| 摘要: | 水泥的水化行為對高性能混凝土的工作性有相當大的影響，亦會影響其硬固性質，如強度、體積穩定性與耐久性等，因此了解及控制水泥水化至凝結期間之化學及力學動態變化便非常重要，而混凝土的凝結時間及硬化速率，係受水泥水化反應及形成水泥顆粒間之化學鍵結所控制。 強塑劑之使用，對高性能混凝土工作性及強度發展有相當大的影響。目前國內各種強塑劑之成份、特性和分子量差異甚大，且水泥之四種主要單礦物各自有不同且複雜的水化機理，但強塑劑與水泥水化間之相互作用機理仍未相當清楚。因此本研究藉由量測孔隙溶液離子濃度、水化熱、凝結時間變化，迷你坍流面積、Marsh cone流動時間、黏滯度等流變行為，配合吸附行為及熱重分析、SEM、X光繞射分析等試驗，以探討SNF、SMF及PCA型強塑劑、卜作嵐材料對C3A、C3S及水泥材料水化行為之影響，以期對各材料之應用有較佳之掌握。 研究結果顯示，添加強塑劑時，由於吸附作用將延緩C3A、C3S及水泥之水化行為和各水化產物之成長速率及形態，使得凝結時間及水化放熱峰因強塑劑的添加而延緩，且隨劑量之增加，延緩之現象更為明顯，而吸附於C3A上之量大於C3S者。水泥對SNF及SMF型強塑劑之吸附行為均屬單層吸附，低濃度時吸附量會隨劑量之增加而增加，但當吸附飽和時，吸附量反會緩慢減少，但PCA型強塑劑之吸附行為則異於前二者。 SNF和SMF強塑劑的特性相似，在拌合後短時間內即可使漿體產生流動性，羧酸類強塑劑因作用機理不同，其效益在30分鐘後才顯現。水泥、卜作嵐材料對強塑劑的吸附特性，與漿體的流動性有相當程度的關係。迷你坍流度試驗和Marsh cone流動時間試驗可相互印證，即坍流度大，則Marsh cone流動時間減少。利用Marsh cone流動時間試驗，可量測SNF和SMF強塑劑的飽和點，二者的飽和點均為1.2%，羧酸類強塑劑因作用機理不同，不適合利用Marsh cone流動時間試驗量測其飽和點。在各種不同卜作嵐材料使用策略中，以飛灰取代15%、30%水泥會降低漿體的流動性。以水淬爐石粉取代50%水泥可增加漿體的流動性。 Improvement in the engineering properties of high performance concrete relate not only to strength and durability, but also workability, fluidity and feasibility of adaptation on constructions. Better understanding and control of the dynamic properties of cement during hydration is very important. Slump loss, setting time and hardening rate depend on hydration reaction of cement, and on the establishment of chemical bonds between cement particles. The workability and the strength development of high performance concrete are highly dependent on the addition of superplasticizer(SP). However, the compositions, properties, and molecular weight for various brands of SP are quite different. The four major components contained in cement have complicate hydration mechanism. The interactions between SP and cement during hydration are not fully understood. This study is to investigate the effects of sulphonated naphthalene formaldehyde condensates (SNF), sulphonated melamine formaldehyde condensates (SMF) and polycarboxylic acid (PCA) SP on the hydration of tricalcium aluminate, tricalcium silicate and cements. Measurements included setting time, heat of hydration, the spread area of mini slump, the flow time of Marsh cone, and the rheological behavior of the pastes. adsorption characteristics of SP on cement particles, ion concentrations in the aqueous phase of cement paste, thermogravimetric analysis, SEM and X ray diffraction analysis, in order to have a better information of the application strategy of every materials. Test results showed that the adsorption of SP on solid particles resulted in retardation of C3A, C3S and cement hydration, the rate and morphology of hydration products. The setting time and the peak of hydration heat were delayed by the addition of SP. The retarding effect of SP is more apparent along with increasing of dosage. A larger amount of SP was rapidly adsorbed onto C3A compared to that on C3S. The adsorption of SNF and SMF SPs on cement particles was monolayer adsorption. The amount of adsorption was increased with increasing the concentration of SP. When the adsorption has attained saturation, the amount of adsorption was decreased if the concentration of SP was still increased. But, the PCA SPs is Different on adsorption behavior. The that SNF and SMF SPs are equally effective in making the paste flowable within a few minutes. The PCA SP added paste showed its flowability after 30 minutes of mixing. The flowability of the paste was closely related to the adsorption characteristics of SP on cement particles. A good correlation exists between the results of the minislump test and these of the Marsh cone test. The increase in the spread area of the mini slump test was increased when the flow time was decreased in the Marsh cone test. The Marsh cone test was good for measuring the saturation points of SNF and SMF SPs both of which were 1.2%. It was not suitable for PCA SP. The use of fly ash to replace a portion of cement could reduce the flowability of the paste. However, the flowability was increased when blast furnace slag was used to replace 50% of cement. |
