TASK 1: NEW CONSTRUCTION MATERIALS

Description of the laboratory testing procedures needed for the testing of construction materials based on PG and FA has been given in Finnish in the report "Laboratoriotutkimusten referenssimenetelmät" and will be given in English in the Design Guide based on the project (2002).

After several preliminary test series the laboratory tests for the first pilot concentrated on two basic alternatives. The first one was to make a new road base course by using a mix of by-products (PG, FA and binder) and the second one was to use a by-product mix to stabilise the current (crushed stone) base course of a road section.

For the new road base course different mixture alternatives were tested for the strength properties affected by external loads, e.g. saturation with water, freeze-thaw cycles. The best mixture for this PG and FA was PG + 10 % FA. One of the best binders was a mixture of blast-furnace slag and cement (7:3) which was then selected for further studies. The studies continued by optimising the binder quantity, as the amount of binder should be kept as low as possible because of the relatively high costs. The tests resulted in a recommended binder quantity of 3 – 6 %. After this the heat conductivity and frost susceptibility were determined for some potentially final mixes. The heat conductivity value tells the insulation capacity of the material, i.e. the lower the heat conductivity value is the better the material insulates and the lower will be the depth of frost. The frost susceptibility is determined by segregation potential. According to the tests all the materials would be slightly frost susceptible.

The laboratory testing for the stabilisation was done similarly. Crushed stone used in these tests was taken from the pilot road: Käänninniementie in Maaninka. Determining of the basic recipe was done in two stages. First, the strength properties of different PG+FA+binder -mixes with crushed stone were tested after a curing time of 28 and 90 days and after water saturation and freeze-thaw tests. For the further testing the mix of crushed stone + 8%(PG+10 % FA) + binder 7:3 was chosen because of satisfactory strength level reached with it. After this the quantity of the binder was optimised. Mixes for this study were made with binder quantity of 3-6 %. The mix having 4 % of binder reached satisfactory good strength levels. According to the tests all the materials would be probably frost resistant. The heat conductivity of crushed stone decreased when it was mixed with phosphogypsum and other materials.

Testing and development of the new material mixes for the sealing purposes, e.g. for groundwater protection and the landfill capping, to demonstrate in the second pilot have been carried out adjacent with the former tests. The final tests concentrated on the water permeability of two basic alternatives: a material containing moraine with PG+FA and binder and the other as a mix of PG+FA+binder.

Tests for the permeability of PG+FA+binder-stabilised crushed stone course were made with crushed stone mixed with 5 – 10 % ( PG+ 10 % FA) and with 0 – 4 % bentonite. The test pieces were made of mixtures made with conventional method and counterstroke mixer. The FA was mainly dry, but also FA that had been deposited in the open air was used. The open-air storage of FA seems to increase the permeability of the mixes. Smallest permeability was obtained with dry FA and with a mixture of 8 % (PG+10% FA+ 4 % bentonite. It was evident, however, that none of the mixtures could fulfill the permeability requirements for a landfill sealing course, i.e. k £ 1 x 10^-8 m/s. Therefore, the use of PG and FA for this kind of application was not found economically feasible.

In order to determine the applicability of PG+FA+binder- structure material as a sealing course material the final permeability tests were made with the basix mixture (PG + 10 % FA) mixed with cement and bentonite after several test rounds with different mixtures. With 3 % cement and 4 % bentonite the strength development of test pieces was satisfactory (0,75 – 0,95 MPa), but the permeability was too high, 4 x 10^-7 m/s. Segregation potential was 0,8 mm²/Km, which indicates a slightly susceptible for frost damage. The permeability would not meet the required level even with 6 - 8 % bentonite when the mixtures have been made with conventional methods.

The studies did show that the effective counterstroke mixing and a water content clearly higher than the optimal water content (w = 15 %) helped to decrease permeability. Therefore, the material mixes were tested at different water contents. The final tests showed that an optimum mixture that in this case gives satisfactory permeability would be PG+ 10 % FA + 3 % Ce + 2 % bentonite when mixed with the counterstroke or other as effective method.

The homogeneous mixing of a gypsum-ash material is relatively difficult to achieve which the laboratory tests as well as the first pilot construction have proved. In 1999 the mixing for the pilot road was made with available, conventional equipment and the results were satisfactory for a road base. However, impermeable sealing courses cannot be achieved without more homogeneous mixing results. The adequate density for a sealing structure cannot be achieved with existing mixing methods for construction materials. There exists need for a new, more effective mixing equipment like explained also in the original technical project plan (in 1998).

The tests for environmental acceptability included determination of the concentration and leaching of potentially harmful elements and substances of the by-product materials and their mixes. The concentrations were determined with the EPA Method 3051 / ICP-MS analysis and compared with recommended guide values for the clean and polluted soil in Finland. The leaching was determined by using the Dutch standard for diffusion test, NEN 7345. The results indicate that the environmentally most critical substances are sulphate, fluoride and phosphorus.

The report of Task 1 (in Finnish) was submitted to the project partners and sponsors at the beginning of 2001.

The first demonstration site was chosen to be Käänninniementie in Maaninka, which is a countryside road suffering from heavy frost damage every spring. The pilot road construction was carried out in June (7. -18.6.1999). Before the construction work started the site was inspected with georadar and reference samples were collected in order to get background information for the follow-up.

The pilot road consists of two pilot sections, the other with a new structure course of PG+FA+binder and the other stabilised with a binder mixture described above. Both sections are around 1,7 kilometres long. Part of the road, about 1,6 kilometres, was repaired using traditional methods and materials, and this will serve as a reference section.

The design and plans for the pilot construction are given in detail in the report "Koerakenteiden rakennustöiden työkohtaiset laatuvaatimukset ja työohjeet". The construction of the pilot road is also explained on a thesis for M.Sc. in engineering " Fosfokipsin ja lentotuhkan hyötykäyttö maarakentamisessa". The report of the construction was submitted to the management group and other interested parties in February 2000.

PG and FA were delivered by trucks and stored in piles at the mixing station. The binder admixture was kept in a silo to keep it dry and to have it easier to portion for the mixing. The materials were mixed twice with a compost windrow turner and moved immediately after mixing to the construction site. The counterstroke mixer was not used, because it (a prototype) is available only for laboratory purposes.

For the structure course with by-products the road surface was levelled with a planing machine and some material was pushed to the sides into low banks to give support during compaction. The material mixture was spread and levelled into a 20-cm course. Driving over with trucks did the first compaction. The actual compaction was made with a vibrating roller on the crushed stone course that was spread as a surface for the by-product course.

At the stabilisation section the first task was to harrow out all big stones. The road surface was levelled and banks were formed like for the structure course above. The mixture of by-product binder admixture was spread in a 5-cm course over the road surface and mixed with a 20-cm course of crushed stone of the old road structure. Mixing was done using a milling cutter and water was added during this work when necessary. Compaction was performed with a vibrating roller. Next week a part of the surface course (crushed stone) was spread and the surface was completed later in August.

During the pilot construction quality control measurements were made according to the quality assurance plan. FinnRa employees that had been trained and supervised by Viatek did in-situ laboratory work. Main control was on the water content and thickness of the structure courses and on the success of the compaction. During construction several test pieces were made of the materials used in construction. These test pieces were tested later in Viatek SGT laboratory in Luopioinen, together with the samples taken from the structures after construction.

The sustainable construction is quite obvious as we look at the use of materials for the construction. About 3200 tons by-product materials have been used in the 1^st pilot. In case the constructions were done with conventional stone materials it would have needed over 8000 tons gravel and crushed stone.

Groundwater protection

The demonstration will take place in Maaninka municipality in August 2001. The road section for the demonstration will be 4 kilometres long. Apart from the construction the implementation will include following stages:

1. Technical and environmental investigations at the site and its environment before construction
2. Detailed design of the structures for the construction including instrumentation for the follow-up testing or monitoring (electronic instruments to measure e.g. moisture in the structure; possibly groundwater pipes)
3. Detailed instructions for the construction and follow-up tests
4. Quality control before and during construction. The quality of gypsum-ash will be controlled throughout the construction process emphasis being on the mixing
5. Follow-up / monitoring at the site. This will continue to the end of the project. After the project the follow-up of the long-term behaviour of the structures will be continued.

After starting the project an information leaflet about the project and its targets was sent to the civil engineering and soil construction journals. During the pilot road demonstration the following activities have been carried out:

• press meeting was held for the local and the national newspapers and TV and radio stations
• an article about pilot road was published in a local newspaper (Savon Sanomat 10.6.1999)
• an article about pilot road was published in a Finland’s leading newspaper (Helsingin Sanomat 11.6.1999)
• an interview in a local radio station (16.6.1999)
• An information leaflet (A4 size) about the project was posted to different parties
• Web- pages was made public in June 2001
• Seminar in Huelva, Spain in April 2002

• publication of the Design Guide at the end of the project