Evaluation Of Concrete Mix Ratio And Temperature Control Measyres For Laxiwa High Arch Dam

Laxiwa dam is logarithmic spiral double-curvature thin arch dam with the height of 250 m,the annual average temperature 7.2? the annual temperature in the range of 24.7?,the temperature variation are lager,dry climate,big evaporation,a longer winter construction,combined with the higher strength grade dam concrete?the annual construction.The superposition of a variety of factors make the laxiwa arch dam temperature control problemsget extremely challenging and become one of the key issues affecting the safety of the dam.This article has made the detailed introduction for the selection of proportion of raw materials and performance test of concrete,and put forward temperature control measures.for high arch dam in the cold areas and high altitudes.During later observation,the dam is found no apparent temperature cracks,and the dam temperature control effect is good.Finally get the following conclusions:(1)The optimization of concrete raw materials,optimization of the mix proportioning of the concrete and the heat no.42.5 in Portland cementadding high quality I grade fly ash and high efficiency water reducing agent,air-entraining agent,The dosage of fly ash can be increased to 35%to reduce the cement hydration heat temperature rise and improve anti-cracking performance of concrete itself;(2)Concrete anti-cracking requirementfor the high arch dam is high in the cold area,the dam has the more strict temperature controls.Temperature and stress the "double standards" should be adopted to control.The foundation concrete anti-crack safety coefficient should not be less than 1.8?2.0;(3)Winter concreting is given priority to with heat storage construction,try to avoid low temperature opening concreteat night time;If the average temperature is below-10?,the comprehensive heat storage method must be adopted.Heating water and preheating aggregate should be taken to increaseconcrete machine outlet temperatureto ensure the concrete pouring construction temperature at 5??8?.(4)Strengthen the dam surface heat,prevent concrete surface from producing cracks.For a permanent exposed surface,such as the upstream and downstream dam surface,annual heat preservation should be taken;The side face of dam block should be taken ways of temporary heat preservation.From the monitoring data,the effect of temperature control measures is good.During construction,the control of concrete warehousing temperature,pouring temperature is good,the early and late cooling temperature of concrete meet the design requirements;At run time,the dam does not appear cracks that influence dam safety.