Effect of Fineness and Heat Treatment on the Pozzolanic Activity of Natural Volcanic Ash for Its Utilization as Supplementary Cementitious Materials

Abstract

The aim of this study was to investigate the influence of fineness and heat-treatment on the pozzolanic and engineering properties of volcanic ash. To this end, two different fineness levels of volcanic ash, ultra-fine (VAF) and fine (VA), without and after heat treatment at different temperatures (VA550, VA650, and VA750), were partially substituted for cement. In addition to the control (100% cement), five binary mortar mixes, each containing 20% of the different types of volcanic ash (VAF and VA; heat-treated and not), were prepared. First, X-ray fluorescence (XRF), X-ray powder diffraction (XRD), particle size analysis, and modified Chappelle tests were used to characterize the material. All mortar mixes were then tested for compressive strength development, water absorption, and apparent porosity. Finally, the microstructure of each of the mixes was evaluated by performing XRD, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) analyses on paste samples at 91 days post-formation. The XRD and Chappelle reactivity results revealed increased pozzolanic reactivity with increasing volcanic ash fineness. In contrast, heat treatment adversely affected the pozzolanic reactivity of the volcanic ash due to the formation of crystalline phases at high temperatures. The mortars containing VAF20 (VAF, no heat, at 20%) showed slightly improved compressive strength (69.6 MPa) than the control (68.1 MPa) and all other binary mixes (66.7, 63.5, 64.2, and 63.9 MPa for VA20, VA20-550, VA20-650, and VA20-750, respectively) at 91 days. The mortar containing VAF20 demonstrated the lowest level of water absorption (9.3%) and apparent porosity (19.1%) of all mixes, including the control. The XRD results for the paste samples show that both VA and VAF showed the least intensity of portlandite phase, as compared to the control and other binary mixes. TGA results also show that binary mixes of VA and VAF have a reduced amount of portlandite, resulting in the densification of the mixes’ microstructures. With the addition of VAF, there is a significant shift in the FTIR band from 980 to 992 cm−1, which causes the formation of additional C–S–H gels that lead to the densification of the paste matrix. These results demonstrate that VAF exhibits high pozzolanic reactivity, making it suitable for use as a natural pozzolan that can partially substitute cement in the production of strong, durable, and environmentally friendly concrete.

Study of Microstructure, Crystallographic Phases and Setting Time Evolution over Time of Portland Cement, Coarse Silica Fume, and Limestone (PC-SF-LS) Ternary Portland Cements

“…This finding was more evident in mortars containing 5% of silica fume. Through the pozzolanic reactions, coarse silica fume combined with calcium hydroxide, providing a denser microstructure and rendering free lime unavailable for acid or sulphates attacks [31]. Kwon et al reported that specimens incorporating silica fume showed a denser microstructure, which is explained by the pore filling effect [32].…”

The impact of thermal treatment on the mechanical properties and thermal insulation of building materials enhanced with two types of volcanic scoria additives

“…The XRD analysis results of red and black scoria after thermal treatment showed differences between the crystal structure phases and minerals of the two scoriae. As the thermal treatment temperature increased, the intensity of the peaks in red scoria decreased, whereas the peaks in black scoria presented new phases of minerals and a decrease in the amount of amorphous phase (hump), possibly causing the degradation of mechanical properties [ 4 ]. Nevertheless, owing to the complexity of the chemical compositions of volcanic scoria, the spectra of likely minerals expanded with thermal treatment.…”

“…Environmental pollution has been exacerbated by increased CO 2 levels in the air, particularly from the manufacture of building materials such as cement, thus contributing to climate change and global warming [ [1] , [2] , [3] , [4] ]. Moreover, the growing demand for building insulation to save energy consumption has necessitated the identification of environment friendly and cost-effective substitutes for cement.…”

“…Previous studies have reported the important technical advantages of partially substituting Portland cement with scoria. The compressive strength of mortar containing 20 % volcanic ash (69.6 MPa) was observed to improve owing to the high fineness of volcanic ash compared to that of the control samples (68.1 MPa), particularly at 91 days of curing [ 4 ]. Nevertheless, the partial replacement of cement with volcanic material lowered the early age strength of the treated specimen compared to that of control specimens.…”

Durability of Reinforced Concrete with Additions of Natural Pozzolans of Volcanic Origin

“…Among the various types of industries, the cement sector is one of the largest contributors to CO 2 , estimated at around 8% of total anthropogenic greenhouse gas (GHG) emissions [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. One of the ways to reduce this impact is to reduce cement consumption by partially replacing it with supplementary cementitious materials (SCMs), which can be by-products from industry or natural pozzolans (NP), such as fly ash (FA), ground granulated blast furnace slag (GGBS), silica fume (SF), metakaolin (MK), limestone (L), fine glass powder (GP), rice husk ash (RHA), and volcanic tuffs (natural pozzolans) [ 5 , 6 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. These latter SCMs include both pozzolanic tuffs and those from the extraction of quarry aggregates.…”