Influence of sulphate attack on compressive strength of millet husk ash as an alternative to silica fume in internally cured high performance concrete

Due to the difficulties in maintaining failing concrete structures built with normal concrete (NC), high-performance concrete (HPC), which is extremely dense and has a low water-binder content, has been developed. However, it has been observed that inadequate internal curing in HPC can lead to autogenous shrinkage and micro-cracking. Previous research has indicated that internal curing (IC) agents, such as pre-saturated lightweight aggregate (LWA) and superabsorbent polymers (SAP), are frequently used to address this issue. It is also noteworthy that the production of HPC necessitates the use of additional supplementary cementitious materials (SCM), particularly silica fume, which is not easily accessible in Nigeria or other Sub-Saharan African countries. This article presents the report of an effort to replace silica fume in HPC with millet husk ash (MHA) as a SCM material. The HPC specimens produced was internally cured with pre-soaked pumice as LWA and SAP respectively, with the view to establish the effectiveness of MHA for production of HPC. The results of 28, 56 and 90 days for concrete specimen immersed in ordinary water and in 5% of MgSO4 for C55/67 HPC mixtures for 100 mm concrete cubes having 7.5% silica fume content is compared with MHA based HPC of varied MHA contents of 2.5%, 5%, 7.5%, 10% and 15%).The results reveal 2.5%MHA performed best when compare with the control (i.e 7.5%SF) in resisting 5% MgSO4 attack with a strength loss factor of 1.89, 1.81 and 1.31% at 28, 56 and 90 days of age and was recommended for use as SCM and IC-agent in HPC.