Concrete sewer pipe corrosion induced by sulphuric acid environment

Corrosion of concrete sewer pipes induced by sulphuric acid attack is a recognised problem worldwide, which is not only an attribute of countries with hot climate conditions as thought before. The significance of this problem is by far only realised when the pipe collapses causing surface flooding and other severe consequences. To change the existing post-reactive attitude of managing companies, easy to use and robust models are required to be developed which currently lack reliable data to be correctly calibrated. This paper focuses on laboratory experiments of establishing concrete pipe corrosion rate by submerging samples in to 0.5 pH sulphuric acid solution for 56 days under 10ºC, 20ºC and 30ºC temperature regimes. The result showed that at very early stage of the corrosion process the samples gained overall mass, at 30ºC the corrosion progressed quicker than for other temperature regimes, however with time the corrosion level for 10ºC and 20ºC regimes tended towards those at 30ºC. Overall, at these conditions the corrosion rates of 10 mm/year, 13,5 mm/year and 17 mm/year were observed

Schematic diagram of health systems conceptual framework.

<p>Schematic diagram of health systems conceptual framework.</p

Description and summary of findings of studies evaluating complex national or regional interventions incorporating components from more than one health system building block.

<p>Description and summary of findings of studies evaluating complex national or regional interventions incorporating components from more than one health system building block.</p

Findings of quantitative studies examining the association of health insurance status with hypertension outcomes.

<p>RR, risk ratio; SES, socioeconomic status.</p

Findings of studies examining health systems arrangements relating to health systems delivery and governance.

<p>APR, adjusted prevalence ratios.</p

PRISMA flowchart.

<p>PRISMA flowchart.</p

Findings of quantitative studies examining the association of physician remuneration models with hypertension outcomes.

<p>Findings of quantitative studies examining the association of physician remuneration models with hypertension outcomes.</p

District balanced Scorecard stratified by domain.

<p>This figure shows district scores stratified by domain. The domain comprised six indices, each made up from an aggregate of indicators. Across the three study districts the basic infrastructure score was similar at 76%. Basic equipment and laboratory capacity scores showed major variation with Kafue and Luangwa having lower scores when compared to Chongwe. For basic equipment Luangwa scored lowest (65%), followed by Kafue (67%). Chongwe had the highest basic equipment score of 84%, and the laboratory capacity score was lowest in Kafue (63%) and highest in Chongwe (77%). Infection control scores were highest in Luangwa (90%) and lowest in Kafue (80%).</p

Sample profile for the baseline study in the three BHOMA districts.

<p>Sample profile for the baseline study in the three BHOMA districts.</p

Baseline demographic characteristics of the health facilities in the BHOMA study.

<p>Baseline demographic characteristics of the health facilities in the BHOMA study.</p