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大掺量矿物掺合料高性能混凝土 1

水泥的相容性 1

矿物掺合料 1

聚羧酸系减水剂 1

质量控制 1

质量稳定性 1

配制与施工 1

高性能混凝土 1

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Effect of mineral additives and permeability reducing admixtures having different action mechanisms on

《结构与土木工程前沿（英文）》 2021年第15卷第5期页码 1277-1291 doi: 10.1007/s11709-021-1752-2

摘要： In this paper, the effect of usage of the permeability reducing admixture (PRA) having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined. For this aim, three commercial PRAs were used during investigation. The effective parameters in the first and third PRAs were air-entraining and high-rate air-entraining, respectively. The second one contained the insoluble calcium carbonate residue and had a small amount of the air-entraining property. Mortar mixes with binary and ternary cementitious systems were prepared by partially replacing cement with fly ash and metakaolin. The hardened state properties of mortar mixtures such as compressive strength, ultrasonic pulse velocity, water absorption, drying shrinkage and freeze–thaw resistance were investigated. The ternary cement-based mixture having both fly ash and metakaolin was selected as the most successful mineral-additive bearing mix in regard to hardened state properties. In this sense, PRA-B, with both insoluble residues and a small amount of air-entraining properties, showed the best performance among the mixtures containing PRA. The combined use of mineral additive and PRA had a more positive effect on the properties of the mixes.

关键词： cementitious system mineral additive permeability reducing admixture mechanical properties durability performance

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Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

Branavan ARULMOLY; Chaminda KONTHESINGHA; Anura NANAYAKKARA

《结构与土木工程前沿（英文）》 2022年第16卷第11期页码 1453-1473 doi: 10.1007/s11709-022-0877-2

摘要： Construction industries have started to utilize manufactured sand (MS) as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain MS, which also produces a considerable amount of microfine aggregate (MFA). The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying MFA levels, specifically 0%, 3%, 6%, 9%, and 12% (by weight) as the partial replacements of MS on bleeding and plastic shrinkage cracking of concrete. In addition to the varying MFA levels, some concrete mixes also included fly ash (FA) and superplasticizer to investigate the effect of free-water content in the mixes. The bleeding test data were taken as on-site measurements, while the cracks from the plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life gradually decreased, while a progressive increase was observed for crack width, crack length, and crack area.

关键词： manufactured sand fresh concrete microfines admixtures shrinkage cracking