Abstract
Superplasticizer (SP) is essential to enhance the groutability of microfine cement (MC) in civil engineering, however, combined effects of cement type, SP type, amount of SP and water-solid ratio (W/S) on engineering performance of MC are not clear currently. In this research, workability and mechanical properties of superplasticized microfine cement grouts (SMCG) with various SPs are evaluated systematically. Three different MCs (CEM I, CEM II/B-M and CEM III/B based on EN 197-1) and four SPs (one naphthalene-based (N), one melamine-based (M) and two polycarboxylate-based (PCE)) were used to study the effect of grout formulation. The properties investigated included rheological behavior (mini-slump, flowability, time-dependent viscosity and initial viscosity), fresh-state property (bleeding, effective W/S and final setting time), mechanical performance (shrinkage, flexural strength (FS), unconfined compressive strength (UCS), and FS/UCS) and microstructure. The new method of static viscosity was adopted and viscoelasticity was evaluated. The ranges of W/S and SP content were 1.0–2.0 and 0–2.5%, respectively. The results show that the dispersion effects of SP on rheological behavior were followed by PCE, M and N in order of the influence degree. The instability, long-setting and oversaturation were easily caused by excessive SP. SP could be helpful for improving FS or bending toughness. Considering workability and mechanical performance of SMCG, the W/S is suggested to be within 1.5, the optimal amounts of N, M and PCE are recommended as 1.5–2.0%, 1.2–1.5% and 0.9–1.2%, respectively.
Highlights
The grouting technique is achieved mainly through injecting cementitious suspension or chemical liquid under pressure into cracks of concrete structures, openings of rocks, voids of soils, etc. [1–3]
The grouting material should be selected precisely based on workability, practical application requirements, long-term performance, environmental friendliness, etc. [7–9] the cost and environmental friendliness of ordinary Portland cement (OPC) are good, OPC has obvious deficiencies such as low injectability, significant filtration effect, insufficient stability, long setting time, etc
Portland microfine cement (MC) (CEM I), Portland-based MC (CEM II/B-M) and blast-furnace slagbased MC (CEM III/B) from Sunnsy Company were selected as three typical types of cements in Shandong Province in China, considering multiple factors such as performance, practicability and cost
Summary
The grouting technique is achieved mainly through injecting cementitious suspension or chemical liquid under pressure into cracks of concrete structures, openings of rocks, voids of soils, etc. [1–3]. The grouting technique is achieved mainly through injecting cementitious suspension or chemical liquid under pressure into cracks of concrete structures, openings of rocks, voids of soils, etc. The injectability and grouting effects of OPC suspensions are poor especially for micro-cracks (≤0.5 mm) and small voids [10–12]. The injectability of chemical grout is high, they were not environmental friendly especially after the acrylamide poisoning incident in 1974 in Fukuoka. They present poor bonding in moist environment and insufficient long-term performance (chemical stability and creeping) [13,14]. The large-scale application of chemical grout has great limitations especially under the current big backgrounds of green sustainable development, water conservancy and ecological environment restoration
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