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This article aims to investigate and optimise the properties of lightweight self-consolidating mortar (LSCM) by using the response surface method (RSM). Silica fume (SF), nano silica (NS), water-cement ratio (W/C) and superplasticiser (SP) were chosen as variables. Also, part of the aggregates was replaced with lightweight expanded clay aggregate (LECA). Due to the advantages of RSM in accommodating multi-response optimisation of LSCM properties, the investigation and analysis were carried out for the stability, segregation and compressive strength. The optimised results recommended acceptable ranges of the required rheological and hardened criteria for LSCM. The mixtures achieved in these ranges include an LSCM with sufficient stability and low segregation. In particular, the results showed that the ultimate segregation must be < 8% for structural concrete. In addition, the results proved that increasing the fraction of NS and SF improves the properties of the LSCM by reducing the segregation and increasing the stability and compressive strength. It was found that adding 6% of NS at a high W/C ratio decreased the segregation by at least 15%. Adding 6% NS and %SF to LSCM within 0.5 W/C increased the compressive strength up to 15.1 MPa for the former and 3.8 MPa for the latter. [ABSTRACT FROM AUTHOR]

Cement–bentonite (CB) slurry cutoff walls are extensively utilized to restrict the horizontal flow of fluids. In this study, cement was replaced by four various contents of 0%, 10%, 20%, and 30% by natural zeolite to evaluate its effects on the unconfined compressive strength, flexural strength, tensile strength, and the coefficient of permeability of cement–bentonite–zeolite (CBZ) specimens. Since underground cutoff walls are always in danger of sulfate attack, the CBZ specimens were immersed in three different containers with three different pH values of 2, 5, and 8 to study the sulfate resistance of this material. Results have indicated that the strength of specimens decreases with an increase in zeolite content at early ages; however, increasing the amount of zeolite up to 20% improves the mechanical properties and permeability of cutoff wall materials at late ages. The bentonite/cement (B/C) ratio equal to 0.2 shows a relatively better response than B/C ratios equal to 0.14 and 0.3. Curing specimens in the sulfate environment increased the mechanical strength of specimens and decreased the coefficient of permeability at first ages. At the late ages, curing in sulfate solutions manifested disadvantageous effects on specimens; however, specimens containing zeolite indicated higher sulfate resistance than specimens without zeolite. [ABSTRACT FROM AUTHOR]

Cut off walls are used under dams for the control of sub surfaces seepage and permeability of cut off wall was important. In the construction of cut off walls, plastic concrete is used and the amount of plastic concrete permeability is important. In this study, the permeability of plastic concrete was investigated and the effect of replacing nano silica instead of cement to reduce permeability was studied. So in this research, compressive strength, elastic modulus, and permeability parameters of plastic concrete specimens at different ages (7, 14, 28, and 56 days) and with different percentages of nano silica (0, 1.5, 3, 4.5, and 6%) were investigated. Also, scanning electron microscopy was used to investigate the effect of nano silica on plastic concrete specimens. The results show that as the age of the specimens increases, the compressive strength and elastic modulus increase, and the permeability of the plastic concrete decreases. Also, by adding nano silica to plastic concrete, the compressive strength of the plastic concrete increases and the plastic concrete permeability decreases significantly while its elastic modulus is almost constant. [ABSTRACT FROM AUTHOR]

Tehran, the capital city of Iran, is a dense city with more than 12 million dynamic population. The city is located next to the seismically active zone of the Alborz Mountains, with many active faults surrounding it. Because of Tehran's significant economic and political position at the national level, earthquakes in this city or its vicinity could eventually affect the entire country. This can explain how important the identification and assessment of seismic risk in this city can be. In this study, an OpenQuake-engine has been employed to quantify the earthquake risk of one of the districts of Tehran. Initially, a probabilistic hazard assessment was carried out for Tehran; then, after disaggregating the result of a 475-year PSHA, the main contributing earthquake scenario was selected as the hazard input. In addition, an exposure model was developed for the residential buildings of the study area, indicating building typology and locations. Further, a set of fragility and vulnerability functions that are consistent with the exposure model was selected from past studies. Finally, the seismic loss for residential buildings in District 2 of Tehran municipality was assessed in the event of the 475-year hazard scenario. The results show the complicated intensity and spatial distribution of damages and losses in various subdivisions of the study area. Such analysis can provide essential information for disaster management decision-makers to become prepared for possible future events. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the Time-Accelerated ICA (TA-ICA) algorithm to accelerate the ICA speed almost with the same separation quality. For this purpose, we apply the ICA to the minimum required length of sensors signals determined based on human perception to calculate separating matrices. The latter matrices are then applied to the rest of sensors signals in closed form. Using computer simulations it is shown that in average the TA-ICA is about five times faster than the ICA, while the separation quality is almost preserved from human perception aspect. [ABSTRACT FROM AUTHOR]