含貝殼海砂混凝土工程性質研究

Abstract

為探討海砂做為混凝土細骨材使用之可行性，本研究將含有貝殼之海砂做 為研究對象，探討台灣西海岸及澎湖地區海砂骨材中，含有不同數量及形 狀的貝殼，對混凝土工程性質的影響。研究中海砂骨材採取五種貝殼含量 ､兩種貝殼形狀，配比設計採兩種坍度､四種水灰比的條件下，探討各種 含貝殼海砂混凝土的工程性質，其中包括工作度､抗壓強度､抗拉強度､ 耐久性､透水性､凝結､乾縮等。並依試驗結果來評估海砂中貝殼形狀及 貝殼含量，是否會對混凝土工程性質造成不良的影響。研究結果顯示海砂 中貝殼含量增加會提高海砂細度模數，且降低海砂混凝土乾縮量，對抗壓 強度沒有不良影響，但是對混凝土耐久性會有不良影響。以貝殼形狀而言 ，扁平貝殼對海砂混凝土之工作性與擴散係數均會產生不良影響；圓形貝 殼對提昇海砂混凝土之工作性與抗壓強度均有幫助。扁平貝殼用水量及乾 縮量較圓形為大，但其抗拉強度較圓形貝殼高。評估結果認為海砂中圓形 貝殼含量越多，配比設計較具經濟性。 而海砂混凝土與河砂混凝土比較 ， 海砂中含圓形貝殼60﹪以上，配比用水量比河砂少，但海砂之抗拉強 度及耐久性較河砂差。 In order to conform the usability of offshore sand for concrete aggregate , the effects of sea-shells in marine aggregate will be studied . Five different shell contains amount and two different shapes of sea-shells will be discussed . Under the conditions of two slump and four water-cement ratio , some fresh and hardened concrete properties will be investigated . The properties include workability , settling , compressive strength , shrinkage , durability etc . Based on the test results , we expect that the permissible amount and shape or size of sea-shells in fine aggregate can be determined . Form the studies , it shows that increasing contents of shell will increase fineness modulus , improve compressive strength and dry shrinkage of concrete , but have loss of durability . For shell shape , flat shell reduce the workability and increas cofficient of diffusion , but have the advantage of splitting tensile strength . Cycloid shell will be advantage of workability , compressive strength and reduce cofficient of diffusion of offshore sand concrete . Flat shell need more water and have more dry shrinkage than cycloid shell . That of using more cycloid shell will get an economic concrete mixing proportioning .