The impact of variation in chemical and physical properties of PFA and BPD semi-dry cement paste on strength properties

The effect of Pulverised Fuel Ash (PFA) and By-Pass-Dust (BPD) in ternary semi-dry cement pastes was reported. As well as this, the variability over 6 months in chemical composition and particle distribution was reviewed to determine impact on strength. The addition of BPD in ternary pastes resulted in a reduced strength when combined with PFA. PFA and BPD samples obtained over a 6 month period showed variability in both chemical composition and particle distribution. For PFA, it was reported that at 14 days the particle size distribution had greatest impact on strength and at 28 days the SiO2 content had greatest impact. The high variability in BPD particle size distribution resulted in finer particles achieving the greatest strength

The density and distribution of the dominant phytoplankton in the southern Caspian Sea

The research project was comprised of four sampling cruises, which were carried out in summer 94; spring, autumn and winter 95 in the southern part of the Caspian Sea, where Chrysophyta (Diatoms) and Pyrrophyta were found to be the dominant phytoplankton. The maximum density of phylum Chrysophyta (Diatoms) was observed mainly during the autumn in the coast line (below 20 m) and in the central part of the southern Caspian Sea, while the highest density of phylum Pyrrophyta occurred during the spring in the subcoastal zone (below 50 m.). The dominant species in the phylum Chrysophyta (Diatoms) were Rhizosolenia calcar-avis, Thalossionema nitzschiodes, Sceletonema costatum, Cyclotella meneghiniane and three members of genus Coscinodiscus, among which R. calcar-avis had the highest density. Members of phylum Pyrrophyta, i.e. Exuvialla cordata, Prorocentrum scutellum and Glenodinium penardii had the highest density during the spring in the central part of the southern Caspian Sea, where E. cordata was the most abundant

Development of strength models for prediction of unconfined compressive strength of cement/byproduct material improved soils

© 2017 ASTM International. All rights reserved. This paper presents the possible inclusion of pulverized fuel ash (PFA) and ground granulated blast slag (GGBS) in cement deep soil mixing for enhancement of unconfined compressive strength (UCS) of weak soil materials for construction purposes. The main focus of this paper was to investigate the UCS of cement-, cement/PFA-and cement/PFA/GGBS-improved soils, and development of mathematical and graphical models for prediction of UCS for use in design and construction. Samples of cement, blends of cement and PFA, and cement/PFA/GGBS were prepared using 5 %, 10 %, 15 %, and 20 % by weight of dry soil and tested for UCS after 7, 14, 28, and 56 days. A multiple regression analysis was conducted using the SPSS computer program. The results showed that soil materials with lower plasticity show higher strength development compared to those of higher plasticity for cement improvement. The study has also revealed that the inclusion of PFA and GGBS can cause a reduction in the amount of cement in deep soil mixing, which can result to reduced cost and emission of carbon dioxide (CO2) during construction. The developed mathematical and graphical models could give reliable predictions of UCS for weak soil materials with initial UCS less than or equal to 25 kPa and for water to binder ratio of unity based on the observed agreement between experimental and predicted data. The developed multiple regression models have also been validated using different mixtures of 6 %, 8 %, 12 %, and 16 % of binders

An investigation on the critical success factors of total quality management implementation in Libyan construction organisations

The paper presents an investigation on the Critical Success Factors (CSFs) of the implementation of Total Quality Management (TQM) in Libyan construction organisations. A thorough review of literature has been carried out to identify the CSFs, which were then used to develop a questionnaire. Of 200 questionnaires distributed to contractors in Tripoli, 130 were completed and returned, representing a response of 65 per cent. Among of these participating organisations about two-third are from the public sector, and the rest from the private sector. The data were analysed using Principal Component Analysis (PCA) which revealed the internal structure of the data in a way which best explains the relationships between CSFs. The findings identified five reliable and valid TQM constructs, namely ‘organisation management’, ‘communication to improve quality’, ‘training and development’, ‘employee’s involvement and recognition’ and ‘culture’. The findings revealed a low level of CSFs implementation, which might be originated from little understanding of the fundamental TQM principles

Hydrology and hydrobiology data analysis collected during 1998-2007

Annually, many data of hydrology and hydrobiology of the southern Caspian Sea at Iran's coasts were collected by Caspian Sea Research Institute of Ecology. The data which had been collected by researchers submitted annually in several reports but has not been processed all at once. Fluctuations of various parameters were surveyed and the relationships between them were analyzed. The main goal of this research is to analysis the data were obtained from 1994 to 2006 and show changes the concentration of various parameters in the Caspian Sea. Physicochemical data indicated that the average trend of transparency and salinity was decreased from 1994 to 2006 annually, where the salinity value was decreased from 12.37 ppt (part per thousand) to 11.5 ppt. The average of dissolved oxygen was increased from 6.4 to 8.6mg/l. pH has slightly fluctuated from 8.15 to 8.31. However, with increasing depth from surface to bottom, the average of dissolved oxygen was sharply decreased (DO concentration in surface and 800 m was 7.18 and 1.45 mg/l, respectively). The trend of salinity and pH fluctuation was very slow with depth but the salinity has an increasing with incrementing of depth but pH has a decreased trend. The average of organic and inorganic phosphorus and TP was nearly increased. The average of Nitrate and Silica sharply increased comparing to depth but the average of Nitrite and organic Nitrogen decreased. The results showed that the temperature fluctuation in different water layers was low in winter but the dramatic decreasing of temperature was occurred at 10-20 m (in spring), 20-50 m (in winter) and 50-100 m (in autumn). With increasing of depth (Slope of the Sea), transparency and salinity values have an increasing while DO and pH showed decreased. As a whole, 335 species of phytoplankton were identified, there are 70 species in advance as these species were not seen in this period but 96 of novel's species have been recorded. The lowest and the most of phytoplankton biomass was recorded in 2006 and 2001 while the biomass was 59 and 1034 mg/m^3, respectively. Albet, the lowest biomass was recorded at the depth of 100 m (24.1 mg/m^3) but the maximum was observed in surface layer (1344.1 mg/m^3). The average of phytoplankton biomass was increased after arrival of the ctenophore. There was a significant difference between the average of biomass in different seasons before and after of the ctenophore invasion (P0.137, P>0.782). Before the presence of ctenophore, the worms had been constituted a dominate group with an approximately %45 of total abundance and also %20 of their biomass. After this period, their frequency was sharply increased (more than %85) but the maximum value pertains to Cardidae (more than %90). The species diversity, evenness and richness were varied between .69-2.51, 0.23-0.63 and .011-3.79, respectively. AMBI software, Shanon-Viner parameter was moderate in all seasons from 1994 to 1996 but this parameter was reduced in a bad limit (boundary) in the most seasons from 2002 to 2005. The main parameter of M-AMBI consists of several parameters and also approximately showed similar changes such as Shanon -viner parameter. On basis of this parameter, the ecological quality condition of Caspian Sea was superior limit in all seasons from 1994 to 1996 but after the following years were decreased from good to moderate limits (After the presence of ctenophore). Relationship between abiotic variants and phytoplankton indicated that there was a direct relationship between transparency and salinity while there was a powerful and reversal significant relationship between transparency water temperature, transparency in organic Nitrate, phytoplankton number and transparency phytoplankton biomass. The comparison between different variants average in two periods (before and after the ctenophore invasion) indicated that the average of Kilka catch was decreased, the relative frequency of clupeonella engrauliformis and clupenoella grimmi was sharply reduced but the relative frequency of Clupeonella cultriventris was sharply increased, the species diversity, evenness and richness and the number of zooplankton species were sharply decreased, the average of biomass and transparency was sharply reduced, the average of dissolved oxygen and liza saliens or liza auratus catch were increased. These difference were often significant (P<0.05). Therefore, with the ctenophore invasion into the Caspian Sea, the primary production was increased, the biomass value of zooplankton and specially Kilka which fed on zooplankton were sharply decreased while the fish such as Rutilus frisii kutum and mullet (Liza salins or Liza aurratus) which fed on benthic were increased