煅烧白云石-废弃混凝土对水泥性能的影响

Influence of Calcined Dolomite-Waste Concrete on the Properties of Cement

为促进白云石和废弃混凝土在水泥基材料中的应用,将白云石和废弃混凝土在1200℃下混合煅烧2 h制备一种新型复合掺和料。采用X射线衍射(XRD)仪分析了煅烧白云石-废弃混凝土的矿物组成,研究了煅烧白云石-废弃混凝土对水泥水化、强度和膨胀性能的影响。结果表明,煅烧白云石-废弃混凝土的矿物组成主要为β-硅酸二钙(β-C_(2)S)、CaO和MgO。掺入煅烧白云石-废弃混凝土能有效加快水泥水化,并降低水泥的水化放热量。掺入10%煅烧白云石-废弃混凝土能够有效提高水泥砂浆的后期强度,其60 d抗折和抗压强度分别提高4.7%和3.2%。这是因为煅烧白云石-废弃混凝土中的β-C2S后期水化生成水化硅酸钙(C-S-H)凝胶,有效提高强度。此外,煅烧白云石-废弃混凝土中的MgO和CaO会水化生成Mg(OH)_(2)和Ca(OH)_(2),导致固相体积增加,促进水泥砂浆的膨胀。

In order to promote application of dolomite and waste concrete in cement-based materials,a new type of composite admixture was prepared by calcining dolomite and waste concrete at 1200℃for 2 h.The mineral composition of calcined dolomite-waste concrete(CDW)was analyzed by XRD,and the effects of CDW on hydration,strength and expansion of cement were investigated.The results showed that CDW was mainly composed ofβ-C_(2)S,CaO and MgO.The incorporation of CDW accelerated the hydration of cement and reduced the hydration heat.The later strength of cement mortars could be effectively improved with the addition of 10%CDW,and the 60 d flexural strength and compressive strength were increased by 4.7%and 3.2%,respectively.This is due to the hydration ofβ-C2S contained in CDW generating C-S-H gel in the later age,thus increasing the later strength.Additionally,the hydration of MgO and CaO contained in CDW could produce Mg(OH)_(2)and Ca(OH)_(2),resulting an increase in solid volume and promoting the expansion of cement mortar.