Performances of high performance polymer modified concrete for mining engineering
Although ordinary concrete is used in mining engineering, it has many defects such as high brittleness and low flexibility. It is urgent to exploit a kind of high performance polymer modified concrete for mining engineering which has low cost price, high performance, high bond strength, great convenience and excellent durability. Mechanical properties and durability were studied on ordinary concrete, concrete with polyacrylic acid latex and concrete with polyacrylic acid, styrene-acrylic two latexies and silica fume. The results are as follow. First, compression strength of concrete with polyacrylic acid latex is lower than that of ordinary cncrete. And its rupture strength, tensile splitting strength, bond strength and impermeability is higher by 28.6%, 37.5%, 55.3% and 77.2% than ordinary concrete respectively. Second, concrete with polyacrylic acid, styrene-acrylic two latexies and silica fume has higher compression strength than common concrete. At the same time, its rupture strength, tensile splitting strength, bond strength and impermeability is higher by 48.8% 53.1% 73.0% and 83.3% than ordinary cncrete respectively. So, it is called high performance polymer modified concrete. Third, it was analysed by scanning electron microscope. Last, the experiments in a mine shows that its performances and bond strength with tunnels are higher than ordinary concrete while its price is only higher by 0.6% for 1 stere concrete.
Study on Performance of Silica Fume Modified Rubberized Concrete
In order to alleviate environment pollutions and improve toughness of concrete pavement,road performance of silica fume modified rubberized concrete were studied.The variation vegularity of basic mechanical properties and physical characteristics of silica fume modified rubberized concrete were studied by tests of density,flexural strength,compressive strength and indirect tensile strength.Impact toughness of rubberized concrete was analyzed.Vibration and noise reduction of rubberized concrete were studied by noise instrument and ultrasonic instrument.The experimentation results present that(1) flexural strength,compressive strength and indirect tensile strength of rubberized concrete incorporated with silica fume is better than those of plain concrete;(2) density,flexural strength,compressive strength,indirect tensile strength,and rate of compressive strength of flexural strength of rubberized concrete decrease due to augments of rubber particles volume fraction of concrete;(3)impact toughness of concrete can be enhanced and noise level can be reduced by mixing rubber particles in concrete;(4)the effect of damping and noise reduction is remarkable with increasing volume fraction of rubber particles;(5)when volume fraction of rubber particles does not exceed 30% of volume fraction of aggregate,good performance of rubberized concrete for concrete pavement material can be attained.
A technique for large-field, superficial electron therapy.
The application of electron beams to radiation therapy has received increased attention in recent years. This interest stems largely from the special characteristics of the electron depth-dose distribution; the fall-off in depth dose near the end of the range of the electrons is particularly rapid for electron beams having energies less than about 10 Mev. Such an electron beam is suitable for the treatment of widespread, superficial lesions, where it is desirable to minimize the dose to deep tissues. All the common sources of super-voltage x-rays, apart from radioactive substances, are inherently capable of producing an external beam of electrons, though with varying degrees of complexity. Electrons of about the energy suitable for superficial therapy (several Mev) may be used to produce an x-ray beam which is sufficiently penetrating for the treatment of even the deepest lesions. The Stanford medical linear accelerator was designed to provide both x-rays and electron beams. The accelerator and its applic...