Researches show that concretes containing 25 to 35 % slag powder (as alternation for Protland cement) obtain COMPRESSIVE STRENGTH CS about 85% and 97% of the control specimens (without slag) at the ages of 28 and 90 days respectively. These concretes, also, recorded less growth rate of the CS than the control specimen at early ages (<28 days). In order to increase the early CS of these concretes and acquire 28-daysold CS about control specimens, this investigation was carried out using various percentage of the silica fume replaced with known quantities of Prortland cement. The results revealed that specimens containing 5% silica fume along with 25 to 35% slag powder displayed 5.2% and 13.3% higher than CS of control specimens at the 28 and 90 days respectively. In other part of the study the CS of the concretes containing slag powder cured with water comprising 2.5% MgSo4 as well as 2.5% NaCl were evaluated. Slag-contained specimens, which were placed in above mentioned curing situation, showed less CS at 28 days than control specimens whereas at the age of 90 and 180 days CS of the specimens were higher than the control specimence. The 25% slag-contained speciemens placed in sulphated situation at 180 day old stage showed 325 Kglcm2 CS which was 14.44% higher than the control sample attaining the best result. here with material and geometric nonlinear analysis. In this paper, buckling behavior and ultimate capacity of built up castellated compound columns are investigated using ANSYS software. A brief of results is reported on for a number of CPE sections in different boundary conditions. Also is presented slenderness-load curve by using of Jandel software, which is a useful tool for investigation of ultimate capacity of the columns.

Nowadays, the better performance of lightweight structures during earthquake has resulted in using lightweight concrete more than ever. However, determining the COMPRESSIVE STRENGTH of concrete used in these structures during their service through a none-destructive test is a popular and useful method. One of the most original approach of non-destructive testing to obtain of COMPRESSIVE STRENGTH of concrete used in structures is ultrasonic pulse velocity test. The purpose of this research is predicting the COMPRESSIVE STRENGTH of LWA concrete by proposing an accurate mathematical formulation. Many samples of lightweight aggregate concrete, made by expanded clay, have been produced and tested. After determining the actual COMPRESSIVE STRENGTH and indirect ultrasonic pulse velocity for each sample, a relationship was derived to estimate the COMPRESSIVE STRENGTH through Gene Expression Programming (GEP). The results show the presented equation shows high accuracy in predicting the COMPRESSIVE STRENGTH of LWA and the estimated outcomes have a considerable compatibility with actual samples.

This study introduces, two models based on Gene Expression Programming (GEP) to predict COMPRESSIVE STRENGTH of high STRENGTH concrete (HSC). Composition of HSC was assumed simplified, as a mixture of six components (cement, silica fume, super-plastisizer, water, fine aggregate and coarse aggregate). The 28-day COMPRESSIVE STRENGTH value was considered the target of the prediction. Data on 159 mixes were taken from various publications. The system was trained based on 80% training pairs chosen randomly from the data set and then tested using remaining 20% samples. Therefore it can be proven and illustrated that the GEP is a strong technique for the prediction of COMPRESSIVE STRENGTH amounts of HSC concerning to the outcomes of the training and testing phases compared with experimental outcomes illustrate that the.

Objectives: Maintaining pulp vitality is a main goal in restorative dentistry. Introduction of pulp capping agents paved the way to eliminate the shortcomings of these materials and obtain successful restorations. On the other hand, nanotechnology is an emerging field of science with increasing use in dental materials. This study sought to assess the effect of addition of nano-TiO2, nano-SiO2 and nano-Al2O3 on COMPRESSIVE STRENGTH of five hydraulic cements.Methods: In this in vitro, experimental study, three experimental formulations of nano hybrid MTA, MTA Angelus and MTA Angelus+nano-oxide particles cements were placed in molds measuring 4±0.1mm in internal diameter and 6±0.1mm in height made of stainless steel (ISO9917-1). Ten samples were fabricated for each of the five groups of materials. Sound samples were stored at 37oC and 95±5% humidity and were subjected to COMPRESSIVE STRENGTH testing in a universal testing machine at a crosshead speed of 0.5mm/minute after 24 hours and one month. Two-way ANOVA, one-way ANOVA and independent samples t-test were used for comparison of COMPRESSIVE STRENGTH of groups at different time points.Results: The highest COMPRESSIVE STRENGTH belonged to MTA Angelus+nanohydroxyapatite and nano-hybrid MTA C at 24 hours and 30 days, respectively. The lowest COMPRESSIVE STRENGTH belonged to nano-hybrid MTA B and MTA Angelus at 24 hours and 30 days, respectively (P<0.05).Conclusion: Addition of nanoparticles affected the COMPRESSIVE STRENGTH of cements. COMPRESSIVE STRENGTH significantly increased over time in all groups.

This paper presents a new model for predicting the COMPRESSIVE STRENGTH of steel-confined concrete on circular concrete filled steel tube (CCFST) stub columns under axial loading condition based on Artificial Neural Networks (ANNs) using a wide range of experimental investigations. Based on the previous theoretical and experimental studies the input variables considered in developing the ANNs model are outer diameter of column, COMPRESSIVE STRENGTH of unconfined concrete, length of column, wall thickness and tensile yield stress of steel tube. After the learning step, the neural network can be extracted the relationships between the input variables and output parameter. The criteria for stopping the training of the networks are Regression values and Mean Square Error. After constructing networks with constant input neurons but with different number of hidden-layer neurons, the best network was selected. The neural network results are compared with the existing models which showed the results are in good agreement with experiments.

The present work is aimed at studying the effect of re-vibration on the COMPRESSIVE STRENGTH of concrete using 53 grade Ordinary Portland Cement, with wide range of w/c ratios varying from 0.35 to 0.7 and with more number of re-vibration time lag intervals ranging from ½ hour to four hours. The effect of re-vibration on the density of concrete is also studied. The results have shown that the COMPRESSIVE STRENGTH of the concrete with various w/c ratios have increased up to certain time lag interval i.e. within the initial setting time (IST) and decreased thereafter. The percentage increase in the COMPRESSIVE STRENGTH also nearly followed the above trend.

Objective: Nowadays, composite restorations have gained more popularity and are widely used due to their high esthetic properties, rapid application, ease of use and low costs. There are various composite resins of different brands available in the market and it is necessary to find the most favorable one in terms of reliability and long term prognosis. The present study aimed at evaluating and comparing the COMPRESSIVE STRENGTH of hybrid and nanocomposites.Methods: In this experimental in-vitro study 4 different types of composite resins were used as follows: Group 1- Filtek Z 250 (3M) (hybrid composite) Group 2- Filtek Supreme (3M) Group 3-Gradia Direct X(GC) Group 4-Herculite XRV Ultra (Kerr Hawe)composite resins (groups 2, 3 and 4 are nanocomposites). Twelve samples were made in stainless steel molds of 4mm diameter and 6mm height of each composite. Following photopolymerization of cylindrical samples using Radi plus light curing unit (SDI limited), the specimens were stored in distilled water at 37°C for 48 hours. The specimens were subjected to COMPRESSIVE stress test using Mechanical Testing Machine (Zwick/Roell) at cross head speed of 0.5 mm/min. One way ANOVA and Tukey’s Post-hoc tests were employed for statistical analyses and determining level of significance.Results: The obtained results were as follows: Group 1: 362.51 group 2: 266.70 group 3: 268.72 and group 4: 275.75 Newton. COMPRESSIVE STRENGTH of group 1 (Filtek Z 250) was higher than other three groups and it was statistically significant (P<0.05). No statistically significant difference was detected among groups 2, 3 and 4.Conclusion: Hybrid composite showed more COMPRESSIVE STRENGTH than nano composites.

In this study COMPRESSIVE STRENGTH of carbon nanotube (CNT)/cement composite is computed by analytical method. For this purpose representative elementary volume (REV) as an indicator element of composite is chosen and analyzed by elasticity relationships and Von mises' criterion applied to it. It is assumed that carbon nanotubes are distributed uniformly in the cement and there is perfect bonding in the interface of cement and nanotube. At first for simplicity of computations, carbon nanotubes (CNTs) are assumed to have unidirectional orientation in the cement matrix. In following, the relations are generalized to consider random distribution of nanotubes in cement, and a new factor suggested for random orientation of fibers in the CNT/cement composite. The results of analytical method are compared with experimental results.