high early -age strength and environmental benefits. The physical-mechanical properties, transport properties, high tem-perature resistance, acid resistance and microstructure of PAG are investigated. The results show that PAG has a high hardened unit weight due to the high aggregate content, and that changing the precursor composition has little effect on it. In general, increasing the early curing temperature reduces the apparent porosity of the PAG, resulting in a reduction in water absorption and an increase in strength. The 8-h flexural and compressive strengths of PAG reach 3-6 and 35-70 MPa, respectively. The use of mineral admixtures to replace some of the slag in the slag-metakaolin system reduces the mass loss of PAG at high temperatures and improves its resistance to high temperatures, mainly due to the higher thermal stability of N-A-S-H and/or N-(C)-A-S-H) compared to C-S-H gels with low Ca/Si ratio and/or C-A-S-H gels. Sulfuric acid-soaked PAG samples have a relatively high damage degree compared to hydrochloric and nitric acid-soaked samples due to the reaction of calcium-based products to form more gypsum and AFt phases. In addition, the economic and environmental benefits of PAG are assessed and appropriate changes to the precursor composition are able to reduce the carbon footprint and cost of PAG.