Data on the physical and mechanical properties of soilcrete materials modified with metakaolin

During the last decades eco-friendly, low-cost, sustainable construction materials for utilization in civil engineering projects have attracted much attention. To this end, soilcretes are non-conventional construction materials produced by mixing natural soil such as natural clay or limestone sand with a hydraulic binder and are recently under detailed and in-depth investigation by many researchers. In this paper the results of the physical and mechanical characteristics of a large set of cylindrical specimens under uniaxial compression, are presented. Specifically, two types of soils such as sand and clay with metakaolin as a mineral additive have been used. This database can be extremely valuable for better understanding of the behavior of soilcrete materials. Furthermore, the results presented herein expected to be of great interest for researchers who deal with the prediction of mechanical properties of materials using soft computing techniques such as artificial intelligence (AI) techniques.


a b s t r a c t
During the last decades eco-friendly, low-cost, sustainable construction materials for utilization in civil engineering projects have attracted much attention. To this end, soilcretes are nonconventional construction materials produced by mixing natural soil such as natural clay or limestone sand with a hydraulic binder and are recently under detailed and in-depth investigation by many researchers. In this paper the results of the physical and mechanical characteristics of a large set of cylindrical specimens under uniaxial compression, are presented. Specifically, two types of soils such as sand and clay with metakaolin as a mineral additive have been used. This database can be extremely valuable for better understanding of the behavior of soilcrete materials. Furthermore, the results presented herein expected to be of great interest for researchers who deal with the prediction of mechanical properties of materials using soft computing techniques such as artificial intelligence ( The research data are important for researchers who deal with eco-friendly, low-cost, new, sustainable construction materials with improved mechanical properties for utilization in civil engineering projects.
The experimental data can be extremely valuable for the development of a mix design process focused on soilcrete materials and to elucidate the relation between physical and mechanical properties through the comparison of macroscopical observations with experimentally measured mechanical characteristics.
The experimental data presented herein expected to be of great interest for researchers who deal with the prediction of mechanical properties of materials using soft computing techniques such as artif icial intelligence (AI) techniques and provide an initial dataset point to generate and validate numerical and/or analytical models.

Data
Data on the synthesis and physicomechanical characteristics of 2 types of environment-friendly soilcrete materials are presented. Soilcrete samples contained different contents of natural clay ground soil or crushed quarry sand of a limestone origin as replacement of the aggregate phase. Metakaolin has been added at variable contents as a mineral additive to the ordinary Portland cement-based binder mix, at different water/binder ratio values (W/B). Specifically, the Research Database presents measured physical and mechanical properties such as the 28 days compressive strength (f c ), the modulus of elasticity (E c ) and the strain at maximum strength (ε 0 ) (Fig. 1) of a large set of cylindrical specimens with a height-to-diameter (h/d) ratio equal to 2 (h/d¼ 2) which have been tested under uniaxial compression [1][2][3].

Experimental design
Three categories of binders (B), variable in synthesis, were investigated; the 1st that consisted of 100% w/w CEM I 42.5 N Portland cement (PC) used as reference, the 2nd produced by mixing 90% w/ w PC and 10% w/w metakaolin (MK) in the dry mix and the 3rd by mixing 80% w/w PC and 20% w/w MK (in the dry mix) as partial replacement. Homogeneity of all 3 categories of blends was reached after mixing MK and PC without further grinding in a laboratory swing mill for 1 h [1][2][3].
Batches of samples that correspond to 2 specific types of soil materials were investigated; natural clay ground soil (CGS) and crushed quarry limestone sand (CQLS) were used as replacement of the aggregate phase. First type soilcrete material, entitled as clay-based soilcrete, produced by mixing 50% and 70% w/w CGS (in the dry mix) with 50% and 30% w/w binder at 2 different water/binder (W/B) ratio values of 0.48 and 1.2. High workability and optimal flow properties for samples with W/B equal to 0.48 was achieved by the addition of 2.0% w/w (of the cementitious materials) superplasticizer (SP), as presented in Table 1. Second type soilcrete material, entitled as sand-based soilcrete, produced by mixing 50% and 70% w/w CQLS (in the dry mix) with 50% and 30% w/w binder at 3 different W/B ratio values of 0.4, 0.7 and 1.0. As Similarly to the first type soilcrete material samples, high workability and optimal flow properties for samples with W/B equal to 0.4 were achieved by the addition of 2.0% w/w SP (of the cementitious materials), as listed in Table 2. Refs. [1][2][3] provide a detailed description of the experimental set-up.

Materials
Raw materials used for the preparation of samples were:  (iii) Natural clay ground soil (CGS) since it corresponds to a typical worst case scenario of a low plasticity stiff soil [1]. (iv) Crushed quarry sand of a limestone origin (CQLS) was selected since it corresponds to a widespread typical natural rock that can be found in a wide range of soil strata (clean sands) [1,3]. (v) Type E and F according to ASTM C494/C494M-08a common superplasticizer (SP) manufactured by Domylco Ltd. (CHEM SLP P) at appropriate percentages in order to retain high workability and optimal flow properties of the produced soilcrete. (vi) Tap water (W) of moderate hardness (14°F).

Methods
Particle size distribution for CGS (before sieving at 2 mm) and CQLS (before sieving at 4.75 mm) resulted by conducting sieve analysis according to ASTM D6913-04, ASTM E11 and C136 standards, respectively [1][2][3]. CGS and CQLS were dried at 105°C for 5 days and at 105°C for 24 h respectively, in an electrical laboratory oven and then sieved in order to pass a 2.00 and 4.75 mm sieve respectively [1][2][3]. Mixing of binder batches was performed in a laboratory swing mill for 1 h without further grinding of solid constituents until homogeneity of the blends was reached [1][2][3]. Soilcrete samples were prepared by mixing the binder-CGS and binder-CQLS mixtures with tap water at 20°C in an 80 L capacity laboratory mixer used for concrete production [1][2][3].
All soilcrete specimens were cast in concrete cylinders (100 mm in diameter, 200 mm in high), vibrated for 20 s on a vibration table and then covered to minimize water evaporation [1][2][3]. The molds were stripped after 24 h, and the specimens were immersed in lime-saturated water at 20°C, until testing [1][2][3]. Compressive strength measurements were conducted at 28 days. For each sample, four to eight soilcrete specimens were tested and the mean values of the measured physical and mechanical properties such as the 28 days compressive strength, the modulus of elasticity, the strain at maximum strength and the ultrasonic velocity are presented at Tables 3 and 4.