Empirical Models for Strength Characteristics of Concrete with Wood Ash Using Pebbles as Coarse Aggregates

The determination of flexural and split tensile strengths of concrete is not commonly carried out on construction sites like compressive strength. However, not much research has been conducted on the correlation between flexural, splitting tensile and compressive strengths of concrete made with wood ash cement partial replacement using pebbles as coarse aggregates. This study investigates the correlation between flexural, split tensile and compressive strength of the concrete. Empirical models have been developed that relate the compressive strength with the flexural strength, and with the splitting tensile strength of concrete made with wood ash partial replacement of cement using pebbles as coarse aggregates. The models are for concrete with wood ash content of 5, 10, 15, and 20 % cement partial replacement by weight. Wood ash was obtained by controlled burning of African Birch tree logs, a hard wood in a Honey Trust bread bakery oven at a temperature of 150°C, and the pebbles from Bida town, Niger State, Nigeria. A water-cement ratio of 0.58 and a mix design ratio of 1:2.1:4.1. was used for the study. The strength characteristics data obtained were used to develop empirical models relating the strength properties with the aid of regression analysis tool in Microsoft Excel. The empirical models relating the flexural (fbl = 0.3216√fcu) and splitting tensile (fst = 0.1056√fcu) strengths of concrete with the compressive strength recorded R2 values of 0.99 and 0.818, P-values of 3.53 × 10−4 and 3.50 × 10−2, and standard errors of 0.129 and 0.109 respectively. The models are beneficial in the construction industry for easy determination of flexural strength and splitting tensile strength of concrete using compressive strength data for concrete made with wood ash partial replacement of cement and pebbles as coarse aggregates.