Abstract
Grouts have numerous applications including crack repair as maintenance in construction industries. Microfine cements are intensively used for high strength mortar and grout products. They are ideal for injection grouting in structural repair. Such grouts should have suitable rheological properties to be injectable, especially those used in repair and rehabilitation. The use of superplasticizers (SP) in these products is thus becoming increasingly crucial to achieve favorable workability and viscosity properties. A difficulty in such grouts is the plastic shrinkage due to finer particles used. It is thus necessary to determine optimum SP and shrinkage reducing admixture (SRA) dosages for a microfine cement based grout. In this study, a saturation dosage was decided from two Polycarboxylate ether (PCE) based SPs in relation to neat cement using slump flow and rheological parameters. A range of grout mixtures was formulated containing micro silica (MS) and fly ash (FA), and tested for suitable rheological and mechanical parameters. Based on the results, a grout mixture with MS and FA was selected to determine optimum SRA content. According to the results, a SP dosage of 3% by weight of neat cement is sufficient to achieve saturation. The grout material including MS and FA can produce comparable properties to neat cement grout. MS is found to improve compressive strength within the range considered, whereas a higher FA content provides favourable rheological properties. Finally, a SRA dosage of 4%, which could reduce the shrinkage by about 43% after 28d days, is determined for the grout system.
Highlights
Grouting is intensively used for void filling, sealing joints, soil stabilization, and repair of masonry and structural elements [1,2,3]
The variation in flow diameter within first 40 minutes for a constant SP dosage is minimal with a maximum range of 50 mm, indicating that the plasticizers are stable within that period
The results suggest that, despite replacements by supplementary cementitious materials (SCM), comparable slump and strengths are achievable in comparison to neat cement
Summary
Grouting is intensively used for void filling, sealing joints, soil stabilization, and repair of masonry and structural elements [1,2,3]. The design of the grout as well as the method of its applications must satisfy a series of performance requirements including nature of defects. The efficiency of such grouting depends on the material rheology, injectability, and mechanical strength. The cement itself is sometimes not sufficient to achieve desirable properties In such situations, special admixtures and supplementary cementitious materials are introduced. High strength grouts require low water content, which reduces workability and increases viscosity. For this reason, superplasticizers (SPs) are often used to modify the workability of mixture. Viscosity parameters were measured after 10 minutes after the end of mixing
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