Structural Grouts
Samson Structural Grouts: the obvious choice for excellence. Over 50 years of flooring and concrete repair excellence, transcribed from Samson's Structural Grouts technical guide.
"Non-shrink" explained, "fit for purpose" defined
So-called "non-shrink" structural grouts often fail due to mis-use and an improper understanding of the characteristics of a non-shrink grout. International standards such as those provided by the US Government Corps of Engineers, ASTM, and ISO require that without moisture loss a structural grout must not show dimensional loss within a prescribed number of days. Most cementitious structural grouts show some level of shrinkage due to long-term moisture loss.
Plain cement and sand grouts mixed with special plasticisers, to a flowable or fluid consistency, will shrink within hours due to aggregate settlement and bleeding. With specialised rheology control ingredients, a non-bleed fluid mix provides an initially dimensionally stable plastic phase grout. Expansion-generating chemicals provide longer-term dimensional stability.
Workability and "open times" of structural grouts are also mis-understood. Common expressions such as "dry-pack", "thixotropic", "flowable" or "fluid" need definition:
- Dry-pack often fails due to incorrect installation and insufficient consolidation. A paddle and wooden mallet are needed to hammer the dry-pack in several lifts in order not to leave cavities.
- Plastic pack or thixotropic grout can successfully overcome the arduous process of dry-pack installation.
- Flowable grout is defined by its reaction to flow table drop and is measured by the diameter increase of the grout under kinetic energy.
- Fluid grout is essential for "tortuous path" grouting such as where bolt holes need to be filled, shear keys properly bedded whilst expelling trapped air.
Installation techniques and testing
Installation techniques include shuttering and paddle installation, "letter-box" fluid flow, and pumped and tremie application, as suited for specific circumstances. Samson Advisory services will provide method statements on request.
"Fit for Purpose" means that the grout characteristics enable structural integrity. Expansive grouts without secondary shrinkage compensation are fit for purpose under base plates.
High effective bearing area does not need shrinkage compensation to avoid drying shrinkage cracking, since all the required structural support needed is provided. Conversely, where an exposed area is without vertical restraint, such as a "structural topping", only shrinkage compensation is necessary. Materials such as Samson MicroConcrete should be used. Consult Samson for correct selection and installation method statement.
Testing techniques for fitness compliance are complex if international specifications are adhered to. Simpler laboratory or site tests are capable of separating good quality grouts from unsatisfactory material; Samson can provide simplified fluidity test methods.
International specifications rely on retention of the initial mix water. "Non-shrink" grout placed against a thirsty dry concrete will experience plastic shrinkage and cracking due to moisture loss. Correct pre-saturation is an essential requirement for in-service performance. Where long-term (up to 6 months) drying shrinkage takes place, no cracking will be evidenced unless the shrinkage stress exceeds the tensile resistance of the grout.
Unnecessary high strengths are often quoted as benefits, but adverse side-effects are not mentioned. Realising the need for vastly differing site conditions, Samson provides a variety of grouts to cater for all site conditions.
Before you grout, consult Samson specialists.
There is a myth often repeated by contractors that all grouts are the same
Recognizing that different grout technology is needed to produce "fit for purpose" materials, Samson Technologies offers four different grouts to satisfy different needs on construction sites.
Another common myth is that grout excellence is to be judged by its compressive strength as a main criterion. Strength is the most easily achieved property of a grout mix design. In terms of both ASTM and US Corp of Engineers requirements, grout need only reach 35MPa at 28 days cure. Much more important are properties such as flow retention, total absence of bleed and plastic settlement, effective bearing area, and installation technique.
Samson Grouts have a significant South African track record, having been used in various industrial facilities such as power stations and electrical generating turbines, industrial structures and plants, mining including coal handling plants, and water treatment sluice gates and the like.
Grout selection chart
| Application requirement | SuperFlow | HS60 | MS40 | SDP | MicroConcrete |
|---|---|---|---|---|---|
| Early return to service | Yes | Yes | No | Yes | Yes |
| Base plates with bolt hole pockets | Yes | Yes | Yes | No | No |
| Small base plates, easy access, no shims to encapsulate | No | No | No | Yes | Yes |
| Base plates with shims | Yes | Yes | Yes | No | No |
| Continuous heavy duty rails | No | No | No | Yes | Yes |
| Easy access, no bolt hole, thick sections (60mm up to 150mm depth) | No | No | No | No | Yes |
| Use of non-shrink grout for concrete repairs | No | No | No | Yes | Yes |
| Re-surfacing of industrial floor with grout | No | No | No | No | Yes |
| Thick-set repairs of concrete beams, etc | No | No | No | No | Yes |
| Polymer modification for thin-set application | No | No | No | Yes | Yes |
| Skid mounted machinery | No | No | No | Yes | Yes |
How to choose between SuperFlow, HS60 and MS40
| Requirement | SuperFlow | HS60 | MS40 |
|---|---|---|---|
| Require early strength development and quick setting? | Yes | Yes | No |
| Over 60MPa compressive strength needed? | Yes (minimum compressive strength 60MPa if mixed according to literature) | Yes | No (minimum compressive strength lower) |
| Extended flow in hot weather? | No | No | Yes |
| Cost effective, not dependent on compressive strength? | No | No | Yes |
SuperFlow Grout
Samson SuperFlow structural grout is comprised of rapid hardening Cem I 52,5 portland cement, selected aggregates, flow aides, and an expansive component for the preparation of a fluid flow grout by the addition of specified amounts of water only. SuperFlow grout meets the requirements of ASTM C1107 and US Corp of Engineers CRD-C621 for flow strength and dimensional stability.
SuperFlow grout is placeable by pump, letter-box shutter, or tremie methods. Correctly placed to Samson requirements, it achieves exceptional effective bearing area (over 90%), is totally bleed free, and has mild expansion in the plastic phase to overcome any possible settlement.
Composition
SuperFlow Grout contains very clean, specially graded quartz aggregate (maximum particle size 1400 micron) combined with 52,5 Cem I, binders, and specialised chemicals and minerals. The composition, when mixed with water, produces a fluid flow grout for tortuous path filling of base plates, bolt holes, keyways, and the like, where limited access precludes plastic packing.
Flow
By varying water addition rates, the flowability of SuperFlow Grout can be suited to various applications:
- 16% water to mass of grout produces a thixotropic flowable mortar
- 18% water to mass of grout produces a semi self-levelling mortar
- 20% water to mass of grout produces a fluid flow non-bleeding self-levelling grout
Dimensional stability
SuperFlow Grout is designed to be mildly expansive in the plastic phase to final set. Together with the non-bleeding characteristic of SuperFlow Grout, this mild expansion ensures complete contact of the hydrating grout to its encasement.
Compliance
SuperFlow Grout complies to ASTM C1107/CRD-C621.
Strength range (28 days)
| Water/binder ratio | Water/binder | 28-day strength |
|---|---|---|
| 16% | 0.40 | 60 to 65 MPa |
| 18% | 0.44 | 55 to 60 MPa |
| 19% | 0.47 | 50 to 55 MPa |
| 20% | 0.50 | 45 to 50 MPa |
Placing
Various practical requirements of each circumstance for grout placement determine the method and viscosity needed. Do not use SuperFlow Grout for dry-pack grouting. Typical installation is by "letterbox head" shutter or by pump. Techniques required include allowing the liquid grout to flow through and circulate under a base plate to ensure complete filling and expulsion of air. Mix and place promptly. Contact Samson for a method statement for your requirements.
Yield
When mixed with 16% water, the average yield of SuperFlow Grout is approximately 12.5 litres per 25kg bag and approximately 80 bags per cubic metre. Any increase in water addition will increase the yield.
Structural Grout – HS60
Samson HS60 structural grout is comprised of rapid hardening Cem I 52,5 portland cement, selected aggregates, flow aides, and an expansive component for the preparation of a fluid flow grout by the addition of specified amounts of water only. HS60 grout meets the requirements of ASTM C1107 and US Corp of Engineers CRD-C621 for flow strength and dimensional stability.
HS60 grout is placeable by pump, letter-box shutter, or tremie methods. Correctly placed to Samson requirements, it achieves exceptional effective bearing area (over 90%), is totally bleed free, and has mild expansion in the plastic phase to overcome any possible settlement.
HS60 technical data
Description: Samson HS60 grout is a specially formulated fluid flow Portland cement structural grout with a large number of application suitabilities (see grout selection chart above).
Flow: By varying water addition rates, the workability and flow of the grout can be adjusted to meet a number of site requirements.
Dimensional stability: Tested in accordance with the requirements of international standards ASTM C1107 and US Corp of Engineers CRD-C621. HS60 meets the test requirements for dimensional stability and compressive strength. For the grout to be dimensionally stable upon installation, proper care must be taken to ensure that mix-water is not sucked out of the grout by surrounding or juxtaposed concrete. This should be achieved by ensuring that shuttering is leak-proof and that surrounding encasement is adequately pre-quenched with clean water.
Compliance:
- Volume control: Grade A, expands during set
- Fluid flow: exits flow cone within 30 seconds
- Strength: exceeds 35MPa at 28 days
- Temperatures: may be placed from 4 to 32 degrees C
Strength range (28 days):
| Water/Cement | Water/binder | 28-day strength |
|---|---|---|
| 16% | 0.40 | 60 to 65 MPa |
| 18% | 0.44 | 55 to 60 MPa |
Placing: Flow requirements will vary according to specific site requirements. Do not use HS60 for dry-pack grouting. It is designed for fluid flow, where dry-pack or plastic placement is preferred use Samson SDP grout. For high effective bearing area, request a Samson method statement.
Curing: All exposed areas of grout should be covered immediately after placement until set, after which it should be coated with a good quality curing compound (Samson ResinCure).
Yield: At a water addition rate around 4 litres per 25kg bag, yield is 12.5 litres per bag, approximately 80 bags per cubic metre.
Structural Grout – MS40
Samson MS40 structural grout is comprised of blended cement Cem III 32,5 and selected aggregates, flow aides, and an expansive component for the preparation of a fluid flow grout by the addition of specified amounts of water only. MS40 grout meets the requirements of ASTM C1107 and US Corp of Engineers CRD-C621 for flow strength and dimensional stability.
MS40 grout is placeable by pump, letter-box shutter, or tremie methods. Correctly placed to Samson requirements, it achieves exceptional effective bearing area (over 90%), is totally bleed free, and has mild expansion in the plastic phase to overcome any possible settlement. For details of how to choose between HS60 and MS40, see the grout selection chart above.
MS40 technical data
Description: MS40 is a specially formulated fluid flow blended cement (Cem III 32,5) structural grout with a large number of application suitabilities.
Flow: By varying water addition rates, the workability and flow of the grout may be adjusted to meet a number of site requirements. MS40 is better suited to hot weather conditions than HS60, where very early strength is not required.
Dimensional stability: Tested in accordance with the requirements of international standards ASTM C1107 and US Corp of Engineers CRD-C621. MS40 meets the test requirements for dimensional stability and compressive strength. For the grout to be dimensionally stable upon installation, proper care must be taken to ensure that mix-water is not sucked out of the grout by surrounding or juxtaposed concrete. This should be achieved by ensuring that shuttering is leak-proof and that surrounding encasement is adequately pre-quenched with clean water, or using wetted hessian bags to cool down base plates.
Compliance:
- Volume control: Grade A, expands during set
- Fluid flow: exits flow cone within 30 seconds
- Strength: exceeds 35MPa at 28 days
- Temperatures: may be placed from 4 to 36 degrees C
Strength range (28 days):
| Water/Cement | Water/binder | 28-day strength |
|---|---|---|
| 14% | 0.40 | 55 to 60 MPa |
| 16% | 0.44 | 50 to 55 MPa |
| 17% | 0.47 | 45 to 50 MPa |
| 18% | 0.50 | 40 to 45 MPa |
Placing: Flow requirements will vary according to specific site requirements. Do not use MS40 for dry-pack grouting, since it is designed for fluid flow. Where dry-pack or plastic placement is preferred, use Samson SDP grout. For winter or cold condition grouting, HS60 is preferred because of its Cem I 52,5 content.
Curing: All exposed areas of grout should be covered immediately after placement until set, after which it should be coated with a good quality curing compound (Samson ResinCure).
Yield: At water addition of 4.5 litres per 25kg bag, yield is 12.5 litres per bag, approximately 80 bags per cubic metre.
Structural Grout – SDP
Samson Technologies has used the letters SDP to denote that the grout is designed as a standard dry-pack grout, to distinguish it from the fluid flow grouts. SDP is formulated to be installed either as a classical dry-pack (a crumbly but cohesive mix capable of being caulked into place). Samson experience has shown that site personnel all too often do not put sufficient energy into the caulking process, resulting in insufficiently filled cavities with compromised effective bearing area. By adding the specified amount of water described in the technical data sheet, a plastic consistency "thixotropic" mortar may be prepared, with significant improvement in the ease of placement and achievement of full effective bearing area.
Samson has prepared a case study and method statement as used for heavy duty rail grouting at several coal mines and, in particular, at Sasol 2. The incorrectly filled rail depicted a compromised bearing area and failed in less than six months. The correctly filled rail grout has given many years of excellent service without failure.
Thixotropic means that in the passive state the grout does not flow; however, when subjected to kinetic energy, shear thinning takes place at micro particle level and allows the grout to flow. Dimensional stability of SDP grout in the plastic phase is achieved through the inclusion of a mildly expansive agent, which overcomes any tendency for settlement.
SDP technical data
Description: SDP grout is a blend of selected and graded aggregate with CEM I, CEM III, and other pozzolanic fillers, suitably modified with chemicals to produce either a crumbly caulkable mortar or a plastic mortar with thixotropic properties. The mortar is mildly expansive in the plastic phase. Dimensional stability of SDP grout is achieved through two mechanisms: firstly, through the total absence of bleed-water, and secondly, through the inclusion of expansive agents.
Compliance:
- Volume control: Grade A, expands during set
- Consistency: dry pack, thixotropic pourable
- Strength: see table below
- Temperatures: may be placed at 4 to 32 degrees C
SDP grout is an effective corrosion inhibitor.
Strength:
| Age | 16% water | 14% water |
|---|---|---|
| 1 day | 22 MPa | 32 MPa |
| 3 days | 40 MPa | 50 MPa |
| 7 days | 50 MPa | 60 MPa |
| 28 days | 65 MPa | 75 MPa |
Placing: The placing method for SDP grout varies according to the consistency of mortar chosen. Traditional dry-pack requires caulking with a suitable paddle and wooden hammer to ensure proper consolidation. Plastic consistency SDP should be placed by packing against suitably designed shutters and then paddled into place in lifts without requiring a wooden mallet for consolidation; see the Samson method statement as used for rail grouting at Sasol 2. SDP grout mixed to flowable consistency may be poured, rodded, or pumped into place; see the case study document describing the use of thixotropic pumpable SDP grout as used for tensometer duct grouting at Koeberg Power Station.
Curing: All exposed areas of grout should be covered immediately after placement until set, after which it should be coated with a good quality curing compound (Samson ResinCure).
Yield: One 25kg bag of SDP grout yields approximately 11 to 12 litres of mortar.
Structural Grout – MicroConcrete
Samson MicroConcrete is comprised of rapid hardening CEM I 52,5 and other pozzolanic secondary binders and selected aggregates, including a 5mm chip, flow aides, and two expansive components. The expansive components are designed to induce mild expansion during the plastic phase, and then a second, chemically shrinkage-induced compensation to reduce the effects of longer term drying shrinkage.
By addition of a specified amount of water only, or water and diluted polymer emulsions, consistencies fit for different purposes may be achieved, for example semi-self-levelling MicroConcrete applied to the prepared surface inside concrete sewer pipes. The secondary shrinkage compensation mechanism in MicroConcrete makes it suitable for relatively large area repairs of heavy duty concrete floors (see Samson case studies and method statements). A simple device is used for "Armco" profiling of the final layer, and MicroConcrete may be placed in a number of methods according to site requirements; different consistencies will be required, and consultation with Samson will ensure a "fit for purpose" method for particular intricacies is selected. MicroConcrete may also be placed by tremie.
MicroConcrete technical data
Description: Samson MicroConcrete is comprised of rapid hardening CEM I 52,5 and pozzolanic secondary binders and selected aggregates, including 5mm chip, flow aides, and two expansive components.
Consistencies: Mixed with water at the following rates per 25kg bag, MicroConcrete will have the following fresh and hardened properties:
- 2.5 litres per bag: semi-self-levelling consistency
- 3.0 litres per bag: flowable consistency
- 3.5 litres per bag: self-levelling consistency
Strength expectations (MPa):
| Age | 2.5 L | 3 L | 3.5 L |
|---|---|---|---|
| 1 day | 30 | 25 | 20 |
| 7 days | 50 | 45 | 40 |
| 28 days | 65 | 55 | 50 |
| Water/binder ratio | 0.42 | 0.50 | 0.58 |
Variety: MicroConcrete is available as MicroConcrete X, MicroConcrete P, and MicroConcrete P44.
Dimensional stability: Samson MicroConcrete has mechanisms to prevent settlement and is shrinkage compensated to decrease shrinkage stresses which often lead to screed de-bonding.
Installation: Samson installation requirements must be faithfully followed. These include good practice preparation of surfaces, the use of Samson P3 bonder, and proper after-installation protection and curing.
Curing: All exposed areas of grout should be covered immediately after placement until set, after which it should be coated with a good quality curing compound (Samson ResinCure).
Yield: Mixed with 3 litres water, each 25kg bag will yield 11 to 12 litres of mixed concrete, approximately 80 bags per cubic metre.
TowerBase Grout 100 HW
The function of TowerBase Grout 100 HW is to fill the gap between a tower base and its underlying concrete support. The product must have sufficient strength and dimensional stability to resist dynamic stresses transferred to the grout through the base plate, emanating from wind and other causes of kinetic energy transfer.
Installation characteristics must be such that full effective bearing area is achieved for various installation conditions. Critical installation conditions in South Africa include high heat (over 30 degrees C) and low ambient relative humidity (under 35%). Consideration has been given to typical depth of cavity to be grouted, circumference of annulus, and withstanding typical temperatures of steel base plates.
Constituents
TowerBase Grout 100 HW is formulated with CEM I 52,5 as the primary binder and micron-size pozzolanic secondary binders, including PFA, sub-micron and nano-sized fumed silica particulates, for optimum mechanical packing and rheology control. Dimensional stability is catered for by the grout being non-bleed, slightly expansive in the plastic phase, and shrinkage compensated in the early hardened phase. Chemical admixtures are included to provide flowability and delay of early set at low water addition rates. Siliceous aggregate, optimally graded from 75 micron to 5mm, is included for low water demand and mechanical packing, for high strength and excellent in-service performance.
Initial flow and workability retention
Testing has been conducted at water addition rates of 14% and 16% by mass of grout, by an independent laboratory. The tests indicate excellent initial workability and exceptional workability retention (at ambient temperatures of 26 to 27 degrees C).
Hardened properties
Initial trials on TowerBase Grout 100 HW indicate excellent strength development using locally sourced cements.
ISO strengths at water/cement 0.33:
| Age | 16% water | 14% water |
|---|---|---|
| 1 day | 17.5 MPa | 36.5 MPa |
| 3 days | 55 MPa | 62.5 MPa |
| 7 days | 69 MPa | 75.5 MPa |
| 28 days | 87.5 MPa | 96 MPa |
Case study: Tensometer Duct Grouting – Koeberg Nuclear Power Station
A case study in grouting excellence.
The tensometer ducts require a special grout material and a unique method of installation to meet the requirements of complete void filling without any settlement or bleeding of the grout, and maximum elimination of entrapped air.
Development of appropriate materials. The grout material, after mixing with an appropriate quantity of water, needed to produce a plastic consistency mortar with thixotropic properties. This was met by the use of micro particulates with appropriate admixtures to produce shear thinning under the kinetic energy of pumping, and then chelate and hold its dimensions in the passive state after pumping.
The curved shape of the ducts. The curved shape of the ducts precluded the use of fluid flow grouts if the desired void filling requirement was to be met. The curved shape also required an innovative approach to the placement method of the grout for successful installation. Samson believed that its proposals would achieve the desired result, but tests were needed to confirm this.
The test process. Under the guidance and surveillance of Professor Mark Alexander, a test rig was designed and filled with grout. Suitable pipes were obtained to simulate the ducts, but without the curvature being replicated. On completion of the pumping process the grout was allowed to set. Thereafter, an angle grinder was used to cut open a section of the pipe to examine the results. The void filling was adjudged to be excellent and fit for purpose: a modified SDP was used for pumping, with thixotropic properties to facilitate installation.
The unique placement system used. For satisfactory void filling, the grout needed to be placed continuously from one side of the ducts to the other. To contain the thixotropic grout for maximum void filling, a plastic collar was recommended for attachment to the end of the pump pipe. The concept was that, in a similar way to a tremie, under the pressure of the grout back-filling, the collar would cause the pipe to be withdrawn from the duct, leaving a completed filled duct behind it.
Conclusion. The trials having been declared successful, the system described above was actually implemented at Koeberg, with good results.
Case study: Southern Outfall sewer pipe repair
An example of success with Samson MicroConcrete.
Cause of damage. Scouring of the nadir of the 60mm thick concrete pipe was caused by flow of sewerage and abrasion by chemical and solids impact attack.
Repair materials required. The repair materials should be high strength (over 60MPa), resistant to humic acid attack and physical impact. Once placed, it should be dimensionally stable, with absence of shrinkage stress being transferred to the bond line between the original concrete and the new hardened repair material.
The Samson proposal. Scarify and clean the damaged nadir of the pipes. Apply a slightly flexible but powerful bonding layer: Samson P3 Primer, a triple blend polymer modified bonder, was proposed. A special "Armco" pipe profile for the repairs was proposed to reduce the velocity of flow of the aggressive sewerage. Polymer modification was proposed to protect the alkaline matrix of the cementitious repair material. Lowering the Young's Modulus of the hardened repair material would better absorb impact stress, where the brittleness of a high strength material would shatter under impact.
Installation method and profiling. It was considered prudent to have a wearing layer more than the thickness of the pipe, especially at damaged joints. A simple profiling device was developed to shape and increase the protective layer to about 75mm. The MicroConcrete needed to be semi-self-levelling, thixotropic, and capable of holding its wet-state profile when left passive.
Conclusion. The installation, done by Eigenbau, was well executed under Samson's advisory service. Some 5 years after the installation, an inspection was made to determine damage to the MicroConcrete wearing layer. It was estimated that the repair would last for another 20 years before another repair process would be necessary. The Samson process provided a repair which would make pipe replacement unnecessary.
Samson structural grout range summary
| Product | Description |
|---|---|
| SuperFlow | 60MPa traditional fluid flow grout |
| HS60 | High strength fluid flow grout |
| MS40 | Medium strength fluid flow grout |
| SDP | Thixotropic grout, standard dry-pack |
| MicroConcrete | Double shrinkage compensated small aggregate concrete |
| MicroConcrete X | Microcrystalline, double shrinkage compensated small aggregate concrete |
| MicroConcrete P | Polymer modified, double shrinkage compensated small aggregate concrete |
| MicroConcrete P44 | Polymer modified, double shrinkage compensated small aggregate concrete for dynamic load substrates |
| TowerBase Grout 100 HW | High strength special grout for wind turbines |
For a method statement matched to your site conditions, contact Samson Technologies before you grout.