The present paper of a series deals with the experimental characterisation of flexural toughness properties of structural concrete containing different volume of hooked-end steel fibre reinforcement (75 kg/m3, 150 kg/m3). Third-point flexural tests were carried out on steel fibre reinforced concrete beams having a cross-section of 80 mm × 85 mm with the span of 765 mm, hence the shear span to depth ratio was 3. Beams were sawn out of steel fibre reinforced slab elements (see Part I) in order to take into consideration the introduced privilege fibre orientation (I and II) and the position of the beam (Ba-a, Ba-b, Ba-c) before sawing (see Part I). Flexural toughness properties were determined considering different standard specifications, namely the method of the ASTM (American Standards for Testing Materials), the process of the JSCE (Japan Society of Civil Engineering), and the final proposal of Banthia and Trottier for the post cracking strength. Consequently, behaviour of steel fibre reinforced concrete was examined in bending taking into consideration different experimental parameters such as fibre content, concrete mix proportions, fibre orientation, positions of test specimens in the formwork, while experimental constants were the size of specimens, the type of fibre used and the test set-up and test arrangement.
Authors:Valentin Antonovič, Marius Aleknevičius, Jadvyga Kerienė, Ina Pundienė, and Rimvydas Stonys
The prisms (6 pieces of 40 × 40 × 160 mm) manufactured under slight vibration (5 s) were kept for 48 h in wet conditions at the temperature of 20 °C. Then, the ultrasonic and SEM tests were performed and the bendingstrength of the
Authors:M. Földesová, P. Lukáč, J. Majling, and V. Tomková
137Cs and60Co were sorbed from model solutions and waste water on chemically treated granular zeolite. The zeolite was incorporated into cement slurries based on blast furnace slag (BFS). The compressive and bending strength were measured after different times of hydration. The leaching tests were performed in water, base and acid solutions. The leachability was more pronounced only for samples in acidic solutions.
Authors:M. Szafran, P. Wiśniewski, G. Rokicki, and L. Łukasik
The studies on the application of the emulsions of poly(vinyl acetate-co-allyl ether)s containing nonionic hydrophilic poly(oxyethylene)
fragments as binders in the die pressing of alumina is presented. It was found that introduction of hydrophilic fragments
into molecules of a typical water dispersible polymer led to better polymer affinity to the ceramic powders. It was also shown
that low molecular mass of such copolymers should be relatively low ca 1500 g mol–1 to increase the density and thickening uniformity of the samples before and after sintering. The resultant sinters indicated
exceptionally high mechanical strength (bending strength ca 500 MPa).
The results of experiments on application of NaH2PO4 as a binding agent for ceramic kaolin samples were presented. The experiments were carried out at temperatures of 973, 1073
and 1173 K and NiO and CoO additives were used as tempering agents. The parameters of the obtained samples with NaH2PO4 were compared with the samples compressed with water only. The materials of 3-4 times higher bending strength, lower water
absorption as well decreased open porosity were prepared during these experiments. The binding function of the NaH2PO4 additive relies on creation of some compounds in reaction between the products of its condensation and products of kaolin
decomposition. Finally a ceramic material of prospective properties was created.
The influence of spent catalyst from catalytic cracking in fluidized bed on the hydration process of cement and the properties
of cement mortars were studied. The spent catalyst was used as an additive to cement in the mortars (10 and 20% of cement).
The samples of mortars kept in water for28 days, then they were placed in sulfate and chloride media for 2 months (the control
samples were kept in water for 3 months). After this time they were subjected to bending strength and compressive strength
determinations. Thermogravimetric and infrared absorption studies were performed and capillary elevation, capability of binding
heavy metals, and changes in mass and apparent density were determined too. The studies disclosed the pozzolana nature of
spent catalyst and its influence on cement mortars being in contact with corrosive media.
Authors:A. Khan, H.H. Liu, A. Ahmad, L. Xiang, W. Ali, A. Khan, M. Kamran, S. Ahmad, and J.C. Li
Higher plant population and nitrogen management is an adopted approach for improving crop productivity from limited land resources. Moreover, higher plant density and nitrogen regimes may increase the risk of stalk lodging, which is a consequence of complex interplant competition of individual organs. Here, we aimed to investigate the dynamic change in morphology, chemical compositions and lignin promoting enzymes of the second basal inter-nodes altering lodging risk controlled by planting density and nitrogen levels. A field trial was conducted at the Mengcheng research station (33°9′44″N, 116°32′56″E), Huaibei plain, Anhui province, China. A randomized complete block design was adopted, in which four plant densities, i.e., 180, 240, 300, and 360 × 104 ha−1 and four N levels, i.e., 0, 180, 240, and 300 kg ha−1 were studied. The two popular wheat varieties AnNong0711 and YanNong19 were cultivated. Results revealed that the culm lodging resistance (CLRI) index of the second basal internodes was positively and significantly correlated with light interception, lignin and cellulose content. The lignin and cellulose contents were significantly and positive correlated to light interception. The increased planting density and nitrogen levels declined the lignin and its related enzymes activities. The variety AnNong0711 showed more resistive response to lodging compared to YanNong19. Overall our study found that increased planting densities and nitrogen regimes resulted in poor physical strength and enzymatic activity which enhanced lodging risk in wheat varieties. The current study demonstrated that stem bending strength of the basal internode was significantly positive correlated to grains per spike. The thousand grain weight and grain yield had a positive and significant relationship with stem bending strength of the basal internode. The results suggested that the variety YanNong19 produces higher grain yield (9298 kg ha−1) at density 240 × 104 plants ha−1, and 180 kg ha−1 nitrogen, while AnNong0711 produced higher grain yield (10178.86 kg ha−1) at density 240 × 104 plants ha−1 and with 240 kg ha−1 nitrogen. Moreover, this combination of nitrogen and planting density enhanced the grain yield with better lodging resistance.
A thermal strengthening process, which occurs during low-temperature heating of binder-free silicon nitride, has been investigated
using simultaneous thermal analysis, dilatometry and FTIR and shown to occur in separate stages over clearly identifiable
temperatures. Reactions which give the strengthening are the loss of physically and chemically combined water and the decomposition
of ammonium carbonate and various hydrosilicates. Compacts have bend strengths of 8–10 MPa after strengthening at 500°C and
30–34 MPa after strengthening at 900°C.
High-temperature dilatometry shows several stages of sintering. The maximum rate occurs at 1800°C with shrinkage commencing
at 1450°C. Densities of 98.3% theoretical are obtained on heating to 1900°C.
Authors:Hugo R. Fernandes, Dilshat U. Tulyaganov, Ashutosh Goel, and José M. F. Ferreira
after heat treatment of glass powder compacts at 800 °C for 1 h. Further heat treatment at 850 °C significantly improved densification of G3 compared to G1 and G2 whereas maximum bendingstrength values as 189 ± 8 (G1), 195 ± 9 (G2) and 224 ± 4 (G3) MPa