Multi-scale characterization of lightweight aggregate and superabsorbent polymers influence on autogenous shrinkage and microstructure of ultra-high performance concrete

IF 7.4 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Construction and Building Materials Pub Date : 2024-11-30 DOI:10.1016/j.conbuildmat.2024.139408

Jingjing Lyu , Shuo Feng , Qingsong Zhang

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Abstract

This study investigates the effects of internal curing agents on the autogenous shrinkage, hydration, and microstructure of ultra-high-performance concrete (UHPC). Lightweight aggregate (LWA) and superabsorbent polymers (SAP) were examined across various dosages as representative internal curing agents. Measurements were taken for the mechanical properties, autogenous shrinkage, and internal relative humidity of the UHPC. The mechanisms of internal curing were analyzed using thermogravimetry, pore structure, and microstructural evaluations. Additionally, porosity and microhardness in the matrix around the fibers and internal curing agents were tested to quantitatively assess their impact on the properties of the UHPC matrix. Results indicate that high dosages of LWA or SAP negatively affect the compressive strength of UHPC. A dosage of 15 % LWA increased flexural strength by 11 %, whereas SAP showed no significant improvement in flexural strength. LWA effectively reduced autogenous shrinkage by 49.4 %-88.8 %, while a SAP dosage of 0.3 % reduced autogenous shrinkage by 82 %. Both LWA and SAP increased porosity by 33.9 %-55.9 %. SAP released water within the matrix, forming voids filled with calcium hydroxide. The interface between LWA and the matrix was dense, with porosity near the LWA and SAP interfaces being 23.5 %-53.9 % and 26.0 %-38.2 % lower, respectively, compared to other areas. The microhardness in the LWA and SAP interface regions was 20 % and 16.2 % higher than in different places. The LWA pre-saturated method can effectively reduce autogenous shrinkage, and 15 % LWA has no adverse effect on mechanical strength.

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轻骨料和高吸水聚合物对超高性能混凝土自收缩和微观结构影响的多尺度表征

研究了内固化剂对超高性能混凝土（UHPC）自收缩、水化和微观结构的影响。轻质骨料（LWA）和高吸水性聚合物（SAP）在不同剂量下作为代表性的内固化剂进行了研究。测量了UHPC的力学性能、自收缩率和内部相对湿度。利用热重法、孔隙结构和微观结构评价分析了内部固化的机理。此外，还测试了纤维周围基体和内部固化剂的孔隙率和显微硬度，以定量评估它们对UHPC基体性能的影响。结果表明，高剂量的LWA或SAP对UHPC的抗压强度有不利影响。15% % LWA的剂量增加了11% %的抗弯强度，而SAP则没有明显的抗弯强度改善。LWA有效降低了49.4 % ~ 88.8 %的自收缩率，而0.3 %的SAP有效降低了82 %的自收缩率。LWA和SAP均可使孔隙度提高33.9 % ~ 55.9 %。SAP在基质中释放水分，形成充满氢氧化钙的空隙。LWA与基体界面致密，LWA和SAP界面附近孔隙度分别为23.5% % ~ 53.9% %和26.0 % ~ 38.2 %。LWA和SAP界面区的显微硬度分别比其他地方高20 %和16.2 %。LWA预饱和法能有效降低自收缩率，15% % LWA对机械强度无不利影响。

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来源期刊

Construction and Building Materials 工程技术-材料科学：综合

CiteScore

13.80

自引率

21.60%

发文量

3632

审稿时长

82 days

期刊介绍： Construction and Building Materials offers an international platform for sharing innovative and original research and development in the realm of construction and building materials, along with their practical applications in new projects and repair practices. The journal publishes a diverse array of pioneering research and application papers, detailing laboratory investigations and, to a limited extent, numerical analyses or reports on full-scale projects. Multi-part papers are discouraged. Additionally, Construction and Building Materials features comprehensive case studies and insightful review articles that contribute to new insights in the field. Our focus is on papers related to construction materials, excluding those on structural engineering, geotechnics, and unbound highway layers. Covered materials and technologies encompass cement, concrete reinforcement, bricks and mortars, additives, corrosion technology, ceramics, timber, steel, polymers, glass fibers, recycled materials, bamboo, rammed earth, non-conventional building materials, bituminous materials, and applications in railway materials.