ORIGINAL PAPER Effect of ﬂy ash and polypropylene ﬁbres content on the soft soils Ahmet S ¸ enol Received: 11 February 2011 / Accepted: 20 June 2011 / Published online: 31 August 2011 Ó Springer-Verlag 2011 Abstract Fly ash is a waste produced from the burning of coal in thermal power stations. The staggering increase in the production of ﬂy ash and its disposal in an environ- mentally friendly manner is increasingly becoming a matter of global concern. Efforts are underway to improve the use of ﬂy ash in several ways, with the geotechnical utilization also forming an important aspect of these efforts. An experimental program was undertaken to investigate the effects of multiﬁlament and ﬁbrillated polypropylene ﬁbre on the compaction and strength behavior of CH class soil with ﬂy ash in different proportions. The soil samples were prepared at two different percentages of ﬁbre content (i.e. 0.5 and 1% by weight of soil) and two different percentages of ﬂy ash (i.e. 10 and 15% by weight of soil). A series of tests were prepared including optimum moisture content and laboratory unconﬁned compression strength tests, compaction tests and Atterberg limits test. The ﬁbre inclu- sions increased the strength of the ﬂy ash specimens and changed their brittle behavior into ductile behavior. Keywords Fibre-reinforced soil  Fly ash-soil  Polypropylene ﬁbres Re ´sume ´ Les cendres volantes constituent un de ´chet issu de la combustion du charbon dans les centrales thermiques. L’augmentation vertigineuse de la production de cendres volantes et sa mise en de ´po ˆt dans des conditions respec- tueuses de l’environnement sont de plus en plus des sujets de pre ´occupation ge ´ne ´rale. Des efforts sont en cours pour ame ´liorer l’utilisation des cendres volantes de plusieurs fac ¸ons, l’utilisation de ces produits en ge ´otechnique rep- re ´sentant un aspect important de ces efforts. Un programme expe ´rimental a e ´te ´ entrepris pour e ´tudier les effets, sur les caracte ´ristiques de compactabilite ´ et de re ´sistance, de l’incorporation de ﬁbres de polypropyle `ne multi ﬁlament (M19) et ﬁbrillated (E19) a ` des sols de classe CH com- portant diffe ´rentes proportions de cendres volantes. Les e ´chantillons de sol ont e ´te ´ pre ´pare ´s avec deux teneurs diffe ´rentes en ﬁbres (i. e. 0,5 et 1% en poids de sol) et deux teneurs diffe ´rentes en cendres volantes (i. e. 10 et 15% en poids de sol). Une se ´rie d’e ´chantillons ont e ´te ´ pre ´pare ´s a ` la teneur eau optimum et des essais de compression simple et de compactage ainsi que des mesures de limites d’Atter- berg ont e ´te ´ re ´alise ´s. L’incorporation de ﬁbres a augmente ´ la re ´sistance des e ´chantillons contenant des cendres vo- lantes et modiﬁe ´ leur comportement fragile en un com- portement ductile. Mots cle ´s Sol renforce ´ par incorporation de ﬁbres  Sol contenant des cendres volantes  Fibres de polypropyle `ne Introduction Various laboratory investigations have been conducted on ﬂy ash/lime stabilization of soil and ﬁbre reinforced soil. Fly ash is one of the most extensive waste materials from the manufacturing industry and is continuously being cre- ated due to the increase in energy, utilities and infrastruc- ture in urban areas. Coal burning electric utilities worldwide annually produce millions of tons of ﬂy ash as a waste/by-product and the environmentally acceptable dis- posal of this material has become an increasing concern. A. S ¸ enol (&) Civil Engineering Department, Cumhuriyet University, Sivas, Turkey e-mail: senol@cumhuriyet.edu.tr 123 Bull Eng Geol Environ (2012) 71:379–387 DOI 10.1007/s10064-011-0391-6