Mechanical, Pore Structure, Thermal Conductivity and Microstructure Properties of Silica Aerogel-Incorporated Hybrid Silica Fume Mortars

Abstract

It is a well-known fact that the use of a high amount of silica aerogel in cement-based mixtures contributes significantly to the thermal insulation properties of cement-based materials. However, the current manufacturing cost of silica aerogels is quite expensive compared to traditional insulating materials. This study focuses on the properties of alkali-activated hybrid silica fume mixtures containing silica aerogel powder at a low content rate. For this purpose, aerogel inclusion ratios were designed at 0%, 0.25% and 0.5% by weight of binder and the alkaline activation of the mortar mixtures was carried out with sodium carbonate (Na2CO3) at dosage rates of 0.1% and 0.2%, by weight of binder. After 2, 7 and 28 days of curing, the effect of the inclusion of a small amount of silica aerogel powder on the mechanical, thermal conductivity, pore structure properties and microstructure morphology of the hybrid silica fume mortar samples were investigated in detail. Experimental results show that the thermal insulation properties of the samples can be improved by 28% with a maximum compressive strength reduction of 2.4% in 0.25% aerogel-Incorporated samples. Due to the high level of gel pore formation (≈40%) in hybrid silica fume mortars, the negative effect of silica aerogel addition on the mechanical properties of the samples is limited. This study provides a new perspective on the use of silica aerogels in hybrid silica fume mortar mixtures.

Keywords

• Hybrid mortar
• silica aerogel
• thermal conductivity
• silica fume
• pore structure

Silika Aerojel Katkılı Hibrit Silis Dumanı Harçlarının Mekanik, Por Yapısı, Termal İletkenlik ve Mikro Yapı Özellikleri

Öz

Çimento esaslı karışımlarda yüksek miktarda silika aerojel kullanımının çimento esaslı malzemelerin termal yalıtım özelliklerine üstün düzeyde katkı sunduğu iyi bilinen bir gerçektir. Bununla birlikte, günümüz koşullarında silika aerojellerin üretim maliyeti geleneksel yalıtım malzemelerine kıyasla oldukça yüksektir. Bu çalışma, düşük katkı oranlarında silika aerojel tozu içeren alkali-aktive edilmiş hibrit silis dumanı harç özelliklerine odaklanmaktadır. Bu amaçla aerojel katkı oranları çimento ağırlığınca %0, %0.25 ve %0.5 düzeylerinde tasarlandı ve harç karışımlarının alkali aktivasyonu çimento ağırlığınca %0.1 ve %0.2 dozajlarındaki sodyum karbonat (Na2CO3) ile gerçekleştirildi. 2, 7 ve 28 günlük kür sürelerinin tamamlanmasından sonra, az miktardaki silika aerojel ilavesinin hibrit harç numunelerinin mekanik, termal iletkenlik, por yapısı özellikleri ve mikro yapı morfolojisi üzerindeki etkisi ayrıntılı olarak araştırılmıştır. Deneysel sonuçlar, % 0.25 aerojel katkılı numunelerde maksimum % 2.4'lük basınç dayanımı düşüşüne karşın numunelerin termal yalıtım özelliklerinin % 28 düzeyinde gelişebildiğini göstermektedir. Hibrit silis dumanı harçlarında jel gözenek oluşumunun yüksek seviyesine (≈% 40) bağlı olarak, silika aerojel ilavesinin harç numunelerinin mekanik özellikler üzerindeki olumsuz etkisi sınırlanmaktadır. Bu çalışma hibrit silis dumanı harç karışımlarında silika aerojellerin kullanımı hakkında yeni bir bakış açısı sunmaktadır.

Anahtar Kelimeler

• hibrit harç
• silika aerojel
• termal iletkenlik
• silis dumanı
• por yapısı

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