Combined with strain gauge measurement method, the modified split Hopkinson pressure bar was adopted to investigate the behavior of normal concrete and steel fiber reinforcement concrete exposed to 400°C and 800°C under axial impact compressive loading. The experimental results show that compared with normal temperature, the compressive strength and elasticity modulus of normal concrete exposed to 400°C and 800°C decrease obviously. The transformation of concrete exposed to high temperature in microstructure is analyzed by SEM. The influence of high temperature on macro mechanics performance is discussed.
This paper reviewed a variety of methods of polymer surface modification, which mainly includes Solution processing method, Plasma treatment,Surface grafting method,Irradiation treatment and method of Atomic force microscopy probe shock , and the specific polymer material combined with the modification method and its modification mechanism was introduced in detail.Polymer has very extensive application both in chemical fields and in daily life, but due to its poor surface hydrophilicity and wear resistance, the further application of polymer materials were limited. In order to improve its surface properties, modification are needed on the surface of the polymer. Polymer surface modification means to operate on the surface of polymer within the scope of nanometer level, and give some new properties on material surface, such as hydrophilicity, scratch resistance, under the premise of without affecting the material ontic properties.There are many methods of polymer surface modification. This paper reviewed Solution processing method, Plasma treatment,Surface grafting method,Irradiation treatment and method of Atomic force microscopy probe shock . Different methods of modification combined with specific materials are introduced as follow.
Based on polycarboxylate chemistry, polycarboxylate superplasticizers (PCs) with hydrophobic side chains were synthesized through radical copolymerization reaction. The molecular weight and polydispersity index were analyzed by gel permeation chromatograph (GPC), and the results showed the same structural information. The performances of PCs in cement paste were tested by measuring the fluidity and fluidity retention. The slump and the compressive strengths of concrete were also determined. Additionally, the foaming behavior of PCs was investigated by the foam volume, the surface tension of PCs aqueous solution,and the air content of concrete. According to the data, the hydrophobic side chains of PCs may affect the hydration reaction of cement resulting in better workability.
In order to study the effect of fly ash (FA) and slag powder (SP) on coefficient of thermal expansion (CTE) of concrete, the influence of FA and SP to CTE of concrete was compared, the influence of replacement proportion of FA to CTE of concrete was tested, and the unhydrate mineral admixture particles were observed with SEM and validate with Energy Spectrometry. The results showed that the influence of FA and SP to CTE of concrete is different, the CTE of SP concrete is near to the norm concrete,but is higher than the FA concrete; With the replacement proportion of FA increased, the CTE of concrete decreased; The per strength CTE increased obviously when the replacement proportion exceed 10%, and the decrease of strength badly when the replacement proportion of FA exceed 30%; The unhydrate mineral admixture particles is one of the most important factors that influence the CTE of concrete, and the mineral admixture could influence the composite and the microstructure of cement paste, then cause the change of porosity and density.
Cable Anchor Supporting mechanism theory analysis, combined with high geostress, composite roof and complex geological conditions, the deep well under conditions of coal roadway by small aperture, anchor on the form of the structure and high prestressed construction technology, engineering practice shows that the technology is simple and applicability,is deep well solve the high stress soft rock tunnel, large sections into bifurcation point supports of the effective way of the problem. Not only reduces the support cost, reduce the workload of the Lane repair, and also greatly reduce the labor intensity of construction personnel, improve the reliability of the engineering safety. Accumulated experience, has broad application prospects for the deep well under the conditions of the other coal mine soft rock roadway
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