Drying shrinkage of self-compacting concrete incorporating fly ash

The present research is conducted to investigate long term (more than two years) free and confined drying shrinkage magnitude and behaviour of self-compacting concrete (SCC) and compare with normal concrete (NC). For all SCCs mixes, Portland cement was replaced with 0-60% of fly ash (FA), fine and coarse aggregates were kept constant at 890 kg/m3 and 780 kg/m3, respectively. Two different water binder ratios of 0.44 and 0.33 were examined for both SCCs and NCs. Fresh properties of SCCs such as filling ability, passing ability, viscosity and resistance to segregation and hardened properties such as compressive and flexural strengths, water absorption and density of SCCs and NCs were also determined. Experimental results of free drying shrinkage obtained from this study together with collected comprehensive database from different sources available in the literature were compared to five existing models, namely the ACI 209R-92 model, BSEN-92 model, ACI 209R-92 (Huo) model, B3 model, and GL2000 model. To assess the quality of predictive models, the influence of various parameters (compressive strength, cement content, water content and relative humidity) on the drying shrinkage strain are studied. An artificial neural network models (ANNM) for prediction of drying shrinkage strains of SCC was developed using the same data used in the existing models. Two ANNM sets namely ANNM1 and ANNM2 with different numbers of hidden layer neurones were constructed. Comparison between the results given by the ANNM1 model and the results obtained by the five existing predicted models were presented. The results showed that, using up to 60% of FA as cement replacement can produce SCC with a compressive strength as high as 30 MPa and low drying shrinkage strain. SCCs long-term drying shrinkage from 356 to 1000 days was higher than NCs. Concrete filled elliptical tubes (CFET) with self-compacting concrete containing FA up to 60% are recommended for use in construction in order to prevent confined drying strain. ACI 209R-92 model provided a better prediction of drying shrinkage compared with the other four models. However, a very high predictability with high accuracy was achieved with the ANNM1 model with a mean of 1.004. Moreover, by using ANNM models, it is easy to insert any of factors effecting drying shrinkage to the input parameters to predict drying shrinkage strain of SCC.Ministry of Higher Education, Liby

Long-term drying shrinkage of self-compacting concrete: experimental and analytical investigations

YesThe present study investigated long-term drying shrinkage strains of self-compacting concrete (SCCs). For all SCCs mixes, Portland cement was replaced with 0–60% of fly ash (FA), fine and course aggregates were kept constant with 890 kg/m3 and 780 kg/m3, respectively. Two different water binder ratios of 0.44 and 0.33 were examined for both SCCs and normal concrete (NCs). Fresh properties of SCCs such as filling ability, passing ability, viscosity and resistance to segregation and hardened properties such as compressive and flexural strengths, water absorption and density of SCCs and NCs were also determined. Experimental results of drying shrinkage were compared to five existing models, namely the ACI 209R-92 model, BSEN-92 model, ACI 209R-92 (Huo) model, B3 model, and GL2000. To assess the quality of predictive models, the influence of various parameters (compressive strength, cement content, water content and relative humidity) effecting on the drying shrinkage strain as considered by the models are studied. The results showed that, using up to 60% of FA as cement replacement can produce SCC with a compressive strength as high as 30 MPa and low drying shrinkage strain. SCCs long-term drying shrinkage from 356 to 1000 days was higher than NCs. ACI 209R-92 model provided a better prediction of drying shrinkage compared with the other models.Financial support of Higher Education of Libya (469/2009)

In Vitro Pathogenicity of Pseudomonas savastanoi Isolated from Olive Trees in Iraq on Fruits of Various Plant Species and Their Molecular Characterisation

AbstractThe present study was carried out to determine the pathogenicity of Pseudomonas savastanoi on carrots and some other fruits, and to characterize the isolates using molecular methods. Pathogenic Pseudomonas savastanoi bacterial samples were collected from olive trees with olive knot after a field survey of olive trees from around Duhok province in Iraq. The study period was determined to include the beginning of March until the end of May, after collecting the samples and transferring the samples to the laboratory and growing them on culture media. The samples were cultured on Blood agar, MacConkey agar and Cetrimide agar mediums for the diagnosis of Pseudomonas savastanoi and further studies. After activation, bacteria were inoculated on the carrots and other fruits of plants such as lemons, beans, local apples, and commercial apples. These fruits were subjected to the same environmental conditions of humidity, temperature, and incubation period. Results revealed that infection symptoms did not appear on the fruits after bacterial exposure. However, only some of the carrots were found to be infected after 13 days of incubation. On the other hand, when the incubation period was pro-longed to 20 days, all the carrots samples were infected. Bacteria were re-isolated from infected carrots and some basic microscopic, phenotypic and biochemical tests including oxidase, catalase and urease were performed on them. In addition, VITEK2 system were used for determining the isolates in species level. Also, PCR and RT-PCR and sequencing of 16S rRNA were performed to detect possible mutations. Keywords: Pseudomonas savastanoi, 16S r RNA, RT-PCR, VITEK2, Sequencing</p

Self-compacting concrete with recycled aggregates

This work investigates the state of the art on innovative and sustainable self-compacting concrete prepared with coarse and fine recycled concrete aggregates (up to 100% of total amount of aggregates). Fresh state behavior is presented and related to the hardened state and durability characteristics of the conglomerate. Studies on this new research topic in the field of construction industry highlight that self-compacting properties can be maintained when recycled concrete aggregates are used and their good qualities enhance effective mechanical properties thus promoting its successfully use not only for non-structural elements, but also structural and highly reinforced structures which hinder the vibration procedures