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Streszczenie:
For possible application of gamma radiation in processing of fresh concrete, like surface processing at precast plants or 3D printing, it is essential to evaluate effects of irradiation on the early hardening of cementitious binders. The influence of gamma irradiation with the dose rate of 4.6 kGy/h on the early strength, pore size distribution and qualitative phase composition of mortar was investigated. The range of investigation comprises the effects selected micro- and nano-additions to Portland cement mortar used to control the kinetic of setting and early hardening of cement. Results show that gamma irradiation of hardening mortar results in the early strength increase of about 56–100%, in reduction of capillary porosity and pore size refinement. The gamma-irradiation sensitivity of early strength of cement mortar is equivalent to increased temperature wet curing. A correlation of heat evolution characteristics of hardening mortar and the temperature-equivalent of gamma irradiation is discussed.

Słowa kluczowe:
boron minerals, early hardening, gamma irradiation, pore size distribution, strength, temperature equivalent

Streszczenie:
The effects of gamma irradiation on concrete properties during early hardening were studied towards radioactive waste storage or accelerated processing at precast plants. Concrete mixtures containing different mineral aggregates (baryte, magnetite, amphibolite) were investigated. During initial 16 hours of hardening the mixes were irradiated using 60Co gamma source at the rate of 3.5 kGy/h. The mechanical properties and microstructural features of irradiated early-age concrete were tested: the secant elastic modulus, the compressive strength, the porosity and pore size distribution. XRD and SEM analysis were also performed. The results indicate both the stiffening and pore refinement in concrete due to early gamma irradiation. Effects of early irradiation on microstructural features of cement matrix were found in the subsurface layer up to the depth of 2 mm. The influence of different mineral aggregates in concrete on the radiation-induced changes of early age properties is discussed.