Optimizing design of high strength cement matrix with supplementary cementitious materials

• Design of high strength cement matrix with supplementary cementitious materials.
• Effect of silica fume, slag and fly ash on strength of low water to binder ratio matrix.
• Tensile properties of PVA-steel hybrid fiber reinforced high strength cementitious composite.

In present paper, high strength cementitious matrix, special for high strength engineered cementitious composite (ECC) is designed using two kinds of cement, ordinary Portland cement (OPC) and calcium sulfoaluminate cement (SAC), two sand types (fine and coarse sand) and three supplementary cementitious materials (SCMs), silica fume (SF), slag (SG) and fly ash (FA). Optimized binder proportion with the addition of SF, SG and FA of high strength matrix are obtained through three series compressive and bending tests. The tensile performance of ECC utilizing above high strength matrix is investigated through uniaxial tensile tests. The test results show that through optimizing on the binder composition with SCMs, compressive and bending strength of the low water to binder ratio cement matrix is significantly increased. With a similar fluidity of the fresh mortar and under general curing condition, the compressive strength at 3, 7 and 28 days changes from 25.5, 43.0 and 59.8 MPa to 35.4, 61.9 and 85.6 MPa for SAC mortar with fine sand before and after binder optimization. For OPC fine sand mortar, the compressive strength at 3, 7 and 28 days changes from 45.0, 57.8 and 77.9 MPa to 62.0, 80.6 and 108.0 MPa. Similar trend is observed on the bending strength of those mortars as well. Based on the present study, the optimized binder composition with SF, SG and FA additions in weight are cement:SF:SG:FA = 0.7:0.1:0.1:0.1. Using present optimized binder as cementing matrix, the primary tensile results on polyvinyl alcohol (PVA)-steel hybrid fiber reinforced composites show the tensile strength and strain can achieve 7.3 MPa, 0.6% and 8.1 MPa, 0.5% respectively for SAC and OPC cementing system.