Nano-scale hydrogen-bond network improves the durability of greener cements

Abstract

More than ever before, the world's increasing need for new infrastructure demands the construction of efficient, sustainable and durable buildings, requiring minimal climate-changing gas-generation in their production. Maintenance-free “greener” building materials made from blended cements have advantages over ordinary Portland cements, as they are cheaper, generate less carbon dioxide and are more durable. The key for the improved performance of blends (which substitute fine amorphous silicates for cement) is related to their resistance to water penetration. The mechanism of this water resistance is of great environmental and economical impact but is not yet understood due to the complexity of the cement's hydration reactions. Using neutron spectroscopy, we studied a blend where cement was replaced by ash from sugar cane residuals originating from agricultural waste. Our findings demonstrate that the development of a distinctive hydrogen bond network at the nano-scale is the key to the performance of these greener materials.

Cause of the fragile-to-strong transition observed in water confined in C-S-H gel

“…66 A similar result was also obtained for water in montmorillonite (hydrated clays) 67 and more recently in hydrated ordinary Portland cement where a decrease in the elastic intensity occurs at about 190 K and attributed to the activation of OH − motions. 68 In addition, studies on dried amorphous polysaccharides (cellulose and dextran) with two and three hydroxyl groups per ring, respectively, have shown on a weak relaxation similar to the here obtained process 1, however, with a somewhat higher activation energy of 0.33 eV. 69 Intriguingly, a similar fast process with a relatively low value of the activation energy is also found in other systems containing large amounts of hydroxyl groups such as, for instance, MCM-41 and various biological systems.…”

Non-conventional cement-based composites reinforced with vegetable fibers: A review of strategies to improve durability

“…The term pozzolan has been extended to cover all siliceous/aluminous materials, which in finely divided form and in the presence of water, will chemically react with calcium hydroxide (CH) to form compounds with cementitious properties. Blended Portland cement production from the combustion of silicon-rich plant residues such as sugar cane bagasse ash, rice husk ash are reported elsewhere (25,(84)(85)(86)(87)(88)(89)(90)(91). The use of regional agro-industrial residues is a constructive way to save energy in transport and for a more simplified logistics to attend the global civil construction market.…”

“…‡ 1 Gigatonne of carbon = 1 GtC = 1015 grams of carbon = 1 Petagram of carbon = 1 PgC. This corresponds to 3.67 GtCO 2 Cordeiro et al suggested that the sugar cane bagasse ash presents physico-chemical properties appropriate for its use as mineral addition and its reactivity was mainly dependent on particle size and specific surface area (87) Jacobsen et al (90) concluded that pozzolan reaction has promoted changes to the C-S-H structure so that it can interact more strongly with water molecules than a common C-S-H structure of an OPC paste.…”

“…The pozzolanic reaction between amorphous silica and calcium hydroxide must be optimised to produce blended Portland cement with good mechanical and physical properties. It is optimized when an amorphous (non-crystalline) silica is obtained with high surface area (particle size less than 45 µm) is combined in the appropriate proportion with Al 2 O 3 and Fe 2 O 3 (at least 70% by weight) (25,90,92). ‡ 1 Gigatonne of carbon = 1 GtC = 1015 grams of carbon = 1 Petagram of carbon = 1 PgC.…”

Investigation on the Effectiveness of Aqueous Carbonated Lime in Producing an Alternative Cementitious Material

“…Nowadays, the world's increasing need is to control the global warming and environmental pollution minimizing the emission of the climate changing gasses (Jacobsen et al 2013;Phair 2006). It is stated in the Kyoto protocol 6 that including the carbon dioxide, some other gasses such as methane, nitrous oxide, sulfur dioxide, sulfur hexafluoride, hydrocarbons, chlorofluorocarbons, and perfluorocarbons, etc., are responsible for the greenhouse effect and global warming.…”