A laboratory study was conducted to study the effect of heat on the mechanical properties of diabase, granite and quartzitic schist at temperatures of 400◦C, 750◦C and 1100◦C. Unheated samples were also studied. The reasoning behind this study was to understand the effect of elevated temperatures on the rock mass, such as in the event of a fire in a rock tunnel. Samples from the aforementioned rock types were heat treated at temperatures shown above, cooled slowly to room temperature and then subjected to uniaxial compression and Brazilian tests. Thin sections were extracted from the heat treated samples for microscopic analyses, which assisted in explaining the reasons for the mechanical behaviour observed from the mechanical test results. The uniaxial compression test showed that the strength of the rock specimens increased by 6% for granite to 29% for diabase at 400◦C when compared to the UCS values of the unheated specimens. From 750◦C to 1100◦C the decay in the strength was very rapid. From the microscopic analyses it was concluded that the increase in the strength of the rock specimens at 400◦C is attributed to the initial reaction of the rock forming minerals, hence the rock specimens were less brittle but more plastic. The rapid drop in the strength from 750◦C to 1100◦C is attributed to the mineralogical changes, micro-cracking and dehydration due to the loss of crystal bound water. At 1100◦C the rocks were highly friable and crumbled very easily when tested mechanically. The effect of mineralogical changes was obvious in diabase where the physical appearance of the samples mimicked that of natural iron, which is believed to be due to the alteration of pyroxene. The result was an increase in strength by 29% at 400◦C compared to the unheated specimens. Even at 750◦C the strength was slightly higher than unheated specimens. In summary; the mechanical behaviour of the rock specimens depended on the temperature level and the mineralogical and physical changes that occur at that temperature.

The drill cuttings method is used for qualitative evaluation of rock aggregate in the road alignment during the road project stage

Testing of selected, critical rocks samples concerning their mechanical properties for calibration of LA-method as an EU standard for testing of rock fragmentation.

The detrimental influence of mica rich aggregates on structural deterioration of road pavement has been discussed in the literature for over a half century. This negative effect is of great importance especially for regions with crystalline, mica-rich bedrock and temperate, subarctic climates. Recent investigations reveal that elevated fractions of free mica particles in unbound granular materials, used in road constructions, greatly reduce bearing capacity and influence the hydraulic behavior of the road structure. Despite the awareness of mica's potential harmful effect, the absence of properly adapted analytical methods is noticeable. The scope of the current study was to test two possible analytical methods which, are susceptible to mica content and could be used as an indicating technique for quantitative determination of free mica particles in unbound granular materials. Two standard methods: Sand equivalent test and methylene blue (MB) test were assumed as the most sensitive to mica presence. The rock samples used in the tests are representative for the common crushed rock aggregates for construction purposes with different contents of mica. Both methods showed susceptibility to mica content and gave strong correlation in terms of mica content. The result of the MB test can be explained by the schistose structure of mica particles and the ability of mica to absorb liquids. Another important explanation is the increased reaction surface of mica particles, which leads to an increase in the total reaction surface of the sample. The receptiveness of the sand equivalent test to mica content could be caused by the ability of mica to stay in suspension due to its flake-shaped grains.

There is a need for an effective method to estimate the quality of crushed rock aggregates and its usability in the early stages of project planning, e.g., for road and railway constructions and quarry prospecting. The proposed method is based on mineralogical and petrographic analyses of drill cuttings and analysis of the coarse fraction to estimate the homogeneity/heterogeneity of the bedrock. The geological analyses are followed by an estimation of the rock materials' mechanical properties and their potential technical usability. Development and practical applicability (field and laboratory) of the method have been performed and correlated to three road projects from regions of different geological and climatic zones in Sweden. The study confirms the capability of the proposed method as a surveying tool.

In regions of temperate climate, the destructive influence of frost is the main contributor to damage of a road structure. Commonly, the frost susceptibility of base-course aggregates is often ignored in road construction. However, a number of studies on aggregates for construction purposes, and field observations of road failures, indicate a negative influence of mica-rich rock aggregates (used in unbound applications) on the service life of road construction. The scope of the current work investigates the capillary properties of unbound base-course aggregates with varying free mica grains. The materials studied in this research are commercially available road construction aggregates, and originate from different regions of Sweden. The mineral composition of the samples has been determined by polarizing microscopy using a point-count method. The parameter characterizing the capillarity was measured using the test for determining capillary rise (VVMB24). The results show that there is a direct correlation between mica content of the aggregates and water suction by capillary forces. Therefore, mica-rich materials susceptible to frost heave, thus confirming the tendency for frost damage of unbound aggregates.

The need to evaluate free mica grains in fine fraction of aggregate products has initiated the development of a statistically and scientifically acceptable method. The proposed method is based on a modified point-counting approach using digital micro photos of thin sections of aggregate grains and a software package to sustain sample analysis. A thin section of aggregate grains provides permanent sample documentation readily available for complimentary or other analysis. Statistical analysis, together with a repeatable analysis of samples (permanent mounts), confirms the robustness of the method. The method is appropriate as a complementary assessment tool to estimate and trace changes or variations in quality of rock aggregate. Though, the estimation of free mica particles in fine fraction needs to be combined with other analyses, e.g., petrographic analysis and analyses of mechanical properties, to assess the quality of any rock material. As the samples can be collected from drill cuttings, i.e., an accessible residual product obtainable from surveying or production, the present method is particularly useful as a surveying tool and in prospecting and projecting activities.