Effect of different ways of STPP retarder addition on properties of recycled gypsum
Effect of different ways of STPP retarder addition on properties of recycled gypsum
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STPP缓凝剂不同添加方式对再生石膏性能的影响
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Xingxing Qiu
中科院分区：
文献类型：
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作者：
Zhixin Li;J. Peng;Xingxing Qiu
研究了聚磷酸钠对再生石膏性能的影响。采用两种不同的三聚磷酸钠（STPP）添加方式：一种是将STPP添加到巴黎石膏（POP）中，再经过一系列的处理得到再生石膏（R-SP），另一种是将STPP直接添加到再生石膏（R-PS）中。结果表明，STPP增加了R-PS的需水量，延缓了R-PS的水化。就其硬化性能而言，STPP提供了具有松散结构的硬化再生石膏，这导致了比不含STPP的再生石膏（R-P）更低的强度和更高的吸水率。相反，三聚磷酸钠降低了R-SP的需水量，缩短了凝结时间。R-SP还具有致密的结构，这有助于高强度和低吸水率。分析表明，STPP选择性地化学吸附在R-PS晶体的（111）面上，抑制了R-PS晶体c轴方向的生长，导致凝固时间延长和形貌转变，使硬化后的R-PS晶体粗化，导致W/P高，强度低。而低W/P是由于R-SP所具有的小长度半径的棒状晶体和-（PO_3Ca）在R-SP表面所引起的较高的电位绝对值共同作用，使晶体发育完整，重叠紧密，从而使强度提高。
We analyzed the influence of sodium polyphosphate (STPP) on the performances of recycled gypsum (RG). This analysis was performed with two different ways of STPP addition: One was that the STPP was added into Plaster of Paris (POP), then recycled plaster (R-SP) was obtained after a series of processes and the other was that the STPP was directly put into recycled plaster (R-PS). The conclusions confirmed that STPP increased the water demand and delayed the hydration of R-PS. With regard to its hardened performance, STPP provided hardened recycled gypsum with a loose structure which led to the lower strength and higher water absorption than recycled plaster (R-P) without STPP. On the contrary, the water requirement and the setting time were decreased and shortened by STPP in R-SP, respectively. A dense structure was also possessed by R-SP which contributed to the high strength and low water absorption. The analysis shows that STPP is selectively chemisorbed on the (111) face of R-PS crystals, it inhibits the growth in c axis direction, resulting in the extending of setting time and the transformation of morphology, making the hardened R-PS crystals coarsened, which results in high W/P and low strength. Whereas the low W/P is made by both the rod-like crystals of low length-radius possessed by R-SP and the relatively high ζ-potential absolute value caused by — (PO3Ca) on the surface of R-SP, leading to the complete development of crystals and their close overlapping, thus bringing about the increase of strength.