This article is an investigation to determine mixture proportion of high strength structural light weight concrete in order to reduce the weight of concrete by using expanded aggregate clay (Leca), which in Iran is produced by industry. In order to reach to high strength concrete mineral and chemical admixtures additives have been used. Also stone POWDER has been used to reduce porosity and to increase compressive strength. Regarding the performance of this type of concrete, the variables in different mix designs are as follow: The ratio of water to cementitious materials, the amount of light weight aggregate to the total volume of concrete, the amount of cement and stone POWDER. Test for compressive strength, indirect tensile strength and flexural strength were carried out on the specimens. The specimens made in the concrete laboratory of Mazandaran University were kept under the water. In order to investigate the effect of curing on the compressive strength of these types of concrete from each mix design some specimens were kept in the open air. The results of this research show that by using light weight aggregate (Leca) it is possible to reach to a light weight structural concrete with dry unit weight of 1610 – 1965 kg/m3 with cube compressive strength of 34 to 71 MPa. Also, it has been observed the role of stone POWDER for the improvement of mechanical properties of concrete with light weight aggregate is very important.

Concrete is among the widely used materials in all industries and mineral and civil activities worldwide, highlighting its significance. Most natural and non-natural phenomena can influence the concrete's physical and mechanical properties, causing many irreparable damages. Acid rain is a natural inevitable phenomenon, particularly in industrial zones with high pollution percentages. This work investigates the effect of acid rain on the concrete specimens containing MICRO-SILICA and limestone POWDER. To this end, the concrete specimens are divided into six groups. Throughout this paper, CN represents the concrete without MICRO-SILICA and limestone POWDER under no-rain conditions, CO is the concrete without MICRO-SILICA and limestone POWDER under normal rain conditions, CA is the concrete without MICRO-SILICA and limestone POWDER under acid rain conditions, CMLN is the concrete containing MICRO-SILICA and limestone POWDER under no-rain conditions, CMLO is the concrete containing MICROSILICA and limestone POWDER under normal rain conditions, and CMLA shows the concrete containing MICRO-SILICA and limestone POWDER under acid rain conditions. The measured physical properties are the effective porosity, dry density, water absorption, and velocity of longitudinal waves. The mechanical properties including the Brazilian tensile strength, uniaxial compressive strength, triaxial compressive strength, cohesion, and internal friction angle are also measured. For the samples of CN and CMLN, they are tested under no rainfall conditions, whereas the samples of CA and CMLA are tested after 20 cycles of acid rain (pH = 2). The samples of CO and CMLO are also tested after undergoing 20 normal rain cycles (urban water with pH = 7). In each test cycle, there is 1 hour of rain and 1 hour of no rain. The results obtained show that adding MICRO-SILICA and limestone POWDER improves its properties so that the decrease in the effective porosity, longitudinal wave velocity, dry unit weight, water absorption, Brazilian tensile strength, uniaxial compressive strength, cohesion, and internal friction angle of the specimens of CMLA is less than those for the specimens of CA.

Fracture toughness is one of the most important properties of concrete that controls the conditions for crack propagation and ultimately concrete failure. This research uses the Brazilian disk test to prediction of crack propagation and fracture toughness in ordinary concrete samples without MICRO-SILICA and lime POWDER and ordinary concrete samples containing MICRO-SILICA and lime POWDER has been investigated. MICRO-SILICA replaces 10% by weight of cement and limestone POWDER replaces 5% by weight of cement. The crack propagation process was investigated from pre-existing cracks in the specimens as well as fracture toughness in modes I, II and hybrid mode I-II. Fracture toughness tests have been performed on Brazilian disk specimens at angles of 0, 15, 28.83, 45, 60, 75 and 90 degrees relative to the pre-existing crack direction. After laboratory studies, it was found that the onset of fin cracks at angles less than 60 degrees (0

The purpose of this work is to investigate the possibility of using mine wastes in the improvement of concrete properties. This research work investigates the physical and mechanical properties of the concrete specimens. These concrete specimens include concrete-lacking fibres, MICRO-SILICA and limestone POWDER (C), concretecontaining glass fibres without MICRO-SILICA and limestone POWDER (GC), concretecontaining MICRO-SILICA and limestone POWDER without fibres (CML), and concretecontaining glass fibres, MICRO-SILICA, and limestone POWDER (CGML). The physical and mechanical properties including the effective porosity, longitudinal wave velocity, water absorption, unit weight, tensile strength, uniaxial compressive strength, triaxial compressive strength, cohesion, and internal friction angle are investigated. The results obtained show that adding glass fibres to the concrete (GC) improve its properties compared to the fibre-less concrete (C). However, the properties of GC are improved significantly less than CGML. The Brazilian tensile strength and uniaxial compressive strength of GC increase by 13. 6% and 10. 95% relative to C. The Brazilian tensile strength and uniaxial compressive strength of CGML increase by 21. 8% and 45. 94% relative to C. Finally, it can be concluded that adding the MICRO-SILICA and limestone POWDER to the glass fibre concrete as well as the use of mine wastes also significantly improves the properties of the concrete.

The influence of different contents (0, 5 and 10% W/W) of SILICA and poplar wood POWDER (30, 40 and 50% W/W of total weight of composite) on strength properties of polypropylene/wood POWDER/SILICA composite was evaluated. Various compositions of the composite was melt mixed using two screw counter rotating extruder, followed by cooling and granulizing. Composite granules were injected into test samples. The results of strength properties measurements revealed that almost all strength values were improved. At higher content of SILICA, the MOR increased from 47.9 to 53.3 MPa, flexural MOE from 2625 to 4517 MPa and MOE in tensile increased from initial value of 4525MPa (without SILICA) to 6884MPa (10% SILICA in composite). Marginal increase in tensile strength and Izod impact strength was observed, and the hardness of the composite was improved from 66 to 73.77 shore D. At higher SILICA content, the density of the composite was higher, as expected.

The use of concrete in the industry is expanding. Self-compacting composite concrete is known as a cement composite with high performance and adhesion. This composite has a lot of psychological capabilities and efficiency, so the use of this concrete, in addition to reducing construction time, also reduces costs. Self-compacting composites fit into the mold without the need for vibration and pass through the smallest seam. In this study, the effects of adding MICROSILICA, fly ash and GGBFS pozzolan on the mechanical properties of self-compacting cement composite were investigated in 8 mixing designs. In making samples, 3 alternative cement additives at the rate of 10% were used in different mixing designs. In the compressive strength test, the sample with 10% MICROSILICA increased the resistance by 5.4% more than the reference sample, which showed that the addition of MICROSILICA increases the strength and water absorption in the samples. However, these pozzolans reduce the flow of self-compacting concrete. On the other hand, in the design of air ash mixtures, the resistance was reduced, but no significant changes were observed for slag. In total, other experiments such as tensile strength, flexural strength, water absorption, capillary, ultrasonic pulse velocity and impact resistance were performed on the mixing design.

The present study analyzes the bond stress in steel reinforcements embedded in concrete containing polymer fibers, MICRO-and nano-SILICA particles. For this purpose, 36 cylindrical (with a diameter of 10cm and height of 15cm) and 36 cubic (10 10 10cm) specimens containing different contents of additives and three types of cement strength grade (i. e. 32. 5, 42. 5 and 52. 5MPa) were constructed and subjected to pull-out and compressive strength tests, respectively. The experimental observations were then compared to previously proposed models available in the literature. The results indicated that MICROand nano-SILICA particles, compared to fibers, had more impacts on improving the reinforcement-concrete bond strength. Moreover, the highest bond strength was observed for the specimen containing equal content of MICROand nano-SILICA particles. An acceptable agreement was also obtained between the results of current study and previous models, highlighting the capability of the proposed models in prediction of the actual behavior of such specimens.

The increasing use of concrete and easy access to these materials has led to its use in a variety of environments. Concrete structures in areas with high corrosion rates cause irreparable damages. Therefore, studying concrete and improving its capabilities, which is favorable in these conditions, is very important. In this study, the effect of corrosion conditions caused by chlorine ion and sodium sulfate salt on concrete containing zeolite POWDER and MICRO SILICA as an alternative to the weight percentage of concrete cement has been investigated. In this study, after creating three types of ordinary concrete, concrete containing zeolite POWDER and concrete containing MICRO-SILICA, physical properties of concrete including effective porosity, weight loss percentage, water absorption, and longitudinal wave velocity, as well as mechanical properties including uniaxial compressive strength and Brazilian tensile strength concrete has only been studied. In this study, pozzolanic concrete with a percentage of replacing 10% of zeolite POWDER or MICRO-SILICA instead of cement; Sodium sulfate and chlorine ion were set in a corrosive medium for 15 days, and the results were compared with non-corrosive water conditions. The results of this study show that concretes containing pozzolanic MICRO-SILICA or zeolite POWDER performed better in corrosive and non-corrosive environmental conditions than ordinary concrete. In samples containing pozzolans including MICRO-SILICA and zeolite POWDER with effective porosity, water absorption decreased, and longitudinal wave velocity, tensile and compressive strength increased compared to ordinary concrete. Also, in the presence of corrosive water conditions containing chlorine ion and sodium sulfate salt, concrete containing zeolite POWDER had the best performance compared to the two types of ordinary concrete and concrete containing MICRO-SILICA.

The current study is focused on gaining optimum concrete mixture design which contains nano-SILICA or mirco-SILICA, by employing different evaluation factors such as water to the cement ratio, cement grade and different age of investigation (7 and 28 days), using a robust predictive method that is called Taguchi. Nine mixture designs are optimized by Tguchi method to achieve maximum compression strength, maximum bonding strength between concrete and rebar and minimum water absorption. Obtained mixture designs are then employed in the laboratory and the results are investigated for the optimization process. In this study the XRD test is used in addition to mechanical concrete tests and permeability test in the macro scale. Obtained results show the reliability of the Taguchi method in the prediction of the concrete mixture design.