Engineering properties at early ages of pumping high-strength mortar containing various sand types

Abstract

This study mainly focused on investigating the engineering properties (i.e., fluidity, compressive strength, and drying shrinkage) at early ages of high-strength mortars using four different types of sand. The fixed composition ratios of high-strength mortars were selected, including a sand-to-cement ratio of 1.5; a silica fume-to-cement ratio of 10%; a superplasticizer-to-cement ratio of 1.5% and a water-to-cement ratio of 29%. Four types of sand with various fineness moduli (M_dl = 2.46, 3.66, 4.04, and 3.16) were selected. The results showed that the fluidity of the four fresh mortars ranged from 235 – 290 mm and the compressive strength at ages of 1, 3, and 7 d ranged from 52.1 – 58.4 MPa, 80.1 – 90.3 MPa, and 87.3 – 98.4 MPa, respectively. After aging for 7 d, the mortar samples had drying shrinkage values ​​ranging from 0.031 – 0.045% of the initial length. The use of fine aggregates with coarse grain sizes (i.e. high fineness moduli) reduced the fluidity of the fresh mortar but improved the compressive strength from 6.19 – 12.71% at 7 d and reduced the drying shrinkage up to 7 d of the hardened mortar samples. Consequently, the mortar using sand with a fineness modulus of 3.16 was proposed as the optimal one owing to its suitable fluidity for the pumping method, relatively high compressive strength (92.7 MPa at 7 d) and low drying shrinkage (0.031% at 7 d).