Physic-mechanical properties of fly ash filling material at early age and its hydration process

Fly ash filling materials at early age have low strength, large deformation, poor liquidity and severe water bleeding. Several experiments on the fly ash filling materials with three different mixing ratios at early age were carried out to study the bulk electrical resistivity, the electrical resistivity of pore solution, the uniaxial compressive strength and the elastic modulus varied with time. The porosity variation with time was analyzed with the initial porosity and measured 1 d porosity of the filling material. The bulk resistivity was found to increase-decrease-increase with time. The resistivity of pore solution decreased firstly then tended to a stable value. Both the bulk resistivity and the resistivity of pore solution were influenced by the dosage of fly ash. The uniaxial compressive strength and elastic modulus increased with the extending of the hydration time, but decreased with the increase of the dosage of fly ash. The porosity decreased inversely exponentially with the extending of hydration time and decreased firstly then increased with the dosage of fly ash. In the late age of hydration, both the uniaxial compressive strength and elastic modulus were related to bulk resistivity logarithmically. The hydration process at early age can be divided into four stages, such as adsorption period, a dissolution period, setting period and hardening period. © 2016, Science Press. All right reserved.