Experimental study on performance of cement-based grouts admixed with fly ash, bentonite, superplasticizer and water glass

This paper deals with the coupled effect of temperature and silica fume addition on rheological, mechanical behaviour and porosity of grouts based on CEMI 42.5R, proportioned with a polycarboxylate-based high range water reducer. Preliminary tests were conducted to focus on the grout best able to fill a fibrous network since the goal of this study was to develop an optimized grout able to be injected in a mat of steel fibers for concrete strengthening. The grout composition was developed based on criteria for fresh state and hardened state properties. For a CEMI 42.5R based grout different high range water reducer dosages (0%, 0.2%, 0.4%, 0.5%, 0.7%) and silica fume (SF) dosages (0%, 2%, 4%) were tested (as replacement of cement by mass). Rheological measurements were used to investigate the effect of polycarboxylates (PCEs) and SF dosage on grout properties, particularly its workability loss, as the mix was to be injected in a matrix of steel fibers for concrete jacketing. The workability behaviour was characterized by the rheological parameters yield stress and plastic viscosity (for different grout temperatures and resting times), as well as the procedures of mini slump cone and funnel flow time. Then, further development focused only on the best grout compositions. The cement substitution by 2% of SF exhibited the best overall behaviour and was considered as the most promising compared to the others compositions tested. Concerning the fresh state analysis, a significant workability loss was detected if grout temperature increased above 35 °C. Below this temperature the grout presented a self-levelling behaviour and a life time equal to 45 min. In the hardened state, silica fumes increased not only the grout’s porosity but also the grout’s compressive strength at later ages, since the pozzolanic contribution to the compressive strength does not occur until 28 d and beyond.

https://repositorio.ipl.pt/bitstream/10400.21/2796/2/Development%20of%20an%20injectable%20grout%20for%20concrete%20repair%20and%20strengthening.rep.pdf

Development of an injectable grout for concrete repair and strengthening

Performance and hydration study of ultra-fine sulfoaluminate cement-based double liquid grouting material

Rheological and mechanical properties of microfine-cement-based grouts mixed with microfine fly ash, colloidal nanosilica and superplasticizer

Investigation on fundamental properties of microfine cement and cement-slag grouts

Three different cements (CEM I, CEM II/B-M and CEM IV/B according to EN 197-1) containing 0%, 23.5% and 38% of pozzolan, respectively, were pulverized to obtain three additional gradations from each cement, with nominal maximum grain sizes of 40, 20 and 10 μm. Cements with the two finer gradations are classified as “microfine” cements. Suspension properties, groutability and effectiveness of all cements were evaluated for water-to-cement ratios (W/C) of 1, 2 and 3 by weight. A superplasticizer was used to optimize rheological properties. The properties and performance of all suspensions tested are affected primarily by W/C ratio and cement fineness. All microfine cement suspensions have acceptable apparent viscosity, behave as Bingham fluids, are stable for W/C = 1, have reasonable setting times for field applications, have mostly predictable groutability and provide satisfactory strength to grouted sands. The finer gradations of II/B-M cement exhibited the best overall behavior and are considered as the most promising compared to similar gradations of the other two cements.

Development of microfine cement grouts by pulverizing ordinary cements

The hydraulic conductivity of 54 sand-sized crushed limestone materials was measured by conducting constant head tests in a rigid-wall permeameter and was estimated using six predictive equations requiring easily obtainable parameters. The gradations tested had effective grain size, D10, from 0.079 to 2.15 mm; uniformity coefficient, Cu, from 1.19 to 15.79; and void ratio, e, from 0.42 to 0.76. The measured hydraulic conductivity had a range of about three orders of magnitude (3.4*10−3 to 3.3 cm/s). Four of the predictive equations, based on the square of the effective grain size, D102, yielded closely grouped results differing by not more than a factor of 2. Long existing equations by Terzaghi (1925) and by Hazen (1892), adjusted for void ratio according to Taylor (1948), were found to have a high predictive efficiency with a ratio of predicted to measured values between 1/2 and 2 for 70% of the materials tested. The Kenney et al. (1984) equation, based on D52, was also efficient but underestimated measured values for 63% of all cases. The Kozeny–Carman equation (Taylor 1948; Chapuis 2012), based on specific surface, overestimated measurements for 90% of the tested materials by a factor of up to 3.

Predicted and measured hydraulic conductivity of sand-sized crushed limestone

An experimental investigation was conducted to evaluate the influence of factors pertinent to the suspension and the sand on the effectiveness of microfine cement grouts under quick loading conditions, that is, conditions, where the grouted soil mass is loaded at a rate which is much faster than the rate of pore water pressure dissipation and total stress behavior may be of interest Unconfined compression and unconsolidated-undrained triaxial compression tests were conducted on grouted sand specimens obtained by injecting suspensions of 12 cements with three water to cement (W/C) ratios into four sands with different grain sizes A Mohr–Coulomb type linear failure criterion describes satisfactorily the shear strength behavior of cement grouted sands in total stress terms The values of the activated shear strength parameters generally increase with increasing axial deformation during loading Grouting with suspensions having W/C = 1 yields unconfined compression strength of grouted sands up to 9 MPa, adds cohesion to the sands reaching 17 MPa, increases by 6–14 times the initial modulus of elasticity, reduces by 5–10 times the failure deformation and may increase up to 20% the angle of internal friction of the sands The stress–strain–strength behavior of sands grouted with suspensions having W/C = 1 is similar to that of cement suspension sediments with the same W/C ratio, whereas the behavior of sands grouted with suspensions having W/C = 3 is similar to that of the clean sands

Performance of Microfine Cement Grouted Sands Under Quick Loading Conditions

An experimental investigation was conducted in order to evaluate the effectiveness of six new microfine cement grouts obtained by pulverizing three ordinary cements with different chemical composition. Both consolidated-undrained with pore pressure measurement (CU-PP) triaxial compression and hydraulic conductivity tests were conducted on each grouted sand specimen. Grouting increased the stiffness and reduces the hydraulic conductivity of the sands. The shear-strength behavior of the grouted sands was described satisfactorily by the Mohr-Coulomb failure criterion. The bleed capacity of the injected suspensions was a good indicator of the grouting-induced mechanical and hydraulic behavior improvement. Grouting with stable [water to cement ratio (W/C)=1] microfine cement suspensions was superior to grouting with coarser cements at W/C=1, yielded hydraulic conductivity values as low as 5.5×10−8 cm/s, added cohesion reaching 2 MPa and, on the average, increased the initial modulus of elasticity by 10 times, reduced failure deformation by 5 times, and increased the peak strength by 8.5 times. Grouting with unstable microfine cement suspensions provided measurable, but not as pronounced, improvement. A change in stress–strain–strength behavior of grouted sands, associated with the beginning of cementitious bonds breakage, was systematically observed at low axial deformation (0.2%–0.7%). 

Stress–Strain–Strength and Hydraulic Performance of Microfine Cement Grouted Sands

Unconsolidated-undrained (single and multi-stage) and consolidatedundrained triaxial compression tests with pore water pressure measurement were conducted to evaluate the deformability and shear strength parameters of microfine cement grouted sands. The effects of cement type and gradation, grout water-tocement ratio (W/C), test type and distance from injection point were investigated. Grouting with microfine cement suspensions improves significantly the stress-strainstrength behavior of sands, the improvement primarily controlled by the W/C ratio of the suspensions, and is, generally, superior to grouting with ordinary cements. Grouting with a thick or a thin suspension (W/C=1 or 3), respectively, increases the initial tangent modulus of the sands by a factor of 13 and 3.5, reduces the strain at failure of the sand by a factor of 7.5 and 1.5 and provides the sand with cohesion of about 1500 kPa and 350 kPa.

Ioannis A. Pantazopoulos

Papers

Development of microfine cement grouts by pulverizing ordinary cements

Predicted and measured hydraulic conductivity of sand-sized crushed limestone

Performance of Microfine Cement Grouted Sands Under Quick Loading Conditions

Stress–Strain–Strength and Hydraulic Performance of Microfine Cement Grouted Sands

Triaxial Compression Testing of Microfine Cement Grouted Sands