Properties of alkali-activated lightweight concrete

Alkali activated concretes have emerged as a prospective alternative to conventional concrete wherein diverse waste materials have been converted as valuable spin-offs. This paper presents a wide experimental study on the sustainability of employing waste sawdust as a fine/coarse aggregate replacement incorporating fly ash (FA) and granulated blast furnace slag (GBFS) to make high-performance cement-free lightweight concretes. Waste sawdust was replaced with aggregate at 0, 25, 50, 75, and 100 vol% incorporating alkali binder, including 70% FA and 30% GBFS. The blend was activated using a low sodium hydroxide concentration (2 M). The acoustic, thermal, and predicted engineering properties of concretes were evaluated, and the life cycle of various mixtures were calculated to investigate the sustainability of concrete. Besides this, by using the available experimental test database, an optimized Artificial Neural Network (ANN) was developed to estimate the mechanical properties of the designed alkali-activated mortar mixes depending on each sawdust volume percentage. Based on the findings, it was found that the sound absorption and reduction in thermal conductivity were enhanced with increasing sawdust contents. The compressive strengths of the specimens were found to be influenced by the sawdust content and the strength dropped from 65 to 48 MPa with the corresponding increase in the sawdust levels from 0% up to 100%. The results also showed that the emissions of carbon dioxide, energy utilization, and outlay tended to drop with an increase in the amount of sawdust and show more the lightweight concrete to be more sustainable for construction applications.

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Alkali-Activated Matrix Based on Metakaoline with Lightweight Aggregate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.787.250 ◽

2013 ◽

Vol 787 ◽

pp. 250-255 ◽

Cited By ~ 1

Author(s):

Jaroslav Válek ◽

Petr Novosad ◽

Lenka Bodnárová

Keyword(s):

Mechanical Properties ◽

High Temperatures ◽

Thermal Load ◽

Lightweight Concrete ◽

Polypropylene Fiber ◽

Size Fraction ◽

Fiber Reinforcement ◽

Lightweight Aggregate ◽

Mix Design ◽

Alkali Activated

The paper focuses on design and verification of mix-design of lightweight concrete with alkali-activated matrix with lightweight aggregate Liapor. Alkali-activated matrix was designed on the basis of ground metakaoline and micronized limestone. Mixes of concrete with alkali-activated matrix and lightweight porous aggregate Liapor of size fraction 8 mm were designed and their rheological and physico-mechanical properties were tested. To reduce shrinkage and to increase resistance to high temperatures, dispersed polypropylene fiber reinforcement was used and testing specimens made from this concrete with alkali-activated matrix were exposed to thermal load and tested.

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Effect of Calcium Carbonate on Compressive Strength and Physical Properties of Alkali-Activated Lightweight Concrete

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.751.550 ◽

2017 ◽

Vol 751 ◽

pp. 550-555 ◽

Cited By ~ 2

Author(s):

Watcharapong Wongkeo

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Calcium Carbonate ◽

Physical Properties ◽

Sodium Hydroxide ◽

Bulk Density ◽

Lightweight Concrete ◽

Sodium Hydroxide Solution ◽

Atomic Ratio ◽

Alkali Activated

This study presents the compressive strength and physical properties of alkali-activated lightweight concrete. Alkali-activated lightweight concrete was synthesized with fly ash, calcium carbonate and sodium hydroxide solution. Calcium carbonate was designed to replace part of fly ash at 5 and 10 wt.%. Sodium hydroxide solution at 5, 7.5 and 10 M was used as a liquid solution. Liquid to ash ratio (L/A ratio) at 0.45 was designed and aluminium powder was used as a foaming agent. The results showed that, the compressive strength of alkali-activated lightweight concrete made with fly ash was increased with NaOH concentration increased. The maximum compressive strength at 6.0 MPa was obtained from 10M NaOH mixture. For fly ash-calcium carbonate system, the compressive strength of lightweight concrete was improved when containing calcium carbonated, especially at 5 and 7.5 M NaOH mixtures. The maximum of compressive strength at 8.1 MPa and bulk density were obtained from the 5 wt.% calcium carbonated with 10M NaOH mixture. Water absorption and voids of all mixtures trend to decrease with increased NaOH concentration. XRD showed the sodium aluminum silicate hydrated as an alkali-activated product and composed of Si/Al atomic ratio at 2.1 and Na/Al atomic ratio at 1.4, respectively. Bulk density and compressive strength of alkali-activated lightweight concrete made with both fly ash and fly ash-calcium carbonated were acceptable in accordance with the specified criteria of TIS 2601. The well pore structure distribution of alkali-activated lightweight concrete was acceptable.

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Properties of a Lightweight Fly Ash–Slag Alkali-Activated Concrete with Three Strength Grades

Applied Sciences ◽

10.3390/app11020766 ◽

2021 ◽

Vol 11 (2) ◽

pp. 766

Author(s):

Huailiang Wang ◽

Yuhui Wu ◽

Lang Wang ◽

Huihua Chen ◽

Baoquan Cheng

Keyword(s):

Tensile Strength ◽

Elastic Modulus ◽

Fly Ash ◽

Fracture Energy ◽

Lightweight Concrete ◽

Pulse Velocity ◽

Normal Weight ◽

Splitting Tensile Strength ◽

Alkali Activated Concrete ◽

Alkali Activated

Lightweight alkali-activated concrete (LAAC) is a type of highly environmentally friendly concrete, which can provide the benefits of both alkali-activated material and lightweight concrete. The study aimed to investigate the influence of different water/solid (W/S) ratios on the properties of normal-weight/lightweight fly ash–slag alkali-activated concrete manufactured at ambient temperature. The relative performance of the alkali-activated concrete (AAC) mixes with limestone and sintered fly ash lightweight aggregates as the coarse aggregates was also compared to the conventional ordinary Portland cement (OPC) concrete mix in terms of their compressive stress–strain relationship, splitting tensile strength and fracture parameters. The morphologies and microstructure of the four types of interfacial transition zones (ITZs) were characterized by scanning electron microscopy (SEM). Results indicated that the AAC had a higher tensile strength, stress intensity factor, brittleness and lower elastic modulus than its cement counterpart. With the decrease in the W/S ratio, the density, compressive and tensile strength, ultrasonic pulse velocity, fracture energy, brittleness and elastic modulus of the AAC increase. However, the influence of the W/S ratio on the mechanical properties of the LAAC with lightweight porous aggregates was less than that of the normal-weight AAC. Predictive models of the splitting tensile strength, fracture energy and elastic modulus of the AAC were also suggested, which were similar to those of the OPC concrete. Furthermore, the microstructure investigation showed that no wall effect occurred in the ITZ of the AAC. The ITZ structure of the hardened AAC was also more compact and uniform than that of the OPC concrete.

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