Supplementary cementitious materials: New sources, characterization, and performance insights

Metakaolin as cementitious material: History, scours, production and composition – A comprehensive overview

The effects of sodium hydroxide (NaOH) concentration on setting time, compressive strength and electrical properties at the frequencies of 100 Hz–10 MHz of high calcium fly ash geopolymer pastes were investigated. Five NaOH concentrations (8, 10, 12, 15 and 18 molar) were studied. The liquid to ash ratio of 0.4, sodium silicate to sodium hydroxide ratio of 0.67 and low temperature curing at 40 °C were selected in making geopolymer pastes. The results showed that NaOH concentration had significant influence on the physical and electrical properties of geopolymer paste. The pastes with high NaOH concentrations showed increased setting time and compressive strength due to a high degree of geopolymerization as a result of the increased leaching of silica and alumina from fly ash. The dielectric constant and conductivity increased with NaOH concentration while tan δ decreased due to an increase in geopolymerization. At the frequency of 103 Hz, the dielectric constants of all pastes were approximately 104 S/cm and decreased with increased frequency. The relaxation peaks of tan δ reduced with an increase in NaOH concentration and ranged between 2.5 and 4.5. The AC conductivity behavior followed the universal power law and the values were in the range of 3.7 × 10−3–1.5 × 10−2 at 105–106 Hz.

Effects of NaOH concentrations on physical and electrical properties of high calcium fly ash geopolymer paste

Durability of mortar using waste glass powder as cement replacement

The management of construction and demolition (C&D) waste and waste glass is a serious concern in Hong Kong, as well as other countries due to their non-combustible and non-putrescible nature, and the running out of disposal outlets. However, mineral wastes derived from C&D activities and waste glass are considered to have potential to be re-used as construction materials, especially as aggregates. In addition, Hong Kong urgently needs alternative and sustainable sources of aggregate, as the local quarry sites for aggregate production are expected to be exhausted soon. Many experimental studies have demonstrated that recycled aggregates from C&D waste and waste glass can be potentially recycled for various engineering applications in Hong Kong, but no study has yet attempted to assess the sustainability by lifecycle assessment (LCA) techniques. In order to increase the environmental awareness in the construction industry, assessment of the environmental performance of construction materials by LCA is therefore needed. The present study was conducted to assess and compare the environmental consequences of recycled aggregates production from C&D waste and waste glass, and natural aggregate production from virgin materials by LCA by using case specific and first hand data. The results reveal that compared with natural coarse aggregates, recycled coarse aggregates produced from C&D waste reduce 65% greenhouse gases (GHGs) emission with a saving of 58% non-renewable energy consumption. Similar environmental benefits are observed for producing recycled fine aggregates from C&D waste. In addition, compared with the production of natural fine aggregates from river sand, producing recycled fine aggregates from waste glass saves 54% energy consumption and reduces 61% GHGs, and 46% SO2 eq emissions. According to the IMPACT 2002+ Method, significant health, resource, climate change and ecosystem damages can be saved in producing recycled aggregates from both waste materials compared to producing and importing aggregates from virgin sources. This is the first ever LCA study on producing recycled aggregates from waste glass. Therefore, it can be concluded that substantial net environmental benefits can be realized for producing recycled aggregates from C&D waste and waste glass. The results can provide a guidance to maximize C&D waste and waste glass recycling, resourceful treatment of wastes and conserve natural resources.

Comparative environmental evaluation of aggregate production from recycled waste materials and virgin sources by LCA

Use of fine glass as ASR inhibitor in glass aggregate mortars

Mixed glasses of different colors are economically difficult to reuse for the fabrication of new glass products but their use in cement-based materials is a promising way to recycle this material. This paper deals with the pozzolanic activity of mixed glass cullet, by evaluating the pozzolanic behavior of a large range of glass particle sizes, from less than 40 μm (540 m2/kg) up to 2.5 mm (2.2 m2/kg). Five different classes of glass are assessed separately, in terms of compressive strength tests on mortars, consumption of lime (TG), morphology (SEM) and composition of hydrates (EDX and X-ray fluorescence). The results show that the pozzolanic activity increases with glass fineness and that, compared to a reference material without glass, equivalent or superior compressive strength can be obtained when using up to 40% of glass of 540 m2/kg fineness. A transition fineness around 30 m2/kg (140 μm) is highlighted, for which the pozzolanic activity becomes substantial. However, a slight but significant pozzolanic activity is detected for coarse particles (>1 mm), as confirmed by the consumption of Ca(OH)2, the formation of C–S–H-like hydrates and an increase of 10% (5 MPa) in the compressive strength compared to an inert admixture. The chronology of the reaction (pozzolanic and alkali-reactive) for coarse glass particles is discussed.

Pozzolanic properties of fine and coarse color-mixed glass cullet

This study presents the results of experiments aiming to produce geopolymers from glass cullet, a non-traditional material compared to those usually found in the manufacture of geopolymers (e.g., metakaolin and fly ash). The study gives the principal formulation parameters affecting the behavior of glass cullet geopolymers. The glass used comes from recycled glass bottles. The parameters studied are the fineness of the glass (Blaine of 1000 to 4000 cm2/g), the temperature of synthesis (20, 40 and 60 °C), and the nature and concentration of the activation product (KOH, NaOH). The properties are evaluated in terms of compressive strength and durability. The results show that cullet of soda-glass can be used as a base material for the production of geopolymers and, contrary to metakaolin-based geopolymers, no waterglass is necessary for its setting and hardening since cullet glass already contains a high proportion of alkalis. Thermal activation at 40 or 60 °C is necessary but sufficient to obtain strength of more than 50 MPa, especially for the finer glass (4000 cm2/g). The durability of glass cullet geopolymers is affected by water conservation.

Rachida Idir

Papers

Use of fine glass as ASR inhibitor in glass aggregate mortars

Pozzolanic properties of fine and coarse color-mixed glass cullet

Properties of inorganic polymer (geopolymer) mortars made of glass cullet

Use of metakaolin to stabilize sewage sludge ash and municipal solid waste incineration fly ash in cement-based materials.

Concrete based on recycled aggregates – Recycling and environmental analysis: A case study of paris’ region