Conventional superplasticizers based on polycarboxylate ether (PCE) show an intolerance to clay minerals due to intercalation of their polyethylene glycol (PEG) side chains into the interlayers of the clay mineral. An intolerance to very basic media is also known. This makes PCE an unsuitable choice as a superplasticizer for geopolymers. Bio-based superplasticizers derived from starch showed comparable effects to PCE in a cementitious system. The aim of the present study was to determine if starch superplasticizers (SSPs) could be a suitable additive for geopolymers by carrying out basic investigations with respect to slump, hardening, compressive and flexural strength, shrinkage, and porosity. Four SSPs were synthesized, differing in charge polarity and specific charge density. Two conventional PCE superplasticizers, differing in terms of molecular structure, were also included in this study. The results revealed that SSPs improved the slump of a metakaolin-based geopolymer (MK-geopolymer) mortar while the PCE investigated showed no improvement. The impact of superplasticizers on early hardening (up to 72 h) was negligible. Less linear shrinkage over the course of 56 days was seen for all samples in comparison with the reference. Compressive strengths of SSP specimens tested after 7 and 28 days of curing were comparable to the reference, while PCE led to a decline. The SSPs had a small impact on porosity with a shift to the formation of more gel pores while PCE caused an increase in porosity. Throughout this research, SSPs were identified as promising superplasticizers for MK-geopolymer mortar and concrete.

中文翻译：

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由淀粉制成的生物基增塑剂对新鲜和硬化的偏高岭土-地质聚合物砂浆性能的影响：基本调查

由于聚乙二醇 (PEG) 侧链嵌入粘土矿物的夹层中，基于聚羧酸醚 (PCE) 的常规超塑化剂对粘土矿物不耐受。对非常基本的媒体的不容忍也是众所周知的。这使得 PCE 不适合用作地质聚合物的超增塑剂。源自淀粉的生物基减水剂在水泥体系中表现出与 PCE 相当的效果。本研究的目的是通过对坍落度、硬化、压缩和弯曲强度、收缩率和孔隙率进行基础研究，确定淀粉超塑化剂 (SSP) 是否可以作为地质聚合物的合适添加剂。合成了四种 SSP，它们的电荷极性和比电荷密度不同。两种常规的 PCE 减水剂，在分子结构方面不同的，也包括在本研究中。结果表明，SSP 改善了偏高岭土基地质聚合物（MK-地质聚合物）砂浆的坍落度，而 PCE 研究显示没有改善。超塑化剂对早期硬化（最多 72 小时）的影响可以忽略不计。与参考相比，所有样品在 56 天的过程中都看到较少的线性收缩。固化 7 天和 28 天后测试的 SSP 试样的抗压强度与参照物相当，而 PCE 导致下降。SSPs 对孔隙率的影响很小，会形成更多的凝胶孔隙，而 PCE 导致孔隙率增加。在整个研究过程中，SSP 被确定为有前途的 MK-地质聚合物砂浆和混凝土的减水剂。结果表明，SSP 改善了偏高岭土基地质聚合物（MK-地质聚合物）砂浆的坍落度，而 PCE 研究显示没有改善。超塑化剂对早期硬化（最多 72 小时）的影响可以忽略不计。与参考相比，所有样品在 56 天的过程中都看到较少的线性收缩。固化 7 天和 28 天后测试的 SSP 试样的抗压强度与参照物相当，而 PCE 导致下降。SSPs 对孔隙率的影响很小，会形成更多的凝胶孔隙，而 PCE 导致孔隙率增加。在整个研究过程中，SSP 被确定为有前途的 MK-地质聚合物砂浆和混凝土的减水剂。结果表明，SSP 改善了偏高岭土基地质聚合物（MK-地质聚合物）砂浆的坍落度，而 PCE 研究显示没有改善。超塑化剂对早期硬化（最多 72 小时）的影响可以忽略不计。与参考相比，所有样品在 56 天的过程中都看到较少的线性收缩。固化 7 天和 28 天后测试的 SSP 试样的抗压强度与参照物相当，而 PCE 导致下降。SSPs 对孔隙率的影响很小，会形成更多的凝胶孔隙，而 PCE 导致孔隙率增加。在整个研究过程中，SSP 被确定为有前途的 MK-地质聚合物砂浆和混凝土的减水剂。