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The article contains a roughly translated summary and excerpts from the Scientific Report: V. Prikhodko and E. Kotlyarsk, “Construction of an experimental section of the foundation from the soil, strengthened with Portland cement using the additive Renolith on the educational and scientific base MADI (STU),” Ministry of Education and Science of the Russian Federation, Moscow, 2008
The investigation and construction work on pavement layers made of soil consolidated with Portland cement and Renolith additive was carried out in June-July of 2008 at the Institute for Automotive and Road Construction Moscow (MADI) State Technical University (STU) test field.
The objectives were:
Because heavy transport in Russia and in neighboring countries continues to increase, it is necessary to adapt quickly to the growing volume of traffic and to expand the road network. This problem can be solved thanks to new technology, which can use the on-site soil for the road substructure and thus greatly reduce dependence on foreign materials in road construction. The use of soil stabilized with various binding materials is in ever wider use in road construction. The consolidation (stabilisation) of local soils allows a much greater range of usable materials in road construction. Recycling and use of local soil means reducing the materials to be delivered (e.g. gravel, coarse and small-grain sand); reducing the costs and transport impost for the construction of base layers in road construction.
The existing soils, with the addition of cement and special admixture (Renolith), can be used for the construction of the road substructure and achieve the necessary physical-mechanical properties (pressure and deformation resistance, frost resistance). High load capacity of the road substructure can be achieved. The biggest benefit of using this binder is that the mixtures can be prepared directly on site. Special mixing plants are required such as road milling machines and stationary mixing plants. Generally, such methods have application in the technical-economic effectiveness in road construction. However, traditional stabilisation construction methods have a number of significant disadvantages:
To improve the structural properties of soils solidified with cement, various additives are used here and abroad. Additives can make soils and aggregates hydrophobic and increase frost resistance of the material, or improve physical-chemical interactions with soil fines to form a denser and firmer material structure.
The additive to be examined – Renolith – can enable otherwise unsuitable soils to be utilised in road bases.
The first test field was constructed on 05 June 2008. The composition of the solidified soil mixture was:
The sandy soil had a moisture content of 10%. 500 m3 of large grain sand was obtained from a pit near Moscow, bulk density 1.5 g/cm³.
Storage of the sand at the MADI test field
Portland cement brand 400 was made in Turkey and delivered in bulk bags. Because of improper storage and/or transport, the cement lost some effectiveness. Also, lumps had accumulated, causing partial malfunctions of the dosing device and affecting homogeneity of the mixtures.
The preparation of the above composition was made using a Bertoli brand mixer. This mixing plant has an output of 100 m³/h.
Bertoli mixing plant
The delivery of the mixture to the installation site was no more than 200 meters. Transportation was carried out using Kamaz trucks with a load capacity of 15 tons.
The application was done with the Vogele brand paver with a layer thickness of 18 cm installed.
Delivery of the cement soil mixture by truck and its unloading into the bunker of the brig. Application of the test section to the fire brigade aisle of the MADI test field
The pavement was compacted with a 12 ton two-roller vibrating roller brand DU 82 at a running speed of 1.3 km/h. 5-6 passes on each track were required to achieve full compaction.
Compaction of the mixture using a large roller
During the work process, the MADI specialist laboratory was used to determine the properties of the ingredients and mix. Reference samples were manufactured from 20kg of sand, 5kg of Portland cement and 2 litres of Renolith additive.
During the installation process, the layer density, layer thickness and width of the applied mixture was checked, as well as the number of rolling passes.
9 series of core samples (total of 63 cylinders) were drilled after 28 days cure.
Scheme of the test track on MADI test field with indication of the places where the cement soil mix samples were taken (9 places)
Laboratory tests were carried out in accordance with GOST 23558-94.
The second test field was constructed on 15 June 2008. The technology for the construction of this road bed as well as the machines, mechanisms and soil mix were the same as for test field #1.
Core samples were taken from the installed base after 28 days curing. The sampling scheme for the core samples was similar to test field #1.
Sample core drilling
Drilled core sample
Control samples were prepared and stored for 28-days storage in a climate controlled chamber. The physico-mechanical properties of core samples the control samples were determined.
Tests were conducted on specimens and core samples to determine:
Capillary water absorption test of the cement soil samples
Flexural strength test of 28d cured sample
The ratio of compressive strength to bending strength to a certain extent characterizes the crack resistance of asphalt concrete pavements on soil bases reinforced with mineral binders. The ratios of compressive strength to bending (tensile) strength obtained from the results of testing samples and cores with 95% reliability lie in the range from 2.38 to 2.81. In accordance with the requirements of GOST 23558-94, these ratios should be no more than 5.00. The obtained ratios of compressive strength and tensile strength during bending suggest a higher crack resistance of soils reinforced with Portland cement and Renolith additive, which increases crack resistance of asphalt concrete pavements on cement-soil bases.
Water absorption of core samples selected from the base layer of the test site was determined in accordance with clause 6.1 of GOST 23558-94. To do this, the samples were placed in a bath filled with water at 1/3 of the cylinder height, and after 6 hours they were filled with water completely and kept for 42 hours. It is necessary to note the low values of water absorption, [the average values were between 0.75 and 1.09 M.-%], which creates the prerequisites for obtaining a material with high water and frost resistance.
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