Durability of geopolymers and geopolymer concretes: A review

Geopolymers are green materials with three-dimensional silicon and aluminum tetrahedral structures that can be serving as environmentally friendly construction materials and therefore have the potential to contribute to sustainable development. In this paper, the mechanism and research progress regarding the carbonation resistance, structural fire resistance, corrosion resistance, permeation properties and frost resistance of geopolymer concretes are reviewed, and the main problems with the durability of geopolymer concretes are discussed. Geopolymers possess the superb mechanic property and their compression strengths could be higher than 100 MPa. Generally, the higher the GPC strength, the better the carbonation-resistant. GPC has excellent fire resistance, due to geopolymers are acquired an inorganic skeleton which is affected by the alkali content, alkali cation, and Si/Ai ratio. There are a large number of Al-O and Si-O structures in geopolymers. Geopolymers do not react with acids at room temperature and can be used to make acid-resistant materials. Besides, GPC owning low porosity volume shows good resistance to permeability. The freezing-thawing failure mechanism of geopolymer concretes is mainly based on hydrostatic and osmotic pressure theory. GPC has poor frost resistance, and the freezing-thawing limit is less than 75 times.

Effect of Dwell Time and Heating Rate on Thermal Residual Stresses in Co-Cured Aluminum/Composite Hybrid Shaft

In this work, thermal residual stresses and deformation of an aluminum/composite hybrid shaft was studied using ABAQUS FEM software. In order to reduce the thermal residual stresses and deformation produced during co-cure bonding stages due to the difference of coefficients of thermal expansions (CTE) of the composite and the aluminum tube, the curing temperature field was optimized. The effects of dwell time and heating rate were investigated. The results show that residual stresses can be reduced obviously by reasonable dwell time and slow heating rate. The dwell time and heating rate also effect the degree of cure which influenced the mechanic property of aluminum/composite hybrid structure directly.

Investigation of Thermal Residual Stresses in Co-Cured Aluminum/Composite Hybrid Shaft Using Finite Element Method

In this work, thermal residual stresses and deformation of an aluminum/composite hybrid shaft was studied using ABAQUS FEM software. First, the thermo-chemical model of the curing process was described, and the curing parameters were determined. Then, a FEM model of the co-cured aluminum/composite hybrid shaft was build up using ABAQUS FEM software. Finally, the distribution of the thermal residual stress and deformation in the co-cured aluminum/composite hybrid shaft due to curing was obtained, and the effect of cooling rate was analyzed. The results show that residual stresses can be reduced obviously by reasonable cooling rate. The cooling rate also affect the degree of cure which influenced the mechanic property of aluminum/composite hybrid structure directly.

Research on the Impact Mechanic Property of the Silicon Carbide with Tungsten (SiC-W) Composite Material

This article does some research on SiC-W composite material. Getting the material with SPS, the micro-structure was observed. The micro-structure of SiC is mainly lamellar structure and the Tungsten did not infiltrate the SiC. Via mechanics performance test of SiC-W, we found although both SiC and SiC-W show the characters of brittle material, but the Tungsten mixing can improve the toughness in certain level.

A Finite Element Method to Simulate Ice Based on Multi-Surface Failure Criterion

A finite element method is introduced to simulate ice failure based on multi-surface criterion. The effects of porosity, temperature and strain rates on the ice mechanic property are taken into consideration. The main principle to simulate environment is explained. Through second developed to the finite element software, the process of ship-ice interaction is simulated. And the ship motion, ice force and ice failure mode are predicted by this method. The result is compared with other papers. the numerical simulation phenomenon is nearly same with the actual process. It suggests that simulation is reasonable, and the model has potential value in simulations of assessing ship strength. The fatigue damage is pointed out to be a special problem in ice-going ship design.

The Experiment to Research the Mudstone Interbeds which Affect the Mechanical Characters of the Layered Rock Salt

Since mudstone interlayer has a big influence on the mechanic property of layered rock salt, and in order to research its law, the mudstone which strength is lower than pure rock is used as a interlayer to make the regular layer of salt formation, then both the uniaxial and triaxial compression test are carried out on the layer of salt formation. The result indicates: (1) As the thickness of interlayer increases the uniaxial compressive strength and elastic modulus of layer type salt decrease. (2) On the condition that the thickness of interlayer does not change, the more the interlayer number, the stronger the uniaxial compressive strength. (3) If the total thickness of interlayer is stable and the interlayer number is same, then as the distance of interlayer increases the uniaxial compressive strength and elastic modulus of layer type salt decrease. The result provides practical value and theoretic basis on the further research of the mechanic property of layered rock soil and on the analysis of the stability of Karst underground salt cavity reservoir.

Experiment Research on Basic Mechanic Property of Recycled Concrete with Different Ratio of Recycled Aggregate

The test confects C20, C25, C30, C35 and C40 recycled aggregate concrete, and the percentage of recycled aggregate are 0%, 20%, 30%, 50%, 70% and 100%,the test age of sample are 7d,28d and 56d.Through test, the cube crushing strength,prismatical compressive strength and elasticity modulus of recycled aggregate concrete with different recycled aggregate percentage and different ages are studied, and compare with general concrete. Test show that, with the development of age, the strength development law of recycled aggregate concrete is similar to general concrete; with the increase of amount of recycled aggregate, the strength and elasticity modulus of recycled aggregate concrete shows the trend of decline, and the basic mechanic property of recycled concrete meet the demand of existing criterion.