Mechanical and microstructural properties of Pistacia Atlantica Ash concrete

Concrete is the most used building material in the world. Many studies have targeted concrete due to its numerous benefits over other building materials. Being a moldable and rather cheap building material, it has provided good motives for engineers to further investigate the mechanical and microstructural properties of concrete with the incorporation of different kinds of additives. To do so, waste materials admixtures were suggested into the matrix to lessen the amount of cement through cement replacement as Pozzolanic mineral admixtures. These admixtures are used in concrete to enhance the mechanical properties. Waste materials not only reduces the cement content but enhances the qualities of concrete such as mechanical and the microstructural properties. However, only limited amounts of replacement were suggested. In this research, a new waste material is introduced to use in concrete as a pozzolanic material. In this paper, for the first time, Pistacia Atlantica Ash is used into the matrix of concrete to reduce the amount of cement and then, the effects of Pistacia Atlantica Ash on the concrete are investigated. Pistacia atlantica is a species of wild pistachio tree. In Iran, it is called Baneh or Van.
Fruit of Pistacia Atlantica is collected from the Saghez city located in north Kurdistan, Iran. The fruit of Pistacia Atlantica is first burned at 500 ºC for 3 hours. Then, Pistacia Atlantica Ash is sieved. Cement is replaced Pistacia Atlantica Ash. To do so, 5, 10, 15 and 20% Pistacia Atlantica Ash is admixed in the concrete samples. The Water to cement (W/c) ratio are kept constant at 0.45 for the entire mixes. Amount of aggregates are kept constant for all series of mixes. All of the samples are cured in water.
Four design mixes of Pistacia Atlantica Ash separately are casted for compression tests, slump, modulus of elasticity, ultrasonic pulse velocity (UPV), and microstructural properties. The compressive strength of samples at ages of 7, 14, 28, and 90 days are recorded. Cement replacement with Pistacia Atlantica Ash decreased the early age compressive strength. However, the compressive strength in the specimens increased in the course of time. The target compressive strength of control samples is set to be 39MPa at 28 days. Compressive strength of samples with 20% Pistacia Atlantica Ash is improved up to 18.3% at 28 days.
 One of the major findings is that concrete that incorporates twenty percent of Pistacia Atlantica Ash weight of cement showed better mechanical properties. Concrete slump in the specimens are considerable decreased comparing to the control samples. The replacement of Pistacia Atlantica Ash with cement increased the elastic modulus. Also, scanning electron microscopy (SEM) results showed that admixing Pistacia Atlantica Ash led to improvement in the microstructure, and pozzolanic behavior of mixtures. The results from microstructural analysis are conclusive that C-S-H formation increased when of Pistacia Atlantica Ash is added to the samples. In general, the results are conclusive that the addition of 20% Pistacia Atlantica Ash enhances the properties of concrete such as compressive strength modulus of elasticity and density of microstructure.