High-performance Cement Grouts Research Articles

Experimental study on preparation and optimization of high-performance cement grouts mixed with chemical additives for capsule grouting technology

With the development of underground space, underground construction inevitably affects the safety of surrounding structures. Capsule grouting technology (CGT) is proposed to protect adjacent structures from the impact of underground construction. This study developed a high-performance cement grout (HPCG) for CGT using chemical additives. The orthogonal test was performed to optimize the material composition and study the synergistic effect of cement additives of HPCG. Then, the microstructure of HPCG was further analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results show that the water-cement ratio shows a significant influence on flowability, bleeding, and compressive strength of HPCG. Then, the retarder presents a dramatic effect on prolonging the setting time (more than 70 h) by hindering the hydration reaction process. As the polycarboxylate superplasticizer content increases from 0 to 0.2%, the flowability of HPCG increases by 81.7%, while the bleeding increases 115.4%. However, the influence of each factor on the performance is not a single target but a synergistic influence, so a comprehensive analysis should be considered to determine the optimal dosage of additives. Accordingly, the optimal design of HPCG can be recommended that 1.0 for water-cement ratio, 0.45% for retarder, 0.2% for polycarboxylate superplasticizer, and 3% for fluid loss additive, which shows high performance for CGT, with the flowability of 28.3 cm, bleeding rate of 1.61%, initial setting time of 71.1 h, 7 days compressive strength of 2.3 MPa.

Effect of solid concentration and shear rate on shear-thickening response of high-performance cement suspensions

Flow performance, placement, and consolidation of concrete are mainly related to its rheology. Rheology of paste plays a key role on rheology of concrete. Cement pastes exhibit complex rheological behavior affected by several physical and chemical factors, including the solid concentration, type and dosage of high-range water-reducer (HRWR), cement characteristics, and shear history. An experimental investigation was carried out to investigate the effect of solid concentration, HRWR–cement combinations, and shear rate regime on pseudoplastic behavior of high-performance cement grouts. Grout mixtures proportioned with w/c of 0.30, various cement–HRWR combinations, 8% silica fume, and different limestone powder additions were investigated.Solid concentration and shear rate regime are shown to be key factors affecting shear-thickening response of concentrated cement-based suspension (i.e. low w/c). Concentrated high-performance grout mixtures are shown to exhibit shear-thickening behavior. The use of polycarboxylate HRWR acting by hindrance effect exhibited greater shear-thickening behavior compared to polynaphtalene type acting by electrostatic effect. The use of finer particles enhances the powder skeleton and ensures polydisperse systems, hence resulting in lower shear-thickening response. For concentrated cement-based suspensions, shear-thickening is due to disorder state, and at higher shear rate, hydrocluster formation is prevailing.

Shear-thickening behavior of high-performance cement grouts — Influencing mix-design parameters

Rheology of concrete is of great importance to its flow performance, placement and consolidation. A full understanding of fresh concrete flow behavior can be achieved through a good understanding of paste rheology. Cement pastes exhibit a complex rheological behavior affected by several physical and chemical factors, including water-to-cement ratio (w/c), high-range water-reducer (HRWR) type and dosage, and cement characteristics. An experimental investigation was carried out to evaluate the effect of w/c, HRWR–cement combinations, and supplementary cementitious materials (SCM) on the pseudoplastic behavior of high-performance cement grouts. Grout mixtures proportioned with w/c of 0.30, 0.33, 0.36, and 0.40, various cement–HRWR combinations, and cement substitutions by 8% silica fume were investigated. The incorporation of HRWR can lower the yield stress of mixtures, thus enhancing deformability, while silica fume improves mechanical and durability performances. High-performance structural grouts are shown to exhibit shear-thickening behavior at low w/c and shear-thinning behavior at relatively higher w/c. Mixtures made with polycarboxylate HRWR acting by steric effect exhibited greater shear-thickening behavior compared to those made with polynaphthalene sulfonate-based HRWR acting by electrostatic effect. The paper discusses the effect of mixture parameters on non–linear rheological behavior of various grout mixtures prepared with different w/c, HRWR–cement combinations, and silica fume.

Repair of 130-Year Old Masonry Bridge using High-Performance Cement Grout

The restoration of a masonry bridge pier built in 1887 was carried out using cement-based grout. Erosion of the pointing mortar of the pier core outer surface and cracks and voids in the pier core were encountered. This paper presents the methodology used to develop high-performance cement grouts for injection of deteriorated joints and cracks in the stone pier and describes the repair and monitoring operations. Portland and microfine cement-based grouts were optimized in the laboratory. An epoxy resin grout was used as a benchmark to compare the performance of the cement-based grouts. The effectiveness of the grout injection was assessed with core samples testing and nondestructive testing using the sonic tomography method to compare the quality of the medium before and after grouting. High penetrability of the grout was achieved for the high-performance mixtures. The use of high-early-strength cement with some silica fume replacement resulted in a relatively economical mixture exhibiting high performance. The results of this pilot study were later recommended for the rehabilitation of similar masonry piers.

Experiment design to evaluate interaction of high-range water-reducer and antiwashout admixture in high-performance cement grout

The injection of cement grout in water-saturated medium and the sealing of anchorages require the use of grout with high resistance to water dilution to enhance in-situ performance. This can be achieved by reducing the W/C and incorporating an antiwashout admixture (AWA) to enhance the stability. Such admixture can increase the viscosity and yield stress and necessitate higher dosage of high-range water-reducer (HRWR) to maintain the desired fluidity. Cement-based grouts with 0.30 to 0.50 W/C and different combinations of AWA and HRWR were evaluated. The study was undertaken to highlight the influence of W/C and dosage of chemical admixtures on fluidity, washout resistance, and residual compressive strength (RCS) of the underwater-cast grout. Statistical models established using a statistical design of experiments indicate that the W/C has greater effect on changes in minislump flow, washout, and RCS than the concentrations of HRWR and AWA. On the other hand, for mixtures prepared with a fixed W/C of 0.40, the models show that measured responses are highly affected by the dosages and interaction of both admixtures. Trade-off between fluidity and washout resistance and means to optimize mixture proportioning to enhance the resistance to water dilution without adversely affecting fluidity are discussed.

High-performance cement grout for underwater crack injection

An investigation was carried out to compare the performance of cement and epoxy resin grouts used for the underwater crack injection of four damaged concrete bridge pier shafts and footings. A blended silica fume cement and microfine cement and a welan gum and a cellulose-based antiwashout admixtures were considered in the grout optimization study. The mixtures were tested for fluidity, viscosity, stability, penetrability, rate of setting, and strength. This paper presents the results of the laboratory evaluation and field repair, including provisions adopted for surface preparation, crack sealing and injection, and quality control. Test results showed that the use of a microfine cement grout with water-to-cement ratio of 0.6 and a high-range water reducer dosage of 2% can produce a balance between critical rheological and mechanical properties. Such grout was found to be tolerant to changes in water-to-cement ratio, high-range water reducer content, and temperature. The grout developed bond strength to submerged concrete similar to that of a high-quality epoxy resin. Despite the lower injection pressure used for the less viscous cement-based grout, the grout intake was 2.8 times greater per linear meter of surface crack than that observed for the epoxy resin grout. The use of sonic tomography to reconstitute the spatial distribution of stress wave velocities within the massive pier footings indicated that the quality of concrete was significantly improved following injection with cement-based grout. This was attributed to the high penetrability of the microfine cement grout. Such quality improvement was less pronounced in the case of injection grouting with epoxy resin. Resume : Une Otude a OtO entreprise afin de comparer la performance des coulis ‡ base de ciment et ‡ base de rOsine-Opoxie utilisOs pour liinjection sous lieau des fissures dans le fst et liempattement de quatre piliers de pont. Un ciment avec fumOe de silice, un ciment microfin, une gomme welan et un autre agent anti-lessivage ‡ base de cellulose ont OtO considOrOs dans lioptimisation du coulis. Les mOlanges ont OtO testOs pour leur fluiditO, viscositO, stabilitO, pOnOtrabilitO, taux de prise, et

High-performance cement grout for underwater crack injection

High-performance cement grout for underwater crack injection

Effect of Welan Gum-High-Range Water Reducer Combinations on Rheology of Cement Grout

The effects of combined additions of welan gum, a commonly used rheology modifier, and naphthalene-based high-range water reducer on the rheological properties of cement grouts are investigated for mixtures made with 0.40 water-to-cement ratios. Grouts with dosages of rheology-modifying admixture varying from 0 to 0.075 percent by mass of cement were prepared. For each group of grout, the concentration of high-range water reducer was varied to obtain four mixtures of various fluidity levels. Measured properties included apparent viscosities at different shear rates, and estimates of plastic viscosity and yield value. Other measurements of consistency included the ease of spread and flow of grout evaluated using the mini-slump and Marsh cone tests, respectively. The grout stability was evaluated by measuring its resistance to water dilution when cast in water as well as its ability to retain water when subjected to sustained pressure (forced bleeding). Initial setting times were determined for selected mixtures. In all, a total of 27 grout mixtures were evaluated. Test results show that the increase in the dosage of rheology-modifying admixture increases significantly the yield value and plastic and apparent viscosities of cement grouts. Combined with an adequate dosage of high-range water reducer, losses in fluidity are regained without significant reduction in stability. With the increase in high-range water reducer dosage, the apparent viscosity at low rates of shear decreases more dramatically than that at high rates of shear due to the pseudo-plastic behavior of such grouts. The combined use of proper dosages of rheology-modifying admixture and high-range water reducer is shown to clearly contribute to securing high-performance cement grout that is highly fluid, yet cohesive enough to reduce water dilution and enhance water retention. For equal fluidity level, greater stability is obtained with mixtures containing high contents of viscosity modifying admixture. The initial setting time is shown to be delayed by the incorporation of high-range water reducer and rheology-modifying admixture with the latter additive exhibiting greater influence on retardation of setting.

High performance cement-based grouts for use in a nuclear waste disposal facility

National and international agencies have identified cement-based materials as prime candidates for sealing vaults in which nuclear fuel wastes will be isolated from the biota. Insufficient information is currently available to allow for reasonable analysis of the long-term performance of these sealing materials in a vault. This paper details some of the major findings from combined laboratory and modelling research programs intended to provide the necessary information for a specially developed high-performance cement-grout. The results indicate that acceptable performance is likely for at least thousands of years and probably for much longer periods. The materials, which have been proven to be effective in field applications, are shown to be virtually impermeable and highly leach resistant under vault conditions. Special plasticizing additives used in the material formulation enhance physical characteristics without detriment to chemical resilience. Neither modelling nor laboratory testing has as yet provided for definitive assessment of longevity. However, none of the results of the studies, to date, have contra-indicated the use of high-performance cement-based grouts in vault sealing applications.