This paper reports an experimental study of the influence of marble powder used as partial substitute for Portland cement (PC) on the mechanical properties and durability of high performance concretes. The analysis of the experimental results on concrete at 15% content of marble powder with a fineness modulus of 11500 cm 2 /g, in a chloride environment, showed that it contributes positively to the perfection of its mechanical characteristics, its durability with respect to migration of chloride ions and oxygen permeability. On the basis of the experiments performed, it can be concluded that the marble powder is suitable for formulation of high performance concretes (HPC) and their properties are significantly better compared to the reference concrete (RC).

This paper presents the results of an experimental study which investigates the effect of the use of marble powder (MP), as partial cement substitution, on the fresh and hardened properties of fibre-reinforced self-compacting concrete (FRSCC) of nonuniform size (length) and aspect ratio of fibres used. For each length of steel fibre (25, 30 and 50 mm), three percentages (.5, .8 and 1%) were used to improve the performance of FRSCC. All mixtures of concrete specimens prepared with 30% of MP were evaluated. Slump flow time and diameter, sieve stability and L-Box were performed to assess the fresh properties of the (FRSCC). Compressive strength, splitting tensile strength, flexural strength and ultrasonic pulse velocity of the FRSCC and self-compacting concrete (SCC) were determined for the hardened properties. The results were compared with ordinary concrete (without steel fibre) containing 30% of MP (SCC). The results suggest that the incorporation of steel fibre in the SCC requires the use of high volume of superplasticiser to overcome the workability loss resulting from the elongated shape and large surface area of fibres. The sieve stability, Slump flow diameter, L-Box and Slump flow time for RSCC dropped to 1, 10, 12 and 65%, respectively. The workability loss is significant in the case of 1% and 50 mm length fibre which revealed the highest length and percentage. On the other hand, the use of steel fibre and MP has a significant effect on the mechanical performances. The increase in ultrasonic pulse velocity, compressive strength, splitting tensile strength and flexural strength reaches 2, 8, 16 and 29%, respectively. The addition of fibre enhanced the ductility significantly. The optimum volume fraction and aspect ratio of fibre for better performance in terms of strength was found to be .8% and 30 mm, respectively. The results indicated that high volume of MP can be used to produce FRSCC.

Self-compacting concrete (SCC) offers several economical and technical benefits, the use of steel fibers extends its possibilities. This study was performed to compare the properties of SCC and fiber reinforced self-compacting concrete (FRSCC) with high volume of mineral addition. Six mixtures were elaborated in this study. The content of the cementitious materials and the water/cementitious materials ratio were kept constant, 500 kg/m3 and 0.34 respectively.The self-compacting mixtures have been prepared with a cement replacement of 30% by weight of marble powder. Two different types of steel fibers were used in combination with different lengths (50 mm and 30 mm), keeping the total fiber content constant at 60 kg/m3. Slump flow time and diameter, sieve stability, and L-Box were performed to assess the fresh properties of the SCC and FRSCC. Compressive strength, splitting tensile strength, flexural strength and ultrasonic pulse velocity were determined for the hardened properties. A marginal improvement in the ultimate strength was observed. The addition of steel fiber enhanced the ductility significantly and the results indicated that high-volume of marble powder can be used to produce FRSCC, even though there is some decrease in the compressive strength because of the fiber geometry which affects the properties of SCC mixtures not only in the fresh state but also in the hardened state.

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This work focuses on the reuse of recycled brick waste (RBW) as aggregates in the fabrication of concrete blocks. The experimental study was focused on six different concrete compositions with a w/c ratio of 0.56, a relatively constant compactness and a slump value of zero. The six compositions consist on a control concrete with natural sand and five compositions with 10 %, 20 %, 30 %, 40 % and 50 % of RBW as a partial substitute for the natural sand. The physical and mechanical properties of concrete blocks were studied, analyzed and compared. The obtained results showed that it is possible to manufacture concrete blocks based on RBW, and that the compressive strengths of these concrete blocks are comparable to that of the control concrete, but with an appreciable reduction in weight. The blocks made with 30 % of RBW showed an improvement in the compressive strength of 42 % and a reduction in weight of 11 % compared to the control concretes. Keywords: recycled brick waste, concrete block, compactness, slump, mechanical strength Delo je usmerjeno v ponovno uporabo recikliranih odpadkov opeke (RBW) kot sestavina pri izdelavi betonskih zidakov. Eksperimentalno delo je bilo usmerjeno v {est razli~nih sestav betona z razmerjem w/c je 0,56, z relativno enako kompaktnostjo in brez zmanj{anja vrednosti. [est sestav je predstavljalo kontrolni beton z naravnim peskom in pet sestav z dodatkom 10 %, 20 %, 30 %, 40 % in 50 % RBW, kot delnim nadomestkom za naravni pesek. Prou~evane, analizirane in primerjane so fizikalne in mehanske lastnosti cementnih zidakov. Dobljeni rezultati so pokazali, da je mogo~a izdelava cementnih zidakov na osnovi RBW. Tla~ne trdnosti teh betonskih zidakov so primerljive s tistimi iz kontrolnega betona, ob~utno pa je zmanj{anje te`e. Zidaki izdelani z 30 % RBW so pokazali izbolj{anje tla~ne trdnosti za 42 % in zmanj{anje te`e za 11 %, v primerjavi z zidaki iz kontrolnega betona. Klju~ne besede: reciklirani odpadki iz opeke, betonski zidak, kompaktnost, padec vrednosti, mehanska trdnost