Comparative analysis of different qualities of bricks and blocks in relation to rising dampness.

Abstract

The occurrence of rising dampness in masonry buildings results in material deterioration, energy waste, water-related damage, unpleasant indoor air, and mould growth. The rising damp process in a wall is influenced by the material quality of the masonry units and mortar, workmanship, and environmental conditions. In this study, we sought to investigate how rising dampness is influenced by masonry qualities that is; moisture absorption capacity, bulk density and salt content for both brick and concrete block masonries. Compressive strength, efflorescence and mould growth parameters were used to quantify the effect of rising dampness Wallets made of burnt clay bricks and concrete hollow blocks were constructed and used in water-rising experiments lasting a duration of 47days under controlled conditions in the laboratory. The results demonstrated that the quality of masonry units directly affected the rising speed, height of wetting front, compressive strength, mould growth and efflorescence occurrence in masonry walls. The study found that during the first 2 days of simulation, test walls constructed with locally manufactured bricks exhibited a rising dampness speeding 1.5 times faster than those built with standard bricks. Similarly, test walls made from locally produced concrete blocks demonstrated a 1.3 times higher rising speed compared to the standard concrete block walls. These results highlight the superior resistance to rising dampness in test walls constructed with standard manufactured burnt clay bricks and concrete hollow blocks which was consistent with the lower water absorption of standard samples over using locally made bricks and blocks. The compressive strength of test walls constructed with locally manufactured bricks decreased in strength after simulation by 8-33%. In contrast, the test wall constructed with standard bricks exhibited a 45% increase in strength, attributed to continued curing and strengthening of mortar joints. However, the compression strength of block test walls for both standard and locally manufactured concrete hollow blocks increased in strength due to continued curing process of the concrete blocks and mortar joints. Mould growth was visually detected in test walls of locally manufactured brick after 25 days of simulation. However, test walls constructed with standard bricks, locally made blocks and standard blocks showed no visible mould growth, consistent with their lower moisture rise rates observed in the study. Efflorescence, in form of white powdery deposits, was observed on test walls constructed with only locally manufactured bricks on the 25th day of simulation indicating potential salt contamination in locally manufactured bricks making them unsuitable for masonry construction.