高水灰比普通混凝土材料性質與力學行為之研究

Abstract

由於國內有些工地，為彌補新拌混凝土在運送過程中所損失的水份，加水 泵送混凝土成很普遍的情況，卻也因未能有效控制用水量，使得混凝土的 品質與原來設計的不符合，之後養護又不確實，導致混凝土品質大大低落 ；再加上近年來許多公共工程弊案叢生，使得一般民眾對於營建工程的品 質，產生很大的疑慮。 本研究乃參考ACI配比設計，以3000psi(W/C=0.75)為標準配比，在材 料組成不變的情況(骨材、水泥量)，模擬工地加水量到水灰比W/C=0.90 與1.15，且同時依照ACI建議配比出兩組水灰比W/C=0.90與1.15試體，再 加上各施以28天水中養護與空氣中養護，以比較之間的力學行為與材料性 質差異。 研究結果顯示，在相同水灰比下，(A/C)骨材/水泥比值愈高抗壓強度 愈大。28天水中/空氣中養護抗壓強度比值，W/C愈低抗壓強度比值愈大， 表示水灰比愈低，養護更加重要；在固定水灰比下，骨材含量愈多抗壓強 度比值愈小。劈裂強度約為抗壓強度的0.09~0.17左右，強度愈低比值愈 大。乾縮量也是水灰比愈高乾縮量愈大，在固定W/C下，水泥含量愈高則 乾縮量愈大。 It is a common condition that transporting fresh concrete by adding water to solve the problem of lossing water during the transporting process in some worksite in internal.However, because they don*t effectively control the water use amount,so they can*t get the concrete quality they designed.And the concr ete quality is bad because of incorrectly curing.Further more,public engineeri ng abuses occures so often recently. Based on the above descriptions,many peop le feel suspect on the quality of structure e The study takes 3000PSI(W/C=0. 75) as the standard proportion design according to ACI code.We take the same c omponent(aggregate,cement) of conerete in each experiment,adding water to W/C =0.90 and W/C=1.15. We make two set specimens of W/C=0.90 and W/C=1.15 accordi ng to ACI code,and treat them of 28days water curing and air curing to compare the differences of mechanic behavior and material property. The research re sult points out that under the condition of same water-cement ratio,the compre ssive strength increases with the increasing of the value of (A/C)aggregate/ce ment.The value of 28days water-curing/air-curing compressive strength will be larger when W/C is lower.It indicates that curing is more important when W/C i s lower.When the aggregate content is more,the value of 28days water-curing/ai r-curing compressive strength is lower.Splitting tensile strength is about 9%~ 17% of compressive strengt