No abstract

No abstract

SUMMARYThis paper presents the effect of elevated temperatures up to 700°C on compressive strength and water absorption of two alkali-activated aluminosilicate composites (one of them is river sand aggregate geopolymer concrete; the other one is crushed sand aggregate geopolymer concrete) and ordinary Portland cement based concretes. To obtain binding geopolymer material, Elazığ ferrochrome slag was ground as fine as cement, and then it was alkali activated with chemical (NaOH and Na 2 SiO 3 ). Geopolymer concrete samples were produced by mixing this binding geopolymer material with aggregates. At each target temperature, concrete samples were exposed to fire for the duration of 1 h. Fire resistance and water absorption of geopolymer and ordinary Portland cement concrete samples were determined experimentally. Experimental results indicated that compressive strength of geopolymer concrete samples increased at 100°C and 300°C temperatures when compared with unexposed samples. In geopolymer concrete samples, the highest compressive strength was obtained from river aggregates ones at 300°C with 37.06 MPa. Water absorption of geopolymer concrete samples increased at 700°C temperature when compared with unexposed samples. However, a slight decrease in water absorption of concrete samples was observed up to 300°C when compared with unexposed samples. SEM and X-ray diffraction tests were also carried out to investigate microstructure and mineralogical changes during thermal exposure.

Heritage masonry constructions constitute an important percentage of the structures in many countries. These structures are highly vulnerable to environmental changes (such as earthquakes), and significant losses in masonry historical constructions occur even in a moderate earthquake. For this reason, damage assessment studies of these structures before earthquakes are of great importance. After an earthquake, historical buildings in Turkey were examined and it was found that many buildings underwent damage. In these structures, damage occurs during the earthquake due to the use of low‐quality materials and a lack of sufficient connections between the layers. In these buildings, damage especially occurs in the parts that undergo restoration. Since low‐strength repair mortars are generally used in the restored sections, wide cracks have occurred in the building elements under the effect of earthquakes. This study aimed to produce alternative materials that could be used as geopolymer binders in restorated buildings. The mechanical, physical, and microstructural characteristics of the geopolymer samples were investigated in detail using laboratory tests. As a result, the strength of geopolymer repair materials with 8 M and 5% calcium hydroxide (Ca[OH]2) was very high when compared with other values. High‐strength compatible alternative geopolymer repair mortars that could be used for restoration were produced. For this reason, mortar is considered a significant application for repairing and strengthening buildings.

No abstract