(Note that some of this is also shown on the previous screen)
Pairs of reinforced concrete slabs were held in clamps, braced against deflection and spaced apart with shims to form cracks of various widths, which were grouted. At the centre of the upper slab of each pair, grout was applied through standpipe fittings identical with those on regular grout holes, and then it travelled out from the hole After the grout had set the slabs were separated and the quality of the filling was examined. Bleed voids and discontinuous filling were found to be dominant apart from tests where thick grout had been used. Various crack sizes were tested using grouts of differing water : cement ratios, mixing methods and sometimes additives.
The tests were given particular validity by the use of full size equipment operated by regular grouting crews on a large grouting site. There was no scaling down such as can be necessary in laboratory testing. Supervision and direction of the research was by site engineers and by the author who were all employees of a State Government organisation: the Water Conservation and Irrigation Commision, NSW, Australia.
A full report has not previously been publicly available although extracts were included in the 1985 paper "Cement grouting: water minimising practices." by A.C.Houlsby, Issues in Dam Grouting. American Society of Civil Engineers, Denver, pages 34-75.
A fuller description of the results follows later.
The cracks between slabs tapered from 0.06 inch [1.5 mm] or 0.12 inch [0.3mm] to zero. The water : cement ratios were by volume.
This photo shows examples of grouting found when upper slabs were lifted off. The crack width in the two tests at mid-photo were open 0.06 in [1.5 mm] at the near side and zero at the far side. The grout was 3 : 1 starting mix (Tests 4 and 5).
Poor grouting produced by very thin grout. This was 8 : 1. The floor of the crack has only a paint-thickness of hard cement on it; grout reached up to the roof of the crack in only a few isolated places. The matchbox gives scale (Test 8).
Good crack-filling produced by 1 : 1 grout. A few pockets of bleed water were found. The crack had been filled to the top. (Test12) The soft rubber used to close off the perimeter of the crack can be seen.
Assessment of the success (or otherwise) of the grouting was made in terms of the degree of filling, leading to these conclusions:
The tests were carried out during foundation grouting at Burrendong Dam, near Wellington New South Wales, Australia.
Closeup of part of a test using 3 : 1 grout from a paddle mixer, at right (Test 4).
This test also used 3 : 1 grout, but it was mixed in a high-speed, high-shear mixer (Test 5). Note the improved amount of filling but bleed passages persist. This photo is at the same scale as that above.
Almost zero filling resulting from use of 5 : 1 grout, paddle mixed. Just a coating of grout on the floor with large areas of bleed passages and some bleed craters (Test 2). At same scale as the other photos.
1 : 1 grout in a fine crack. Note the fringe around the limit of penetration at about 1.5 ft [0.4 mm] and the many bleed passages left. The injection hole is at the centre. This photo shows almost the full slab and is at a different scale to the photos above. (Test 6).
The tests were carried out between pairs of reinforced concrete slabs each 3 ft x 3 ft x 2 in[0.9 m x 0.9 m x 50 mm], securely braced against deflection and bolted and clamped together with shims between the slabs to provide test cracks of various sizes. The cracks were tapered with zero opening one side and either 0.06 inch [1.5 mm] or 0.12 inch [3 mm] the other side. At the centre of the upper slab, grout was applied through standpipe fittings identical with those on regular grout holes. The grout was thus able to travel radially. After it had hardened the slabs were taken apart and the nature of the grout film was observed and photographed.
The photos show the test setup. Grout was allowed to flow freely out from all four edges of the 0 to 0.06 inch cracks (if it reached them), except in test No. 1. However, a different arrangement was necessary with the 0 to 0.12 inch cracks because of the excessively free flow which would otherwise occur. Therefore foam rubber was used between these slabs near their edges wherever the crack widened out beyond 0.06 inch. This restriction affected radial penetration in these wider cracks and should be kept in mind when reviewing the results. There could, however, occur free bleeding upwards around the bolt holes located near the corner of the slabs.
FEATURES TESTED WERE THE EFFECTS OF:
Prior to grouting, the cracks were saturated with water and this water was drained off except in tests 20 and 21. Grout injection pressure was 30 p.s.i. [2 bars] for the first 15 minutes usually and was then increased to 50 p.s.i. [3.5 bars] and kept at this until 30 minutes after refusal. However, test 1 was kept at 30 p.s.i. throughout because of its very high take.
Most of the tests included attempts to fill bleed voids by giving one or more applications additional to the first at intervals of not less than 24 hours.
All tests were carried out to absolute refusal and pressure was then held on the grout for half an hour.
The following table summarises the testing variables in terms of the test features.
The high speed mixer used was a Colcrete mixer made by Colcrete Ltd., England. The paddle mixer was locally improvised with a vertical spindle. having blades rotating at about 100 revs per minute. The Mono pump was a standard CD 68 unit supplied by Mono Ltd. Australia. The piston pump was a duplex Gardner-Denver, air-operated. In some tests as indicated in the table, the mix was thickened during the application to simulate actual rock grout procedures.
Three tests (Nos. 14, 15 and 16) used additives then marketed in Australia as GF1 and GF2, thought to be lignosulphanites.
Tests 20 and 21 simulated grouting against flowing groundwater pressure, by passing water at 15 ft. head through the crack before, during and after the grouting.
Cement takes are shown in bags or sacks of 94 lbs size, approximately 1 cu. ft. loose volume of cement in each.
In some tests much of this cement left the test slabs at the perimeter or through the bolt holes acting as vents. Even though this was happening grouting was continued until refusal was reached in order to simulate as far as possible conditions around a grout hole from which grout is penetrating to a distance beyond the 1.5 ft [0.5 m] limit represented by the edge of the test slabs. A disadvantage of this method of permitting grout to escape is that cement takes reflect escape conditions rather than being indicative of crack filling considerations. The cement takes in the table and the refusal times shown there should, therefore, not be regarded by themselves, as giving indicative comparisons between the various factors.
The dominant feature of all tests was the degree of unfilled crack where bleed water had been trapped.
Because the prime purpose of grouting is to effectively fill cracks, an important part of the testing was the assessment of the degree to which this was achieved. In some cases grout did not reach to the roof of the crack. Therefore assessment of the degree of filling was made in three ways:
These estimates were made visually by three engineers including the author. They are subjective, and as can be seen from the photos, very difficult to form.
Cement taken in each application: (a) 0.04 bags in first application, (b) 3.47 in second, (c) 0.01 in third
Time to reach refusal: (a) 15 minutes (b) 45 (c) 15
(a) Grouted up to roof of crack = 40 % of area.
(b) Grouted to within 95% of height (includes (a)) = 90 % of area.
Volume of crack grouted = 90 %
Enlargement of part of the result.
Cement taken in each application: (a) 2.15 bags in first application, (b) 0.01 in second.
Time to reach refusal: (a) 60 minutes (b) 15
(a) Grouted up to roof of crack = 50 % of area.
(b) Grouted to within 95% of height (includes (a)) = 50 % of area.
Volume of crack grouted = 70 %.
Broke up when upper slab lifted. Assessment carried out on broken remains (not shown in photo). Surface was fine powder
Cement taken in each application: (a) 1.12 bags in first application, (b) 0.01 in second.
Time to reach refusal: (a) 15 minutes (b) 15
(a) Grouted up to roof of crack = 5 % of area.
(b) Grouted to within 95% of height (includes (a)) = 5 % of area.
Volume of crack grouted = 30 %
Surface was fine powder
Cement taken in each application: (a) 0.31 bags in first application, (b) 0.02 in second.
Time to reach refusal: (a) 30 minutes (b) 15
(a) Grouted up to roof of crack = 5 % of area.
(b) Grouted to within 95% of height (includes (a)) = 40 % of area.
Volume of crack grouted = 50 %. Surface was fine powder
Cement taken in each application: (a) 2.46 bags in first application, (b) 0.02 in second.
Time to reach refusal: (a) 30 minutes (b) 15
(a) Grouted up to roof of crack = 5 % of area.
(b) Grouted to within 95% of height (includes (a)) = 5 % of area.
Volume of crack grouted = 30 %. Much weak soft powder
Cement taken in each application: (a) 16.43 bags in first application, (b) 0.03 in second.
Time to reach refusal: (a) 45 minutes (b) 15
(a) Grouted up to roof of crack = 15 % of area.
(b) Grouted to within 95% of height (includes (a)) = 40 % of area.
Volume of crack grouted = 50 %.
Cement taken in each application: (a) 0.40 bags in first application, (b) 0.03 in second.
Time to reach refusal: (a) 15 minutes (b) 15
(a) Grouted up to roof of crack = 10 % of area.
(b) Grouted to within 95% of height (includes (a)) = 90 % of area.
Volume of crack grouted = 90 %.
Cement taken in each application: (a) 0.20 bags in first application, (b) 0.07 in second.
Time to reach refusal: (a) 15 minutes (b) 15
(a) Grouted up to roof of crack = 25 % of area.
(b) Grouted to within 95% of height (includes (a)) = 25 % of area.
Volume of crack grouted = 30 %.
A different photo of the result, taken in colour and under different light conditions. The limits of penetration can be seen and also the weak fringe effect.
Cement taken in each application: (a) 0.20 bags in first application, (b) 0.07 in second.
Time to reach refusal: (a) 15 minutes (b) 15
(a) Grouted up to roof of crack = 40 % of area.
(b) Grouted to within 95% of height (includes (a)) = 40 % of area.
Volume of crack grouted = 60 %.
A colour enlargement of the top left hand corner. The bond to the upper slab was sufficiently strong to tear its mortar face off in some areas, as seen in the upper photo.
Cement taken in each application: (a) 1.42 bags in first application, (b) 0.02 in second.
Time to reach refusal: (a) 30 minutes (b) 15
(a) Grouted up to roof of crack = 5 % of area.
(b) Grouted to within 95% of height (includes (a)) = 5 % of area.
Volume of crack grouted = 30 %.
Cement taken in each application: (a) 13.05 bags in first application, (b) 0.02 in second.
Time to reach refusal: (a) 90 minutes (b) 15
(a) Grouted up to roof of crack = 5 % of area.
(b) Grouted to within 95% of height (includes (a)) = 40 % of area.
Volume of crack grouted = 60 %.
Cement taken in each application: (a) 7.34 bags in first application, (b) 0.03 in second.
Time to reach refusal: (a) 45 minutes (b) 15
(a) Grouted up to roof of crack = 5 % of area.
(b) Grouted to within 95% of height (includes (a)) = 20 % of area.
Volume of crack grouted = 40 %.
Cement taken in each application: (a) 2.88 bags in first application, (b) 0.03 in second.
Time to reach refusal: (a) 30 minutes (b) 15
(a) Grouted up to roof of crack = 5 % of area.
(b) Grouted to within 95% of height (includes (a)) = 5 % of area.
Volume of crack grouted = 15 %.
Cement taken in each application: (a) 117.88 bags in first application, (b) 0.08 in second.
Time to reach refusal: (a) 210 minutes (b) 15
(a) Grouted up to roof of crack = 50 % of area.
(b) Grouted to within 95% of height (includes (a)) = 95 % of area.
Volume of crack grouted = 95 %.
At right is an enlargement of top left hand corner.
Cement taken in each application: (a) 11.46 bags in first application, (b) 0.07 in second. Note error on sign.
Time to reach refusal: (a) 30 minutes (b) 15
(a) Grouted up to roof of crack = 25 % of area.
(b) Grouted to within 95% of height (includes (a)) = 25 % of area.
Volume of crack grouted = 30 %.
The small photo at right is an enlargement of the top, left of centre and the photo below shows the test in colour.
Cement taken: 0.47 bags. One application only.
Time to reach refusal: 15 minutes
(a) Grouted up to roof of crack = 75 % of area.
(b) Grouted to within 95% of height (includes (a)) = 75 % of area.
Volume of crack grouted = 85 %.
Cement taken: 1.07 bags. One application only.
Time to reach refusal: 30 minutes
(a) Grouted up to roof of crack = 75 % of area.
(b) Grouted to within 95% of height (includes (a)) = 75 % of area.
Volume of crack grouted = 85 %.
Enlargement of top left hand corner.
Cement taken: 0.40 bags. One application only.
Time to reach refusal: 15 minutes
(a) Grouted up to roof of crack = 75 % of area.
(b) Grouted to within 95% of height (includes (a)) = 75 % of area.
Volume of crack grouted = 85 %.
Enlargement of top left corner.
Cement taken: 9.73 bags. One application only.
Time to reach refusal: 15 minutes
(a) Grouted up to roof of crack = 25 % of area.
(b) Grouted to within 95% of height (includes (a)) = 40 % of area.
Volume of crack grouted = 80 %.
A coloured photo of this test is at right.
Cement taken: 1.45 bags. One application only.
Time to reach refusal: 45 minutes
(a) Grouted up to roof of crack = 30 % of area.
(b) Grouted to within 95% of height (includes (a)) = 40 % of area.
Volume of crack grouted = 50 %.
The result is shown in colour at right.
Cement taken: 61.13 bags. One application only.
Time to reach refusal: 240 minutes
(a) Grouted up to roof of crack = 30 % of area.
(b) Grouted to within 95% of height (includes (a)) = 70 % of area.
Volume of crack grouted = 70 %.
Coloured photo of the result. Damage to the grout occurred during stripping.
Cement taken: 0.40 bags. One application only.
Time to reach refusal: 15 minutes
Grout mostly washed away
Coloured enlargement. Small area damaged where grout torn away.
Cement taken: 0.46 bags. One application only.
Time to reach refusal: 15 minutes
Grout mostly washed away
A coloured photo of the result.
This test used repeated passages of grout through the same crack. For details see comments below.
Some of the percentage filling results are plotted below graphically against the various w : c ratios. Average curves are drawn as a continuous line in the cases of tests using high speed mixing and Mono pumping. and as a dashed line for paddle mixing and piston pumping tests. Tests 1 - 13 and 17 are shown. Omitted are the other tests because of their special variations. Attention is drawn to the fact that only single tests were made for all but one of the factors plotted. This exception was in the case of tests 13 and 17 which were identical in nature. As a measure of the tolerance with which the other results should be viewed it should be noted that tests 13 and 17 gave:
NARROW SIDE OF CRACK
WIDER SIDE OF CRACK
NARROW SIDE OF CRACK
WIDER SIDE OF CRACK
Trends discernible from the graphs and tables and information from the testing are:
Assessment of the success of the grouting in terms of the degree of filling gave these conclusions (also shown earlier in this Report):