The Effect of Lightweight Aggregate Water Absorption on the Reduction of Water-cement Ratio in Fresh Concrete

Abstract

The aim of this paper is to present the problem of water-cement ratio reduction in structural lightweight concrete as a result of mixing water absorption by the lightweight aggregate. The research was carried out on eighteen concrete mixtures made of sintered fly ash aggregate and cement pastes of different nominal water-cement ratios. It has been demonstrated that the rate and the extent of the absorption of mixing water by the aggregate in concrete is dependent not only on its water absorption, but also on its moisture content, moisture state, the procedure of concrete preparation and the concrete composition. Moreover, it has been proved that the standard method for calculation of the so-called effective water-cement ratio is accurate only in the case of high initial moisture content of the lightweight aggregate. When dry sintered fly ash aggregate is used, the standard method gives underestimated values of the ratio as compared to its actual values determined in tests. The effect of mixing water absorption by the lightweight aggregate, revealed in tests of fresh concrete as the reduction of watercement ratio, was also reflected in hardened state of concrete as the increase of its strength. The strength increase was higher for mixtures with higher content of lightweight aggregate. Although the porous aggregate is the weakest element in structural lightweight concrete, in this case its higher content may be compensated with excess by the stronger cement matrix resulting from the reduction of water-cement ratio.

Compressive Strength Classification of Lightweight Aggregate Concrete Using a Support Vector Machine Model

“… Amount of water: The water used to manufacture the concrete used as data, ranges from 85 to 287 litres per cubic meter. In this study, only the effective water is considered because the water absorption of the LWA varies depending on the aggregate pore structure [39] and the value differs if the test is carried out in water or in the mass of the concrete [10].  Amount of cement: The LWACs of the study were manufactured with a range of 150 to 640 kg in one cubic meter.…”

Lightweight concrete with copper slag waste as sand substitution

“…The concrete mixtures with the same kind of fine aggregate were additionally varied by assuming different values of w/c ratio (0.50, 0.55, 0.60) as well as different cement content: 200 kg/m 3 and 300 kg/m 3 . In order to take into account the lightweight aggregate absorbability on the effective value of the w/c ratio of the concrete mixtures [29], the aggregate water absorption capacity was determined. The amount of water absorbed by the aggregate during 24 hours was respectively: 16.2% by mass in the case of Certyd aggregate and 21.6% in the case of keramzite.…”

Deniz Dibi Tarama Malzemesi, Kömür Uçucu Külü ve Atık Döküm Kumunun Hafif Agrega Olarak Geri Kazanımı

“…Bu kapsamda, söz konusu atıkların sürdürülebilir bir yaklaşımla [6, 7] ikincil hammaddelere dönüştürülmesi, özellikle "Döngüsel Ekonomi", "Sıfır Atık" ve "Sürdürülebilir Kalkınma, Sürdürülebilir Üretim" kavramlarının Bakanlıklar düzeyinde önem arz ettiği günümüzde, oldukça talep görmektedir [8]. Yapay hafif (kaba) agrega (YHA) özelliklerinin eldesi için sediment, atık cam ve silisli toprak [9], atık yakma tesisi UK [10], palmiye kabuğu ve öğütülmüş yüksek fırın cürufu [11], arıtma çamuru külü [12], uçucu kül [13,14], atık seramik tozu [15], metal çamuru [16], maden atıkları, metal çamuru, şeyl ve atık yakma tesisi UK [17,18] gibi malzemelerin granülasyonu ve sinterlenmesi, bu atıkların geri kazanım yollarından birisidir. Endüstriyel atıklardaki ağır metal içerikleri sinterleme işlemi sırasında silikat yapı içinde hapsedilmekte; böylece, herhangi bir çevresel riske sebebiyet vermeyen çevre dostu YHA elde edilmektedir [16].…”