BEHAVIOR OF CONCRETE ROUND DOUBLE BEAM FRACTURE TOUGHNESS TEST SPECIMENS
Laboratory fracture toughness tests of concrete using wedge-loaded round double beam specimens with a length to diameter ratio of 2:1 show two distinctly different specimen behaviors. Either the crack remains in the plane of the notch, and a valid test result can be obtained, or there is lateral cracking around mid-length which invalidates the results. Results of a controlled study show that the behavior transitions from desired to lateral cracking as the maximum aggregate size in a particular concrete increases. Two theories are proposed to explain this behavior and transition: new crack branching and crack turning. To prevent the lateral cracking behavior, two alternate testing techniques have been developed for use with the RDB specimen.
SUGGESTED METHODS FOR DETERMINING THE FRACTURE TOUGHNESS OF ROCK.
After providing a technical introduction to the fracture toughness of rock, this paper describes in detail two methods for measuring proposed by the isrm commission on testing methods. 'fracture toughness' is a critical value of stress intensity, above which catastrophic crack growth is assumed to occur; its values for rock have several practical applications. The two proposed methods for determining the fracture toughness of rock material both use core specimens. The first method uses a 'chevron bend' specimen with a notch cut perpendicular to the core axis. The specimen rests on two support rollers, and a compressive load is applied to press apart the notch sides, causing transverse splitting of the specimen by crack growth in the unnotched part of the notched cross section during the test. The second method uses a 'short rod' specimen with a notch cut parallel to the core axis. A tensile load is applied to the specimen to pull apart the notch side, causing lengthwise splitting of the specimen by crack growth in the unnotched part of the notched cross section during the test. The use of two methods is justified by the frequent occurrence of anisotropy in rock material; both methods offer two test levels, the first of which can be made with portable equipment, and the second of which is complicated and laboratory oriented. For each method, details are given of scope, specimen description, apparatus, procedure, calculations, validity, and requirements for reports of results.
Studies on the composition, quality and processing of triticale. Part II. Mineral composition of grain and flour.
Mineral composition of grain and flour in 14 promising triticale strains from India are reported. The mean values for whole grain, i.e. Ca (0.47 mg/g), P (2.70 mg/g), K 4.60 mg/g, Na (352 micrograms/g), Zn (41.6 micrograms/g), Cu (7.0 micrograms/g), Fe (73.4 micrograms/g) and Mn (33.6 micrograms/g) were obtained as compared to those of flour, i.e. Ca (0.27 mg/g), P (0.97 mg/g), K (1.64 mg/g), Na (231 micrograms/g), Zn (26 micrograms/g), Cu (4.0 micrograms/g) and Mn (10.5 micrograms/g), respectively. These values were found to be considerably higher than those of wheat. Highly significant positive correlations of ash with sodium and zinc in whole grain were observed. In the case of triticale flour, highly significant positive correlations of ash with manganese, phosphorus and potassium were obtained.