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.
Microstructural aspects in a polymer-modified cement
Scanning electron microscopic observations of polymer-free and polymer-modified cements have shown that the polymer particles are partitioned between the inside of hydrates and the surface of anhydrous cement grains. Differential thermal analysis, thermogravimetric analysis, and porosimetry experiments show the retardant effect of the polymer and provide information on changes in porosity.
Proposed Fracture Theory of a Dispersion‐Strengthened Glass Matrix
A fracture theory is proposed for a composite system based on a continuous glass matrix. It is hypothesized that hard crystalline dispersions within the glass matrix will limit the size of Griffith flaws and strengthen the composite. Quantitative relations are derived for the effect of a dispersed phase on composite strength. At low volume fractions of the dispersed phase, the average flaw size is statistically reduced independent of the size of the dispersed particles. At high volume fractions of the dispersed phase, the average flaw size is governed by the average distance between particles dispersed in the matrix. The strength of a composite should, therefore, be a function of the volume fraction of the dispersed phase at low volume fractions and dependent on both the volume fraction and particle size of the dispersed phase at high volume fractions. For verification of the theory, cross-bending strengths were measured on a sodium borosilicate glass containing varying volume fractions of spheroidized alumina over a range of particle sizes. The average distance between dispersed particles ranged from approximately 15 to 500μ. Good agreement with theory was found. Values of glass surface energy calculated from the experimental data agree well with literature data.