The compressive strength, splitting tensile strength, pulse velocity, and drop weight impact resistance of roller-compacted concrete (RCC) mixtures containing recycled concrete aggregate (RCA) were investigated. The cement contents of the RCC mixtures were chosen as 150, 200 and 250 kg/m3. In addition to the control mixtures containing no RCA, 25, 50, 75, and 100 wt% of the crushed limestone aggregate was replaced with RCA. In this way, 15 RCC mixtures were prepared. The water content of RCC mixtures was determined by the maximum density method. The results showed that increasing the amount of recycled aggregate decreased the mechanical properties of the concrete. However, up to 25% replacement level, recycled aggregate had not a significant detrimental effect on the properties of RCC. Besides, the detrimental effect of RCA substitution was more pronounced in leaner mixtures and reduced by increasing the cement content of the RCC.
With the acceleration of Urban Renewal Program, particularly in large cities of Turkey, the problem of finding land-fills and eliminating construction waste with the least environmental pollution necessitates its value-added recycling. However, the presence of adhered weak mortar layer, comprising 20-70% of recycled concrete aggregate (RCA), limits the use of RCA or lowers its inclusion level in concrete mixtures. Within the scope of this study, limestone- and basalt-bearing RCA obtained from 6 different concrete mixtures with three different water/cement ratios (0.45, 0.60, 0.70) were prepared and their water absorption, specific gravity, dense and loose unit weight, flatness indices, Los Angeles degradation values were determined. The results showed that, increasing w/c ratio of the parent concrete increased water absorption of the resultant RCA. However, the specific gravity, unit weight, abrasion resistance and flakiness index of RCA were decreased by increasing w/c ratio of the parent concrete.
Beton, dünyada en çok kullanılan yapı malzemesidir. Ancak çimento üretimi sırasında yüksek miktarda enerji tüketilmekte ve karbondioksit salımı yapılmaktadır. Çimentoya alternatif bağlayıcıların üretilmesi, uzun süredir üzerinde çalışılan bir konudur. Geopolimerler, çimentoya alternatif olma potansiyeli taşıyan malzemelerdir. Geopolimerlerin iyi bir yüksek sıcaklık direncine sahip oldukları bilinmektedir. Ancak hem geleneksel hem de geopolimer betonların yüksek sıcaklık dirençleri, kullanılan agreganın türü ve özelliklerinden önemli ölçüde etkilenmektedir. Bu çalışmada kireçtaşı, dere, bazalt ve cüruf agregaları kullanılarak üretilen geopolimer betonların 600 ve 900°C yüksek sıcaklık etkisine karşı dirençleri basınç dayanımı kayıpları kıyaslanarak tespit edilmiştir. 900°C sıcaklık etkisinde, kireçtaşı ile üretilen geopolimer beton tamamen parçalanırken dere, bazalt ve cüruf agregaları ile üretilen betonların %32.9, 48.5 ve 53.6 oranında basınç dayanımı kaybına uğradıkları tespit edilmiştir.
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