Study On Control Measures To Crack In Wall Filled With Stone Ballast Concrete Hollow Block

Spot investigating results revealed, subjective factors causing crack in wall filled with stone ballast block can be eliminated by intensifying instruction, strengthening management and strict overseeing. And external causes, out of objective factors, can only be improved step by step, though they can't come to rectification at once.However, it is a key problem that shrinkage of stone ballast block is an internal cause of crack, so the leading idea of remedial works of crack should focus on"eliminating internal causes"rather than"external treatment of crack". If stone ballast block blended with shrinkage-reducing agent, polypropylene fiber and expansion agent can reduce its own shrinkage while can't worsen its own other properties, it is undoubted that modification of stone ballast block is beneficial to prevent crack in wall filled with stone ballast block, because these modification materials can respectively reduce, restrain and compensate shrinkage of concrete.An experimental study on modification of a sort of concrete which stone ballast block is made of was first. The influence of shrinkage-reducing agent, polypropylene fiber and expansion agent on strength and dry shrinkage of the concrete were systematically tested. The testing results and theoretical analysis showed that they can respectively reduce, restrain and compensate shrinkage of the concrete, while can't worsen its mechanical property. Among them, shrinkage-reducing agent and expansion agent were more effective to respectively reduce and compensate early age shrinkage of the concrete, on the contrary, polypropylene fiber was the most effective to restrain medium and long-term shrinkage of the concrete.Next was an experimental study on modification of stone ballast concrete small hollow block. The influence of polypropylene fiber, expansion agent and both of them on permeability-resistance and both moisture expansion and dry shrinkage of the block were systematically tested. The testing results and theoretical analysis slowed that they all can improve its properties, among which polypropylene fiber can most effectively restrain it's moisture expansion and drying shrinkage; however, the block doubly blended with polypropylene fiber and expansion agent will be likely to most beneficially improve crack-resistance of wall filled with the block.After all, there came an experimental study on modification of wall filled with stone ballast block. The influence of polypropylene fiber, expansion agent and both of them on moisture expansion and dry shrinkage of the filled wall were systematically tested. The testing results and theoretical analysis slowed that polypropylene fiber was the most beneficial to restrain it's moisture expansion and drying shrinkage, however, the block doubly blended with polypropylene fiber and expansion agent can most beneficially improve crack-resistance of wall filled with the stone ballast block, at the...