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3 2022

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Mechanical properties of lightweight expanded clay aggregate (LECA) concrete

100%

Issa A. S. , Al-Asadi A. K.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

2022

tom Vol. 31, No. 3

161--175

The construction activities are based on structural concrete, which is one of the most commonly used materials. The fundamental aim of using lightweight concrete (LWC) was to reduce the concrete self-weight of the structure parts. As a result, LWC has been used successfully in a variety of installations for several years. In this paper, the mechanical properties of concrete made with lightweight expanded clay aggregate (LECA) as a full replacement for coarse aggregate are studied. The experimental program shows that LECA with a 32 MPa cube compressive strength and an 1,823 kg×m–3 dry density can be used to make structural light-weight aggregate concrete (SLWC). The results show that the reduction in the strength of lightweight aggregate concrete (LWAC) was found to be higher in the concrete with an estimated compressive strength of 32 MPa due to the lower strength of the LWA (expanded clay). According to the test results, the mechanical properties of LWC were greatly improved by adding silica fume (SF). Furthermore, LECA concrete has a splitting tensile strength that is 47% higher than the ASTM C330/C330M-17A minimum requirement. The LECA concrete has a splitting tensile strength to compressive strength ratio of approximately 13%. Additionally, the results demonstrate a 27% difference in the modulus of elasticity between the calculated and tested values.

Prediction of shear strength of CFRP-strengthened reinforced recycled aggregate concrete beams using various strengthening methods

100%

Sahib H. A. , Al-Asadi A. K.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

2022

tom Vol. 31, No. 4

238--248

Fibre reinforced polymer (FRP) strengthening is a possible option when the load carrying capacity of a structure needs to be increased for various reasons. On the other hand, the focus nowadays aims to save the environment by reducing the waste material. A suggestion was made to use waste concrete as an aggregate. If this new material was used more, it would be possible to use recycled concrete aggregate (RCA) and carbon fibre reinforced polymer (CFRP) to strengthen reinforced concrete (RC) structures and make them more environmentally friendly. An experimental investigation study on the shear behaviour of RC beams strengthened with CFRP strips was carried out. Tests were conducted on six reinforced concrete beams, with variations in the replacement ratio of RCA and strengthened by different configurations of CFRP under four-point loading. The results indicated that the load carrying capacity was increased, on average, by 18.09 and 35.04% for beams strengthened with CFRP with an inclined strip (IS) and continuous strip (CS) configurations respectively. The results also indicated that the increases in the stiffness were 21.08 and 37.31 for beams strengthened with CFRP in the IS and CS configurations, respectively. In addition the ductility of the beams increased after strengthening.

Mechanical properties and flexural behaviour of reinforced concrete beams containing recycled concrete aggregate

100%

Dawood M. H. , Al-Asadi A. K.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

2022

tom Vol. 31, No. 4

259--269

Increasing waste recycling has become an essential process in the construction industry due to the environmental and economic advantages, such as minimizing waste in landfills, saving natural resources, and decreasing pollution. Crushing and sieving waste from standard compression test cubes is used to produce the recycled concrete aggregate (RCA). A set of standard concrete cylinders, cubes, and beam specimens were made by utilizing coarse aggregate replacement ratios of 0%, 30%, 50% and 70%. At the day 28 stage, the specimens were tested to determine compressive strength, stress–strain relationship, splitting tensile strength, and flexural strength. In addition, four reinforced concrete (RC) beams were cast and tested under a four-point load to evaluate the flexural behaviour of RC beams with partial replacement of the natural aggregate with RCA. One was a natural aggregate (NA) control beam, while the others had varying RCA ratios (30%, 50% and 70%). The results show that the compressive strength of RCA concrete with the replacement by 30%, 50% and 70% decreased by 9.10%, 18.88% and 22.57% respectively, in comparison to the compressive strength of normal concrete (NC). The RCA concrete showed a high strain capacity, which indicated high ductility. The maximum RCA type strains ranged from 0.0056 to 0.0072. Concrete flexural strength showed a slight decrease in comparison to NC (18.83% decrease), where the tensile strength showed a 10.61% decrease in comparison to NC. As for RC beams, the load-carrying capacity decreased by 10.5% with increases in the replacement ratio.