Supplementary cementitious materials
TL;DR: The use of silica-rich SCMs influences the amount and kind of hydrates formed and thus the volume, the porosity and finally the durability of these materials.
About: This article is published in Cement and Concrete Research.The article was published on 2011-12-01. It has received 1920 citations till now.
Citations
More filters
TL;DR: The current state of knowledge of cement hydration mechanisms is reviewed, including the origin of the period of slow reaction in alite and cement, the nature of the acceleration period, the role of calcium sulfate in modifying the reaction rate of tricalcium aluminate, the interactions of silicates and aluminates, and the kinetics of the deceleration period as mentioned in this paper.
1,437 citations
TL;DR: In this paper, the synthesis of alkali-activated binders from blast furnace slag, calcined clay (metakaolin), and fly ash is discussed, including analysis of the chemical reaction mechanisms and binder phase assemblages that control the early-age and hardened properties of these materials.
Abstract: The development of new, sustainable, low-CO2 construction materials is essential if the global construction industry is to reduce the environmental footprint of its activities, which is incurred particularly through the production of Portland cement. One type of non-Portland cement that is attracting particular attention is based on alkali-aluminosilicate chemistry, including the class of binders that have become known as geopolymers. These materials offer technical properties comparable to those of Portland cement, but with a much lower CO2 footprint and with the potential for performance advantages over traditional cements in certain niche applications. This review discusses the synthesis of alkali-activated binders from blast furnace slag, calcined clay (metakaolin), and fly ash, including analysis of the chemical reaction mechanisms and binder phase assemblages that control the early-age and hardened properties of these materials, in particular initial setting and long-term durability. Perspectives fo...
862 citations
TL;DR: In this paper, the coupled substitution of metakaolin and limestone in Portland cement (PC) was investigated and the mechanical properties were studied in mortars and the microstructural development in pastes by X-ray diffraction, thermogravimetry analysis, mercury intrusion porosimetry and isothermal calorimetry.
763 citations
TL;DR: In this paper, the growth of C-S-H is the principal factor controlling the main heat evolution peak and after several days space becomes the major factor controlling hydration, but deceleration cannot be attributed to diffusion control.
705 citations
TL;DR: A review of the advances in knowledge provided by research in these areas can be found in this paper, emphasizing the impact of the research on the field and emphasizing the benefits of these advances.
614 citations
Cites background from "Supplementary cementitious material..."
...It is known that the use of SCMs reduces the calcium-to-silicon ratio of C–S–H and also increases themean silica chain length [27]....
[...]
...phases such as stratlingite may precipitate and can be intermixed with the C–S–H [27,72,73]....
[...]
...[27] summarizes the role of SCMs on cement hydration well, describing, in particular, impacts on cement hydration kinetics, phase assemblage in hydrated systems, and composition of C–S–H....
[...]
...This is to distinguish the pozzolanic reaction from so-called “filler effects” derived from increased nucleation sites for hydration products and increased space available for hydration product precipitation [27]....
[...]
...tional space for C–S–H growth [27]....
[...]
References
More filters
TL;DR: In this paper, the influence of the presence of limestone on the hydration of Portland cement was investigated, and it was shown that the stabilisation of monocarbonate in the absence of limestone indirectly stabilised ettringite, leading to a corresponding increase of the total volume of the hydrate phase and a decrease of porosity.
1,089 citations
TL;DR: The use of metakaolin (MK) as a pozzolanic material for mortar and concrete has received considerable attention in recent years as mentioned in this paper, which is part of the widely spread attention directed towards the utilisation of wastes and industrial by-products in order to minimise Portland cement consumption, the manufacture of which being environmentally damaging.
Abstract: The utilisation of calcined clay, in the form of metakaolin (MK), as a pozzolanic material for mortar and concrete has received considerable attention in recent years. This interest is part of the widely spread attention directed towards the utilisation of wastes and industrial by-products in order to minimise Portland cement (PC) consumption, the manufacture of which being environmentally damaging. Another reason is that mortar and concrete, which contain pozzolanic materials, exhibit considerable enhancement in durability properties. This paper reviews work carried out on the use of MK as a partial pozzolanic replacement for cement in mortar and concrete and in the containment of hazardous wastes. The literature demonstrates that MK is an effective pozzolan which causes great improvement in the pore structure and hence the resistance of the concrete to the action of harmful solutions.
1,077 citations
TL;DR: In this paper, the mid-, near-, and far-infrared (IR) spectra of synthetic, single-phase calcium silicate hydrates (C-S-H) with Ca/Si ratios (C/S) of 0.41-1.2 were analyzed.
Abstract: The mid-, near-, and far-infrared (IR) spectra of synthetic, single-phase calcium silicate hydrates (C-S-H) with Ca/Si ratios (C/S) of 0.41–1.85, 1.4 nm tobermorite, 1.1 nm tobermorite, and jennite confirm the similarity of the structure of these phases and provide important new insight into their H2O and OH environments. The main mid-IR bands occur at 950–1100, 810–830, 660–670, and 440–450 cm−1, consistent with single silicate chain structures. For the C-S-H samples, the mid-IR bands change systematically with increasing C/S ratio, consistent with decreasing silicate polymerization and with an increasing content of jennite-like structural environments of C/S ratios >1.2. The 950–1100 cm−1 group of bands due to Si-O stretching shifts first to lower wave number due to decreasing polymerization and then to higher wave numbers, possibly reflecting an increase in jennite-like structural environments. Because IR spectroscopy is a local structural probe, the spatial distribution of the jennite-like domains cannot be determined from these data. A shoulder at ∼1200 cm−1 due to Si-O stretching vibrations in Q3 sites occurs only at C/S lessthan equal to 0.7. The 660–670 cm−1 band due to Si-O-Si bending broadens and decreases in intensity for samples with C/S > 0.88, consistent with depolymerization and decreased structural order. In the near-IR region, the combination band at 4567 cm−1 due to Si-OH stretching plus O-H stretching decreases in intensity and is absent at C/S greater than ∼1.2, indicating the absence of Si-OH linkages at C/S ratios greater than this. The primary Si-OH band at 3740 cm-1 decreases in a similar way. In the far-IR region, C-S-H samples with C/S ratio greater than ∼1.3 have increased absorption intensity at ∼300 cm−1, indicating the presence of CaOH environments, even though portlandite cannot be detected by X-ray diffraction for C/S ratios <1.5. These results, in combination with our previous NMR and Raman spectroscopic studies of the same samples, provide the basis for a more complete structural model for this type of C-S-H, which is described.
1,034 citations
TL;DR: In this article, a number of models for the nanostructure of C-S-H are summarized and compared and it is shown that there is much more of a consensus than might seem apparent at first sight.
908 citations
TL;DR: In this article, the effect of minor additions of limestone powder on the properties of fly ash blended cements was investigated using isothermal calorimetry, thermogravimetry (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques, and pore solution analysis.
849 citations