A sole empirical correlation expressing strength of fine-grained soils – lime mixtures. Soils and

: This paper advances understanding of the key parameters controlling unconfined 9 compressive strength (q u ) of lime stabilized fine-grained soils by considering distinct specimen 10 porosities (  ), different lime types and contents and several curing temperatures and time 11 periods. A sole empirical relationship establishing the normalized unconfined compression 12 strength for lime stabilized fine-grained materials considering all porosities, lime contents, 13 curing temperatures and curing periods studied is proposed. From a practical point of view, this 14 means that a very limited number of unconfined compression tests on specific lime stabilized 15 fine-grained material specimens molded with a given lime type and amount, porosity, moisture 16 content and cured for a given time period at a particular temperature, should be sufficient to 17 estimate the strength for an entire range of porosities and lime contents at any given condition. 18 Examples of the practicality of the proposed relationship are presented.


INTRODUCTION 26
Previous studies of fine-grained materials-lime mixtures (Consoli et al. 2011(Consoli et al. , 2014a and 2015) have shown that their behavior is complex, and affected by many factors, such as 28 grain size distribution of the soil, lime type and content, molding moisture content, porosity of 29 the material, and curing temperature and time period. Consoli et al. (2009)

EXPERIMENTAL PROGRAM 43
The experimental program has been carried out in two parts. First, the properties of the several 44 fine-grained materials were characterized. Then a number of unconfined compression tests were 45 carried out for fine-grained materials -lime blends considering different amounts of lime, up to 46 five dry unit weights varying from low to high density values, up to four moisture contents, 47 curing temperatures and distinct curing time periods (from 1 to 360 days of curing). 48

Materials 49
Several fine-grained materials with distinct characteristics were considered in the present 50 research, such as non-plastic and low plasticity soils, as well as industrial by-products such as 51 powdered rock obtained from a cutting rock place and coal fly ash from a coal thermo-electrical 52 power plant. The physical properties of the materials are presented in Table 1. Seven individual  53  or combinations between different fine-grained materials were used as host matrix: dispersive  54 clay, clayey sand (BRS), BRS + 25% powdered rock, BRS + 12.5% coal fly ash, BRS + 25% 55 coal fly ash, coal fly ash, clayey soil from Italy and sulphated clay from Paraguay. The 56 percentages of powdered rock and coal fly ash are calculated by mass of the BRS soil. 57 Quicklime [CaO -product of calcination of limestone, consists of the oxides of calcium], 58 dolomitic and calcitic hydrated lime [Ca(OH)2 -manufactured by treating quicklime with 59 sufficient water to satisfy its chemical affinity for water, thereby converting the oxides to 60 hydroxides] and calcitic carbide lime [Ca(OH)2 -a by-product of the manufacture of acetylene 61 gas] were used as binders. The combinations host materialbinder used are presented in Table  62 2. 63

Molding and Curing of Specimens 65
For the unconfined compression tests, cylindrical specimens 50 mm in diameter and 100 mm 66 high were used. Given a certain amount of fine-grained material (enough for molding a 67 specimen), the amount of lime for each mixture was calculated based on the mass of dry fine-68 grained material. A target dry unit weight for a given specimen was then established through 69 the dry mass of fine-grained materials-lime divided by the total volume of the specimen. As a 70 general procedure, in order to keep the dry unit weight of the specimens constant with increasing 71 lime content, an equivalent amount of the fine-grained material was replaced by lime. Porosity 72 () is defined as the ratio of voids (in volume) over the total volume of the specimen and as 73 shown by Eq. (1), it is a function of dry unit weight (d) of the blend, lime content (L) and the 74 unit weight of solids of host material (ss -see Table 1) and lime sLsee Table 2) respectively 75

78
After each fine-grained material and lime was weighed, both materials were mixed until 79 the mixture acquired a uniform consistency. Tap water between 13 and 18% by dry mass of 80 host fine-grained material was then added, continuing the mixing process until a homogeneous 81 paste was created. The specimen was then constructed in three layers each layer being statically 82 compacted inside a cylindrical split mold, so that each layer reached the prescribed dry unit 83 weight. In the process, the top of each layer was slightly scarified. After the molding, the 84 specimen was immediately extracted from the split mold and its weight, diameter and height 85 measured with accuracies of about 0.01g and 0.1mm, respectively. The specimens were cured 86 in a humid room at specific temperatures (see Table 2) and relative humidity above 95%. The 87 specimens were considered suitable for testing if they met the following tolerances: (i) Dry unit 88 weight (d): degree of compaction between 99% and 101% (the degree of compaction being 89 defined as the value obtained in the molding process divided by the target value of d); and (ii) 90 Dimensions: diameter to within ±0.5mm and height ±1 mm. 91 Before carrying out testing, the specimens were submerged in a water tank for 24 hours for 100 saturation to minimize suction (Consoli et al. 2012). The water temperature was controlled and 101 maintained at 23º±2ºC. Immediately before the test, the specimens were removed from the 102 water tank and dried superficially with an absorbent cloth. Then, the unconfined compression 103 test was carried out and the maximum load recorded. Because of the typical scatter of data for 104 unconfined compression tests, for each point, three specimens were tested. The testing program 105 was chosen in such a way as to isolate, separately, the influences of the lime content, dry unit 106 weight and porosity/lime index. The specimen molding conditions (lime contents, dry unit 107 weights, moisture content and curing time period and temperature) of all tested fine-grained 108 material are presented in Table 2.  Table 1. 156 The former soil was treated with quicklime and the latter was treated with hydrated calcitic lime 157 Curing time period was short (7 days) from the Italian soil and long (90 and 180 days) for 158 Paraguayan soil, validating the relationship use for distinct soils and a significant range of 159 curing time periods. 160 Regarding the clayey soil from Italy, data were taken from the average of specimens with 161 0.12 = = 32.6 and { 0.12 = 32.6} = 870 (see Table 2 Table 2